This publication provides preliminary data on the response of various weeds to various herbicides and application methods at sites around the state of Hawaii

Motooka, Philip

ScholarSpace at University of Hawai'i at Manoa

The tables herein summarize herbicide trials for thecontrol of pasture, range, and non-cropland weedsconducted by the College of Tropical Agriculture andHuman Resources, University of Hawaii at Manoa; theHawaii Department of Agriculture; the Division of For-estry and Wildlife of the Hawaii Department of Landand Natural Resources; and other cooperators. Thesepreliminary data are published to assist applicators ex-perimenting with herbicides for weed control. The her-bicide applicator is cautioned to confirm that any herbi-cide use, rate, or method of application conforms to theproduct label.Rating weed response to herbicidesWeed response to treatment is evaluated by differentmethods. Plant injury may be scored on a 0–100 scalein which the score is a subjective evaluation of the se-verity of injury:0 No symptoms10–30 Insignificant to poor weed control; little or nodefoliation40–60 Inadequate weed control; moderately severesymptoms; less than 70% defoliated70 Adequate weed control; severe symptoms; allleaves chlorotic or more than 70% defoliated80 Good weed control; very severe symptoms; 80%defoliated90 Excellent weed control; very severe symptoms;90% defoliation100 Complete control; no sign of lifeSummaries of Herbicide Trials for Pasture, Range,and Non-Cropland Weed Control—2001Philip Motooka, Department of Natural Resources and Environmental ManagementIn addition to the scale described above, efficacy of treat-ments may be determined by estimation of defoliationor its opposite, remaining weed cover. The method useddepends on the growth habit of the weed. Response mayalso be measured by counting the number of survivingplants or stems, by measuring weed height, or a combi-nation of these.Methods of herbicide applicationSeveral methods of herbicide application were used inthe trials described here, including foliar, cut-surface,basal bark, stump bark, and soil applications (SeeCTAHR publication WC-4, 1999, Woody plant controlfor the home, pasture, and forest. Also, low-volume andvery low-volume variants of foliar application (drizzlemethod) and basal bark and stump bark treatments wereevaluated (see Motooka, P., G. Nagai, and L. Ching,1983, “The ‘magic wand’ method of herbicide applica-tion,” Proc. Ninth Asian Pacific Weed Sci Soc. Conf.,Suppl. Vol., p. 550–553; and Motooka, P., J. Powley, M.DuPonte, L. Ching, G. Nagai, and G. Kawakami, 1999,“Drizzle herbicide application for weed management inforests,” Proc. West. Soc. Weed Sci. 52:136–139).Mention of a trademark, company, or proprietary name does notconstitute an endorsement, guarantee, or warranty by the Uni-versity of Hawaii Cooperative Extension Service or its employ-ees and does not imply recommendation to the exclusion of othersuitable products or companies.Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June30, 1914, in cooperation with the U.S. Department of Agriculture. Andrew G. Hashimoto, Director/Dean, Cooperative Extension Service/CTAHR, Universityof Hawaii at Manoa, Honolulu, Hawaii 96822. An Equal Opportunity / Affirmative Action Institution providing programs and services to the people of Hawaii withoutregard to race, sex, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or veteran status.CTAHR publications can be found on the Web site <http://www2.ctahr.hawaii.edu> or ordered by calling 808-956-7046 or sending e-mail to ctahrpub@hawaii.edu.Weed ControlApr. 2002WC-7WC-7 Herbicide Trial Summaries—2002 CTAHR — Apr. 20022Materials testedHerbicides Trade name and manufacturerClopyralid Transline (Dow Agrosciences)2,4-D Amine salt formulation,  various brandsEster formulation, various brandsDicamba Banvel (BASF)Glyphosate Rodeo (Monsanto)Roundup (Monsanto)Hexazinone Pronone Power Pellets (DuPont)Velpar L (DuPont)Imazapyr Stalker (Syngenta)MCPA MCP Amine (Clean Crop)Metsulfuron Escort (DuPont)Triclopyr Garlon 4 (Dow AgroSciences)Remedy (Dow AgroSciences))Redeem (Dow AgroSciences)Pathfinder II (Dow AgroSciences)Tebuthiuron Spike 20P (Dow AgroSciences)WeedsBamboo (Phyllostchys niger (Lodd.) Munro var.henionis (Mitf.) Rendle)Bushy beardgrass (Schizachyrium condensatus (Kunth)Nees)Christmasberry (Schinus terebinthifolius Raddi)Downy rosemyrtle (Rhodomyrtus tomentosa (Aiton)Hassk.)Fayatree (Myrica faya Aiton)Fountaingrass (Pennisetum setaceum (Forssk.) Chiov.)Guava (Psidium guajava L.)Huehue (Cocculus trilobus (Thunb.) DC)Huehue haole (Passiflora suberosa L.)Madagascar ragwort (formerly fireweed) (Seneciomadagascariensis Poiret)Shoebutton ardesia (Ardesia elliptica Thunb.)Spiny emex (Emex spinosa (L.) Campd.)Strawberry guava (Psidium cattleianum Sabine)ObservationsDowny rosemyrtle and fayatree are among the speciestolerant to triclopyr. To determine if the cause of the thistolerance was lack of uptake, downy rosemyrtle wastreated with triclopyr ester in crop oil. One set of treat-ments was the application of triclopyr with oil as theonly carrier to ensure uptake increase. Although therewas initial brownout with the oil carrier, recovery wasrapid indicating that the high uptake caused transloca-tion of the herbicide to cease before enough migratedinto the stem and roots. The lower oil concentrationscaused greater though still temporary injury (Table 1).The tolerance of downy rosemyrtle is apparently notrelated to uptake of triclopyr. Oil increased efficacy oftriclopyr in drizzle applications on fayatree. However,three applications over nearly 3 years did not kill theplants although it did cause severe injury (Table 2).Fayatree was very susceptible to basal bark applicationof triclopyr in crop oil but not to basal bark applicationof glyphosate augmented with the adjuvant Quiksorb(Monsanto) (Table 3). Though basal bark treatment withglyphosate has not been traditionally used, such use isbeing developed on the mainland for thin-stemmedplants.Fountaingrass was susceptible to drizzle applicationsof glyphosate in drizzle applications (Table 4). How-ever the fountaingrass must be in good condition at treat-ment. Drought stricken fountaingrass did not succumbto drizzle application of glyphosate (see Summaries2000). Drizzle application of glyphosate was also effec-tive on the vines huehue and huehue haole (Table 5).The fast spreading Madagascar ragwort or fireweedwas tolerant to herbicides in rank stages of growth (TheWeed Science Society of America has adopted the com-mon name Madagascar ragwort). Although herbs areusually sensitive to herbicides, ragwort has proved tol-erant to triclopyr and higher rates of hormone type her-bicides were required to kill rank ragwort. It is impor-tant that the weed be succulent and that environmentalconditions be suitable for plant growth when it is treated.MCPA and triclopyr were ineffective under droughtyconditions (Table 6). Madagascar ragwort was very sus-ceptible to clopyralid (Table 7, 8). However because ofthe high cost of clopyralid, MCPA even at 2 lb/A wouldbe much more economical (Table 7, 8).Shoebutton ardesia, though severely injured bydrizzle applications of 2,4-D and triclopyr, was not killed3WC-7 Herbicide Trial Summaries—2002 CTAHR — Apr. 2002by two applications of each of these herbicides (Table9). Conventional spraying may still be required.Spiney emex, despite flooding followed by droughtafter treatment, was susceptible to dicamba in drizzleapplication (Table 10). The Polygonaceae, the familyto which emex belongs, is very sensitive to dicamba andwill succumb to 0.25 lb/acre or 0.5 pint/acre with con-ventional spraying.Strawberry guava proved susceptible to very-lowvolume basal bark application of triclopyr/oil applied inhorizontal streaks (Table 11) and two vertical streaks tothe base of the trunk (Table 12). Strawberry guava treescan be killed more efficiently in remote areas sincesmaller volumes of the oil carrier need to be transported.Table 4. Fountaingrass control with drizzle application ofglyphosate (K00-4).Date installed: 12/14/00. Location: Puuanahulu. Investigator:P. Motooka.Glyphosate Defoliation (%)rate(lb/acre) (01/12/01) (03/28/01)0 0 01 85 922 91 993 92 99Table 1. Downy rosemyrtle response to triclopyr appliedwith water and oil carrier (G00-11).Date installed: 08/24/00. Date rated: 01/30/01. Location:Wailua. Investigators: Lincoln Ching, Philip Motooka. Notes:Oil as carrier applied only for research purposes, impracticalin normal use.Triclopyr rate Adjuvant/carrier Weed cover(lb/acre) (%) (%)0 0 872 3.9 294 7.8 162 100 724 100 60Table 2. Response of fayatree to triclopyr applied by thedrizzle method with water or with oil (K99-9).Date installed: 05/28/99. Location: Keauhou Ranch, Volcano.Investigators: M. du Ponte, P. Motooka. Notes: Retreated 11/09/99, 08/02/00, 03/06/01.Triclopyr Defoliation (%)rate Carrier(lb/acre) (11/09/99) (08/02/00) (03/06/01) (09/06/01)0.5 Water 38 32 55 610.5 Oil 53 42 71 831.0 Water 42 48 78 821.0 Oil 59 60 95 90Table 3. Response of fayatree to low-volume basal barkapplications of glyphosate and triclopyr (K00-3X).Date installed: 08/02/00. Date rated: 03/07/01. Location:Keauhou Ranch, Volcano. Investigators: M. duPonte, P.Motooka. Notes: Glyphosate as Rodeo was applied at 40%plus 10% surfactant in water, triclopyr amine was applied at25% plus 10% Quiksorb in water. Fayatrees dbh 4–6 inches.Seven replicates in blocks. Average volume per tree, 3.0 fl oz.Herbicide Conc. Surfactant Defoliation(%) (%)Check 0 0 0Glyphosate 40 Excell NF 90 24Glyphosate 40 Quiksorb 28Triclopyr Amine 25 Quiksorb 39Pathfinder II 100 None 100Table 5. Huehue and huehue haole control by drizzleapplication of glyphosate (K01-08).Date installed: 06/20//01.  Location: MacFarms. Investigators:T. Lilly, P. Motooka.Defoliation (%)Glyphosaterate (07/25/01) (10/17/01)(lb/acre) Huehue H. haole Huehue H. haole2 68 99 85 1003 82 98 92 100WC-7 Herbicide Trial Summaries—2002 CTAHR — Apr. 20024Table 10. Spiny emex control with drizzle application ofdicamba (K00-3).Date installed: 12/14/00. Date rated: 03/28/01). Location:Waimea, Hawaii. Cooperator: S. Bannister Sr. Investigators:P. Motooka, A. Kawabata. Note: Drought and flooding afterapplication.Dicamba rate Emex cover(lb/acre)  (%)0 650.25 440.5 121.0  9Table 7. Madagascar ragwort (fireweed) response to MCPAand clopyralid (K01-5).Date installed: 05/02/01. Location: Kamuela. Cooperator: M.Yamasaki. Investigator: P. Motooka. Note: Average initialfireweed cover 31%.Herbicide Rate Fireweed cover (%)(lb/acre) (05/16/01) (06/21/01) (07/03/01) (07/31/01)Check 0 29 31 23 23MCPA 1 20 11  6  8MCPA 2 10  5  6  9Clopyralid 0.5 20  0  1  0Clopyralid 1 12  0  0  0Table 8. Madagascar ragwort (fireweed) control withclopyralid, dicamba, MCPA, and metsulfuron (K01-09).Date installed: 07/03/01. Location: Honokaa. Investigators: M.du Ponte, P. Motooka. Cooperator: Antone DeLuz. Note:Average initial fireweed cover 19%.Fireweed cover (%)Herbicide Rate(lb/acre) (07/31/01) (09/05/01)Check 0 11 25Clopyralid 0.12  8  9Clopyralid 0.25  7  2Clopyralid 0.5  5  0Dicamba 0.5 15 12Dicamba 1.0  5  6MCPA 2.0  2  0Metsulfuron 0.4 oz/acre  4  7Table 11. Strawberry guava response to vertical streakvery-low volume application of triclopyr/oil. (G01-07)Date installed: 05/07/01. Date rated: 09/25/01. Location:Kokee. Investigators: L. Ching, G. Kawakami, P. Motooka.Notes: Triclopyr ester, 20% in crop oil, applied in two verticalstreaks from ground to waist height.Treatment Defoliation(%)Check  0Triclopyr 97Table 6. Madagascar ragwort (fireweed) control with MCPAand triclopyr (K01-03).Date installed: 01/28/01. Date rated: 03/28/01. Location: WaikiiRanch. Investigators: G. Fukumoto, P. Motooka. Notes:Drought after application.Herbicide Rate Adjuvant Defoliation(lb/acre) (%)Check 0   0     2MCPA 1 NF90 12MCPA 2 NF90 28Triclopyr E 0.5 NF90 10Triclopyr E 0.5 FCO 18Triclopyr E 1.0 NF90 10Triclopyr E 1.0 FCO 24Table 9. Response of shoebutton ardesia to drizzleapplications of herbicides (G00-8)Date installed: 03/09/00. Location: Princeville Ranch.Investigators: L. Ching, G. Nagai, P. Motooka. Notes:Herbicides applied at 1 lb/acre. Reapplication 01/31/01.Treatment Defoliation (%) (07/18/00) (01/31/01)  (09/24/01)0 0 0 02,4-D ester/water 65 52 55Triclopyr ester/water 72 50 75Triclopyr ester/oil 60 30 585WC-7 Herbicide Trial Summaries—2002 CTAHR — Apr. 2002Table 12. Very-low volume basal bark treatment ofstrawberry guava with triclopyr/oil (V98-6)Date installed: 12/01/98. Date rated: 02/27/01. Location:Waihee Ridge Trail, Maui. Investigators: J. Powley, P. Motooka.DBH Streaks/side No. of trees Defoliation(inches) (%)1–4 2 18 89+ 6 6 4 88+ 10 8 7 66+ 18 10 2 82Table 13. Results of demonstration trials.Weed Herbicide Rate/Conc. Method Control Reps Duration Site (%) (mo)Bamboo Imazapyr 9% Basal 90 1 16 KainaliuBushy beardgrass Hexazinone 4 lb/acre Soil 99 1 plot 20 Nualolo Crossover TrailFaya tree Hexazinone 4 lb/acre Soil 0 3 20 Nualolo Crossover TrailGuava Triclopyr 20% Basal bark 85 1 20 Nualolo Crossover TrailGuava Tebuthiuron 2 lb/acre Soil 89 18 20 Nualolo Crossover TrailMadagascar ragwort Clopyralid 1 lb/acre Drizzle 88 2 1.5 KamuelaStrawberry guava Triclopyr 20% VLV basal 75 30 20 Nualolo Crossover TrailStrawberry guava Hexazinone 2 lb/acre Soil 95 2 20 Nualolo Crossover TrailStrawberry guava Tebuthiuron 2 lb/acre Soil 82 4 plots 20 Nualolo Crossover Trail

Summaries of Herbicide Trials for Pasture, Range, and Non-Cropland Weed Control--2001

Summaries of Herbicide Trials for Pasture, Range, and Non-Cropland Weed Control--1999

Summaries of Herbicide Trials for Pasture, Range,and Non-Cropland Weed Control—2002Philip Motooka, Department of Natural Resources and Environmental ManagementMention of a trademark, company, or proprietary name does notconstitute an endorsement, guarantee, or warranty by the Uni-versity of Hawaii Cooperative Extension Service or its employ-ees and does not imply recommendation to the exclusion of othersuitable products or companies.Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June30, 1914, in cooperation with the U.S. Department of Agriculture. Andrew G. Hashimoto, Director/Dean, Cooperative Extension Service/CTAHR, Universityof Hawaii at Manoa, Honolulu, Hawaii 96822. An Equal Opportunity / Affirmative Action Institution providing programs and services to the people of Hawaii withoutregard to race, sex, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or veteran status.CTAHR publications can be found on the Web site <http://www2.ctahr.hawaii.edu> or ordered by calling 808-956-7046 or sending e-mail to ctahrpub@hawaii.edu.Weed ControlFeb. 2003WC-9The tables herein summarize herbicide trials for thecontrol of pasture, range, and non-cropland weedsconducted over the past year by the University of Ha-waii at Manoa College of Tropical Agriculture and Hu-man Resources, the Hawaii Department of Agriculture,the Division of Forestry and Wildlife of the Hawaii De-partment of Land and Natural Resources, and other co-operators. These preliminary data are published to as-sist applicators experimenting with herbicides for weedcontrol. The herbicide applicator is cautioned to con-firm that any herbicide, rate, or method of applicationused conforms to the label.Rating weed response to herbicidesWeed response to treatment is evaluated by differentmethods. Plant injury may be scored on a 0 to 100 scalein which the score is a subjective evaluation of the se-verity of injury:0 No symptoms10–30 Insignificant to poor weed control. Little orno defoliation.40-60 Inadequate weed control. Moderately severesymptoms. Less than 70% defoliated.70 Adequate weed control. Severe symptoms. Allleaves chlorotic or more than 70% defoliated.80 Good weed control. Very severe symptoms.80% defoliated.90 Excellent weed control. Very severe symp-toms. 90% defoliation.100 Complete control. No sign of life.In addition to the scale described, efficacy of treatmentsmay be determined by estimation of defoliation or itsopposite, remaining weed cover. The method used willdepend on the growth habit of the weed. Response mayalso be measured by counting the number of survivingplants or stems or by measuring weed height, or a com-bination of these.Methods of herbicide applicationSeveral different methods of herbicide applications wereused in the trials described herein: foliar, cut-surface,basal bark, stump bark, and soil applications; plus very-low-volume foliar and basal bark applications. See:Motooka, Philip, Lincoln Ching, and Guy Nagai. 2003.Herbicidal weed control methods for pastures and natu-ral areas of Hawaii. Univ. of Hawaii, College of Tropi-cal Agriculture and Human Resources, Weed Controlpublication WC-8. 35 pp. [Downloadable from theCTAHR Web site: www.ctahr.hawaii.edu/oc/freepubs/pdf/wc-8.pdf].WC-9 Herbicide Trial Summaries—2002 CTAHR — Feb. 20032Materials testedHerbicide Trade name and manufacturerClopyralid Transline (Dow Agrosciences)Dicamba,dimethylamine salt Banvel (BASF)Dicamba,diglycolamine salt Clarity (BASF)Vanquish (Syngenta)Glyphosate Rodeo (Monsanto).Roundup (Monsanto andseveral other manufacturers).Imazapyr Stalker (American Cyanamid)Imazapyc Plateau (American Cyanamid)MCPA MCP Amine (Clean Crop)Metsulfuron Escort (DuPont)Triclopyr Garlon 4 (Dow AgroSciences).Remedy (Dow AgroSciences)).Garlon 3A (Dow AgroSciences)Pathfinder II (Dow AgroSciences).Tebuthiuron Spike 20P (Dow AgroSciences)WeedsCoral berry (Rivina humilis L.)Clidemia, Koster’s curse (Clidemia hirta [L.] D. Don)Downy rosemyrtle (Rhodomyrtus tomentosa [Aiton]Hassk.)Fayatree (Myrica faya Aiton)Green kyllinga (Kyllinga brevifolia Rottb.)Guava (Psidium guajava L.)Ironwood, Australian pine (Casuarina equisetifolia L.)Karakanut (Corynocarpus laevigatus J.K. Forster & G.Forster)Largeleaf lantana (Lantana camara L.)Madagascar ragwort (fireweed) (Senecio madagascar-iensis Poiret)Olive (Olea europaeus L.)Senna pendula (Humb. & Bonpl. ex Willd.) H. Irwin &BarnebyShoebutton ardesia (Ardesia elliptica Thunb.)Sicklepod, habucha (Senna obtusifolia [L.] H. Irwin &Barneby)Strawberry guava (Psidium cattleianum Sabine)Thimbleberry (Rubus rosifolius Sm.)ObservationsIn a series of trials to evaluate very-low-volume verti-cal streak basal bark applications (which are useful wherenon-target plants are in close proximity) ironwood (Table2), karakanut (Table 3), and strawberry guava (Table 8)were sensitive to triclopyr as Pathfinder II. Olive how-ever, was not (data not presented). Imazapyr was inef-fective on karakanut (Table 3).Lantana and faya tree, both tolerant of triclopyr, weretreated with 0.5 lb/acre of clopyralid. No injury wasobserved at 3 MAT (data not shown). Clidemia was sen-sitive to triclopyr in foliar applications but not to dicambaor MCPA (Table 1). Green kyllinga populations werereduced by foliar applications of imazapyc (Table 4) butcentipedegrass was stunted by the high rate. Madagas-car ragwort control with MCPA at 1 lb/acre was enhancedby the adjuvant LI-700®, and with clopyralid with SilwetL-77® (Table 5). The herbicide rates used in this experi-ment were half the recommended rates in order to de-tect the effect of the adjuvants. Ragwort was more sen-sitive to the diglycolamine salt of dicamba than to theold dimethylamine salt (Table 6). Stawberry guava wastolerant to both types of dicamba and sensitive totriclopyr amine in foliar applications (Table 8). Sicklepodwas somewhat sensitive to dicamba and tolerant toMCPA and triclopyr in foliar applications. However thesicklepod stand was very dense so herbicide coveragewas not ideal. Efficacy would probably have been bet-ter if the herbicides were applied at younger stages ofsicklepod growth with a more open canopy. Downyrosemyrtle, tolerant to most brush killers, was sensitiveto dicamba at 2 lb/acre in conventional sprays but lessso with drizzle applications (Table 10).In long-term trials, guava was very sensitive to soil-applied tebuthiuron at 19 MAT (months after treatment)whereas strawberry guava response was inadequate at17 MAT (Table 10).3WC-9 Herbicide Trial Summaries—2002 CTAHR — Feb. 2003Table 3. Karakanut response to very- low volume verticalstreak applicaton of triclopyr and imazapyr in oil (G01-08).Date installed:09/25/01. Date rated: 09/09/02. Location: Kokee.Investigators:L. Ching, g. Nagai, G. Kawakami, C. Koga, S.Soto, P. Motooka. Notes: Fine straight stream application ofherbicides to opposite sides of the main stem from soil level towaist height.Treatment Defoliation Kill1(%) (%)Check 24 10Imazapyr 13 0Triclopyr 82 441Smaller diameter stems were killed.Table 4. Green Kyllinga control in turf with imazapyc (K02-06).Date installed: 06/10/02. Date rated: 07/29/02. Investigator: P.Motooka. Location: Kailua-Kona. Notes: Kyllinga brevifoliaRottb., Fimbristylis dichotoma (L.) Vahl,, Cyperus sp.Imazapyc rate Sedge inflorescence Turf height(lb/acre) (no./yd2) (inches)Check 28  4.80.2  7  3.90.4  7  2.8Table 6. Madagascar ragwort response to dicamba anddicamba DGA.Date installed: 06/25/02. Date rated: 08/13/02. Investi-gators: J. Powley, P. Motooka. Cooperators: Heleakala Ranch.Location: Kaluapulani.Herbicide Rate Control(lb/acre) (%)Check 0 34Dicamba 1 61Dicamba 2 83Dicamba DGA 1 86Dicamba DGA 2 86MCPA 2 83Table 5. Madagascar ragwort response to variousherbicides and surfactants (V02-1).Date installed: 06/25/02. Date rated: 08/13/02. Investiga-tors: J. Powley, P. Motooka. Cooperators: Haleakala Ranch.Location: Maui. Notes: Control based on weed cover reduction.Rate ControlHerbicide (lb/acre) Surfactant (%)Check 0 0MCPA 1 Spreader 90 (0.5%) 67MCPA 1 LI 700 (0.5%) 83MCPA 1 Silwet L-77 (0.25%) 72Clopyralid 0.25 Spreader 90 14Clopyralid 0.25 LI 700 26Clopyralid 0.25 Silwet L-77 62Metsulfuron 0.03 Spreader 90 33Metsulfuron 0.03 LI 700 54Metsulfuron 0.03 Silwet L-77 57Table 1. Clidemia response to foliar herbicides (K02-07).Date installed: 07/09/02. Date rated: 09/20/02. Location:Keaau. Investigators: K. Onuma, M. DuPonte, P.Motooka.Cooperator: Sam Taka. Notes: Four-nozzle boom, SS 8003,30 psi, spray-volume rate 34 gpa. All herbicides at 1 lb a.e./acre.Herbicide Adjuvant Defoliation (%)Check  81MCPA Silwet L-77‘, 0.25% 26Dicamba Silwet L-77‘ 0.25% 34Dicamba DGA Silwet L-77‘, 0.25% 30Triclopyr ester Silwet L-77‘, 0.25% 94Triclopyr ester Forest Crop Oil‘, 0.5% 98Triclopyr ester Liberate‘, 0.5% 891Drift injury.Table 2. Response of ironwood to vertical streakapplications of triclopyr (G02-07).Date installed: 06/04/02. Date rated: 09/09/02. Location:Kokee. Investigators: L. Ching, G. Nagai, A. Kiyono, G.Kawakami, C. Koga, S. Soto, P. Motooka. Notes: Pathfinder IIapplied in vertical streaks on opposite sides of the basal stems.Defoliation Kill1Herbicide (%) (%)Check 17 10Triclopyr 84 701Smaller diameter stems were killed.WC-9 Herbicide Trial Summaries—2002 CTAHR — Feb. 20034Table 7. Strawberry guava response to foliar herbicides.Date installed: 07/09/02. Date rated: 09/20/02. Investigators:K. Onuma, M. DuPonte, P. Motooka. Cooperator: Sam Taka.Location: Keaau. Notes: Four-nozzle boom, SS8003LPnozzles, 30 psi, spray-volume rate 34 gpa. Applied to regrowthup to 5 ft tall. All herbicides applied at 1 lb a.e./acre.Herbicide Defoliation(%)Check  0Dicamba 38Dicamba DGA 24Triclopyr amine 88Table 9. Response of sicklepod to herbicides (K02-10).Date installed: 08/15/02. Date rated: 09/17/02. Location:Kainaliu. Cooperator: Ed Nobriga. Notes: Herbicides appliedat 1 lb active/acre.Herbicide Surfactant Defoliation(%)Check 0MCPA 0.25% Silwet L-77 25Dicamba 0.25% Silwet L-77 75Dicamba DGA 0.25% Silwet L-77 70Tricopyr E 0.25% Silwet L-77 53Triclopyr E 0.5% Liberate 50Table 8. Strawberry guava control with very-low volumevertical streak applications of triclopyr/crop oil (G01-07).Date installed: 05/25/01. Date rated: 06/04/02. Location:Kokee. Investigators: L. Ching, G. Kawakami, P. Motooka.Notes: Fine straight stream application of Pathfinder II appliedon opposite sides of main stem from soil level to waist height.Average volume applied to tree, 9.4 ml, cost = $0.08.Treatment Defoliation Kill(%) (%)Check 0 0Pathfinder 100 100Table 10. Unreplicated or unrandomized demonstrations.Weed Herbicide Rate Method Injury Reps Duration Site(lb/acre) (%) (mo)Coral berry Triclopyr 1 Drizzle 65 2 large plots 3 S. KonaDowny rosemyrtle DicambaDGA 2 Spray 98 1 long plot 3 KauaiDowny rosemyrtle DicambaDGA 2 Drizzle 60 1 large plot 3 KauaiGuava Teb1 10 Soil 96 3 large plots 19 KauaiLantana Gly + LI 700 1 Drizzle 60 2 large plots 3 S. KonaLantana Gly + QS2 1 Drizzle 75 1 large plot 3 S. KonaLantana Gly + QS 2 Drizzle 75 1 large plot 3 S. KonaLantana Gly + LI 700 2 Drizzle 75 1 large plot 3 S. KonaS. pendula Triclopyr 1 Drizzle 85 2 large plots 3 S. KonaThimbleberry Triclopyr 1 Drizzle 95 4 large plots 3 KeaauWaiwi Teb 10 Soil 56 6 large plots 17 KauaiTeb = tebuthiuron, 2QS = Quiksorb‘, an experimental adjuvant supplied by Monsanto.

Summaries of Herbicide Trials for Pasture, Range, and Non-cropland Weed Control--2002

Cooperative Extension Service Weed ControlMarch 2001WC-6The tables herein summarize herbicide trials for the con-trol of pasture, range, and non-cropland weeds conductedby the College of Tropical Agriculture and Human Re-sources, University of Hawaii at Manoa; the HawaiiDepartment of Agriculture; the Division of Forestry andWildlife of the Hawaii Department of Land and NaturalResources; and other cooperators. These preliminary dataare published to assist applicators experimenting withherbicides for weed control. The herbicide applicator iscautioned to confirm that any herbicide use, rate, ormethod of application conforms to the product label.Rating weed response to herbicidesWeed response to treatment is evaluated by differentmethods. Plant injury may be scored on a 0–100 scalein which the score is a subjective evaluation of the se-verity of injury:0 No symptoms10–30 Insignificant to poor weed control; little or nodefoliation40–60 Inadequate weed control; moderately severesymptoms; less than 70% defoliated70 Adequate weed control; severe symptoms; allleaves chlorotic or more than 70% defoliated80 Good weed control; very severe symptoms; 80%defoliated90 Excellent weed control; very severe symptoms;90% defoliation100 Complete control; no sign of lifeSummaries of Herbicide Trials for Pasture, Range,and Non-Cropland Weed Control—2000Philip Motooka, Department of Natural Resources and Environmental ManagementIn addition to the scale described above, efficacy of treat-ments may be determined by estimation of defoliationor its opposite, remaining weed cover. The method useddepends on the growth habit of the weed. Response mayalso be measured by counting the number of survivingplants or stems, by measuring weed height, or a combi-nation of these.Methods of herbicide applicationFoliarSeveral methods of herbicide application were used inthe trials described here, including foliar, cut-surface,basal bark, stump bark, and soil applications (SeeCTAHR publication WC-4, 1999, Woody plant controlfor the home, pasture, and forest. Also, low-volume andvery low-volume variants of foliar application (drizzlemethod) and basal barak and stump bark treatments wereevaluated (see Motooka, P., G. Nagai, and L. Ching,1983, “The ‘magic wand’ method of herbicide applica-tion,” Proc. Ninth Asian Pacific Weed Sci Soc. Conf.,Suppl. Vol., p. 550–553; and Motooka, P., J. Powley, M.DuPonte, L. Ching, G. Nagai, and G. Kawakami, 1999,“Drizzle herbicide application for weed management inforests,” Proc. West. Soc. Weed Sci. 52:136–139).Mention of a trademark, company, or proprietary name does not constitute an endorsement, guarantee, or warranty by the Universityof Hawaii Cooperative Extension Service or its employees and does not imply recommendation to the exclusion of other suitableproducts or companies.Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June30, 1914, in cooperation with the U.S. Department of Agriculture. Andrew G. Hashimoto, Director/Dean, Cooperative Extension Service/CTAHR, Universityof Hawaii at Manoa, Honolulu, Hawaii 96822. An Equal Opportunity / Affirmative Action Institution providing programs and services to the people of Hawaii withoutregard to race, sex, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or veteran status.CTAHR publications can be found on the Web site <http://www2.ctahr.hawaii.edu> or ordered by calling 808-956-7046 or sending e-mail to ctahrpub@hawaii.edu.WC-6 Herbicide Trial Summaries—2000 CTAHR — Mar. 20012Materials testedHerbicides Trade name and manufacturer2,4-D Amine salt formulation, various brandsEster formulation, various brandsGlyphosate Rodeo (Monsanto)Roundup (Monsanto)Hexazinone Pronone Power Pellets (DuPont)Velpar L (DuPont)MCPA MCP Amine (Clean Crop)Triclopyr Garlon 4 (Dow AgroSciences)Remedy (Dow AgroSciences))Redeem (Dow AgroSciences)Pathfinder II (Dow AgroSciences)Tebuthiuron Spike 20P (Dow AgroSciences)Adjuvants ManufacturerActivator 90 Loveland IndustriesExcell 90 NF Brewer Environmental IndustriesQuicksorb MonsantoForestry Crop Oil    Platte ChemicalWeedsBushy beardgrass Schizachyrium condensatus (Kunth)NeesChristmas berry Schinus terebinthifolius RaddiFayatree Myrica faya AitonKahili ginger Hedychium gardnerianum Ker-GawlGuava Psidium guajava L.Hau Hibiscus tiliaceus L.Hiptage Hiptage benghalensis (L.) KurzKarakanut Corynocarpus laevigatus J.R. Forster & G.ForsterKiawe Prosopis pallida (Humb-Bonpl. ex Willd.) KunthKikuyugrass Pennisetum clandestinum Chiov.Lantana Lantana camara L.Madagascar fireweed Senecio madagascariensis PoiretMangrove Rhizophora mangle L.Mauritius hemp Furcraea foetida (L.) Haw.Shoebutton ardesia Ardesia elliptica ThunbShrimp plant Justicia betonica L.Strawberry guava Psidium cattleianum SabineThimbleberry Rubus rosaefolius Sm.Yellow Himalayan raspberry Rubus ellipticus Sm.Wild olive Olea europaeus L.ObservationsA number of species were treated with soil applicationsof hexazinone granules and tebuthiuron pellets at 1, 2,and 4 kg/ha (1kg/ha = 0.9 lb/A) in 5 m diameter circularplots. Efficacy was poor on bushy beardgrass (Table 1),kahili ginger (Table 6), karakanut (Table 7), kikuyugrass(Table 9), wild olive (Table 17) and strawberry guava(Table 19). Tebuthiuron was evaluated for selectively innative koa (Acacia koa A. Gray) and koa displayed verylittle injury (Table 10). Further tests are warranted indifferent ecozones. Christmas berry was very susceptibleto soil applications of hexazinone pellets in grid or “hotspot” applications (Table 2). Fayatree was somewhat tol-erant of triclopyr applied with water in drizzle applica-tions although an oil carrier increased efficacy somewhat(Table 3). Fayatree has a dense canopy which makes goodcoverage difficult with low-volume methods. It is ex-pected that repeat applications will gradually strip upperlayers of the canopy, reduce biomass, and eventually al-low good coverage and control. A third application wasmade late in year and has yet to be evaluated.Guava and shoebutton ardesia were susceptible tovery-low volume basal bark applications of triclopyr butthe much larger hau stems, still connected to the motherplant, were somewhat tolerant (Table 4). Hiptage wassomewhat susceptible to very-low volume basal barkapplications of triclopyr and efficacy would probablybe increased with coverage completely around the basalstems (Table 5). Young kiawe plants were very suscep-tible to very-low volume basal bark treatments withtriclopyr, and even larger trees were severely damaged,suggesting that higher doses may successfully controlthe larger trees (Table 8).Basal bark applications of glyphosate in high con-centrations with 10% of surfactants proved very effec-tive on lantana that had coppiced (Table 11) but erraticon lantana with intact stems (Table 12). The latter trialwas also in a higher rainfall area which may have influ-enced response.Rank Madagascar fireweed was tolerant of 0.5 and1.0 kg/ha of MCPA and to 0.5 kg/ha of triclopyr amine.MCPA at 2 kg/ha was effective (Table 13). An earliertrial had established that succulent Madagascar fireweedwas susceptible to 1 kg/ha of 2,4-D and triclopyr.3WC-6 Herbicide Trial Summaries—2000 CTAHR — Mar. 2001Basal bark application with glyphosate was ineffec-tive on mangrove but triclopyr in oil was very effective(Tables 14, 15).Response of Mauritius hemp, susceptible to triclopyrin oil in foliar treatments in other trials, was confoundedby flowering and senescence and by lost tags in densevegetation (Table 16).Shoebutton ardesia was moderately susceptible todrizzle foliar applications of 2,4-D and triclopyr in wa-ter and oil carriers (Table 18). Repeat applications areexpected to increase efficacy since the plants were tootall initially for good coverage. Strawberry guava wasalso moderately susceptible to drizzle foliar applicationsof triclopyr in water and somewhat more susceptible toapplication with the oil carrier (Table 20). YellowHimalaylan raspberry was susceptible to triclopyr in twodrizzle applications 6 months apart. The oil carrier in-creased efficacy (Table 21).Table 1. Efficacy of soil applied hexazinone andtebuthiuron on bushy beardgrass (G99-15).Date installed: 08/16/99. Date rated: 05/03/00. Location:Kokee, Kauai. Investigators: A. Kiyono, G. Nagai, L. Ching, P.Motooka. Notes: Herbicides applied to 5-m diameter circularplots. High defoliation result of drought.Herbicide Rate Defoliation(kg/ha) (%)Check 0 48Tebuthiuron 1 382 424 43Hexazinone 1 272 554 8Table 2. Control of christmasberry trees by hotspotapplication of hexazinone pellets to the soil. (V99-6).Date installed: 10/14/99. Date rated: 08/30/00. Location: KaupoRanch. Investigators: J. Powley, A. Franco, P. Motooka. Notes:Large pellets applied in 3-ft intervals along four transectsaround the base of each tree, 12 pellets per tree. There were13 trees, 4–14 inches in basal diameter.Treatment Defoliation (%)Check  0Hexazinone 96Table 4. Response of guava, hau and shoebutton ardesiato very-low volume basal bark applications of triclopyr (G00- 7, 9, 10).Date installed: 03/09/00. Date rated: 07/18/00. Location:Princeville Ranch. Investigators: L. Ching, G. Nagai, P.Motooka. Notes: Pathfinder II‘ applied with drizzle unit.Species Defoliation Number of plants(%)Guava 99 21Hau 52 22Shoebutton ardesia 89 52Table 3. Response of fayatree to triclopyr applied by thedrizzle method with water or with oil (K99-9).Date installed: 05/28/99. Location: Keauhou Ranch, Volcano.Investigators: M. du Ponte, P. Motooka. Notes: Retreated 11/09/99, 08/02/00.Triclopyr Carrier Defoliation (%)rate(kg/ha) 09/08/99 11/09/99 08/02/000.5 Water 38 38 320.5 Oil 48 53 421.0 Water 55 42 481.0 Oil 54 59 60Table 5. Hiptage response to very-low volume basal barkapplications of triclopyr (G99-8).Date installed: 05/19/99. Date rated: 05/03/00. Location: HuleiaNational Wildlife Reserve, Kauai. Investigators: L. Ching, G.Nagai, P. Motooka. Notes: Pathfinder II applied in four streakson one or both sides of basal stem.Treatment Killed plants(%)Check 02-sided treatment 40 (another 40% had cracked bark)1-side treatment 46 (another 11 % with cracked bark)WC-6 Herbicide Trial Summaries—2000 CTAHR — Mar. 20014Table 9. Efficacy of soil applied hexazinone andtebuthiuron on kikuyugrass (G99-20).Date installed: 09/14/99. Date rated: 05/02/00. Location:Kokee, Kauai. Investigators: A. Kiyono, L. Ching, G. Nagai, P.Motooka. Notes: Herbicides applied to 5-m diameter circularplots.Herbicide Rate Defoliation(kg/ha) (%)Check 0 3Hexazinone 1 82 274 40Tebuthiuron 1 172 74 18Table 6. Efficacy of soil applied hexazinone andtebuthiuron on kahili ginger (G99-18).Date installed: 08/18/99. Date rated: 05/02/00. Location:Kokee, Kauai. Investigators: C. Koga, L. Ching, G. Nagai, P.Motooka. Notes: Herbicide applied to 5-m diameter circularplots.Herbicide Rate Defoliation(kg/ha) (%)Check 0 10Hexazinone 1 32 84 30Tebuthiuron 1 172 424 10Table 7. Efficacy of hexazinone and tebuthiuron onkarakanut trees (G99-21).Date installed: 09/14/99. Date rated: 05/02/00. Location:Kokee, Kauai. Investigators: G. Kawakami, G. Nagai, L. Ching,P. Motooka. Notes: Herbicide applied to 5-m circle around baseof tree. Basal diameter of trees 5–10 inches.Herbicide Rate Defoliation(kg/ha) (%)Check 0 0Hexazinone 1 02 284 0Tebuthiruon 1 02 34 8Table 8. Kiawe tree control with very-low volume basalbark application of triclopyr (K99-23).Date installed: 11/05/99. Date rated: 01/21/00. Location:Kohanaiki, Kona. Investigators: G. Fukumoto, P. Motooka.Notes: Pathfinder II‘ applied.Basal diameter Defoliation(inches) (%)≤2 1002 ≤ 4 994.1 ≤ 6 94> 6 93Table 10. Tolerance of koa trees to soil applied tebuthiuron(G99-16).Date installed: 08/16/99. Date rated: 05/02/00. Location:Kokee, Kauai. Investigators: A. Kiyono, G. Kawakami, G.Nagai, L. Ching, P. Motooka. Notes: Tebuthiuron pellets appliedin 5-m circle around base of tree.Herbicide rate Defoliation(kg/ha) (%)Check 131 222 104 17Table 12. Response of lantana to basal bark applicationof glyphosate (K00-2).Date installed: 06/02/00. Date rated: 09/06/00. Location:Keaukaha, Hawaii. Investigators: M. DuPonte, P. Motooka.Notes: High-rainfall area.Treatment Defoliation (%)Check 0Spray, 50% glyphosate/10% Excell 90 50Spray, 50% glyphosate/10% Quiksorb 69VLV, 50% glyphosate/10 Quiksorb 57Spray, Triclopyr (Pathfinder II) 245WC-6 Herbicide Trial Summaries—2000 CTAHR — Mar. 2001Table 11. Lantana control by basal bark applications of glyphosate (G00-10).Dated installed: 06/10/00. Date rated: 0718/00. Location: Kapaa. Investigators: L. Ching, P. Motooka. Notes: Lantana plants weremowed and had coppiced.Treatment Method of application Volume/plant Defoliation(ml) (%)Check 0 0Glyphosate 50% + 10% Activator 90 Conventional spray 124 96Glyphosate 25% + 10% Quiksorb Conventional spray 125 100Glyphosate 50% + 10% Quiksorb Conventional spray 148 100Glyphosate 50% + 10% Quiksorb Very low volume 9 97Triclopyr ester 20% with crop oil Low volume spray 74 76Table 13. Madagascar fireweed control with MCPA foliarsprays (V00-1).Date Installed: 08/29/00. Date rated: 12/04/00. Location:Makawao, Maui. Investigators: J. Powley, P. MotookaHerbicide Rate Fireweed cover Control(kg/ha) (%) (%)0 0 84 0MCPA 0.5 83 2MCPA 1.0 57 32MCPA 2.0 10 88Triclopyr amine 0.5 84 11Table 14. Mangove response to very-low volume basal barkapplications of triclopyr or glyphosate (K00-1a)Date installed: 01/21/00. Date rated: 02/28/00. Location:Kohanaiki, Kona. Investigators: G. Fukumoto, P. Motooka.Treatment Defoliation(%)Check 10Glyphosate 50% / Quicksorb 10% 28Triclopyr 20% / Oil 95Table 15. Very-low volume basal bark application ofglyphosate or triclopyr to control mangrove (G00-3).Date installed: 01/25/00. Date rated: 03/09/00. Location:Nawiliwili. Investigators: L. Ching, G. Nagai, P. MotookaTreatment Defoliation (%)Check 050% Glyphosate + 10% Quiksorb 20Triclopyr (Pathfinder II) 100Table 17. Efficacy of soil applied hexazinone and tebu-thiuron on wild olive (G99-17).Date installed: 08/16/99. Date rated: 05/02/00. Location:Kokee, Kauai. Investigators: A. Kiyono, G. Nagai, L. Ching, P.Motooka. Notes: Herbicide applied to 5-m diameter circle atbase of trees.Herbicide Rate Defoliation(kg/ha) (%)Check 0 20Hexazinone 1 132 134 20Tebuthiuron 1 32 134 13Table 16. Response of flowering and non-floweringMauritius hemp to drizzle applications of triclopyr esterin oil (K00-1).Date installed: 02/10/00. Date rated: 08/10/00. Location:Kaupulehu, Kona. Investigators: L. Hadway, P. Motooka. Notes:Plants treated with triclopyr ester, 15% in crop oil. There were10 replicates but many plants collapsed and tags could not befound.Plant growth stage Defoliation No. plants  / treatment (%)Nonflowering/ check 17 6Nonflowering/ triclopyr 74 8Flowering/check 100 2Flowering/triclopyr 93 6WC-6 Herbicide Trial Summaries—2000 CTAHR — Mar. 20016Table 19. Efficacy of soil applications of hexazinone andtebuthiuron on strawberry guava.Date installed: 09/13/99. Date rated: 05/03/00. Location:Wailua, Kauai. Investigators: L. Ching, G. Nagai, P. Motooka.Notes: Granular hexazinone and pelleted tebuthiuron wereapplied in a 5-m circle around the base of the target tree.Herbicide Rate Defoliation(kg/ha) (%)Check 0 0Hexazinone 1 282 174 43Tebuthiuron 1 232 534 27Table 20. Response of strawberry guava to drizzleapplications of triclopyr in water and in oil (K99-8).Date installed: 05/14/99. Location: Kurtistown. Investigators:M. DuPonte, P. Motooka. Notes: Triclopyr applied at 1 kg/ha,retreated 11/18/00.Carrier Defoliation (%)11/18/99 06/02/00Water 40 46Oil 61 62Table 18. Response of shoebutton ardesia to drizzleapplications of herbicides (G00-8)Date installed: 03/09/00. Date Rated: 07/18/00. Location:Princeville Ranch. Investigators: L. Ching, G. Nagai, P. Motooka.Treatment Defoliation (%)Check 02,4-D ester 65Triclopyr ester/water 72Triclopyr ester/oil 60Table 21. Response of yellow Himalayan raspberry todrizzle applications of triclopyr in water and in oil (K99-10).Date installed: 05/28/99. Location: Volcano. Iinvestigators: M.DuPonte, A. Kawabata, P. Motooka. Notes: Reapplication on11/09/99, 08/02/00.Triclopyr Carrier Defoliation (%)rate(kg/ha) 09/08/99 11/09/99 06/01/000.5 Water 70 48 740.5 Oil 73 70 871.0 Water 78 63 781.0 Oil 99 88 94Table 22. Results of demonstration trials.Weed Herbicide Rate/ Conc. Method Control (%) Reps  Duration(mo) SiteFayatree4 inch basal diameter Glyphosate 50%/10% Quiksorb VLV basal bark 49 12 7 KeauhouRanchFayatree7 inch basal diameter Glyphosate 50%/10% Quiksorb VLV Basal bark 31 7 7 KeauhouRanchKiawe Glyphosate 1 lb/A Drizzle 72 8 2.5 KohanaikiKiawe Glyphosate Conc. Notch 88 4 2.5 KohanaikiKiawe Triclopyr 0.5 lb/A Drizzle 58 5 2.5 KohanaikiMadagascar fireweed Tebuthiuron 2 kg active/ha Soil 95 1 large plot 3 MakawaoMadagascar fireweed Triclopyr amine 1 kg active/ha Drizzle 0 1 large plot 3 MakawaoShrimp plant MCPA 1 kg active/ha Foliar 90 1 small plot 3 MakawaoThimbleberry Triclopyr   ester/water 1 lb/A Drizzle 80 1 7 KurtistownThimbleberry Triclopyr   ester/oil 1 lb/A Drizzle 95 1 7 Kurtistown

Summaries of Herbicide Trials for Pasture, Range, and Non-Cropland Weed Control--2000

Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June30, 1914, in cooperation with the U.S. Department of Agriculture. Charles W. Laughlin, Director and Dean, Cooperative Extension Service, CTAHR, Universityof Hawaii at Manoa, Honolulu, Hawaii 96822. An Equal Opportunity / Affirmative Action Institution providing programs and services to the people of Hawaii withoutregard to race, sex, age, religion, color, national origin, ancestry, disability, marital status, arrest and court record, sexual orientation, or veteran status.Cooperative Extension Service Weed ControlMay 1999WC-1The tables herein summarize herbicide trials for the con-trol of pasture, range, and non-cropland weeds conductedby the College of Tropical Agriculture and Human Re-sources, University of Hawaii at Manoa; the HawaiiDepartment of Agriculture; the Division of Forestry andWildlife of the Hawaii Department of Land and NaturalResources; and other cooperators. These preliminary dataare published to assist applicators experimenting withherbicides for weed control. The herbicide applicator iscautioned to confirm that any herbicide use, rate, ormethod of application conforms to the product label.Rating weed response to herbicidesWeed response to treatment is evaluated by differentmethods. Plant injury may be scored on a 0–100 scalein which the score is a subjective evaluation of the se-verity of injury:0 No symptoms10–30 Insignificant to poor weed control; little or nodefoliation40–60 Inadequate weed control; moderately severesymptoms; less than 70% defoliated70 Adequate weed control; severe symptoms; allleaves chlorotic or more than 70% defoliated80 Good weed control; very severe symptoms; 80%defoliated90 Excellent weed control; very severe symptoms;90% defoliation100 Complete control; no sign of lifeIn addition to the scale described above, efficacy of treat-ments may be determined by estimation of defoliationor its opposite, remaining weed cover. The method usedSummaries of Herbicide Trials for Pasture, Range,and Non-Cropland Weed Control—1998Philip Motooka, Extension Specialist in Weed Sciencedepends on the growth habit of the weed. Response mayalso be measured by counting the number of survivingplants or stems, by measuring weed height, or a combi-nation of these.Methods of herbicide applicationFoliarSee: Motooka, Philip, Guy Nagai, and Lincoln Ching.1982. Weed and brush control in pastures and ranges ofHawaii: I. Foliar application of herbicides. HITAHRBrief 16. CTAHR. 6 p.Basal bark and basal stumpSee: Motooka, Philip, Guy Nagai, and Lincoln Ching.1982. Weed and brush control in pastures and ranges ofHawaii: II. Basal bark method of herbicide application.HITAHR Brief 17. CTAHR. 3 p.Cut-surfaceSee: Motooka, Philip, Guy Nagai, and Lincoln Ching.1982. Weed and brush control in pastures and ranges ofHawaii: III. The notching method of herbicide applica-tion. HITAHR Brief 18. CTAHR. 4 p.Soil applicationSee: Motooka, Philip, Guy Nagai, and Lincoln Ching.1982. Weed and brush control in pastures and ranges ofHawaii: IV. Soil application of herbicides. HITAHRBrief 19. CTAHR. 3 p.Drizzle applicationSee: Motooka, P., G. Nagai, and L. Ching. 1983. The“magic wand” method of herbicide application. Proc.Ninth Asian Pacific Weed Sci Soc. Conf. Suppl. Vol. p.550–553.Mention of a trademark, company, or proprietary name does not constitute an endorsement, guarantee, or warranty by the Universityof Hawaii Cooperative Extension Service or its employees and does not imply recommendation to the exclusion of other suitableproducts or companies.WC-1 Herbicide Trial Summaries—1998 CTAHR — May 19992Herbicides testedChemical Trade name and manufacturer2,4-D Amine salt formulation, various brandsEster formulation, various brandsDicamba Banvel (Sandoz)Glyphosate Rodeo (Monsanto)Roundup (Monsanto)Imazapyc Plateau (American Cyanamid)Metsulfuron Escort (DuPont)Triclopyr Garlon 4 (DowElanco)Remedy (DowElanco)Redeem (DowElanco)Pathfinder II (Dow Elanco)WeedsAlbizia Albizia lebbeck (L.) Benth.Bahiagrass Paspalum notatum FluggeBermudagrass,   manienie Cynadon dactylon L.Catsclaw Caesalpinia decapetala (Roth)   AlstonDowny rosemyrtle Rhodomyrtus tomentosa   (Aiton) Hassk.Gorse Ulex europaeus L.Ivy gourd Coccinea grandis (L.) VoigtJobs tears Coix lachryma-jobi L.Kahili ginger Hedychium gardnerianum   Ker-Gawl.Lantana Lantana camara L.Madagascar fireweed Senecio madagascariensis Poir.Melastoma Melastoma candidum D. Don.Pangolagrass Digitaria pentzii Stent   (Syn. D. decumbens).Paragrass,   californiagrass Brachiaria mutica (Forssk.)   Stapf.Strawberry guava Psidium cattleianum SabineSmutgrass Sporobolus indicus (L.) R. Br.Uluhe, Dicranopteris linearis   false staghorn fern   (Burm.) Underw.Water hyacinth Eichhornia crassipes (Mart.)  SolmsWild olive Olea europaea L.ObservationsSeveral trials in 1998 involved the very-low-volume(VLV) drizzle application method developed by ShigeoUyeda of Kauai. Because the method employs very lowvolumes (1.5 gal/A), it is very labor-efficient (1998, Proc.West. Soc. Seed Sci., p. 124–127). In foliar applicationswith water as the carrier, triclopyr at 0.25 to 2 lb/A waseffective on catsclaw (Tables 2, 3). Although there waseventual resprouting, that appeared to be because of ashadow effect, as most of the resprouting was on theside of the plant opposite the direction of application.Thus a repeat application or split applications from op-posite directions would probably provide almost com-plete control of catsclaw at relatively low rates of appli-cation. Glyphosate was effective on lantana (Table 10).Where plants are tolerant of herbicides in water carrier,non-phytotoxic crop oil may increase efficacy by pro-moting uptake of oil-soluble herbicides. Gorse, tolerantof triclopyr in water, was susceptible to triclopyr in cropoil (Table 7). Triclopyr in crop oil was also effective asa VLV basal bark application on albizia and strawberryguava (Table 1, 16). Melastoma and Formosan koa weresomewhat tolerant of VLV basal bark applications (Table1, 5) but may be susceptible to applications from oppo-site sides of the plants and repeat applications, as wasdowny rosemyrtle (Table 4).In conventional herbicide applications, crop oil waseffective as an adjuvant in the control of gorse (Table6). A new herbicide, imazapyc, was evaluated for selec-tively controlling bunch grasses in non-crop situations.Imazapyc severely injured guineagrass (Table 8). Thesymptoms included chlorosis, necrosis, and stunting.Imazapyc was less effective on guineagrass in a road-side environment (Table 9), but that area suffered adrought after application. Imazapyc suppressed smut-grass without injury to bahiagrass, but pangolagrass waseliminated from all treated plots (Table 15). The rapidlyspreading Madagascar fireweed was not as susceptibleto 2,4-D and triclopyr as in previous trials, but the fire-weed in this trial was very rank (Table 12). Wild olivesaplings were susceptible to conventional basal barkapplications of triclopyr but less so to 2,4-D (Table 13).Large olive trees were sensitive to notching applicationsof triclopyr, glyphosate, and 2,4-D but somewhat lesssusceptible to dicamba (Table 14).In a non-herbicide study, the viability of ivy gourdseed (Table 10) remained high when stored under dry3WC-1 Herbicide Trial Summaries—1998 CTAHR — May 1999conditions at ambient temperatures or refrigerated forone year but demonstrated no dormancy in soil exposedto the weather. This suggests that ivy gourd can be eradi-cated from small areas with a diligent control program.Table 1. Response of albizia, melastoma, and straw-berry guava to very-low-volume basal bark applica-tions of triclopyr (G97-1-3).Date installed: 04/10/97; Date rated: various; Location:Wailua, Kauai; Investigators: G. Kawakami, G. Nagai,L. Ching, P. Motooka; Notes: Ready-to-use PathfinderII (DowElanco) used.Species Defoliation (%) on date:04/10 01/28Albizia1 84 79Melastoma2 43 63Strawberry guava3 88 931Very susceptible; trees 8 inches dbh survived but wereseverely injured; smaller plants killed; six replicates.2Sprouted multiple roots at nodes; four replicates.3Ten replicates.Table 2. Catsclaw response to drizzle application oftriclopyr ester in a crop oil carrier (K98-2).Date installed: 06/09/98; Date evaluated: various; Lo-cation: Captain Cook; Cooperator: Kealakekua Devel-opment Corp.; Investigator: P. Motooka; Notes: Sprayvolume rate (SVR) 1.5 gal/A, 1 lb a.e./A triclopyr.Defoliation (%) on date:Adjuvant 07/10 09/16 12/14No treatment check  0  0 0Bivert (4%) 96 76 35Silwet L-77, 0.25% 95 81 56Forest Crop Oil (10%) 98 97 75Forest Crop Oil (50%) 97 93 68Forest Crop Oil (100) 96 84 60Table 3. Catsclaw response to drizzle applications oflow rates of triclopyr (98-8).Date installed: 10/06/98 Date rated: 12/14/98; Location:Kealakekua; Investigator: P. Motooka; Cooperator:Kealakekua Development Corp.; Notes: Branches on leeside of the application were less injured.Rate (kg/ha) Defoliation (%) on 12/14Check 00.25 660.5 622 94Table 4. Clearing downy rosemyrtle on trails by very-low-volume basal bark applications of triclopyr (G97-27).Date installed: 10/30/97; Location: Wailua, Kauai; In-vestigators: G. Kawakami, L. Ching, G. Nagai, P.Motooka; Notes: 20% triclopyr ester in crop oil. Reap-plied 05/21/98. Two-pass treatment applied from oppo-site directions.Treatment Defoliation (%) on date:1/28/98 04/27 08/12Check 11 22  5One pass 35 18 40Two passes 54 25 84Table 5. Control of Formosan koa by very-low-volume basal bark applications of triclopyr (G97-23).Date installed: 10/30/97; Date rated: 04/27/98; Loca-tion: Wailua; Investigators: L. Ching, G. Nagai, G.Kawakami, P. Motooka; Cooperator: J. Sanchez; Notes:Check = no treatment, Conv = Conventional applica-tion of 4% triclopyr product in diesel, Die = very-lowvolume basal bark application of 20% triclopyr productin diesel, Hbi = 20% triclopyr product in Herbimax, Path= Pathfinder II.Treatment Defoliation (%)Check  11Die  15Hbi  18Path  58Conv 100WC-1 Herbicide Trial Summaries—1998 CTAHR — May 19994Table 6. Gorse response to triclopyr ester with cropoil adjuvant (K98-4).Date installed: 06/30/98;  Date rated: varies; Location:Humuula; Investigators: A. Kawabata, M. DuPonte, P.Motooka; Cooperator: Parker Ranch; Notes: Triclopyrapplied at 1 lb a.e./A, SVR 34 gpa. L-77  =  Silwet L-77,FCO  =  Forest Crop Oil.Defoliation (%) on date:Adjuvant 08/04 09/30Check 0 0L-77 0.25% 76 86FCO 1.5% 83 91FCO 3% 82 91FCO 6% 84 89Table 7. Gorse response to drizzle applications oftriclopyr ester with crop oil (K98-4).Date installed: 06/30/98; Date rated: various; Location:Humuula; Investigators: M. DuPonte, A. Kawabata, P.Motooka; Cooperator: Parker Ranch.Triclopyr rate Crop oil Defoliation (%) on date:(lb a.e./A) conc. (%) 08/04 09/300 0 0 01 50 41 801 100 45 802 50 58 912 100 66 90Table 8. Guineagrass response to imazapyc (G98-10).Date installed: 08/24/98; Location: Lawai; Investigators:G. Nagai, L. Ching, P. Motooka; Cooperators: G.Uyenten; Notes: Guineagrass mowed, treated when re-growth at knee high. Same treatments reapplied to re-spective plots on 11/23/98.Rate Injury rating Height (inches)(kg/ha) 09/22* 10/20** on 11/18***0 0 0 600.28 49 66 260.56 69 79 200.84 72 81 26*Stunting, chlorosis. ** Stunting, chlorosis, necrosis.*** No visible symptoms except height.Table 9. Control of guineagrass on roadsides withimazapyc (G98-8).Date installed: 08/24/98; Date rated: 12/08/98; Loca-tion: Hanamaulu; Investigators: L. Ching, G. Nagai, P.Motooka; Cooperators: Hawaii DOT; Notes: Grass keptmowed throughout trial. Drought after application untilshortly before evaluation. Burmudagrass survived treat-ment.Rate (kg/ha) Guineagrass cover (%)0 890.28 790.56 650.84 41Table 10. Viability of ivy gourd seed. (K97-3)Date installed: 08/01/97; Date rated: 08/10/98; Investi-gator: P.Motooka; Notes: Coccinea grandis fruit col-lected in Kona, seed extracted, washed and dried. Bur-ied seed placed in nylon bag and buried in pots under 10cm of soil and pots placed on open bench in Kailua-Kona.Germination (%) atIncubation period (mo)Treatment 0 3 6 12Room temperature 94 88 67 85Refrigerated (15°C) 91 93 90Buried 10  2  2Table 11. Lantana response to drizzle application ofglyphosate (G97-13).Date installed: 05/29/97; Date rated: various; Location:Kokee; Investigators: G. Kawakami, G. Nagai, L. Ching,P. Motooka; Notes: Drizzle application at 1.5 gal/A SVR.Rate Defoliation (%) on date:(lb/A) 10/28 01/27/98 04/29 10/200 0 10 4 00.5 88 95 72 701.0 98 98 97 905WC-1 Herbicide Trial Summaries—1998 CTAHR — May 1999Table 12. Madagascar fireweed response to 2,4-D andtriclopyr (K98-1).Date installed: 04/30/98; Date rated: various;  Location:Kamuela; Investigators: A. Kawabata, P. Motooka; Co-operator: A. Lindsey.Herbicide Rate Fireweed cover /mo (%)(lb/A)  1  4Check 0 55 382,4-D amine 0.25 12 185.5 17 371.0  8 252,4-D ester 0.25 13 20Triclopyr amine 0.25 16 35Table 13. Control of large olive trees by notching (G-97-21).Date installed: 10/28/97; Date rated: 10/21/ 98; Loca-tion: Kokee; Investigators: G. Kawakami, G. Nagai, L.Ching, P. Motooka; Notes: Notches at base of trunksmade with a machete every 4 inches around circumfer-ence. 1 ml of herbicide applied to each wound.Herbicide Defoliation (%) Kill (%)Check 4 02,4-D 74 0Dicamba 56 0Glyphosate 80 20Triclopyr 92 30Table 14. Contol of olive saplings by basal bark ap-plications of 2,4-D and triclopyr (G-97-22).Date installed: 10/28/97;  Date rated: 04/29/98; Loca-tion: Kokee; Investigators: G. Kawakami, G. Nagai, L.Ching, P. Motooka; Notes: Application of 4% ofcommericial product in diesel oil.Herbicide Defoliaton (%)Check  82,4-D 49Triclopyr 90Table 15. Smutgrass response to imazapyc (G98-6).Date installed: 08/23/98; Date rated: 11/23/98; Loca-tion: Wailua, Kauai; Investigators: L. Ching, G. Nagai,P. Motooka; Notes: Pangolagrass, initially present in allplots, eliminated by imazapyc. Bahiagrass, present in afew plots, was tolerant.Rate (lb/A) Injury rating0 40.56 550.84 68Table 16. Response of strawberry guava to very-lowvolume basal bark applications of triclopyr (G97-15).Date installed: 05/29/97; Date rated: 05/19/98; Loca-tion: Kokee; Investigators: G. Kawakami, L. Ching, G.Nagai, P. Motooka; Notes: Streaks  =  number of streaksmade across stems. Triclopyr ester diluted to 20% ofproduct in Herbimax oil adjuvant.Streaks Volume/stem (ml) Defoliation (%)0 0  84 2.7 696 4.0 918 5.4 87Continued, overWC-1 Herbicide Trial Summaries—1998 CTAHR — May 19996Table 17. Unreplicated or unrandomized demonstrations.Weed Herbicide* Rate*/Conc. Method Injury Reps Duration (mo) SiteJobs tears Glyphosate 2 lb /A drizzle 100% 1 1 KauaiKahili ginger Metsulfuron 0.4 oz/A foliar spray 90% 1 3 KonaKahili ginger Triclopyr 1 lb /A drizzle 40% 1 3 KonaKahili ginger Triclopyr 2 lb/A drizzle 65% 1 3 KonaParagrass Glyphosate 0.5 lb/A drizzle 100% 1 1 KauaiUluhe Triclopyr 2 lb/A drizzle 75% 1 3 WailuaUluhe Glyphosate 0.5 lb/A drizzle 70% 1 3 WailuaWater hyacin Glyphosate 0.5 lb/A drizzle 100% 1 1 Kauai* Active.Mention of a trademark, company, or proprietary name does not constitute an endorsement, guarantee, or warranty by the Universityof Hawaii Cooperative Extension Service or its employees and does not imply recommendation to the exclusion of other suitableproducts or companies.