Trials were conducted at a commercial cut-chrysanthemum nursery in Mountain View, Hawaii to evaluate biological control of chrysanthemum insect pests. No chemical pesticides were applied throughout the growing season. Numerous parasitoids and predators of the agromyzid leafminer, Liriomyza trifolii (Burgess), the green peach aphid (GPA), Myzus persicae (Sulzer), and the variegated cutworm (VC), Peridroma saucia (Hubner), were recovered. The two dominant parasitoid species of L. trifolii, Diglyphus intermedius (Girault), and Ganaspidium utilis Beardsley, provided biological control during the first 7 to 9 weeks after planting when the unmarketed portion of the chrysanthemum foliage was growing. Additional biorational or chemical control methods are necessary for GPA. VC, and L. trifolii when their damage affects the marketable portion of the crop

Hara, Arnold H.

Matayoshi, Shinsuke

Proceedings of the Hawaiian Entomological Society

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Vol. 30, December 31,1990 53Parasitoids and Predators of Insect Pestson Chrysanthemums in HawaiiARNOLD H. HARA1 and SHINSUKE MATAYOSHI2ABSTRACTTrials were conducted at a commercial cut-chrysanthemum nursery in Mountain View,Hawaii to evaluate biological control of chrysanthemum insect pests. No chemical pesticideswere applied throughout the growing season. Numerous parasitoids and predators of theagromyzid leafminer, IMompa tri/alii (Burgess), the green peach aphid (GPA), Myius prrriaie(Suker), and die variegated cutworm (VC), Peridmma saucia (Hubner), were recovered. Thetwo dominant parasitoid species of/., trifolii, Dtglyphus intemedius (Girault), and Ganaspidiumutilis Beardsley, provided biological control during the first 7 to 9 weeks after planting whenthe unmarketed portion of the chrysanthemum foliage was growing. Additional biorationalor chemical control methods are necessary for GPA. VC, and L. trifolii when their damage affects the marketable portion of the crop.Major insect pests of chrysanthemums on the Island of Hawaii includethe agromyzid leafminer, Liriomyza trifolii (Burgess), the green peach aphid(GPA), Myzuspersicae (Sulzer), and the variegated cutworm (VC), Peridmmasaucia (Hubner). Numerous parasitoids and/or predators have been purposely introduced into Hawaii since 1890 to bring these insect pests underbiological control (Funasaki et al. 1988). Other natural enemies of thesepests have also inadvertently become established in Hawaii.In Hawaii, most commercial chrysanthemums are grown in open-sidedgreenhouses. As a result, there is unrestricted movement of insects, suchas parasitoids and predators, into and out of the greenhouse. However,growers frequently rely on chemical insecticides for complete insect control to maintain zero aesthetic injury on the chrysanthemum crop. ParrellaandJones (1987) found that the first 5 weeks ofcut-chrysanthemum growthwere never marketed. Therefore, aesthetic injury to these unmarketed portions of the plant can be tolerated. Thus, biological control becomes a viable alternative to chemical insecticides, at least during the early part ofcrop growth.A study was conducted to identify and evaluate the effectiveness of theparasitoids and predators of L. trifolii, M. persicae, and P. saucia on Hawaiianproduced chrysanthemums in which no chemical pesticides were appliedduring the entire crop.■Department of Entomology, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa, 461 West Lanikaula Sl, Hilo, Hawaii 96720.'Hawaii Department of Agriculture, Plant Pest Control Branch. 16 East Lanikaula St.. HUoHawaii 96720.54 Proceedings, Hawaiian Entomological SocietyMATERIALS AND METHODSThe experiment was conducted at a cut-chrysanthemum nursery inMountain View, Hawaii (671 m elev.), in one section of a polyethylene-covered greenhouse (9.1 m X 30.5 m) with open sides. Rooted cuttings ofthe Blue Chip, Polaris, and White Marble cultivars were obtained fromYoder Brothers, Inc. (Barberton, Ohio) and planted into 1.0 m X 7.6 mplots with 150 plants/plot on 16June 1983. Each plot consisted of a singlecultivar planted in 6 rows. A 1.0 m X 1.0 m buffer area with no plantingsbetween plots and a 0.6 m walkway between rows were provided. Ten daysafter planting, plants were soft-pinched and, 18 days later, thinned to 3lateral branches per plant. Two weeks before harvest, the terminal bud ofeach stem was removed. Plants received the grower's standard fertilizationand watering procedures. No chemical pesticides were applied throughoutthe entire crop.The three youngest leaves with developing L. trifolii mines from each of10 plants per cultivar were randomly sampled weekly from each plot for atotal of 30 leaves per sample. Leaves were held at room temperature (23 ±1° C) for one month in 3.8 liter glass jars covered with organdy doth andsecured with rubber bands. They were observed for leafminer and para-sitoid emergences. Plant terminals were also inspected weekly for GPA andVC. GPA infested plant terminals were held in the laboratory in petri dishesfor parasitoid emergences. VC collected from plots were placed in 3.8 literjars similar to leafminers, fed chrysanthemum leaves, and held until VCadult and parasitoid emergences. Egg parasitoids ofVC were not evaluated.At harvest, leafminer damage was assessed by inspecting 50 single-stemchrysanthemums per cultivar. The criterion for leafminer damage was atleast one completed mine.2001B07 B 9 10 11 12 13 14WEEKSFIGURE I. Adults of L. trifoUi, D. mtermtdius, and G. utilis recovered from leaf samples of'Blue Chip' chrysanthemum during 2 to 14 weeks after planting.Vol. 30, December 31,1990 55160140120100806040200L triioliifi. IntermediuaG. utllia8 9WEEKSs—a—b-110 11 12 13 14 15Figure 2. Adulu of L. trifolii, D. inlermedius, and G. ulilis recovered from leaf samples of'Polaris' chrysanthemum during 2 to 15 weeks after planting.140120100'ADU Ik oJMBER Z80 60 40 20 0L. trifoliiQ. intermediuaC. utilla9 10 11 12 13 14 15FIGURE 3. Adults of L trifolii, D. inlermedius, and C. utilis recovered from leaf samples of'White Marble' chrysanthemum during 2 to 15 weeks after planting.56 Proceedings, Hawaiian Entomological SocietyRESULTS AND DISCUSSIONAll leafminers reared from infested chrysanthemum leaves were identified as L. trifolii. The two dominant parasitoid species of L. trifolii were aeulophid, Diglyphus intermedius (Girault) and a eucoilid, Ganaspidium utilisBeardsley, which accounted, respectively for 78% (n=365) and 19%(n=89) of the total parasitoids recovered. D. intermedius was first collectedin Hawaii in 1944 (Higa 1981) and G. utilis introduced from Texas was firstreleased in Hawaii in 1976 (Beardsley 1988). The remaining 3% (n=15)of the recovered parasitoids was composed of the eulophids, Chrysocharissp., Chrysonotomyiaformosa (Westwood), D. begini (Ashmead), Hemiptarsenussemialbiclavus (Girault), and a braconid, Opius dissitus Muesebeck. Figures1-3 present data on leafminers and parasitoids recovered throughout theexperimental period from leaf samples of Blue Chip, Polaris, and WhiteMarble cultivars. High numbers of leafminers and parasitoids wererecovered at 2 to 4 weeks after planting and near harvest at 13 to 15 weeks.Populations of leafminers as well as their natural enemies were low during6 to 11 weeks after planting. At harvest, the percentages of leaves with completed leafmines were 85.5%, 95.2%, and 84.8% for the Blue Chip, Polaris,and White Marble cultivars, respectively. The patterns of leaf production inthe 3 cultivars are shown in Fig. 4. In this chrysanthemum crop, the upper6 to 8 leaves were marketed and the lower leaves produced during the first7 to 9 weeks after planting were removed. Therefore, the concept of aesthetic injury level proposed by Parrella and Jones (1987) can be implemented. In this chrysanthemum crop, growers could have relied on2510 12FIGURE 4. Average number of leaves on "Blue Chip', 'Polaris', and 'White Marble'chrysanthemum plants during 0 to 12 weeks after planting.Vol.30, December31,1990 57parasitoids of L. trifolii during the first 7 to 9 weeks, and an effective chemical insecticide (e.g., abamectin) could have been applied against leafminersonly during the 8th or 10th week to harvest, to prevent aesthetic injury tothe marketed portion of chrysanthemums.Jones et al. (1986) were successful in biological control of L. trifolii in a commercial chrysanthemum greenhouse by inundative releases of D. intermedius and only one application ofabamectin (Avid) near harvest to control L. trifolii.VC also detrimentally affected desired plant characteristics. Theysevered one or more of the lateral branches and induced the growth ofexcessive lateral shoots. Damage to plants averaged 64% during the 4thweek and 85% during the 5th week after planting. The following parasitoidspecies were recovered from VC: Hyposoter exiguae (Viereck) (Ichneu-monidae) —48% (n=21); Cotesia marginiventris (Cresson) (Braconidae) —25% (n=ll); Meteorus laphygmae Viereck (Braconidae) — 25% (n=ll);Chaetogaedia monticola Bigot (Tachinidae) — 2% (n=l). Table 1 shows thattotal percent parasitism ranged from 33.3 to 80.0% during 2 to 6 weeksafter planting.TABLE 1. Number of variegated cutworms and parasitoids collected at Mt. View, Hawaiiin chrysanthemum plots during 2 to 6 weeks after planting.No. parasitoid rearedr£fT 1^ «-~ <***> HyP™*- Ouutogaedia ™' <%>planting larvae , .. . . .. ■". ~ , narasitismr " laphygmae margtmvtntns exiguae monhcola ' mlr™2 10 1 3 43 15 4 0 I4 23 5 4 45 22 0 4 96 9 10 3Mummified aphids consistently yielded the braconid, Lysiphlebus tes-taceipes (Cresson). Also present were Allograpta obliqua (Say) (Syrphidae)and Nesomicromus sp. (Hemerobiidae). All are well known natural enemiesof aphids. However, their combined activity did not provide economic control of aphids as greater dian 50% of the crop was unmarketable becauseof sooty mold.In conclusion, naturally occurring parasitoids and predators providedpartial biological control of these pests, but not economic control. Naturalenemies of L. trifolii can provide biological control of this leafminer forslightly more than half of the crop growth period. Additional biorationalor chemical insecticides are needed for VC, GPA, and L. trifolii when theirdamage affects the marketable portion of the crop. Biorational insecticidesare highly desirable because of their compatibility with parasitoids andpredators. The use of biorational insecticides, such as the entomopatho-genic nematode, Steinemema carpocapsae (Weiser) for leafminers; the fungus,0001080.033.356.563.644.458 Proceedings, Hawaiian Entomological SocietyCephalosporium lecanii (Zimm.) Viegas for aphids; and Bacillus thuringiensis(Berliner) plus S. carpocapsae for cutworms, may provide economic controlof insect pests ofchrysanthemum with minimal use of chemical insecticides.ACKNOWLEDGMENTSThe authors gratefully acknowledge B. Bushe, C. Hirayama, and A.Magno for technical assistance; Mauna Loa Farms, Inc. for cooperation; J.Beardsley and B. Kumashiro for confirming insect identifications; and J.Beardsley, M. Nagao and M.Johnson for critical review of this manuscriptThis research was supported in part by the State of Hawaii, Governor'sAgriculture Coordinating Committee. This is the Hawaii Institute ofTropical Agriculture and Human ResourcesJournal Series No. 3415.REFERENCES CITEDBeardsley, J. W. 1988. Eucoilid parasites of agromyzid leafmincrs in Hawaii (Hymenoplera:Cynipoidea). Proc. Hawaii. Enlomol. Soc. 28:3547.Funasaki, G. Y., P. Y. Lai, L. M. Nakahara, J. W. Beardsley and A. K. Ota. 1988. A review ofbiological control introductions in Hawaii: 1890 to 1985. Proc. Hawaii. Entomol. Soc.28:105-160.Hlga, S. 1981. Notes and Exhibitions. Proc. Hawaii. Entomol. Soc. 23:322.Jones, V. P., M. P. Parrella and D. R. Hodel. 1986. Biological control of Uriomyut trifolii ongreenhouse chrysanthemums. Calif. Agric. 40:10-12.Parrella, M. P. and V. P.Jones. 1987. Development of integrated pest management strategiesin floricultural crops. Bull. Entomol. Soc. Am. 33:28-34.

Parasitoids and Predators of Insect Pests on Chrysanthemums in Hawaii

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Parasitoids and Predators of Insect Pests on Chrysanthemums in Hawaii

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