Three of the seven mealybugs present in Hawaii are of concern to the potted plant for export industry; control options are discussed

Hara, Arnold H.

Jacobsen, Christopher M.

Niino-DuPonte, Ruth Y.

ScholarSpace at University of Hawai'i at Manoa

Cooperative Extension Service Insect PestsMarch 2001IP-6Published 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.Seven species of root mealybug are found in Hawaii,and three of them are of quarantine significance.These root mealybugs are a serious problem for Hawaii’sexport potted-plant industry because root infestationsare not easily detected unless the plants are removedfrom their pots. Potted palms and other slow growingplants are more susceptible to infestation by root mea-lybugs because they require lengthy bench time to at-tain marketable size.Damage caused by root mealybugs is not specific.The most common plant symptoms are slow growth,lack of vigor, and subsequent death. Unless the infesta-Root Mealybugsof Quarantine Significance in HawaiiArnold H. Hara, Ruth Y. Niino-DuPonte, and Christopher M. JacobsenDepartment of Plant and Environmental Protection Sciences• The rhizoecus root mealybugz, Rhizoecus hibisciKawai & Takagi (Figure 1), was discovered in Ha-waii in 1992 and has since spread to the state’s majorpotted foliage plant production areas. This mealybughas been found on palms, calathea, Serrisa spp., and‘Tifdwarf’ bermudagrass.• The coffee root mealybug, Geococcus coffeaeGreen, was discovered prior to 1908. It has a very widehost range, including aglaonema, citrus, cacao, cof-fee, croton, cyperus, dieffenbachia, ferns, mango, ole-ander, palms, philodendron, pineapple, schefflera, andsyngonium.• The pineapple mealybug, Dysmicoccus brevipesCockerelly (Figure 2), was first mentioned as occur-ring in Hawaii in 1910. It can be found on the lowerstem or stalks and exposed roots of pineapple and otherbromeliads, as well as on coffee, banana, caladium,sugarcane, canna, citrus, eggplant, and palms.Mealybug Quarantine PestsThe rhizoecus root mealybug is widely distrib-uted in East and Southeast Asia and has also beenfound in Puerto Rico and Florida. The coffee root mea-lybug occurs throughout the tropics and subtropics,including Central America, South America, Africa,Micronesia, India, Sri Lanka, Philippines, and Florida.The pineapple mealybug is found in South America,Africa, Jamaica, Madagascar, the Dominican Repub-lic, Florida, Louisiana, and Massachusetts.The adult female rhizoecus root mealybug issnow-white and has an elongated oval shape up toabout 2.35 mm long. The adult female coffee rootmealybug is also a snow-white, elongated oval shapevarying from 2 to 2.5 mm in length; it can be distin-guished from other root mealybug species by the pres-ence of anal hooks, which are prominent, stiff, up-turned spines at the tip of each anal lobe. The adultfemale pineapple mealybug is pale pink or white,broadly oval, and approximately 3 mm long.zAlthough six species of Rhizoecus are known in Hawaii, in this publication we use the common name, rhizoecus root mealybug, to referonly to R. hibisci. yFormerly called Pseudococcus brevipes Cockerell.tion is unusually heavy, it is not evident until the plant’spot is removed and the root ball is examined. A white,waxy substance and adult female mealybugs will benoticeable, especially between the pot and the root ball.Plants that are growing slowly, root-bound, or underenvironmental or nutritional stress are more susceptibleto root mealybug infestation.Due to their cryptic habit (preference for dark, hid-den places), little is known about root mealybug biol-ogy. In general, depending on the species, the adult fe-males (Figures 1–3) live from 27 to 57 days. White, cot-tony masses containing egg-laying females and/or eggsIP-6 Root Mealybugs of Quarantine Significance CTAHR — March 20012are normally visible on the outside of the root mass whenan infested plant is lifted from its container. Males ofthe three species discussed here have not been observedin Hawaii, although male pineapple mealybugs havebeen collected in Madagascar, Martinique, and theDomican Republic. The newly hatched, immature crawl-ers (nymphs) are the dispersal stage and are highly mo-bile. Once crawlers find a suitable site, they settle downand begin to feed on roots with their sucking mouth-parts. The entire life cycle of a root mealybug rangesfrom one to four months, depending on the species, cli-matic conditions, and availability of a food source.Root mealybugs can be spread by irrigation water,re-use of previously infested pots, re-use of contami-nated media, and crawlers moving from infested plantsto other plants. Infestation of greenhouse bench plantsby root mealybugs can occur by introducing nurserystock that was already infested when purchased or fromcrawlers that move in from host plants near the green-house.Pest managementBiological controlHawaii has no known natural predators or parasites thatare specific to rhizoecus and coffee root mealybugs.Natural predators and parasites of the pineapple mealy-bug in Hawaii include several encrytid (parasitoid) waspsand lady beetles.Cultural controlBecause root mealybugs are very difficult to detect andcontrol, every effort should be made to prevent theirspread and establishment. The following practices arerecommended:• Inspect roots of newly purchased plants by removingthem from their pots.• Inspect roots of suspected plants, especially slowgrowing ones.• Avoid pot-bound plants by re-potting when necessary.Rhizoecus root mealybugs on palm roots. Pineapple mealybugs on palm roots.1 2Drawing by James Baker, NCSU; photos by Julie Ann Yogi-Chun and A. Hara.Adult27–57 daysNymphalstagesCrawler(dispersalstage)Egg< 24 hoursLife cycle of aroot mealybug3IP-6 Root Mealybugs of Quarantine Significance CTAHR — March 2001• Use pots with inner coatings of copper hydroxide(Spinout®), which prevents root matting and therebyminimizes root mealybug infestations (Figure 4).• Separate pots from the ground on raised benches orwith plastic film over the soil.• Do not allow water from infested areas to run ontoclean areas.• Remove alternate host plants from around the green-house, or control mealybugs on them.• Use clean pots and soil; if infested, wash pots withsoap and water.• Keep the growing area clean of plant debris.Pineapple mealybug populations are tended by sev-eral species of ants, and ant-control measures (physicalbarriers, ant bait or spray) help prevent serious mealy-bug infestations.Biorational controlCTAHR research has demonstrated that hot-water dipsare as effective as insecticides against mealybugs. Ex-periments showed that submerging potted rhapis palmsin water held at 120°F (49°C) until the internal root balltemperature reached 115°F (46°C) was 100 percent ef-fective in killing root mealybugs. Only minor phytotox-icity to raphis was observed, a chlorosis (yellowing) ofolder leaves. Drenching potted palm roots in hot waterat 120°F for 15 minutes will not only control mealy-bugs but will also eliminate burrowing nematodes.Chemical controlChemical control of root mealybugs requires saturationof the root ball and potting medium to a degree that al-lows the pesticide to penetrate the pests’ white, waxysecretion. Research has demonstrated that dipping ordrenching with liquid insecticide is more effective thanapplying a granular formulation. Dursban® Turf & Nurs-ery Product applied twice as a drench or dip at two-weekintervals controls coffee root mealybug; however, it maytake four to six months before the cottony, waxy secre-tions deteriorate completely, making it difficult to de-termine treatment efficacy. This may pose a potentialrisk of shipment rejection by quarantine inspectors.Research trials ranked Dursban® 50 WP andDursban® Turf & Nursery Product as the least phyto-toxic to palms and indicated that watering palms priorto drenching application significantly reduced phytotox-icity. A small group of plants should be treated at therecommended rate under the anticipated growing con-ditions and observed for phytotoxic symptoms for at least14 days before a large number of plants are treated.In the dip method, research findings indicated thatsubmerging the plant’s entire root ball without the potin a diluted Dursban solution (1 pint per 100 gallons)for about 30 seconds with slight agitation is nearly twiceas effective as dipping the plant while still in its pot. Inthe drench method, after premoistening with irrigationor rainfall, the diluted Dursban solution is poured intoeach potted plant container (without removing pots from3 4Life stages of the rhizoecus root mealybug. Palm roots in the pot not treated with copper hydroxide(right) are more compacted and infested with mealybugs.EggAdultNymphIP-6 Root Mealybugs of Quarantine Significance CTAHR — March 20014plants) to saturate the soil at a rate of 10–12 fluid ouncesof solution per gallon of container size.Marathon® 60 WP is applied only as a drench andcan be incorporated with a surfactant or wetting agentto ensure thorough distribution of solution in the pot-ting medium. Drench rates are determined by plant con-tainer size. Over 95 percent control was observed for upto 12 weeks in manufacturer’s trials. Residual activityof Marathon should control most emerging mealybugnymphs.Follow safety precautions given on the product la-bels. Used drench solution should be disposed of byapplying it to approved crops and sites in accordancewith the pesticide label directions.Precautionary statementPesticide use is governed by state and federal regula-tions. Read the pesticide label to be sure that the in-tended use is included on it, and follow all label direc-tions. Consult a chemical sales representative, the Ha-waii Department of Agriculture, or the University ofHawaii Cooperative Extension Service for updated in-formation on available formulations. The pesticide useris responsible for the proper use, application, storage,and disposal of the pesticide.DisclaimerMention of a product name does not imply endorsementor recommendation by the Cooperative Extension Ser-vice, College of Tropical Agriculture and Human Re-sources, University of Hawaii or the United States De-partment of Agriculture and does not imply its recom-mendation to the exclusion of other products that maybe suitable.ReferencesBaker, J.R. (ed.) 1978. Insect and related pests of flowers and foli-age plants. North Carolina Agric. Extension Service, AG-136.Beardsley, J.W., Jr. 1965. Notes on the pineapple mealybug com-plex, with descriptions of two new species (Homoptera: Pseudo-coccidae). Proc. Hawaiian Entomol. Soc. 14(1):55–68.Beardsley, J.W., Jr. 1966. Hypogaeic mealybugs of the HawaiianIslands (Homoptera: Pseudococcidae). Proc. Hawaiian Entomol.Soc. 14:151–155.Beardsley, J.W., T.H. Su, F.L. McEwen, and D. Gerling. 1982. Fieldinvestigations on the interrelationships of the big-headed ant, thegray pineapple mealybug, and the pineapple mealybug wilt dis-ease in Hawaii. Proc. Hawaiian Entomol. Soc. 24(1):51–68.Beardsley, J.W., Jr. 1995. Notes on two Rhizoecus species new tothe Hawaiian Islands, with a revised key to Hawaiian hypogaeicmealybugs (Homoptera: Pseudococcidae:Rhizoecinae). BishopMuseum Occasional Papers No. 42, pp. 28–29.Dekle, G.W. 1965. A root mealybug (Geococcus coffeae Green)(Homoptera: Pseudococcidae). Florida Dept. of Agric., Div. ofPlant Industry, Entomology Circular No. 43.Hara, A. 1988. Control of the coffee root mealybug in potted plants.University of Hawaii at Manoa, College of Tropical Agricultureand Human Resources, Horticulture Digest, No. 86.Kuitert, L.C. and G.W. Dekle. 1966. Control of root mealybug,Geococcus coffeae Green. Proc., Florida State Horticultural So-ciety 79:484–488.Linquist, R.K. 1991. Identification of insects and related pests ofhorticultural plants. Ohio Florists’ Association, Columbus.Merrill, G.B. 1953. A revision of the scale-insects of Florida. StatePlant Board of Florida, Gainesville, Bulletin 1.Poe, S.L. 1973. Infestation and spread of root mealybugs in con-tainer-grown ornamentals. Institute of Food and Agricultural Sci-ences, University of Florida, Florida Foliage Grower 10(2):1–4.Snetsinger, R. 1966. Biology and control of a root-feeding mealy-bug on Saintpaulia. J. Econ. Entomol. 59:1077–1078.Williams, D.J. 1996. Four related species of root mealybugs of thegenus Rhizoecus from east and southeast Asia of importance atquarantine inspection (Homoptera: Coccoidea: Pseudococcidae).J. Natural History 30:1391–1403.Zimmerman, E.C. 1948. Pseudococcus brevipes (Cockerell). In: In-sects of Hawaii; a manual of the insects of the Hawaiian Islands,including enumeration of the species and notes on their origin,distribution, hosts, parasites, etc. Volume 5. (Homoptera: Sterno-rhyncha), pp. 189–201.

Root Mealybugs of Quarantine Significance in Hawaii

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Root Mealybugs of Quarantine Significance in Hawaii

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