Cooperative Extension Service Insect Pests March 2001 IP-6 Root Mealybugs of Quarantine Significance in Hawaii Arnold H. Hara, Ruth Y. Niino-DuPonte, and Christopher M. Jacobsen Department of Plant and Environmental Protection Sciences even species of root mealybug are found in Hawaii, tion is unusually heavy, it is not evident until the plant’s Sand three of them are of quarantine significance. pot is removed and the root ball is examined. A white, These root mealybugs are a serious problem for Hawaii’s waxy substance and adult female mealybugs will be export potted-plant industry because root infestations noticeable, especially between the pot and the root ball. are not easily detected unless the plants are removed Plants that are growing slowly, root-bound, or under from their pots. Potted palms and other slow growing environmental or nutritional stress are more susceptible plants are more susceptible to infestation by root mea­ to root mealybug infestation. lybugs because they require lengthy bench time to at­ Due to their cryptic habit (preference for dark, hid­ tain marketable size. den places), little is known about root mealybug biol­ Damage caused by root mealybugs is not specific. ogy. In general, depending on the species, the adult fe­ The most common plant symptoms are slow growth, males (Figures 1–3) live from 27 to 57 days. White, cot­ lack of vigor, and subsequent death. Unless the infesta­ tony masses containing egg-laying females and/or eggs Mealybug Quarantine Pests • The rhizoecus root mealybugz, Rhizoecus hibisci The rhizoecus root mealybug is widely distrib­ Kawai & Takagi (Figure 1), was discovered in Ha­ uted in East and Southeast Asia and has also been waii in 1992 and has since spread to the state’s major found in Puerto Rico and Florida. The coffee root mea­ potted foliage plant production areas. This mealybug lybug occurs throughout the tropics and subtropics, has been found on palms, calathea, Serrisa spp., and including Central America, South America, Africa, ‘Tifdwarf’ bermudagrass. Micronesia, India, Sri Lanka, Philippines, and Florida. The pineapple mealybug is found in South America, The coffee root mealybug, Geococcus coffeae • Africa, Jamaica, Madagascar, the Dominican Repub­ Green, was discovered prior to 1908. It has a very wide lic, Florida, Louisiana, and Massachusetts. host range, including aglaonema, citrus, cacao, cof­ The adult female rhizoecus root mealybug is fee, croton, cyperus, dieffenbachia, ferns, mango, ole­ snow-white and has an elongated oval shape up to ander, palms, philodendron, pineapple, schefflera, and about 2.35 mm long. The adult female coffee root syngonium. mealybug is also a snow-white, elongated oval shape • The pineapple mealybug, Dysmicoccus brevipes varying from 2 to 2.5 mm in length; it can be distin­ Cockerelly (Figure 2), was first mentioned as occur­ guished from other root mealybug species by the pres­ ring in Hawaii in 1910. It can be found on the lower ence of anal hooks, which are prominent, stiff, up­ stem or stalks and exposed roots of pineapple and other turned spines at the tip of each anal lobe. The adult bromeliads, as well as on coffee, banana, caladium, female pineapple mealybug is pale pink or white, sugarcane, canna, citrus, eggplant, and palms. 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 refer only to R. hibisci. yFormerly called Pseudococcus brevipes Cockerell. Published by the College of Tropical Agriculture and Human Resources (CTAHR) and issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Andrew G. Hashimoto, Director/Dean, Cooperative Extension Service/CTAHR, University of Hawaii at Manoa, Honolulu, Hawaii 96822. An Equal Opportunity / Affirmative Action Institution providing programs and services to the people of Hawaii without regard 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 [email protected]. IP-6 Root Mealybugs of Quarantine Significance CTAHR — March 2001 1 2 Rhizoecus root mealybugs on palm roots. Pineapple mealybugs on palm roots. are normally visible on the outside of the root mass when Root mealybugs can be spread by irrigation water, an infested plant is lifted from its container. Males of re-use of previously infested pots, re-use of contami­ the three species discussed here have not been observed nated media, and crawlers moving from infested plants in Hawaii, although male pineapple mealybugs have to other plants. Infestation of greenhouse bench plants been collected in Madagascar, Martinique, and the by root mealybugs can occur by introducing nursery Domican Republic. The newly hatched, immature crawl­ stock that was already infested when purchased or from ers (nymphs) are the dispersal stage and are highly mo­ crawlers that move in from host plants near the green­ bile. Once crawlers find a suitable site, they settle down house. and begin to feed on roots with their sucking mouth­ parts. The entire life cycle of a root mealybug ranges from one to four months, depending on the species, cli­ Pest management matic conditions, and availability of a food source. Biological control Adult Hawaii has no known natural predators or parasites that Life cycle of a 27–57 days are specific to rhizoecus and coffee root mealybugs. root mealybug Natural predators and parasites of the pineapple mealy­ bug in Hawaii include several encrytid (parasitoid) wasps and lady beetles. Cultural control Because root mealybugs are very difficult to detect and control, every effort should be made to prevent their Nymphal spread and establishment. The following practices are stages recommended: • Inspect roots of newly purchased plants by removing them from their pots. • Inspect roots of suspected plants, especially slow growing ones. Avoid pot-bound plants by re-potting when necessary. Crawler • (dispersal Egg stage) < 24 hours Drawing by James Baker, NCSU; photos by Julie Ann Yogi-Chun and A. Hara. 2 IP-6 Root Mealybugs of Quarantine Significance CTAHR — March 2001 Egg Nymph 3 Adult 4 Life stages of the rhizoecus root mealybug. Palm roots in the pot not treated with copper hydroxide (right) are more compacted and infested with mealybugs. • Use pots with inner coatings of copper hydroxide Chemical control (Spinout®), which prevents root matting and thereby Chemical control of root mealybugs requires saturation minimizes root mealybug infestations (Figure 4). of the root ball and potting medium to a degree that al­ • Separate pots from the ground on raised benches or lows the pesticide to penetrate the pests’ white, waxy with plastic film over the soil. secretion. Research has demonstrated that dipping or • Do not allow water from infested areas to run onto drenching with liquid insecticide is more effective than clean areas. applying a granular formulation. Dursban® Turf & Nurs­ • Remove alternate host plants from around the green­ ery Product applied twice as a drench or dip at two-week house, or control mealybugs on them. intervals controls coffee root mealybug; however, it may • Use clean pots and soil; if infested, wash pots with take four to six months before the cottony, waxy secre­ soap and water. tions deteriorate completely, making it difficult to de­ • Keep the growing area clean of plant debris. termine treatment efficacy. This may pose a potential risk of shipment rejection by quarantine inspectors. Pineapple mealybug populations are tended by sev­ Research trials ranked Dursban® 50 WP and eral species of ants, and ant-control measures (physical Dursban® Turf & Nursery Product as the least phyto­ barriers, ant bait or spray) help prevent serious mealy­ toxic to palms and indicated that watering palms prior bug infestations. to drenching application significantly reduced phytotox­ icity. A small group of plants should be treated at the Biorational control recommended rate under the anticipated growing con­ CTAHR research has demonstrated that hot-water dips ditions and observed for phytotoxic symptoms for at least are as effective as insecticides against mealybugs. Ex­ 14 days before a large number of plants are treated. periments showed that submerging potted rhapis palms In the dip method, research findings indicated that in water held at 120°F (49°C) until the internal root ball submerging the plant’s entire root ball without the pot temperature reached 115°F (46°C) was 100 percent ef­ in a diluted Dursban solution (1 pint per 100 gallons) fective in killing root mealybugs. Only minor phytotox­ for about 30 seconds with slight agitation is nearly twice icity to raphis was observed, a chlorosis (yellowing) of as effective as dipping the plant while still in its pot. In older leaves. Drenching potted palm roots in hot water the drench method, after premoistening with irrigation at 120°F for 15 minutes will not only control mealy­ or rainfall, the diluted Dursban solution is poured into bugs but will also eliminate burrowing nematodes. each potted plant container (without removing pots from 3 IP-6 Root Mealybugs of Quarantine Significance CTAHR — March 2001 plants) to saturate the soil at a rate of 10–12 fluid ounces References of solution per gallon of container size. Baker, J.R. (ed.) 1978. Insect and related pests of flowers and foli­ Marathon® 60 WP is applied only as a drench and age plants. North Carolina Agric. Extension Service, AG-136. Beardsley, J.W., Jr. 1965. Notes on the pineapple mealybug com­ can be incorporated with a surfactant or wetting agent plex, with descriptions of two new species (Homoptera: Pseudo­ to ensure thorough distribution of solution in the pot­ coccidae).