Several natural enemies show promise against hard - to-control leafminer

Control of Liriomyza trifolii

Adult female L. trifolii. with biological agents and growth regulators

Michael P. Parrella 0 Karen L. Robb George D. Christie 0 James A. Bethke

Young Diglyphus feeds on leafminer larva, effectively themum greenhouses to parasitize L. trifolii. stopping mine development. A leafmining , the major pest of chry- santhemums grown for cut flowers and in Following is a brief description of parasites pots, has proved impossible for growers to being reared in our greenhouses. control with currently available , Diglyphus intermedius (Girault) and Di- even with applications at three-day intervals. glyphus begini (Ashmead). For the purpose In a search for other methods of pest suppres- of this article, we will discuss the biology of sion, we have undertaken studies of poten- these species together under the format of a tially effective natural control agents of the generalized life cycle for the genus, although serpentine leafminer, Liriomyza trifolii (Bur- we are studying them individually. Diglyphus gess), and have also evaluated insect growth spp. are characterized by a relatively short regulators for their ability to control the lar- development time-egg to adult in about 11 val and pupal stages. These materials are days, compared with about 20 days for the potentially compatible with natural control leafminer at 78" F. Adult parasites lay their Chrysocharis parksi deposits eggs inside leafminer larva, agents because of their low toxicity and host eggs near leafminer larvae; newly hatched where parasites will develop. specificity. parasite larvae feed externally on the leaf- miner larvae. This effectively stops larval and Search for natural enemies mine development and is important when To determine the parasite fauna associated considering that the mere presence of mines with greenhouses, we placed on a crop such as mums reduces their aesthe- mum plants infested with leafminer larvae tic and, thus, market value. (about 20 larvae per plant) alongside heavily In addition, females of Diglyphus spp. sting and kill more leafminer larvae than their New parasites will emerge from infested chrysanthemum greenhouses in leafminer parasitized by Orange and San Diego counties during per- progeny need for development. After sting- Chrysocharis (left). iods of peak fly activity in July and August. ing a larva, the adult parasite feeds on exu- After five to seven days of exposure, they date from the dying larva, a phenomenon were returned to the laboratory, where they known as host feeding and a positive aspect were held for emergence of parasites. We in reducing leafminer populations in the found several species of parasites and are greenhouse. Females generally live three to conducting biological studies of three of four weeks and lay approximately 40 eggs. them. Chrysocharis parksi (Crawford). This Although our survey of the parasite fauna species is a larval-pupal parasite. It deposits associated with chrysanthemum greenhouses its eggs inside the leafminer larva, and para- is incomplete (approximately 17 species of site development is internal. Parasitized parasites have been reared from Liriomyza in leafminer larvae complete their development western North America), the parasites recov- and drop to the ground, where pupation oc- ered are considered to be among the most im- curs. Then, instead of adult leafminers portant species parasitizing the leafminer in emerging from puparia, parasites emerge. field-grown tomatoes and in Califor- Chrysocharis develops (egg to adult) in bug, Cyrtopeltis modestus, is a leafminer predator but also nia. Under reduced pesticide application approximately the same amount of time as a secondary tomato pest. programs, these parasites move into chrysan- the leafminer. These negative aspects of

CALIFORNIAAGRICULTURE, NOVEMBER-DECEMBER 1982 17 Chrysocharis (allowing complete mine for- the leaf before dropping to the ground to spreader, B-1956, was added to each material mation and possessing relatively long devel- pupate. at 1 milliliter per gallon. IGRs, except meth- opment time) may be offset by the ease with There are still large data gaps, however, oprene, were applied to plants containing which this parasite can be mass-produced for that need to be filled before the tomato bug newly hatched larvae. All IGRs, including release. Parasitized pupae can be instantly could be considered for biological control of methoprene, were also applied to plants con- separated from those unparasitized. Like Di- leafminer larvae. In addition, the possible taining third stage (mature) larvae. There glyphus spp., Chrysocharis females host- movement of the bug from chrysanthemum were 10 plants for each larval age class for feed, killing more hosts than are needed for to tomato may limit the areas where it can be each treatment. development of their progeny. used. After IGR application to newly hatched larvae, plants were placed on greenhouse Feasibility of parasite release Insect growth regulators benches where larval development contin- Our research is directed toward finding the Six insect growth regulators (IGRs) were ued. When larvae were about ready to best parasites for use in an inundative re- evaluated for control of the larval and pupal emerge, leaves were removed and placed on a lease-that is, using them as a biological in- stages of the leafminer-CGA 77622 (mode thin layer of sand in small glass containers, secticide. The low level of mines per plant of action is unknown, but believed to be hor- which were held in an environmental cham- that are acceptable to growers precludes such monal), methoprene, RO 13-5223E, RO ber at 26.7" C, to 50 to 60 percent relative releases for long-term suppression of L. tri- 13-5223W (juvenile hormone mimics), Bay humidity, and 14.5-hour photophase. folii. Instead, parasites would be released SIR 8514, and dimilin (chitin inhibitors). All Pupating larvae were sifted out and placed in into mum greenhouses during the initial five these materials are characterized as nontoxic ventilated containers on moist sand under the to six weeks of crop development. The fo- to mammals and relatively specific to the same conditions. These were checked daily liage on plants during this period is not pres- target pest; they show little or no effect on for emergence of adults. After IGRs were ap- ent when the final flowers are cut. nontarget organisms. plied to plants that contained third stage lar- Ideally, the parasites would keep the leaf- Standard chrysanthemum plants (three- vae, leaves were removed and handled in the miner population at low levels without appli- leaved, 30 days old) of the variety 'White same way. cation of insecticides. After the sixth week, Hurricane' were exposed to large colonies of In addition, methoprene was evaluated as pesticides would be used, if needed, to leafminers for one hour, so that all oviposi- a soil drench in 5-inch pots filled with moist protect marketable foliage-preferably, tion, subsequent egg hatch, and larval devel- soil. The rate used was equivalent to 2.5 insecticides that are compatible with natural opment in all plants would be synchronous. ounces of formulated material per 100 gallons enemy releases. IGRs were applied as foliar sprays to runoff per 1,OOO square feet. Five pots were treated with a 1-gallon sprayer at 60 psi. A sticker- with methoprene, and five (controls) with Other natural agents In conjunction with Harry Kaya, Associate TABLE 1. Effect of selected insect growth regulators on newly hatched larvae of Nematologist at U.C., Davis, and Carolyn Liriomyza trifolii (Burgess) Pickel, Cooperative Extension Area Special- Posttreatment count$ ist, we conducted preliminary efficacy trials Total Total with a predaceous nematode, Neoaplectana Total larval emerging Mean emerging Mean carpocapsae (Weiser), for leafminer control. pretreatment larvae percent adults percent Material Rate* countt 110 plants control 110 plants control This nematode is effective against several Ib % % soil-inhabiting , and is being sold com- CGA 77622 5SC 0.5 181 0 100.0a ...... mercially in northern as an alter- RO 13-5223 1E 0.8 174 141 19.5b 41 74.0a native method of controlling leafminers in RO 13-5223 50W 0.8 108 84 26.0b 68 40.8b . The nematode is applied as BAY SIR 8514 0.5E 0.5 178 115 29.7b 99 41.2b a soil drench and may attack leafminers in Control ... 171 150 11.3b 120~ 22.3b~~ Dimilin 25W 0.5 21 7 187 20.9b 164 34.3b two ways: after mature larvae drop to the soil 'Pounds active ingredient per 100 gallons water before pupation, and as adults emerge from t10 plants per test material with mean f SE = 17.2 + 1.4 larvae per plant. $Mean percent control was calculated with individual plants as replicates. Means followed by the same letter are not the puparia. Preliminary screening trials with significantly different (p>0.05), Duncan's new multiple range lest. No data transformation was necessary. N. carpocapsae at 9 to 400 per square centi- meter of soil surface did not provide consis- TABLE 2. Effect of selected insect growth regulators on late third-stage larvae of tent results. Further evaluations are planned. Liriomyza trifolii (Burgess) Biological studies also are being conducted Posttreatment count$ with the tomato bug, Cyrtopeltis modestus Total Total (Distant), a mirid predator of leafminer lar- Total larval emerging Mean emerging Mean vae and other insects. This insect is com- pretreatment larvae percent adults percent monly found in tomato fields in southern Material Rate' countt 110 plants control 110 plants control Ib % % California, where it is considered a secondary CGA 77622 5SC 0.5 192 0 100.0a ...... pest, primarily feeding on the stems. How- RO 13-5223 1E 0.8 222 216 3.5c 13 94.2a ever, the tomato bug does not feed on chry- Methoprene 5E 4.0 21 2 176 17.4b 17 92.la santhemum. Later stages and adults readily RO 13-5223 50W 0.8 171 156 11.9bc 68 63.76 pierce leafminer larvae within the mesophyll BAY SIR 8514 0.5E 0.5 218 208 3.7c 170 19.5~ Control 157 144 9.lc 129 18.6~ of a chrysanthemum or tomato leaf. The bug Dirnilin 25W 0.5 247 231 9.6~ 217 13.5~ quickly immobilizes the larva, sucking out its 'Pounds active ingredient per 100 gallons water. contents. In addition, the tomato bug attacks ti0 plants per test material with mean f SE= 20.3k 1.2 larvae per plant. *Mean percent control was calculated with individual plants as replicates. Means followed by the same letter are not late third stage larvae that have emerged from significantly different (p>0.05), Duncan's new multiple range test. No data transformation was necessary.

18 CALIFORNIA AGRICULTURE, NOVEMBER-DECEMBER 1982 water. After treatment, 20 mature larvae, within the leaf. However, some materials Those IGRs that provided the best control which had just emerged from chrysanthe- provided significant control of emerging (CGA-77622, RO 13-5223E, and metho- mum leaves to pupate, were added to the soil adults. These IGRs generally provided better prene) are currently being evaluated for in each of the 10 pots. Each pot was capped control when applied to leaves containing phytotoxicity to chrysanthemums and for with a ventilated cage and checked daily for mature larvae rather than to those containing compatibility with selected natural enemies adult emergence. Water was added to the soil newly hatched larvae; RO 13-5223E and of the leafminer. whenever necessary to maintain a consistent methoprene provided greater than 90 percent level of moisture. All pots were kept in an en- control of adult emergence. As a soil drench vironmental chamber as in other treatments. application, methoprene provided only 31 Michael P. Parrella is Assistant Professor, Karen L. Robb and George D. Christie are graduate CGA 77622 was the only IGR to provide percent control of emerging adults, which students, and James A. Bethke is Laboratory 100 percent control of newly hatched and was not significantly different (pX.05, T Assistant. All are with the Department of Ento- mature larvae; all larvae were killed while still test) from the control (19 percent). mology, University of California, Riverside.

Following are articles appearing in California Agriculture, Volume 36, Numbers 1 through 12, 1982 INDEX January through December 1982 (listing first author only).

ANIMAL SCIENCE Potential market for plums and New wasp attacks navel orange- Somatic cell genetics: Goats grazing in chaparral - nectarines in Japan- worm - Legner May-Jun manipulating plants through Sidahmed May-June Moulton Sep-Oct single-cell techniques Reducing pesticide treatments in Innovationsin plant breeding: Observations on Bodmin Trees as energy crops - celery- new concepts in whole-plant Nu-Pulse milking system- Standiford May-June Van Steenwyk Sep-Oct genetics Shultz Mar-Apr INSECT AND PEST MANAGEMENT Single citrus budwood treatment Agricultural applications: CULTURAL PRACTICES, against insects, mites- integrating conventional and FE R T I LIZAT10 N , IR R IC ATlON in almond orchards- Elmer JUI molecular genetics Reil Jul Advantages of polyculture Spider mites can reduce 75 years of citrus cropping - Altieri Jul Applying parasitic nematode to strawberry yields - research Nov-Dec control carpenterworm in fig Sances Jan-Feb (various authors from Citrus Celery yields and uniformity trees - Lindegren Nov-Dec Research Center- Riverside) affected by pre-transplant Trapping black cutworm in straw- Introduction and history berries- Clement practices - Welch Mar-Apr Biological control of ice plant J’l Breeding and development scales - Tassan Sep-Oct Chemical and cultural control of Whitefly problem in southern Cal- Cultural practices kikuyugrass in turf - Cabbage aphid control - ifornia- Johnson Sep-oct Diseases and their control Cudney Jan- Feb McCalley May-June Whi tef Iy- transmi tted disease Insect pests and their control Cotton growth related to plant’s Chemicals losing effect against complex - Duffus Nov-Dec OTHER water status- Grimes Nov-Dec grape mealybug - Flaherty May-June PLANT DISEASES Cumulative effects of ethephon Disease-induced potassium as fruit thinner on French prune deficiency and verticillium wilt Detection of dicofol-resistant Chemical control of phomopsis trees- Sibbett Sep-Oct in cotton- Ashworth Sep-Oct spider mites in cotton - rapevine cane and leaf spot - Dennehy Nov-Dec 8ucuzza Mar-APr Desert soil compaction reduces Drip irrigation in young almond plant cover- Adams Sep-Oct orchards- Fereres Sep-Oct Gypsy moth: here again-Hoy Jul ‘Eureka’. sweet Dotato resistant to soil rot (pox)- Donations for agricultural Late-fall nitrogen application in Improved parasites for filth fly Scheuerman Jan-Feb research, July 1,1980- vineyards is inefficient - control - Legner Sep-Oct June30,1981 Jan-Feb Peacock Jan-Feb GraDevines show seasonal differ- Large-scale releases of pesticide- ences in susceptibility to Ethephon may speed up opening Midwinter irrigation can reduce resistant spider mite predator- eutypa- Petzoldt Mar-Apr of late-planted cotton- deep bark canker of walnuts- HOY Jan-Feb Weir Sep-Oct Teviotdale May-June Tarping to control wilt in pis- Liriomyza trifolii control with bio- tachios- Ashworth MaY-Jun Growing with Master Gardeners- Progress report on narrow-row logical agents and chemicals- Grieshop Jul cotton - Curley Sep-Oct Parrella Nov-Dec SPECIAL PRESENTATIONS Growth control of laurel fig with Trunk injection corrects iron Measuring brown mite injury to Genetic eng’ineering of chlorflurenol- Hield Nov-Dec deficiency in plum trees- avocados- Sances May-Jun rolants -- Aua-0 Yoshikawa Mar-Apr (Various authors from U.C. depart- Master plan for drainage in S J ments active in molecular biology valley- Hanson Midsummer walnut aphid out- May-Jun Vineyard cultural practices may breaks - Sibbett May-Jun research) help reduce botrytis bunch rot- Role of the university in Rebaudi’s stevia: natural Savage Mar-Apr Mites: primary food for two genetic engineering noncaloric sweeteners - predators in San Joaquin Valley Genetic enaineerina: the new Shock SeD-Oct ECONOMICS AND MARKETING cotton - Gonzalez Mar-Apr techniquesand thek potential Plant breeding: and Rice sterility varies with area and Factors affecting sugarbeet Monitoring and modeling oriental limitations variety- Board Jan- Feb yields- Wallace Jul fruit moth - Rice Jan-Feb Plant genes: understanding Two insects offer potential Hired workers on California Monitoring and modeling San mechanisms of gene biological control of common farms-Martin Sep-Oct Jose scale- Rice Jan- Feb expression purslane- Clement Mar-Apr Gene vectors: crossing natural On-farm alcohol fuel Monitoring aphid infestations on barriers to genetic Update: oat hay variety trials- production - Meo Jul broccoli -Trumble Nov-Dec manipulations Schoner Jan-Feb

CALIFORNIA AGRICULTURE, NOVEMBER-DECEMBER 1982 19