Arizona Biological Control Working Group

Minutes of the Spring Meeting: 16 June 2000, Western Cotton research Laboratory

Attendance: E. Andress (USDA-APHIS), J. Gould (USDA-APHIS), T. Henneberry (USDA-ARS), M. Hunter (UA), M. McElween (UA), P. Merten (USDA-APHIS), S. Naranjo (USDA-ARS), B. Roltsch (CDFA)

Items of Business

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Research Briefs

Roltsch: Bill discussed some of his recent efforts with the pink hibiscus mealy bug in Imperial Valley, CA. The insect was first noticed in August of 1999 but is thought to have invaded the area at a previous time. The insect has a 30 day life cycle and females do not fly. Two nymphal parasitoids (Anagyrus and Gyranusoidea) were released last fall and are now being found at various sites in the valley; it is too early to judge impact. Ongoing transect surveys for the mealy bug and parasitoids are focusing on the leading-edge boundary of the infestation. Areas in Calixeco appear to be the most heavily infested. Ten parasitoid release sites are being monitored more intensively. The mealy bug and its parasitoids are being cultured on Japanese pumpkins. Additional Gyranusoidea are currently being released and more releases of Anagyrus will be made in the near future. The coccinellid Cryptolaemus montrouzieri is being purchased and released along the leading-edge of the pest infestation. Work with sweetpotato whitefly is focusing on documenting establishment and impact of exotic parasitoids. Eretmocerus emiratus, E. nr. emiratus, E. mundus and Encarsia sophia (formerly transvena) appear to be well established. Native Eretmocerus and Encarsia are sporadic in abundance. Surveys in 1998 showed 26% of fields (primarily cotton and cantaloupe) with exotic Eretmocerus; this level has increased to 75% in 1999 with exotic Encarsia also found in 40% of the fields. Work on annual refuges for will continue one additional year. Results are showing that rates of parasitism in summer crops (basil and okra) are high but drop to low levels in the winter (cole crops and sunflower) suggesting little transfer between refuge crops.

GOULD: Releases of exotic parasitoids (Eretmocerus mundus and nr. emiratus) for sweetpotato whitefly are continuing in central Arizona. Releases are being conducted in cooperation with area nurseries. Parasitoids are released on infested plants in the nursery and areas where these plants end up are being surveyed for parasitoid activity using sentinel plants, leaf samples and sticky cards. Work is also being conducted on salt-cedar biological control in cooperation with Carruthers in Albany, CA. Older established tree will be very difficult to kill and so effort is focusing on newly developing shoots. Experimental studies are planned to characterize feeding damage at different densities of salt cedar leaf beetle on young plants. APHIS now has permitted open field releases of this beetle at 9 sites in the US (AZ, southern CA and NM excluded). Efforts on giant salvinia are moving slowly. California is initially attempting eradication; some specificity testing of biological control agents in being conducted in Mission, TX. The production of a compendium on sweetpotato whitefly biological control efforts in the US is being explored.

ANDRESS: Working on a regional-scale project to examine impact of sweetpotato whitefly parasitoids in relation to spatial configuration of cropping systems and other factors. Whitefly and parasitoid samples are being taken in cantaloupe, cotton and broccoli. A dot-blot assay is being used to identify the presence (by species) of parasitoids in whitefly nymphs. He is also monitoring dead nymphs on leaves to estimate the effect of factors such as predation and parasitoid host-feeding. Data will eventually be used in a multivariate statistical analysis. Also working with parasitoids of pink hibiscus mealy bug. Sleeve cage studies are being conducted to measure potential impact of parasitoids. Studies are also examining development of mealy bugs on difference agricultural host plants.

McElween: Conducting research with aphids in the pecan system. Two species are common, the black margined aphid which is not considered a pest, and the black pecan aphid, which can cause feeding injury and is considered a more serious pest. Studies of species interactions are suggesting that prior feeding by either aphid causes a decrease in leaf quality leading to reduced performance of black pecan aphid.

HUNTER: Continuing her work with whitefly parasitoids and currently focusing on a uniparental Encarsia pergandiella from Brazil. No Wolbachia have been found in the parasitoids, however, treatment with antibiotics allows female production in F1 but not F2 progeny. A new bacteria, completely unrelated to Wolbachia has been isolated and may be involved in parthenogenesis-induction. A culture of Encarsia sophia will be discontinued.

Naranjo: Continues toxicological studies to examine the impact of two insect growth regulators, buprofezin and pyriproxyfen, on several species of generalist predators. Buprofezin (chitin inhibitor) is benign to all stages of Geocoris punctipes, Orius insidiosus and Collops vittatus regardless of exposure route. Survivorship and reproduction are unaffected even at concentrations up to 10X the field rate. Residual exposure to field rates of pyriproxyfen (JH analog) causes about 50% mortality or wing deformities in adults treated as 5th instar nymphs. Pyriproxyfen did not affect adult survival for any species but did cause a slight reduction in egg viability in Collops. Field studies over the past 3 years indicate that neither insect growth regulator consistently affects abundance of any of the 20+ species of predators examined. A second year of field studies are underway to compare and contrast natural enemy populations in untreated Bt and non-Bt cotton. Results from last year indicate no direct detrimental effects of Bt cotton on populations of predators and parasitoids. Lepidoptera in non-Bt plots were very low and so indirect effects through prey reduction could not be examined. Discussions of further exploration for parasitoids of pink bollworm in Australia are underway with John Goolsby (ARS, Australia)

HENNEBERRY: Briefly discussed the glassy-winged sharpshooter problem in California vineyards. The smoky-winged sharpshooter has been present in CA for many years and has been responsible for vectoring Pierces disease (bacterial infection that clogs xylem vessels) at relatively low levels. The exotic glassy-winged sharpshooter is larger, more active, feeds on vine tissue, and appear to be a more efficient vector of the bacteria. It is estimated that approximately 40% of the vines in the Temecula growing area are now infected.

S. Naranjo & M. Hunter

26 July, 2000

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