Field evaluation of commercial formulations of the codling moth granulovirus (CpGV):

1. Fig.1. Applying CpGV to experimental plots at Moxee, 2003 Field evaluation of commercial formulations of the codling moth granulovirus (CpGV): persistence of activity and success of repeated applications against natural infestations L.A. Lacey1, S.P. Arthurs1, H. Headrick1, R. Fritts, Jr.2, and D. Thomson3 1 USDA-ARS, Yakima Agricultural Research Laboratory, Wapato, WA 2 Certis USA, Clovis, CA;3 Sumitomo USA, Seattle, WA 2. Grower assessments Methods. The impact of CydX as a primary control measure for codling moth within commercial organic orchards was monitored at five locations (Table 2). Individual growers applied Cyd-X treatments within label recommendations; i.e. 3-4 oz in 100-200 gal. + 6-12 oz wetting agent per acre. Applications were timed according to biofix information and sticky pheromone trap data, according to normal monitoring practices. Historically all sites had suffered repeated codling moth attacks with CydX treatments generally confined to known ‘hotspots’ from 2002 where mating disruptors (200-400/ac) and some routine sanitation of infested fruit was also employed. Trees were sampled to estimate damage throughout the season. Damaged fruit was removed to determine the proportion of deep entries caused by larvae surviving treatment. Selected trees were banded to monitor overwintering generations. Results. The grower assessments provide strong circumstantial evidence for the effectiveness of well-timed CpGV applications against codling moth outbreaks (Table 2). In all cases where 1st generation larvae were targeted and treated areas monitored, fruit damage was reduced or eliminated in the 2nd generation, with the majority of neonates killed throughout the season as indicated by the high proportion of failed entries or shallow stings. Adult catches in pheromone traps were also significantly reduced in the second and third generation combined, while trap bands placed around trees indicated the overwintering generations remained low (data not shown). In one case (Moxee), a severe infestation was reduced (when compared to an oil check) but not adequately controlled by late season applications of the virus alone. The codling moth, Cydia pomonella L. is the most significant and widespread insect pest of apples in Washington State and beyond. While chemical control remains the mainstay for most conventional growers, concerns over environmental impact and insecticide resistance [coupled with anticipated loss of registered compounds such as Guthion (azinphos methyl)] has focused efforts to find more integrated approaches. Among the biological control options available, the granulovirus of C. pomonella (CpGV) has offered potential for selective control of this key pest (Lacey et al. 2002; Jaques, 1990). Although CpGV has received considerable attention as a microbial insecticide, problems including a perceived lack of persistence and speed of kill in the orchard agroecosystem and previous quality control issues have to date limited its widespread commercial development and adoption by orchardists (Cross et al. 1999). Table 1. CpGV applications made to experimental plots at Moxee, 2003 • Objectives • Assess the persistence and efficacy of three CpGV products recently certified for use in organic production in an experimental orchard; CydX (Certis), Virosoft (Biotepp), Carpovirusine (Sumitomo) • Monitor the season-long performance of Cyd-X used by several commercial organic growers Fig.2. Live codling moth larvae recovered from apples previously treated with commercial CpGV products. Fruit was challenged with 5-neonate larvae at various intervals after spraying 1. Persistence of CpGV products Methods. This study was conducted in a plot of 224 trees (spur-reds) at the USDA experimental orchard near Moxee, WA. Applications were made on 2 June and 14 July to seventy individual trees using a motorized backpack airblast sprayer (Stihl). Products were applied in a 3×2 factorial design according to Table 1; with 10 randomly selected trees per treatment. Trees were sprayed from multiple angles providing realistic coverage and a large tarp was used to confine treatments (Fig.1). Immediately after spraying and at 1, 3, 7, 10 and 14-day intervals 50 apples per treatment were removed and challenged with 5 neonate codling moth larvae using a standardized laboratory bioassay. After 10 days, apples were destructively sampled to quantify fruit damage and larval mortality. Results. For the June application residual activity of all products (label rates) remained highly effective (>80% larval mortality relative to controls) for 24 hours following application and moderately effective (>70%) after 72 hours (Fig.2). Significant activity in all treatments remained after 14 days, suggesting prolonged survival of the virus in UV-protected locations, such as the calyx of fruit. Fruit damage was also reduced; while overall >97% control larvae formed deep entries, <35% of CpGV-killed larvae’s stings were >3mm. The second application showed similar results (data not shown). Table 2. Fruit injury and adult codling moth activity monitored in commercial orchards following various CpGV applications (2003 season) 1Accumulated degree days; 1st generation = 220-1020, 2nd–3rd = 1100-2300 2A minimum of 30 trees assessed per generation Discussion Our results show that repeated applications of commercial CpGV formulations provide a valuable alternative for management of codling moth in Washington State and elsewhere. Weekly applications timed during peak egg hatch integrated with other strategies such as mating disruption or other soft pesticides will likely provide effective population suppression for many growers with moderate to low codling moth pressure. Future work at YARL will focus on optimizing the application rate and frequency of CpGV applications as well as improving the persistence and uptake through formulation. References Cross, J.V., Solomon, M.G. et al. 1999. Biocontrol of pests of apples and pears in northern and central Europe: 1. Microbial agents and nematodes. Biocontr. Sci. Technol. 9, 125-149 Lacey, L.A., Vail P.V. and Hoffmann D.F. 2002. Comparative activity of baculoviruses against the codling moth Cydia pomonella and three other tortricid pests of tree fruit. J. Invert. Pathol.80, 64-68 Jaques, R.P. 1990. Effectiveness of the granulosis virus of the codling moth in orchard trials in Canada. Proceedings of the Vth international colloquium on invertebrate pathology and microbial control, Adelaide, Australia, 20-24 August 1990