1a. Objectives (from AD-416):
1) Utilize a new large-scale volatile organic compound (VOC) collection system; 2) Collect in-situ pistachio VOCs from select orchards, at specific phenological stages; 3) Evaluate efficacy of collected VOCs in EAG bioassays on NOW; 4) Formulate a simple synthetic blend of EAG active volatiles.
1b. Approach (from AD-416):
Implement a large-scale VOC collection system capable of ambient analyses, to collect pistachio volatiles at specific phenological stages of growth. Collected volatiles will be subjected to electroantennogram analyses (EAG) to determine ability to elicit responses to navel orangeworm. VOCs with positive responses will be formulated into synthetic blends and the blends tested for field efficacy.
3. Progress Report:
Electroantennographic and field trapping studies of volatiles collected from several pistachio and almond sources over the past three years provided a series of blends for further evaluation. Three blends formulated for almond orchards (Blends A, B, and C) and three blends formulated for pistachio orchards (Blends D, E, and F) were forwarded to field trapping studies during the 2011 growing season. A summary of the total navel orangeworm (NOW) captures for the six blends in their respective orchard of May to October were as follows: A, 62; B, 37; C, 52, almond meal, 8, Blank, 1; D, 3; E, 2; F, 32; almond meal, 2, blank, 0. Interestingly, 60% (12 of 20) of the total female A. transitella moths captured were trapped in the 24 Sep trial, 20% (4 of 20) were trapped in the preceding week, 16 Sep, and the remaining four captures were single female A. transitella trapped in various weeks in July, August, and September. The data of weekly moth captures for males (traps baited with virgin female A. transitella) and females (traps baited with Blend F) illustrated the inconsistent attractancy of Blend F for female A. transitella. Though the 2011 season did have high A. transitella activity during critical periods (Jul-Aug), as indicated by the high number of male captures in the virgin baited traps, Blend F was unable to adequately attract female A. transitella in the earlier months. An interesting feature of the weekly captures is the sudden attractiveness of Blend F to female A. transitella in mid-September. These data imply a possible phenological role of volatile emissions in pistachios and the following theories could be postulated: 1) the orchard emits an odor profile in the phenological development period between May and September that is more attractive than Blend F; or, 2) the orchard emits an odor profile in September that enhances the attractiveness of Blend F. Overall, Blend F attracted significantly (defined as P < 0.05) more total moths, e.g. male and female A. transitella combined (one-way ANOVA, F = 3.79, df: 4,95, and P = 0.007, followed by SNK method P < 0.05), than Blend D (P = 0.004), Blend E (P = 0.009), and almond meal (P = 0.016). Analysis of female A. transitella captures demonstrated no significant differences between the different lure treatments due to the number of down dates (zero captures) of activity, though the probability P = 0.085 value (F = 2.12, df: 4,95) was close to declaring significantly greater female captures with Blend F. It should be noted that for Blend F a greater number of female moths were captured than the other Blends or almond meal, just not statistically. Analysis of male A. transitella captures demonstrated significantly different and greater attraction and captures of males with Blend F over the other Blends and almond meal lures, excluding virgin-baited traps (F = 4.75, df: 4,95, and P = 0.0027); Blend D (P < 0.001), Blend E (P = 0.003), and almond meal (P = 0.005). The results and statistical analysis for A. transitella captures in almonds are discussed in the forthcoming paper (Beck et al. 2011c). The results for A. transitella capture in pistachio orchards were not as large in captured numbers or as consistent in moth captures as in almonds and require further optimization. Comparison of the week to week trials for Blend F showed no activity from May to early July and sporadic activity in July, August, and early September. Blend F showed increased attractiveness toward female A. transitella in mid- to late September. However, Blend F overall attracted significantly higher total number of A. transitella moths compared to Blend D, Blend E, and more importantly almond meal. At this time optimization of Blend F is required before further speculation regarding its value for monitoring A. transitella in pistachios is considered. However, the positive results of Blend F provide the best efforts heretofore regarding a kairomonal-based blend for attraction of A. transitella. This project has made considerable progress in objective 1 of the parent project, by developing a lure for NOW to reduce the risk of aflatoxin contamination of pistachios.