1a. Objectives (from AD-416)
1. Obtain three duplicate samplings of ambient almond grove volatiles via Tenax absorption. The three samplings will correlate to flight times of NOW (mid April, late June, mid September). 2. Determine the identity and relative concentrations of the major VOCs in the ambient grove bouquet via GC-MS analyses. The VOCs will be grouped as average of all three runs as well as according to flight of NOW. 3. Develop a minimum number of volatiles necessary for a corresponding synthetic blend. This blend will be utilized in these research laboratories during puff or EAG studies of NOW. 4. Make available via publication the successful volatile mixture for other researchers to utilize for NOW studies.
1b. Approach (from AD-416)
The navel orangeworm (NOW) continues to be one of the most important insect pests of almonds. In 2002, one of the twelve top research priorities in the almond industry included “develop…more refined monitoring systems for NOW” and “study methods to improve pheromone mating disruption techniques and cost effectiveness for NOW…” Additionally, one of the top educational priorities for the almond industry as “new pest management tools as they become available”.1 Statements and plans such as these underscore the need to address the problems associated with NOW for almonds. Research on attractants for NOW monitoring and lure and trap purposes has not yet yielded a commercially viable and dependable product.2 In the laboratory setting, NOW puff (a volatile sample passed across the insect) or electroantennogram (EAG) studies typically utilize laboratory ambient air as the background volatile. This presents the problem that ambient laboratory air is not providing an appropriate bouquet of VOCs that would normally be perceived by the NOW in an almond grove environment. Consequently, any potential VOC puff the NOW receives from researchers may not elicit an appropriate response due to the absence of typical “grove” volatiles, thus researchers may be missing key signals from the NOW. Although the non-quantified VOC make-up of almond groves has been reported,3 and the VOC composition of removed almonds has been investigated,4 the specific, quantified, ambient almond grove VOC composition has not been investigated. This proposed research will provide current and future NOW bioassay investigations with a quantified analysis of ambient almond grove volatiles, thus offering a realistic VOC composition as the background effluent to test potential NOW attractants.
3. Progress Report
A total of 16 large-scale collections were performed in 2009, four duplicated in Kern County and four matching duplicated collections in Colusa County (see ABC 2009-2010 Research Proceedings). Analysis of these collections via gas chromatography-mass spectroscopy (GC-MS) provided a series of tree emissions representative of an almond orchard. All compounds (greater than ~1% of highest peak relative abundance) identified were analyzed via EAG for baseline individual EAG responses (n = 2). The major components of these collections were identified, quantified, and several synthetic background signaling volatile (BSV) candidate mixtures were developed and subjected to EAG analyses (n = 5). Additionally, the major component quantities were tracked over the course of the growing season and were suggestive of a dynamic ratio of BSVs. The components of the blends and the potential dynamic BSV ratios will be discussed in greater detail in a forthcoming peer-reviewed manuscript. One of the blend iterations demonstrated moderate electroantennogram (EAG) signals relative to typical EAG responses of male NOW to the main aldehyde pheromone component. This BSV blend (termed Blend A for this report) was then analyzed via more replicates of EAG and concurrent flight tunnel studies. A total of 16 collections for 2010 will soon be completed, including eight duplicated in Kern County and eight matching duplicated collections in Colusa County. Analysis of 2010 data and comparison to pistachio orchard emissions are underway. Preliminary EAG studies suggest that attention be turned to the analysis of mated vs. virgin female NOW moths. The flight tunnel studies also utilized mated and unmated females and interesting results were obtained from both Blend A vs. blank controls and Blend A vs. almond meal, the current standard female monitoring tool. Mated female moths exhibited ovipositional preference for the egg traps containing Blend A. However, the number of female captures was nearly equal for all comparisons. Again, a detailed analysis of the ovipositional preference will be discussed in the forthcoming manuscript. Current investigations on the third and final year of the funded project include completion of volatile collections in both almond and pistachio orchards, analysis of data from both, formulation of new synthetic blends based on almond and/or pistachio analyses, in vitro bioassay of newly formulated synthetic blends, and combination of blends with known attractants for increased efficacy. The goals of this project, analyzing almond orchard volatiles for semiochemicals for the insect pest navel orangeworm, are directly related to Objective 3 (sub-objective 3-2) of the in-house project.