Project Number: 8042-22000-315-021-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jul 18, 2022
End Date: Sep 30, 2025
Semiochemicals, including plant volatiles and insect pheromones, have been used successfully in other systems to lure pests away from a crop. Previous work has indicated that semiochemicals play a key role in CPB host and mate location, suggesting that they could be used as part of a sustainable CPB management strategy. Specifically, volatile cues from potato plants are attractive to CPB adults and larvae (Visser and Ave 1978; Dickens 2000, 2002). In addition, adults of both sexes are attracted to a male-produced aggregation pheromone (Dickens et al. 2002), and males are attracted to an as-yet unidentified female-produced pheromone (Jermy and Butt 1992, Edwards and Seabrook 1997, Weber et al. 2020, Haber and Weber 2021). A preliminary field study demonstrated promise for using the male-produced pheromone to manipulate CPB behavior (Kuhar et al. 2006), but additional work is necessary to develop effective lures and implement them on a large scale. Therefore, the objectives of this project are: (1) to synthesize a field-useful quantity of CPB male-produced aggregation pheromone; (2) to attempt to discover and synthesize the female sex pheromone; (3) to use (1) and possibly (2) in combination with plant kairomones (green leafy volatiles) in trapping or trap-cropping against Colorado potato beetles at two locations in the field (Beltsville and eastern shore Virginia). This would be expanded with additional cooperators if the initial experiments were promising.
Experimental Approach: Objective 1: Synthesize a field-useful quantity of CPB male-produced aggregation pheromone Neither of these syntheses is difficult, and we propose to make sufficient aggregation pheromone for our field research. Earlier work did not demonstrate dose response or the importance of pheromone purity, both of which are important practical and economic considerations. Furthermore, no one has tested in the field, the combination of pheromone and plant-derived volatiles (known as kairomones), which might prove additive or even synergistic, as in the case of other pests studied, further economizing attraction with off-the-shelf kairomones. Objective 2: Attempt to discover and synthesize the female sex pheromone. While admittedly more risky, this work has so far been rewarding, and we are not requesting funding specifically for analytical or synthetic work. Preliminary analytical chemistry suggests that low volatility cuticular hydrocarbons may be implicated, and any advances will be incorporated into field research. Since we know that live females are attractive to CPB males in the field, plant kairomones and male-produced aggregation pheromone can be combined with live females to test combinations of these three volatiles. Objective 3: Use pheromone(s) in combination with plant kairomones in trapping and trap-cropping. We will take two approaches to testing combinations of attractants. First, we will station individual plants, poisoned with imidacloprid, and coupled with pheromones and/or kairomones in a replicated field microcosm of a trapping or trap-cropping scenario. This will be done in or adjacent to previous year’s potato fields, with overwintering populations in the early season. There will be three targeted experiments: (a) test of dose response; (b) test of importance of isomeric purity (earlier publication was unclear as to field effect); and (c) combination (one-, two- and three-way) of plant kairomones, male-produced aggregation pheromone, and female sex pheromone. Second, we will deploy volatile treatments in a replicated trap-border-row design, similar to what growers might use to focus infestation on a small portion of the crop that is insecticide-treated. Each experiment will include border trap crops treated with one of the following: 1) male-produced aggregation pheromone (CPB I) + imidacloprid (systemic insecticide); 2) CPB I + green leafy volatiles + imidacloprid; 3) imidacloprid only with no semiochemicals; 4) untreated (negative) control; and 5) entire plot treated with imidacloprid (positive control). Each experiment will be arranged in a randomized complete block design replicated 4 or 5 times. In March, 0.5 acre plot of potatoes will be mechanically planted on 30-inch rows; experimental sub-plots will consist of eight 25-ft rows of potatoes, the middle four rows will be untreated and the outer two rows will be the trap crop treatments. Pheromones will be applied in early May at peak adult CPB colonization. CPB will be assessed in both the treated rows and adjacent untreated rows of each plot. Plots will be sampled weekly from early May to mid-June by examining 10 stems per plot for all stages of CPB.