An applicator for high viscosity semiochemical products and intentional treatment gaps for mating disruption of Phyllocnistis citrella

The leafminer, Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), is a global pest of citrus, and contributes to the incidence and severity of citrus bacterial canker, Xanthomonas axonopodis pv. citri. SPLAT‐CLM™ (ISCA Technologies) is an emulsified wax product that provides sustained release of (Z,Z,E)‐7,11,13‐hexadecatrienal, the major component of the P. citrella sex pheromone. Here, we report success in development of a mechanized and automated applicator of SPLAT and other high viscosity products on a large scale in tree crops, and progress in optimization of coverage patterns to minimize the cost of disruption of P. citrella. The applicator (IFM‐5051; International Fly Masters) delivered 1 g dollops of SPLAT‐CLM into a citrus grove canopy within 2% of the targeted application rate. A field trial conducted in Florida (USA) demonstrated effective disruption (>90%) of male moth catch in traps baited with pheromone lures characterized by high potency following each of four applications of 250 or 500 g ha−1 of SPLAT‐CLM containing 0.15% (Z,Z,E)‐7,11,13‐hexadecatrienal. Catch of male moths in pheromone traps deployed as a transect across the border between treated and untreated plots was analyzed to describe the rate of loss of disruption as a function of distance from a treated area. The model was used to estimate a maximum gap of 65 m consisting of untreated rows bounded on both sides by treated rows that could be incorporated into coverage patterns without a significant loss of disruption. A second field trial was conducted to test the feasibility of leaving intentional coverage gaps. No difference in trap catch disruption was observed between plots uniformly treated with SPLAT‐CLM and plots where every fifth row (80% coverage) or every fifth and sixth rows (67% coverage) were left untreated. Incorporation of coverage gaps should be effective in reducing product use and overall cost of mating disruption for P. citrella in citrus and other species for which mating disruption occurs by a non‐competitive mechanism.