Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/11/2011
Publication Date: 10/17/2011
Citation: Lapointe, S.L., Stelinski, L.L. 2011. A GPS-guided applicator for high viscosity semiochemical products and optimal coverage patterns for mating disruption of the leafminer Phyllocnistis citrella (Lepidoptera: Gracillariidae) in citrus. Entomologia Experimentalis et Applicata. 141:145-153. Interpretive Summary: The citrus leafminer is a pest of citrus crops throughout the world. The sex pheromone of this pest has been elucidated, synthetically produced and incorporated into a slow-release matrix for application to citrus groves. When the sex pheromone is allowed to permeate the grove, the ability of male leafminers to locate females is disrupted resulting in population control without insecticides. We developed and field-tested a novel tractor-mounted and computer-controlled applicator for delivery of the pheromone to trees. The device was designed and manufactured by International Fly Masters of Ft. Pierce, FL and consisted of computer-controlled pumps that drew the pheromone product (SPLAT-CLM™, ISCA Technologies, Riverside, CA) and delivered it to nozzles located above blowers located on either side of a frame mounted to a tractor by a three-point hitch. We used this device to apply SPLAT-CLM to approximately 200 acres of citrus in St. Lucie County. The device deposits 1 gram dollops of the SPLAT material into the tree canopy. The results of our experiments demonstrated effective disruption of the leafminer and provided insight into the importance of product viscosity. High viscosity SPLAT results in retention of the 3-dimensional shape of the dollop thereby allowing for prolonged release of the pheromone over several weeks following application. Low viscosity dollops tended to "sheet" and as a result, rapidly lost the pheromone component and the ability to disrupt the leafminer. We generated a mathematical model that predicts how much of a grove needs to be treated by leaving untreated rows thereby reducing the cost of control and making this environmentally friendly method of pest control more affordable for citrus growers.
Technical Abstract: The leafminer Phyllocnistis citrella 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, Inc.) 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 to determine optimal coverage patterns to minimize cost of disruption of P. citrella. The applicator (IFM-5051, International Fly Masters, Inc.) delivered 1 g dollops of SPLAT-CLM into the citrus grove canopy within 5% of the targeted application rate per ha. A field trial conducted in Florida demonstrated effective disruption (>90%) of male moth catch in pheromone traps following each of four applications of 250 or 500 g/ha of SPLAT-CLM containing 0.15% (Z,Z,E)-7,11,13-hexadecatrienal. The rate of loss of disruption activity over time after application appeared to be associated with viscosity of experimental formulations of the SPLAT product. An early application with low viscosity (~160,000 cP) was observed to lose the ability to disrupt trap catch more quickly compared with subsequent applications of a higher viscosity (~300,000 cP) formulation. 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 the maximum gap consisting of untreated 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 in plots uniformly treated with SPLAT-CLM compared with plots were every 5th row (80% coverage) or every 5th and 6th 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.