A Technical Review of MULV-Disp, a Recent Mosquito Ultra-Low Volume Pesticide Spray Dispersion Model.

The authors of a recently published paper summarized the development of a regression model for ground-based ultra-low volume applications, suggesting that their model was sufficiently verified that it could be used extensively for mosquito control. These authors claimed that their statistical model was superior in its predictive capability to the extensively developed and Environmental Protection Agency-validated AGDISP mechanistic model. In this technical review, the assumptions, reduction and interpretation of data, and conclusions reached with regard to their model are discussed, and explicit misstatements and incorrect mathematical relationships are pointed out. Two published versions of the model regression equation give substantially different results without explanation. Petri dish collection was used for very small droplets, with no mention of collection efficiency. Meteorological data were misused based on manufacturer's specification of instrument accuracy. We strongly disagree with many of the model results and show that the model misrepresents the actual behavior of aerosol sprays applied in the manner tested.

Predicting Dendroctonus pseudotsugae (Coleoptera: Curculionidae) antiaggregation pheromone concentrations using an instantaneous puff dispersion model.

An instantaneous puff dispersion model was used to assess concentration fields of the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, antiaggregation pheromone, 3-methylcyclohex-2-en-1-one (MCH), within a 1-ha circular plot. Several combinations of MCH release rate and releaser spacing were modeled to theoretically analyze optimal deployment strategies. The combinations of MCH release rate and releaser spacing used in the modeling exercise were based on results of previous field studies of treatment efficacy. Analyses of model results suggest that a release rate up to six times the initial standard, at a correspondingly wider spacing to keep the total amount of pheromone dispersed per unit area constant, may be effective at preventing Douglas-fir beetle infestation. The model outputs also provide a visual representation of pheromone dispersion patterns that can occur after deployment of release devices in the field. These results will help researchers and practitioners design more effective deployment strategies.

Evaluation of Trapping Schemes to Detect Emerald Ash Borer (Coleoptera: Buprestidae).

Management responses to invasive forest insects are facilitated by the use of detection traps ideally baited with species-specific semiochemicals. Emerald ash borer, Agrilus planipennis Fairmaire, is currently invading North American forests, and since its detection in 2002, development of monitoring tools has been a primary research objective. We compared six trapping schemes for A. planipennis over 2 yr at sites in four U.S. states and one Canadian province that represented a range of background A. planipennis densities, canopy coverage, and ash basal area. We also developed a region-wide phenology model. Across all sites and both years, the 10th, 50th, and 90th percentile of adult flight occurred at 428, 587, and 837 accumulated degree-days, respectively, using a base temperature threshold of 10°C and a start date of 1 January. Most trapping schemes captured comparable numbers of beetles with the exception of purple prism traps (USDA APHIS PPQ), which captured significantly fewer adults. Trapping schemes varied in their trap catch across the gradient of ash basal area, although when considering trap catch as a binary response variable, trapping schemes were more likely to detect A. planipennis in areas with a higher ash component. Results could assist managers in optimizing trap selection, placement, and timing of deployment given local weather conditions, forest composition, and A. planipennis density.

Evaluating High Release Rate MCH (3-Methylcyclohex-2-en-1-one) Treatments for Reducing Dendroctonus pseudotsugae (Coleoptera: Curculionidae) Infestations.

Current recommendations for applying the antiaggregation pheromone 3-methylcyclohex-2-en-1-one (MCH) to protect live trees from Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins, infestation are to space individual passive releasers (MCH bubble capsules) on a 12- by 12-m grid throughout areas to be protected. Previous field studies and a theoretical study using a puff dispersion model to predict pheromone concentrations have shown that releasers emitting higher rates of MCH spaced farther apart may be as effective as the established standard treatment. During 2012 and 2013, we tested higher release rates of MCH at correspondingly wider spacings to keep the total amount of MCH released per unit area equal in all treatments. In 2012 near Challis, ID, treatments included the established standard release rate and spacing, four and six times the standard release rate at correspondingly wider spacings, and an untreated control. In 2013 near Ketchum, ID, treatments included the established standard release rate and spacing, five and seven times the standard release rate at correspondingly wider spacings, and an untreated control. Results from both years indicated that all MCH treatments were equally effective in reducing Douglas-fir beetle infestation. Using higher release rate formulations at wider spacings will reduce labor costs of installing MCH treatments, and, in cases where it is necessary, retrieving the releasers as well. In addition to reducing labor costs, the revised treatment protocol may increase the feasibility of treating areas that currently may not be possible due to treatment costs.

The agricultural dispersal-valley drift spray drift modeling system compared with pesticide drift data.

The coupling of the valley drift (VALDRIFT) atmospheric dispersion/deposition model with the agricultural dispersal (AGDISP) aircraft wake model generates a modeling system for predicting the off-target drift of pesticides sprayed in a mountain valley. The approach uses the AGDISP near-field spray model to estimate the mass fraction of pesticide remaining airborne after initial application, then the VALDRIFT complex terrain model to estimate the drift of pesticide from the target area. The modeling system inputs include detailed spray information, a measure (or estimate) of winds in the valley, and the valley topographic characteristics; the results are pesticide concentrations throughout the valley atmosphere and pesticide deposition to the valley surface. The AGDISP and VALDRIFT models are operated independently, with the results from AGDISP being used as input to VALDRIFT through user-created data files. The modeling system was evaluated using pesticide drift data from spray trials conducted in the Mill Creek Canyon of Utah's Wasatch Mountains, USA, during the late spring of 1993. The predicted deposition compared within a factor of three of the observations (70% of the time) at all sampling locations extending several kilometers down-valley from the spray treatment block. The overall average ratio of predicted-to-observed deposition was 0.9.