Department of Mathematics

Department of Entomology

Insect Behavior Modeling *

The Grape Berry Moth (GBM), Endopiza viteana, is a widespread pest of grapes in Michigan. Control of the GBM has traditionally been through insecticides, but legislated restrictions on their use has reduced grower's control options, mandating the search for effective alternatives. We propose to develop an integrated pest management strategy to provide Michigan grape growers with tools for managing vineyard risk of damage from the GBM and reducing loss from this pest.

Effective pest management requires that farmers can predict when pests are present in their crop and determine the degree of pest pressure so that appropriate selection and timing of controls can be made. This will be more important as selective insecticides are introduced which must be applied at the correct time to be effective. While much of the previous research on GBM management was focused in New York state in the late 1980's and more recently in Ontario, Michigan grape producers will be better served by current and region-specific information to help them make management decisions.

One management method that has been effective in predicting the emergence of pests affecting other fruit crops (for example, apples, pears, etc.) is the use of the ``degree-day model.'' This model essentially integrates the ambient temperature verses time function (derived from meteorological data) and signals imminent pest emergence when the integrated value reaches a certain threshold. The model is also useful for predicting various other insect behaviors such as mating and egg-laying.

Once moths emerge, when should pesticides be applied? The answer to this question is not well known in Michigan because degree-day models for the GBM have not been validated in this state. Also, the degree-day models used in New York and Ontario were not very effective in those places. The poor performance of those degree-day models may be related to the fact that the GBM overwinters on the vineyard floor. This fact indicates that the behavior of the GBM is more closely related to the vineyard floor temperature than to the ambient air temperature. The relationship between temperatures at the vineyard floor and ambient air temperature are unknown at present.

The project objective is to test and validate various degree-day models for the GBM in Michigan vineyards using data collected from seven sites throughout Michigan. The data collected includes the timing of insect behavior (emergence, egg-laying, egg-hatch and larval development) and the temperature (and other weather data) from the closest meteorological station. In addition, temperature data is gathered from single portable temperature probes placed in the vineyard leaf litter.

The ideally completed project deliverable would be a ``degree-day model'' (potentially using various kinds of weather data) that predicts various insect behaviors in Michigan.

*This summary prepared by R. E. Svetic with the assistance of Dr. R. Isaacs of the Michigan State University Department of Entomology.

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