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Project description

Functional use of geographic information systems to model the range and abundance of vine mealybug and its natural enemies. (03XN017)
Program Exotic Pests and Diseases Research Program
A.P. Gutierrez, Division of Ecosystem Science, UC Berkeley
K.M. Daane, Insect Biology, UC Berkeley
Host/habitat Grapes
Pest Vine Mealybug Planococcus ficus
Discipline Entomology
Natural Systems
Start year (duration)  2003 (Three Years)
Objectives Use a weather driven model of grapevine growth and phenology as the basis for developing a model of vine mealybug and selected natural enemies.

Integrate the vine mealybug-natural enemy model in a newly developed geographic information system to predict vine mealybug seasonal abundance and phenology throughout the state, and to evaluate natural enemy efficacy.

Extend information through inclusion of the predictive model in a vine mealybug Web site.

The invasive vine mealybug is rapidly spreading throughout California's wine grape regions. Vine mealybug has a number of biological attributes that has increased its undetected dispersion, rapid population increase and devastating levels of crop damage. Chemical, biological, and cultural control programs are being developed to suppress damage, and a statewide monitoring program has been initiated to detect new populations. Still, these programs are costly. We propose to utilize an improved geographic information system (GIS) in combination with physiologically based development models to help predict statewide mealybug seasonal abundance and damage. This innovative tool will provide valuable information towards the development of a statewide monitoring program and in the selection and timing of control programs matched to specific regions.
The weather driven models for the vine mealybug and its parasitoid(s) and a coccinellid predator have been formulated and programmed as a simulation to include the biology. The insect models have been integrated into the grapevine model developed by A.P. Gutierrez, B. Wermelinger and colleagues based on extensive field data from Davis, California and Switzerland. The phenology, dynamics and distribution of the VMB within the plant canopy (leaf, bark and root) have been captured as three separate but interacting VMB populations. Movement between subpopulations during the crawler stage is motivated by relative sink strengths (supply/demand) of the various vine subcomponents. For example, as vegetative growth begins, movement from the bark and root occurs, and as fruit begin to draw nutrients, movement to fruit by crawlers occurs. As sink strengths decline in leaves and fruit late in the season, movement back to the bark and root occurs. This seasonal within plant dispersion of VMB affects the efficiency of its parasitoids and predators (see below). (Anagyrus pseudococci and Leptomastidea abnormis) The biology of two parasitoids and a coccinellid predator have been added to the system, and additional species may be added as they are introduced. Alternate hosts are not explicitly included in the model, but are included as a background crawler immigration rate that can itself be time varying.

Data from California and South Africa (Walton 2003) will be used to parameterize the VMB/parasitoid system. For example, the effect of temperature on VMB and two parasitoid species development and survival is in progress as part of a project funded by the UC Statewide IPM Program, American Vineyard Foundation, and the California Table Grape Commission (to K. Daane). The competition and dominance of the parasitoids in cases of multiple parasitism remains to be resolved.

The grape/vine mealybug/natural enemy models have been integrated into the GIS. Figure 3 shows preliminary population dynamics output of the model using weather from Davis, CA, but we note that model still needs to be tested against field data. The system has also been successfully run across all of the ecological zones of California where grape is grown using weather data from the UC/IPM to drive the dynamics. Efforts are being made to capture finer scale interpolated NOAA data on a finer grid than represented by the UC/IPM weather data (funded from other sources).

The GIS system allows maps and data to be transferred via the web. Considerable progress will be made to make the linkages fully interactive. Discussion has been held with University of California Kearney Agricultural Center staff Lynn (Programmer Analyst, GIS Research Analyst) and server support (John Rasmussen, Programmer Analyst II) to avoid overlap and to coordinate the GIS development effort. This work will be completed in the next phase of our system development, but it will require a more powerful server.

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