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Project description

Development of Sampling Procedures for Western Flower Thrips, Frankliniella occidentalis, in Greenhouse Flower Production. (96DS029)
Program UC IPM competitive research grants program
M.P. Parrella, Entomology, UC Davis
B.C. Murphy, Entomology, UC Davis
Host/habitat Greenhouse Crops; Flowers; Roses; Chrysanthemums
Pest Thrips
Discipline Entomology
Decision Support
Start year (duration)  1996 (Two Years)
Objectives Determine the within- and between-plant distribution of western flower thrips on roses and chrysanthemums for common cultivars during the growing season and determine the optimal sample unit for estimating western flower thrips (WFT) abundance.

Develop and evaluate a practical, grower-oriented sampling procedure using sticky cards, plant samples, or a combination of the two for monitoring WFT to determine the need for control measures.

Estimate the relationship between WFT density on plants and the degree of feeding injury on foliage and flowers.

Verify effectiveness of the sampling procedures under commercial greenhouse conditions.

During 1997 we completed all major objectives for WFT in fresh cut roses. Spatial distribution data for WTF were obtained from five commercial rose greenhouses in three regions (San Mateo, Monterey, and Santa Barbara counties) over the past two years. Data were used to quantify and assess the within-plant and between-plant distribution of WFT. We also determined a high degree of correlation existed between WFT captured on blue and yellow sticky cards and WFT density in roses demonstrating the potential for a sticky card monitoring procedure. Preliminary sample size estimates for estimating WFT abundance were generated for both a plant and a sticky card monitoring program. Sample size estimates showed development of a plant and/or sticky card monitoring program is feasible and likely cost effective. We also successfully estimated the relationship between WFT density in roses and the degree of feeding damage to foliage and flowers and developed preliminary estimates between WFT density and the proportion of the rose crop showing feeding injury. These results indicate development of a quantitative and meaningful economic and action thresholds for roses is feasible. Work is progressing to develop practical, grower-oriented sampling procedures and action guidelines in roses.

Completion of the objectives for chrysanthemums has progressed more slowly. Preliminary data on the within- and between-plant distribution indicate WFT abundance using plant samples can be estimated cost effectively in mums. Data are still being analyzed for some of this work. The degree of variation found in chrysanthemum cultivars and growing practices, in addition to interference from pesticides sprays, has required additional time and effort to obtain a sufficient database.

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