Khushwinder Singh, Kent Daane, and Luca Brillante*
*Department of Viticulture and Enology, California State University Fresno, 2360 E Barstow Ave, Fresno, CA 93740 (lucabrillante@csufresno.edu)

The control of vine mealybug (Planococcus ficus Signoret) is complex in conventional viticulture, but even harder in organic production. We conducted a large vineyard trial (Pinot noir) to compare the efficacy of commercially available insecticides for organic production: pyrethrins, neem oil, diatomaceous earth, and Chromobacterium subtsugae. We also controlled for side effects on grapevine physiology and grape composition related to spraying dust and oils on leaves and berries. The experiment was set up as a randomized complete block design with four treatments plus control and four replicates. Each replicate was 1 acre large for a total trial size of 20 acres. The products performed similarly and none were effective in controlling mealybugs on the trunk. Pyrethrins were least effective in controlling mealybugs on leaves, while diatomaceous earth and neem oil were most effective, but not significantly different from the control. An inverse relationship appeared between efficacy on leaves and presence in the cluster. The most effective products had more mealybugs inside the clusters and the least effective products on leaves had fewer mealybugs in the clusters. Plants treated with neem oil had significantly lower stem water potentials. Treatments did not have any significant effect on gas exchange measurements, except on one date, when the neem treatment had cooler leaves and more photosynthesis and stomatal conductance. Diatomaceous earth never significantly reduced photosynthesis or stomatal conductance, even though leaves were covered with dust. Although not statistically significant, we observed a strong tendency in sugar content. Total soluble solids were lower in the control than in all other treatments and reached up to 1.9 Brix difference on the second measurement date. This delay in ripening showed as a significant difference in pH, where the control had a significantly lower pH than most other treatments.

Funding Support: American Vineyard Foundation, Bronco Wine Co.,