MSU Berry Crops Entomology Lab Managing potato leafhopper in wine grapes Rufus Isaacs & Steve Van Timmeren Dept. of Entomology Michigan State University Paolo Sabbatini & Pat Murad Dept. of Horticulture, Michigan State University
PLH management components Regular scouting for leafhoppers in spring, especially after weather fronts from the south Scouting for symptoms that develop from feeding If PLH detected, response based on vine susceptibility Consider vine ability to recover and the effect on fruit quality If needed, use effective chemical controls
Potato leafhopper Broad host range: many crop and non-crop plants Adults and nymphs feed on grape leaves Preference for new growth Feeding causes stunted vine growth, yellowing, and leaf cupping Lay eggs inside leaves Can have multiple generations per season
Scouting for potato leafhopper After spring rain storms, populations may increase quickly Check under leaves and on new shoots 100 leaves per vineyard block PLH adults are light green, move sideways if disturbed potato leafhopper grape leafhopper Color bright green light yellow Movement sideways forward Prefers wine grape juice grape Overwinter southern states here
Avg. no. yellow leaves/vine Manage PLH based on cultivar susceptibility Potted vines were exposed to natural PLH population, and the degree of leaf yellowing was recorded. 3 2.5 2 ab a Most susceptible Pinot gris, Pinot noir, Chardonnay, Cayuga white Intermediate Reisling, Vignoles, Cab franc 1.5 1 0.5 0 bc abc c c c bc Highly resistant Niagara, Concord, other labruscas Seyval blanc, Vidal blanc Cultivar
Yellow leaves per vine Susceptibility is related to sensitivity to PLH Potted vines bagged with 0, 5, 10, or 20 PLH for 12 days. Symptoms measured next day. More susceptible cultivar (Pinot gris) has a stronger response to lower infestation levels than resistant cultivar (Vignoles). 2.5 2 1.5 1 0.5 0 Action threshold varies with susceptibility Pinot gris Riesling Vignoles 0 5 10 15 20 25 PLH/vine
% cupped leaves Total wet weight (g) % yellowed leaves Vine tolerance to insect feeding Can vines compensate for initial PLH damage? 1. Potted Pinot gris vines exposed for one week to 0-4.5 PLH per leaf 2. Leaf yellowing and cupping symptoms measured 3. At end of the growth cycle, vines destroyed and tissues weighed Leaf symptoms increase with PLH density Only the highest PLH levels reduce vine weight 300 Leaves Shoots Wood Roots 200 ab ab a bc abc c 100 PLH/leaf 0 0 0.5 1 1.5 3 4.5 PLH/leaf Lenz et al. AJEV 2009
Effect of crop level and PLH level on quality of Pinot noir clusters, 2009 6 vine plots established in a mature Pinot noir vineyard PLH controlled in half of the plots using insecticide Vines cropped to high (4.7T) or low (2.0T) levels on Aug 14 and 19 No significant effect of PLH or crop load on fruit quality parameters measured at harvest, 2009 Crop load PLH Brix TA ph Low No 20.4 8.7 3.6 Low Yes 19.6 8.6 3.5 High No 20.6 8.9 3.6 High Yes 20.6 8.8 3.6 Similar results in 2008 and 2009 Factorial design of H/L crop and +/- PLH infestation
Foliar insecticides for control of PLH Spray trial in 2009 to compare insecticides for their control of PLH. Applied using a backpack sprayer on July 8. PLH infestation measured after treatment. High residual activity from all insecticides tested. PLH per 20 leaf sample Days After Treatment Treatment 1 5 9 Untreated 4.3 a 1.8 a 2.1 a Sevin XLR 0 b 0 b 0.2 a Baythroid XL 0.2 b 0 b 0 a Clutch 50WDG 0.5 b 0.8 b 0.6 a Actara 25WDG 0.8 b 0.4 b 1.4 a Pyganic 0.1 b 0.4 b 1.1 a
Soil applied systemic insecticides for PLH control Chemigation of hybrid vines with insecticides June 6 application (8-10 inch shoots) Admire (16oz), Platinum (16 oz), Belay (20 oz) Measured PLH per leaf every 3 days
No. / 30 leaves PLH Adults/30 leaves No. / 30 leaves PLH Nymphs/30 leaves Activity of soil-applied insecticides on PLH 45 PLH Nymphs 8 Adult PLH 40 35 30 Platinum Admire Belay Untreated 7 6 5 Platinum Admire Belay Untreated 25 20 4 15 3 10 2 5 1 0 0 10 20 30 40 Days After Treatment 0 0 10 20 30 40 Days After Treatment
PLH management components Regular scouting in spring, especially after weather fronts from the south. If PLH is detected, response based on vine susceptibility and vine age (establishing vs. established). Consider vine ability to recover and the effect on fruit quality. If needed, use effective chemical controls.
Acknowledgements Jon Wyma, Geordan Hudson, Adam Young John Wise Marcel Lenz and G. Stanley Howell Doug Welsch and Todd Robbins