Vineyard IPM Scouting Report for week of 26 July 2010 UW-Extension Door County and Peninsular Agricultural Research Station Sturgeon Bay, WI

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1 Vineyard IPM Scouting Report for week of 26 July 2010 UW-Extension Door County and Peninsular Agricultural Research Station Sturgeon Bay, WI Multi-colored Asian lady beetle (MALB) Harmonia axyridis Of all the pests in grape production, MALB is the one pest that does little damage in the vineyard. However, even a small number of harvested grape clusters containing MALB can be detrimental during vinification. MALB when crushed emits a foul smelling yellow fluid that results in Ladybug taint (LBT) in wine. Studies have determined that it takes relatively very few MALB to taint wine. In one study, in which 10% of the population could detect LBT from MALB the threshold was 1.9 beetles/2.2 lbs grape or 0.27 beetles/cluster of Frontenac. The sensory aromas and flavors imparted to wine from LBT have been described as peanut, bell pepper, asparagus, and earth/herbal. As the number of MALB increase in red or white wine the fruit and floral intensities decrease. To reduce the impact of MALB, vineyards must be monitored for MALB infestations daily as harvest approaches. MALB infestations in the vineyard can be reduced by managing other grape pests. Insects, diseases, and birds that injure grape berries provide MALB the opportunity to feed on injured berries. Therefore, keeping your vineyard relatively free of other pests will reduce MALB infestations. Injury from hail can also injure grape berries providing MALB a food resource. There is some evidence that MALB will feed on soft-skinned grapes that have not been compromised by other pests or mechanical injury. The take home message here is to keep vineyard pests under control to reduce MALB infestations. The success of MALB can be partially attributed to it being a generalist feeder. Besides feeding on injured grapes, MALB is predatory and feeds on soft bodied insects such as mites and aphids. Throughout the Midwest, MALB are often found feeding on aphids in soybean fields during mid to late summer. As fall approaches, the aphids migrate to buckthorn that serves as the overwintering host. Last fall, there was a large migration of soybean aphid (Aphis glycines) to buckthorn. Although there was a very large migration of aphids last fall, many of these adult winged aphids were destroyed by entomopathogenic fungi. What does this mean in terms of MALB this season? It is difficult to say, but often when a food source becomes limited this results in reducing insect populations that are dependent on the food source. It is still early in the season for the soybean aphid, and soybean aphid populations may explode if warm dry weather returns. 1

2 Should this happen, MALB populations would likely increase. If soybean aphid numbers remain low, MALB will likely search out alternative food sources. Feeding preference studies have determined that honey, watermelon, cantaloupe, peach and grapes are preferred over soft bodied insects such as the soybean aphid. Since 2000, when the soybean aphid was first confirmed in Wisconsin, many grape growers have observed that MALB infestations in vineyards coincide with the senescence of soybeans. The proximity of your vineyard to soybean fields will play a role in MALB infestations. As soybeans mature and leaves turn brown, the soybean aphid begins migrating to its overwintering host the buckthorn. MALB, however, does not follow the aphid food source, but instead MALB searches out other carbohydrate food sources such as grapes. Some years grapes may mature before soybean senescence and MALB infestations may be limited. In most years, however, MALB will always have some level of infestation in the vineyard. Therefore, monitoring, scouting and applying management techniques for MALB become critical as the grapes approach maturity. If MALB has been an annual problem, realize that you can not eliminate the pest. Scout and monitor your grapes and treat the crop to reduce the pest. You will want to reduce the numbers of MALB in the vineyard and not the winery. Realistic goals are to limit the number between 200 to 400 MALB/ton grapes. MALB is a pest that reduces grape quality as a contaminant and has little or no impact on grape yield. Monitoring MALB in vineyards Use yellow sticky cards to detect MALB arrival and quantify population buildup. Place cards in vineyards 4 weeks prior to harvest with 4 to 6 cards per acre. As harvest approaches, visually monitor grape clusters to determine MALB population densities. Clusters damaged by grape berry moth larvae, black rot, and birds often will have greater densities of MALB. Management of MALB Do not apply control measures for MALB until 1 to 2 weeks before harvest. MALB may be present in the vineyard throughout the growing season and is eating several pests of grapes. Observe pre-harvest interval of products as harvest approaches. 2

3 3 Products for managing MALB Material Rate/acre PHI 1 1 Pre-harvest interval 2 Baythroid XL, Renounce WP, and Mustang Max labels do not list MALB on the label but have been effective in controlling MALB in trials. ounces Clutch 50WG Venom 70SG Baythroid XL Renounce 20WP Mustang Max days References used for this report The lady beetle news. MALB feeding preferences. Wine grapes in the midwest: Reducing the risk of the multicolored Asian lady beetle Impact of Multicolored Asian lady beetles as a pest of fruit and people Soybean aphid overwintering update 5/20/2010 Eileen Cullen, Extension Entomologist Midwest small fruit and grape spray guide Galvan, T. L., E. C. Burkness, Z. Vickers, P. Stenberg, A. K. Mansfield, and W. D. Hutchison Sensory-Based Action Threshold for Multicolored Asian Lady Beetle-Related Taint in Winegrapes. Am. J. Enol. Vitic. 58:

4 4 Development of wine grapes at the Peninsular Agricultural Research Station (PARS) Sturgeon Bay, WI and the West Madison Agricultural Research Station (WMARS), Madison, WI. Buds damaged by frost at PARS on 5/8 and 5/9/ Brianna at PARS Brianna at WMARS Foch at PARS Foch at WMARS La Crescent at PARS La Crescent at WMARS New buds selected at PARS this week for following phenology since buds featured in previous issue (week of ) of the IPM report were damaged by frost.

5 5 Development of wine grapes at the Peninsular Agricultural Research Station (PARS) Sturgeon Bay, WI and the West Madison Agricultural Research Station (WMARS), Madison, WI. Buds damaged by frost at PARS on 5/8 and 5/9/ La Crosse at PARS La Crosse at WMARS Veraison Marquette at PARS Marquette at WMARS Baltica nearing harvest at WMARS Wild grape at PARS Baltica at WMARS New buds selected at PARS this week for following phenology since buds featured in previous issue (week of ) of the IPM report were damaged by frost.

6 6 Degree Day 1 (base 50) Accumulation since April 1, 2010 at Peninsular Agricultural Research Station in Sturgeon Bay, WI Date Year Average 2 7/25/ Modified method. 2 Average from 2005 to Degree Day 1 (base 50) Accumulation since April 1, 2010 at West Madison Agricultural Research Station, Madison, WI Date Year Average 2 7/25// Modified method. 2 Average from 2006 to Accumulated degree days 1 (base 50) for the month of March at Peninsular Agricultural Research Station. Year Degree days (base 50) Modified method. Low temperatures reported at Peninsular Agricultural Research Station, Sturgeon Bay, WI. Date Low F 5/3/ /4/ /5/ /6/ /7/ /8/ /9/ Frost damage reported to some grape varieties in grape variety trial. Please scout your vineyards on a regularly scheduled basis in an effort to manage problem pests. This report contains information on scouting reports from specific locations and may not reflect pest problems in your vineyard. If you would like more information on IPM in grapes, please contact Dean Volenberg at (920) or dean.volenberg@ces.uwex.edu