Ohio Grape Electronic Newsletter

Editor: Imed Dami, PhD
Assistant Professor, Viticulture Specialist
Department of Horticulture and Crop Science
Ohio Agricultural Research and Development Center
1680 Madison Avenue
Wooster, OH 44691-4096
Phone: (330)-263-3882
Fax: (330)-263-3887
E-mail: dami.1@osu.edu

28 September 2005

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Content:

MALB Update
Not another Insect in the East!
Watch out for Downy
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Update on Multi-Colored Asian Lady Beetle (MALB)
Contributions by: Roger Williams, Dan Fickle, Kevin McClure, Joseph Fiola, and Imed Dami

Background:

It’s the time of year again that the Multicolored Asian lady beetle (MALB) whose presence is that of a beneficial predator throughout the growing season becomes an unwelcome pest at harvest. For those not familiar with MALB, here is a background on its biology, life cycle, and identification:

Adults & larvae are generalist predators that feed on aphids, scale insects, mites, and other insects (All of the above pests damage agricultural crops, home, garden, and landscape plantings)
In summer they find food, find a mate, and reproduce. There may be several generations per year with a larger proportion of later generations predisposed to over wintering.
Aggregation behavior (searching for overwintering sites and fruit crops) is triggered by the start of shorter days and cooler temps - when temperatures drop quickly followed by a sunny day.
Adult beetles have been found to vector fungal diseases, and therefore their aggregating nature may be favorable to the dissemination of bunch rot and other diseases from one grapevine to another.
MALB does not cause direct fruit injury but instead will infest fruit previously damaged by other insects, pathogens, rots, birds, and wasps.
When disturbed or crushed, MALB respond by "reflex bleeding" which forces hemolymph out of their joints. This alkaloid is highly unpleasant to taste and smell and can irreversibly taint the aroma and flavor of the resulting wine.
Remember that only a handful (10 to 12 beetles per lug) can be a sufficient number for concern in white grape varieties. If these beetles are present at crush they can taint the juice which in turn may be detectable later in the wine.
There is a major amount of color variation within the MALB
- Red color due to high quality of food eaten as larva (i.e., lots of tasty aphids)
- Yellowish color due to fewer aphids consumed but more pollen as a larva
- More spots, lower temperature and a longer duration of pupa stage
- Fewer spots, higher temperature and a shorter duration of pupa stage
Many beetles have a straw-colored pronotum (top covering of middle body part) with markings that fuse into a regular- to irregularly-shaped "M" if viewed from the front, or "W" if viewed from behind.

Current Situation:

So far this season, the population of MALB is very high in soybean fields across the Midwest, fueled by high populations of the soybean aphid. The long, dry summer has also been good for aphids on other plants also, exacerbating the potential risk from MALB to fruit crops this year.

Many of the MALB will come from local soybeans field after they start senescing or as prey items (aphids, etc.) disappear. The primary host of the MALB the soybean aphid has been reported across the northern counties of Ohio so growers should be on the look out for large numbers of migrating MALB’s as cooler weather triggers their hibernation behavior. Remember ripening vineyards are a favorite stop-over for this pest.

Scouting and Management:

Growers concerned about ladybeetles should be scouting fields regularly for the first signs of the beetle. Monitoring should begin 14 days prior to expected harvest for each cultivar
Control fruit rots, as these will attract the beetles.
Mechanical or hand harvesting during the daytime may sufficiently shake the vines to cause the beetles to leave the grape clusters ahead of the harvester. Night harvesting may not create this effect as the beetle burrows deep into the cluster and becomes much less active.
Remember these are lady beetles, which are typically considered VERY DESIRABLE, so labeled control is limited.
Ladybeetles are efficient predators of pest insects for the majority of the growing season, and most chemical controls for this introduced beetle will also kill native predators thereby allowing other insects and mites to become a problem.
Since the crop typically becomes infested just prior to harvest, growers’ options are restricted by the need for materials with a very short PHI (pre-harvest interval).
While these insecticides do a good job of knocking down the population, dead beetles often times can remain in or on the cluster. If harvested along with the fruit, the dead beetles can still taint the wine for at least 2 days.
Products which have shown repellancy and efficacy against this insect are, azadirachtin (Azatrol, Aza-Direct), and imidacloprid (Provado) both of which have a zero day pre-harvest interval (PHI).
It should be noted that these products lose their effectiveness after 24 hr. We have begun to test a new product this season; Venom (dinotefuran) which is a third generation neonicitinoid with a 1 day harvest interval on grapes. Preliminary results are very encouraging. We think that this product will provide a longer window of opportunity for grape harvest post treatment, but growers will probably not be able to obtain this product from their suppliers in time for implementation into their harvest strategies this season. It should however become available for next season.
Dealing with wines after the beetle flavor has been found has been relatively ineffective to date.

More Information:

Here are some good web sites to check for pictures and fact sheets for more detailed information:
The Ohio State University website: http://ipm.osu.edu/lady/lady.htm
Iowa State Insect Notes: http://www.ent.iastate.edu/ipm/iiin/ladybeetles.html
Michigan State University web site: http://www.ipm.msu.edu/beetleFruit.htm

Not Another Insect in the East!
By Dr. Tim Martinson, Extension Viticulture Specialist, Finger Lakes, NY

Most growers aren't familiar with 'sooty mold', because aphids and mealybugs that are associated with it aren't common as insect pests. However, we saw an unusual and uniform infestation of sooty mold in a Ventura vineyard on Keuka lake. Sooty mold is a surface growth that looks, well, sooty and black. It covers the top sides of leaves and fruits, and you can rub it off the surface with your fingers. It does not directly infect tissue or grapes. Sooty mold is associated with 'honeydew' excreted by aphids and mealybugs. They feed on plant sap through leaves, and excrete some of it out their rear ends. This excretion is rich in sugars that support the growth of sooty mold. In this particular vineyard, we found from 50-200 immature mealybugs per leaf, and the black mold apparently started in late August. The insect in question - tentatively identified as the 'grape mealybug' - is native and usually present at very low levels in vineyards. This is the first time I have ever seen a major infestation in a vineyard.

Watch out for Downy Mildew
By Wayne Wilcox, Plant Pathologist, Cornell University

Downy mildew is again showing up in some vineyards in the Finger Lakes, NY and we should watch out here in Ohio. Here is a note dating from 19 September by Wayne Wilcox:

It would behoove growers to take a look in their blocks of downy mildew susceptible cultivars (esp. any vinifera blocks) right quick. In a poorly-sprayed Delaware block that I'm working with in Geneva, DM was at very low levels through late August. But the soaking rain we got from the remnants of Katrina really multiplied what was there, and vines that weren't protected then have a LOT of disease now. The weather that we're having today, and which we're forecast to continue receiving into next week, will spread anything that's there even further if protection is lacking. And the last two winters have shown us how important it is to maintain a healthy canopy for as long as possible in the autumn, in order to maximize cold hardiness (not to mention ripen late varieties). Bottom line: Check out the undersides of suspect leaves in the morning after a rain or dew the previous night. DM symptoms on the tops of leaves right now are a bit different than earlier in the season, often just a network of "pin point" lesions, but the characteristic sporulation on the bottom side following a wet/damp evening is unmistakable. If a grower sees more than a trace of DM within the next couple of days, and had no DM fungicide on prior to now, he's likely to incur a number of new infections if the wetness forecast for the next few days actually materializes. A shot of one of the phosphorus acid compounds should provide good post-infection activity if they can get it on by Tuesday or Wednesday, and because the material is exempt from residue tolerances, there is no PHI.