Postemergent Herbicides Labeled for Grapes

Every once in a while it is a good thing to check out the herbicides that are labeled for grapes. In the last issue, I wrote about preemergent herbicides. In this issue I will cover postemergent herbicides. Remember, even though I present information here, you need to read the label on the product you purchase to make sure you know when, where, and how to apply it legally.

As a quick review, remember that preemergent herbicides are designed to be applied before the weed seedling emerges. Postemergent herbicides are applied after the weed is present.

Since the Michigan Fruit Management Guide (E-154) page 126 lists herbicides alphabetically by the common name of the chemical, I will list the herbicides in alphabetical order based on the brand name of the herbicide.

Fusilade (fluazifop-P) should only be applied to nonbearing vineyards. It is a systemic herbicide that controls annual and perennial grasses but not broadleaf weeds or sedges. Ideally the grass should be 4 to 8 inches tall.

Gramoxone (paraquat) kills emerged annual weeds by contact. Its response is very rapid. It has no ability to prevent new regrowth from the soil. Two to three applications per season will be needed to maintain control.

Poast (sethoxydim) is a systemic herbicide that controls annual and perennial grasses but not broadleaf weeds or sedges. Ideally grass should be 4 to 8 inches tall. It has a 50-day preharvest interval.

Rely (glufosinate) very similar to paraquat in that it is a non-selective contact herbicide. It provides no residual control. It has a 14-day preharvest interval.

Select (clethodin) non-bearing grapes that will not be harvested for at least one year from application. It provides control of annual and perennial grasses but not sedges or broadleaf weeds.

That wraps up a review of the labeled postemergent herbicides for grapes. For more information on herbicides in grapes including recommended rates, please consult the Michigan Fruit Management Guide (E-154). It is available at your local MSU Extension office or online http://www.msue.msu.edu/epubs/pestpubs/E154/index.htm with each section in pdf format.

For best weed control, you should always practice integrated weed management. That means, in part, knowing the species of weed you are trying to control; knowing the proper timing for best control of that weed; considering usage of herbicides combinations either at the same application time or in separate applications; and not applying herbicides to stressed weeds.

Next column: Weed Management.

There is a very exciting consumer survey being conducted by the wine industry "think-tank" called Wine Vision. Wine Vision is working on mapping out strategies for the growth of the U.S. Wine Industry for the future and one of their initiatives is to gather more information on consumer wine buying behavior. It should be very interesting and valuable to the industry to have the results of this work, to aid marketing activity.

MSU Extension specialists have teamed up with Tim Weigle from the Lake Erie Grape IPM program to produce a handy vineyard scouting guide for grape growers in the north-central and Great Lakes region of the US. At over 100 pages, but small enough to fit in a pocket, this handy guide has been developed to help grape growers identify problems in their own vineyards. Dr. Tom Zabadal wrote the sections on nutritional disorder symptoms and herbicide damage, Dr. Annemiek Schilder wrote the section on grape diseases, and Dr. Rufus Isaacs wrote the sections on insect pests and natural enemies. The guide contains hundreds of photographs and descriptions, and has a scouting calendar for pests and diseases. Members of National Grape Cooperative will each receive a copy, and other copies will be available after July 7th through the MSU Extension Bulletin Office (517-355-0240). The full title is "A Pocket Guide for Grape IPM Scouting in the North Central and Eastern US", by Isaacs, Schilder, Zabadal, and Weigle.   The guide is Bulletin New number E-2889.

Like most people in Agriculture, I pay close attention to the weather. I pay particular attention to winter temperatures because I know that in Michigan, there is always the chance of winter injury. This year we are seeing lots of cold injury and it seems that we are seeing the result several distinct events. Several Horticulturists in Michigan have identified several events they think are responsible for the winter injury we are seeing all around Michigan this year.

As a follow-up to the article in last issue, insecticides available for use in grapes will be compared, with an emphasis on their properties in relation to control of grape berry moth (GBM).

Berry Moth Update

Pheromone monitoring traps placed in vineyards across SW Michigan have been trapping grape berry moth at typical levels during their first flight in the pre-bloom period. This pest that caused such problems last year has survived the cold winter well, and an effective scouting and control program will be required for the 2003 season. Around the time that bloom started in the juice grape vineyards this year, we started to find the first eggs and the first young larvae of this pest (first detected June 12 and 13 in Van Buren and Berrien counties). This first generation of larvae can be controlled with a well-timed insecticide applied after bloom, to target the exposed larvae and eggs in the young clusters.