West central Michigan vegetable regional report – June 17, 2015
Insect pests are developing. Scouting combined with early action can allow you to use a broader range of products, conserve beneficials and benefit your bottom line.
June 17, 2015 - Author: Ben Werling, Michigan State University Extension
Asparagus field shutdown is ongoing as large scale harvest comes to a close this week.
Carrot fields continue to develop nicely.
Cole crops were being damaged by later instars of diamondback moth larvae and imported cabbageworm this week at one location. Coragen is a good product that can provide residual control for a few weeks. Bt products such as Dipel and Javelin are available for organic growers and are good for conserving beneficials, but are best applied when larvae are small.
Cucurbit flowers were being visited by striped cucumber beetles this week.
Onion thrips were present in multiple locations this week. A threshold of one thrip per leaf can be used to make the first application of Movento. Make sure to use the right surfactant. Refer to a fact sheet on onion thrips control by Michigan State University Extension for more information.
Peppers were clean of aphids at one location I checked this week. Prior to fruit set, Extension literature suggests that if aphid populations remain between five and 10 aphids per leaf for two weeks, applications of insecticides targeting aphids can be helpful, but otherwise will have limited value. After fruit set, immediate action should be taken if aphid numbers average over five per leaf as honeydew deposits on fruit create sooty mold. To scout, check two lower and two upper leaves on five plants at five locations, or 25 plants and 100 leaves. Average across these numbers and compare to the above action threshold.
Overall, broad spectrum insecticides like some pyrethroids can actually make aphid problems worse or even create aphid outbreaks by killing their predators and parasites. Selective insecticides targeting aphids do exist, and include Beleaf and Fulfill. With Fulfill, it may take up to a week for aphids to die. These should be softer on beneficials, but will not affect caterpillar pests.
European corn borer populations overall have declined in recent years, so putting out pheromone traps to monitor this pest could help you save insecticide applications if populations are not present. Control of this pest is most important when fruit set is imminent.
Potato and tomato growers should continue to be vigilant about destroying volunteer potatoes, a source of overwintering inoculum of late blight.
Sweet corn growers should be on the lookout for true armyworm damage over the next week. I have found 0.75- to 1-inch size armyworms in three corn fields in west Michigan, but found zero armyworms in even nearby locations. This means scouting is important.
European corn borer larvae could be active; tassel emergence is the best time to target this pest with insecticide applications as larvae move from the whorl to the stalk and are exposed. I did not catch any European corn borer moths in an Oceana County trap this week.