Integrated Pest Management

Integrated Pest Management

Spider Mite Controls

By Lisa Hagerty, The Real Dirt Editor and MG trainee

The end of summer is nearing, which is apparent with the cooler temperatures we have been feeling the last couple of days. I have at least three trees in my yard that had green leaves only weeks ago, but today the leaves are red. On one hand, it makes me a little sad to see summer fade but on the other, the cooler weather may bring my garden the relief it needs from mites. 

An article written by Howard Russell for MSU Extension, “Spider mite populations thrive in hot dry summers,” tells it exactly the way it is. With the high temperatures of July and August, many of us felt the impact that mites have on a garden. The constant struggle to combat them seems never ending at times. They remind me of tiny vampires as they “suck on the sap that bleeds from the wound” created when they scrape “the leaf surface with their pointed mouthparts” (Russell). A clear sign that spider mites are present is the when the leaves are yellowing, browning, speckling and in worst cases, webbing is visible. Although Russell offers some suggestions on chemical control, he reminds us that the ultimate goal is to preserve and restore natural enemy populations to control the spider mites.

Tomato_mites by lisa hagerty

Tomato_mites by lisa hagerty

Christina DiFonzo of MSU Extension discusses spider mites in southern Michigan in her article, “Potential for spider mites, especially in southern Michigan.” She warns against the potential consequences of treatment, which is a concern for anyone with mites. DiFonzo’s example describes the effects of spider mites on soybean fields, but they can destroy many different vegetables.  According to DiFonzo, the beneficial insect population is killed with the application of insecticides, yet not all mites die. With the absence of the beneficials, the population of the spider mites can flare out of control. Because the spider mite eggs are unharmed and will continue to hatch, we must treat more than once. However, it seems the mites build a resistance to insecticides and the resistance increases with the number of treatments—and round and round we go! At times it all feels like an exercise in futility.

I did find some additional information published by David J. Shetlar at Ohio State University Extension. His article titled, “Spider Mites and Their Control” provides a great deal of good information about spider mites. Although of course, Shetlar references Ohio landscapes, we can be certain that the behavior of Michigan spider mites is much the same. In his article, Shetlar offers five different control methods: Syringing, Quarantine and Inspection, Predators, Soft Pesticides, and finally Miticides. They are noteworthy suggestions. 

Commonly, Shetlar, DiFonzo and Russell agree that early detection is the best control method. Know your plants and recognize the first signs of predatory attack so you can manage and possibly eradicate the mite population before they take over your garden. I do know my plants and I recognized the first signs of spider mites, when my tomato leaves were yellowing. I sprayed them vigorously every other day, yet even with my continuous efforts, a few of my plants continued to decline. 

Tomato mites by Lisa Hagerty

At some point, I realized my Impatiens, Daisies, and miniature Roses that were sitting all around my garden were also suffering from mites, so I integrated them into my routine. It has been a long battle, but with the recent rain, and lower temperatures, I think it is finally under control. Thankfully, I should be able to harvest my tomatoes within the next few weeks.

Tomato_mites by lisa hagerty

References:

https://www.canr.msu.edu/news/spider_mite_populations_thrive_in_hot_dry_summers

https://www.canr.msu.edu/news/potential_for_spider_mites_especially_in_southern_michigan/

https://ohioline.osu.edu/factsheet/HYG-2012-11


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