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OSU Extension

College of Food, Agricultural, and Environmental Sciences

July 6, 2021 - 8:00am --

As the growing season moves along so do the potential pests and diseases of our various crops. Scouting at least a few fields of each crop on a regular basis can provide warning of increasing insect and disease pressure which allows for more efficient and tailored control options.

Agronomic Crops

In hay fields, only a few alfalfa weevils are present now, as is expected. Potato leaf hoppers (PLH) are the major insect pest that we will be looking for the rest of the hay season. So far, in the fields that we have been scouting, PLH numbers have been below or just at threshold. Management of PLH may include taking an early cutting to remove the PLH food source or applying an appropriate insecticide to fields that are too young to harvest early.

Corn fields are likely to really take off after the rain last week, which followed several days of high temperatures. Having a good combination of heat and moisture allows corn to stay ahead of potential insect damage compared to when growth is slow and feeding that takes place on smaller plants is more detrimental to development. We have found the European corn borer in some fields with about 10% of the stand showing feeding damage. The threshold for treatment is when 50% of the stand is damaged.

Some Northern corn leaf blight has also been found in corn. It is identified by long brown lesions on the leaves. This fungal disease poses the most risk during wet years and when it becomes widely established in a stand prior to silking. Later in the season, its establishment has limited effects on grain yield. However, severe cases may impact silage yield and quality as leaf tissue is damaged and ear fill can be limited. Remember, fungicides are a preventative control option and must be applied before or at first onset of disease.

Vegetable Crops

Imported cabbage worm eggs are being found on cole crops. Scouting for the eggs as well as the larvae of this insect will allow for better timing of an insecticide treatment when necessary to prevent widespread damage.

Thrips are being found throughout onion crops. These tiny insects hide close to the bulb where the leaves are tight together. Thrip damage appears as silver streaking on leaves, stunted growth, limited bulb development, and plant demise in severe cases. 30 thrips per plant is the threshold which warrants a treatment.

European corn borer damage in sweet corn is more concerning than in field corn due to the relative value of each plant and proper ear fill to maintain a marketable product. When sweet corn is silking, a threshold of 10% of tassels showing feeding warrants a treatment. Some growers have already needed to make treatments to prevent harvest losses.

Fruit Crops

Aphid populations have been relatively high this year in many crops from alfalfa to sunflowers to apples. The wooly apple aphid is of particular concern in orchards as it has fewer natural predators. They congregate and appear as cotton-like tufts, often near pruning sites or new growth. Treatment may be necessary when populations of this aphid are found on new shoots and green growth throughout the orchard.

Other aphid species have been found with growing populations of beneficial insects like ladybug larvae and lacewings. In the case of harmful insects alongside beneficial insects, consideration should be made regarding the ratio of beneficials to pests. (A single ladybug may consume up to 5,000 aphids during its lifespan.)

Spotted wing drosophila (SWD) is a fruit fly of particular concern for various fruits, especially berries and grapes. This pest is now being found in traps here in Wayne County. The female SWD is capable of laying eggs in unripe fruit, so that by the time of harvest, very noticeable white larvae are in the fruit. This is unlike most fly species that can only lay eggs in overripe or rotten fruit. To check for SWD, some fruit can be placed in a 6% saltwater solution (1Tbs. salt/cup water) for 15 minutes. If SWD are present, they will float to the top. Contaminated fruit is not to be sold.

For more information from Wayne County’s Integrated Pest Management Program, check out for weekly updates. You can also contact the program coordinator, Frank Becker, via phone: 330-264-8722 or email: Additional information, especially on agronomic crops can be found at our county website: and by subscribing there to our weekly agriculture e-newsletter.


Matthew Nussbaum is an OSU Extension Agriculture and Natural Resources Program Assistant and may be reached at 330-264-8722.

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