Cereal Leaf Beetle in Corn–Potential of Spider Mites in Soybeans

OSU Extension Entomologists Ron Hammond, Andy Michel and Bruce Eisley provided a concise assessment of the current insect pest situation in the July 7, 2009 CORN newsletter.

Regarding cereal leaf beetle…

As mentioned in earlier articles in this newsletter, cereal leaf beetle was a concern this past spring on wheat and oats. Most of that damage was by larvae of the beetle, which was then followed by larval pupation and then more recently, adult emergence. These adults http://entomology.osu.edu/ag/images/cereal_leaf_beetle_adult.pdf will be the overwintering stage that start populations next year. However, before these adults go into a type of hibernation for the remainder of the summer and then winter, they will feed on available crops, most notable corn. This feeding is often heaviest along the edges, especially in those fields that are across the road or adjacent to wheat or oat fields where the population had built up. This feeding is superficial unless the injury is extremely heavy,. Recommendations for treatment are only when feeding is greater than 50% over the entire plant, the corn is under stress, and beetle populations are extremely large. Because this seldom happens, nothing should usually be done. The feeding will end shortly.

Regarding spider mites…

Reports are coming in about areas of Ohio that are beginning to get very dry, and crops that are starting to show moisture stress. If low rainfall conditions continue, we will enter a period where two-spotted spider mites begin to develop on soybean and cause significant injury. We would recommend that growers begin to scout soybeans in dry and crop-stressed areas for beginning mite populations. The best way to scout at this time is to walk fields, especially field edges at this time, for the presence of yellow stippling on top of leaves that suggests mite feeding. Pictures of this injury are available on our new Agronomic Crops Insects web site, http://entomology.osu.edu/ag/ . The photos can be seen by going into images under the soybean section. Upon seeding the stippling, turn the leaves over to search for the presence of mites. We will keep growers updated on the situation with mites throughout the summer. If mites are found in your area, please contact us or your county extension educator.

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