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Spring Field Crop Insects Update

02 May 2012
Ohio State University

US - With planting occurring at full speed, all crops might be planted within the next few weeks. This is the time of year that numerous insect pests should be taken into consideration when monitoring crop emergence and early plant growth.

Writing for Ohio State University, Ron Hammond and Andy Michel offer the following advice:

Black Cutworm on Corn – This past warm spring allowed for an early migration of adult moths into the Midwest, with some states observing more than usual. Growers should plan on scouting for early signs of plant cutting as corn begins to grow, and use established thresholds to determine need for treatment. Based on experience, we would recommend scouting all corn at risk: especially corn planted no-till into weedy fields, and do not exclude scouting any seed treated corn and/or transgenic hybrids.

Corn Flea Beetle on Corn – Because of the warm winter, corn flea beetle might be heavier than normal, and should be monitored.

Cereal Leaf Beetle on Wheat and Oats – Although we have had no reports yet of problems, we have heard of eggs and young larvae on wheat. Growers should plan on scouting their wheat and oats over the next week as temperatures begin to warm for signs of larger larvae and feeding injury. The threshold for this insect in Ohio is set at 1 larva per stem.

Slugs on Corn and Soybean – Because of the warm winter and March, we would expect slugs to hatch out earlier this spring and begin their feeding sooner. We would recommend to growers who have experienced slug problems to keep a closer watch on their fields.

Bean Leaf Beetles on Soybean – With the warm winter, we also expect these pests to arrive earlier in soybean fields, perhaps in slightly higher numbers. However, it appears that most areas have a large amount of their soybeans already planted and ready for emergence. Experience shows us that the more fields of soybeans in an area, the more the overwintered beetles spread out over all those fields, with few fields getting large numbers. Remember that the threshold is are over 50 per cent defoliation or obvious stunting of the young plants, which hopefully will be uncommon this year with the amount of soybeans already planted.

Insects on Alfalfa – Although most first cuttings are soon to occur, we have received some reports of alfalfa weevil reaching treatable levels. Prior to treating, decide if the alfalfa is tall enough to cut, and if so, consider early cutting. If early cutting is done, scout the regrowth for possible continued feeding by weevil larvae.



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