April’s Ag Advice

April's Ag Advice by April Borders Integrated Pest Management (IPM) is a tool that we have at our discretion to aid us in the production of our field crops. One of the keys to a successful IPM program is regular monitoring of field crop conditions and pest infestations. A scouting trip through a field reveals which pests are present, what stage of growth each pest and the crop are in, whether the pests are parasitized or diseased, whether the pest infestation is increasing or decreasing, and the condition of the crop. This information can be used to determine whether a control measure may be needed.

A scouting program requires keeping accurate record of the field location, current field conditions, history of previous pest infestations and pesticide use, and a map locating the present pest infestation. These records will enable the grower to keep track of each field and anticipate or diagnose unusual crop conditions.

Insect pests can be monitored in several ways. Usually, the insects are counted or the amount of crop damage is estimated. Counts of insects are commonly expressed as number per plant, number per row foot, number per sweep, or number per unit area. Estimated crop damage is usually expressed as a percentage. Plants should also be examined for symptoms of disease and if infected plants are found, the severity of the disease should be determined.

Certain basic principles of crop monitoring apply to most scouting programs. Samples should be taken from representative areas of the field. The sampling sites should be evenly distributed over the field, and plants should be sampled randomly unless certain field characteristics suggest an uneven distribution of pests. Avoid border rows, and field edges unless there are specific reasons for scouting these areas. Scout at least once a week, although some fields may require monitoring more frequently if insect densities begin to increase rapidly.

The most familiar feature of field crop IPM programs is scouting fields for pests and basing treatment decisions on economic thresholds. The economic threshold (ET) is that pest density at which some control should be exerted to prevent a pest population from increasing further and causing economic loss. Damage thresholds can also be used to help make treatment decisions in disease and weed control.

Integrated pest management is far more complex than just scouting fields for pests, having knowledge of economic thresholds and using pesticides in a judicious fashion. A well designed IPM program should integrate several management strategies for insects, plant disease, and weeds while maintaining agricultural profitability and environmental quality. Effective pest management programs should anticipate potential pest problems and attempt to modify the existing crop production practices.

It is recommended that each field be visited at least once a week, although the incidence of pest problems may not require that all fields be scouted each week. Some fields may require checking more that once a week when infestations are approaching economic levels.

It is never too soon to start scouting and we should be hitting the fields now. Reports are already coming in on alfalfa weevil larvae and pea aphids in our alfalfa. Bean leaf beetles have been seen already. Dr. Mike Catangui, SDSU Extension Entomologist, feels that there may be very significant numbers in soybeans this year. They have overwintered and are in alfalfa fields now.

The soybean leaf miner has been found in Iowa and so we need to be watching for this during the season as well. The soybean leaf miner can transmit soybean leaf mottle virus. We also need to be on the look out for the corn rootworm larvae and corn stalk borers.

Proper pest identification is also important. Proper pest management depends in part on synchronization of treatment according to the growth stage of the crop. If you need any information about IPM, economic thresholds or pest identification, call the Extension Office at 677-7111.

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