Look before spraying. That is a basic principle of Integrated Pest Management (IPM) advocated by extension specialists at the University of Missouri-Columbia.
A new 24-page manual, "Introduction to Crop Scouting," expands on that idea. It is available from Missouri Outreach and Extension Centers.
"A regular and systematic field-sampling program--crop scouting--gives field-specific information on pest pressure and crop injury," said Fred Fishel, MU Extension IPM coordinator. "This information is essential to the appropriate selection and application of pest management procedures."
The new manual is one in a series by specialists in the MU Plant Protection Program.
The manual explains the concept of "economic injury level (EIL)." The EIL is the pest density or level of crop injury that will result in yield loss equal to the cost of managing the pest, Fishel said. "Simply put, it's the break-even point."
That point changes with the increase in pest damage, the cost of control, and the value of the crop to be saved. The predicted effectiveness of the control also comes into the equation.
"Producers are less inclined to spend more money as commodity prices drop," Fishel said. "Likewise, high priced controls would take threat of a greater loss, before being applied."
The economic threshold (ET) is the pest density or level of injury at which controls should be applied to prevent an increased pest population from reaching the economic injury level.
Fishel said that considerable research is required to establish those economic thresholds. "So, ETs are not available for all crop pests."
Generally, ETs are more often available for insect pests than for diseases or weeds.
A regular crop-scouting program provides an early-warning system.
Good crop scouts are attentive to many details, Fishel said. "They should observe--and record--environmental conditions including the weather, beneficial insects, pest insects, diseases, weeds, crop growth stages, and general health of the crop."
Scouting reports help develop a field history useful in determining a particular crop damage.
"Corn plants lodged or growing in gooseneck shape can result from corn rootworm pruning, application of growth regulator herbicide, or shallow rooting in wet soil. A field history can help pinpoint which cause," he said.
Those histories should not be in memory only, Fishel said.
Crop scouts rely not only on an insect sweep net, but also various kinds of traps that attract pests.
"A complete and legible scouting report is the essential 'road map' guiding pest management decisions," Fishel said. The reports can result in general field applications, or site-specific controls.
The reports can be used for applying rescue treatments and guide pest management in the next growing season. Overall, scouting can reduce the amount of pesticides applied.
Increasingly, crop scouting is done not only by the producer, but also by hired professional scouts, trained in identifying many insects, diseases and weeds.
Other manuals in the series include soybean diseases, corn diseases, and weed science. The manuals can be obtained from local extension centers in Missouri.
The manual, IMP1006, is also available postage paid for $4.50, plus Missouri sales tax, from MU Extension Publications, 2800 Maguire Blvd., Columbia, MO 65211. Orders can be placed with credit card at 573-882-7216 or toll-free in Missouri at 1-800-292-0969.