It is very important to have a rational pest management system for the production of major grain crops. For maize, in Missouri, the black cut worm (Agrotis ipsilon) and the European corn borer (Ostrinia nubilalis) are the two major pests requiring control. A management plan has been developed which minimizes both environmental risk to human health, water supply and soil contamination and the cost of control of pests. Both environmental and cost requirements are met by an effective system which reduces the amount and frequency of chemical application.
Pest development and corn growth can be simulated through the use of numerical models driven by weather data. In Missouri, the weather data for this system come from automated weather stations which represent the areas where corn production is important. A secondary source of weather data is the NOAA cooperative weather stations in the region.
For the simulation system to operate the weather data must be error free and always available. An insect or plant model can not operate if the data driving the models are missing. The system uses visual checks of the data by a climatologist as it is retrieved from the observing stations each morning. Missing data are replaced by observations from nearby weather stations. In this way insect and corn development are simulated each day.
Beginning in late March predictions are made for the various development stages (instar numbers) for the black cut worm and corn borer. These are updated on a weekly basis using the weather data for the several regions of Missouri important for corn production. The growth stages are predicted based on observed temperatures (accumulated degree days) that have already occurred, with the 30 year averages of the temperature data at each location used for the remainder of the development period. Of course, as the spring progresses more actual temperature data are used and less of the 30 year average temperatures.
The subsequent pest management advisories are made when the projected instar number from the models for the pests reaches a critical level. The advisories are intended to alert the farmers and their advisors to begin "scouting" the fields of corn to record infestation levels. If the economic threshold for each pest is exceeded, chemical treatments are recommended for control. Treatment is never advised on the basis of the simulated insect development, but only after the level of infestation has been determined through field inspection.
Special Session -- Weather Data Requirements for Integrated Pest Management