Sweet Corn Integrated Pest Management

ear of sweet corn on the stalkThe Maine vegetable industry is extremely interested in reducing pesticide use while improving or at least maintaining crop quality. This interest derives from market demands for pest-free vegetables; consumer concern about, and regulatory control of, pesticide residue on fresh produce; and reduced profitability due in part to escalating expenses related to the purchase and application of pesticides. Residential development in rural areas has created conflict when vegetable pesticide applications are opposed by neighboring landowners.

All of Maine’s sweet corn production is for the fresh market. Maine growers make a profit only on sweet corn that can be sold as the highest pest-free quality. Corn that must be sold for lower quality or used for feed may be sold for less than the cost of production.

To produce pest-free quality sweet corn as many as a dozen or more sprays per season may be required, sometimes as often as every two days. The combination of high production expenses and fluctuating market prices has resulted in several growers ceasing sweet corn production, although total acreage has remained fairly constant.

Most Maine vegetable farms are single-family businesses. An individual grower typically functions as a horticulturist, farm laborer, business owner, employer, and more. It is very difficult, if not impossible, for growers to keep up with the state of the art in pest management of various vegetables on their own while attending to the other aspects of running a farm.

The University of Maine Cooperative Extension Sweet Corn IPM Program was initiated in 1983 by UMaine Extension Pest Management Specialist Dr. James Dill. The program now is coordinated in conjunction with Dill by the UMaine Extension Small Fruit and Vegetable Specialist, David Handley, and field scouting is handled by several seasonal employees.

To achieve the goal of helping Maine sweet corn producers implement IPM, the UMaine Extension Sweet Corn IPM Program has three basic functions which are all interrelated. The first is providing information to help vegetable growers apply IPM to their sweet corn pest problems. Managing Insect Pests of Sweet Corn (Vegetable IPM Factsheet 401a, Bulletin #5101) is a bulletin produced by the UMaine Extension Pest Management Program to meet this need. The scouting/monitoring bulletin has been highly rated by Maine growers. It provides information on pest biology and pest damage, color photographs of pests, and instructions for using equipment for monitoring pest conditions in sweet corn. Copies of the Sweet Corn IPM Videotape on sweet corn pests and monitoring procedures are loaned to growers for home viewing.

Another method of reaching the sweet corn industry is the Vegetable Pest Message. This is a recorded phone message “hotline” which is updated weekly during the early part of the growing season, and then twice a week through harvest. It reports on vegetable pest problems, forecasts, timing, and severity of sweet corn insect pest populations across the state; management considerations, grower observations; and as a message service for disseminating information rapidly. Over 300 calls were logged in 1994.

Written sweet corn pest messages are part of the Sweet Corn IPM Newsletter. Subscribers include hobbyist and commercial growers throughout the state. Articles on vegetable pests and/or pesticide topics are also published in the Vegetable Newsletter which reaches most of the commercial industry personnel in Maine.

Educational presentations are given throughout the year. Educational talks are provided for the Maine Vegetable and Small Fruit Growers Association annual summer twilight meetings and annual winter meeting. Lecture and discussion sessions for smaller regional grower meetings are given around the state. Presentations to civic and professional organizations help educate the general public about issues in vegetable pest management.

The second function of UMaine Extension Sweet Corn IPM activities is the educational/on-farm IPM demonstration program for individual growers. From 12 to 16 growers have enrolled in this IPM training program each year. Insect monitoring equipment including pheromone traps is provided for the grower’s use. Weekly, the grower participates in a scouting/training session with the IPM program staff, usually the scout. Together they monitor the pest situation in one sweet corn field. Training sessions include discussion of management options, and a short written report of the observations made and options discussed is left with the grower.

As a third function, the UMaine Extension Sweet Corn IPM Program serves as a resource for growers having difficulty with one or more of the many aspects of sweet corn and vegetable pest management. This has included such things as helping growers identify the cause of damage to corn or other vegetables or to determine the flaws in their management program which allowed the damage to occur. More commonly it takes the form of answering or researching grower questions. Through literature search and contacts with UMaine Extension and research personnel in other states, growers are assisted in resolving difficult to answer questions. Observations made during these grower visits serve as data to formulate the vegetable pest messages.

The UMaine Extension Sweet Corn IPM Program adapts and improves each year in response to the needs of its clientele. End of season survey responses from growers are used to assess the educational needs and an evaluation of previous activities. Growers have rated the UMaine Extension Sweet Corn IPM Program as excellent and very useful to them on these surveys. There are numerous specific examples of the impact of the IPM program in achieving better pest control with reduced use of pesticides. The impact varies from year to year, depending on pest pressure.

UMaine Extension’s success in reaching the sweet corn industry at large makes it difficult to measure the difference in pesticide use directly attributable to the program. This is because there are few growers in Maine not impacted by the UMaine Extension Sweet Corn IPM Program in some aspect. Nevertheless, comparisons made between growers that have and have not yet participated in the educational on-farm demonstration sessions have shown that as a result of contact with the UMaine Extension IPM Program growers have achieved decreases to pest damage, and have maintained or improved insect control usually with decreased use of insecticides. In 1994, growers participating in the UMaine Extension Sweet Corn IPM Program reduced spray applications anywhere from two to ten, with increased profitability of $40 to $230 per acre. Information generated from serving the commercial vegetable industry serves as a resource for UMaine Extension county educators and home gardeners.