A number of important pest problems can affect profitability of alfalfa production in New York. The most important pests are alfalfa weevil, potato leafhopper, alfalfa snout beetle, Verticillium wilt, Phytophthora root rot, anthracnose, crown rot, and weeds. Some additional pests may occasionally cause economic losses. Integrated pest management (IPM) methods can be used to help minimize the impact of these pests (see "Integrated Pest Management for Field Crops". Figure 1 contains valuable information on when key pests of alfalfa can be expected to occur under New York conditions.
Crop monitoring for pest problems is recommended from early May through early September. In areas where alfalfa snout beetles are known or suspected to occur, field monitoring should begin with the first warm days of April. Weekly field monitoring for alfalfa pests is recommended because populations of alfalfa weevil (first cutting) and potato leafhopper (second and later cuttings) can change dramatically over time. Less regular field monitoring would miss early pest detection opportunities and allow for otherwise avoidable losses. Diseases, weeds, and other cropping problems should be assessed during regular field monitoring activities for insect problems. Pre- and postseason weed surveys identify potential problems and current and future weed control needs. Information on significant pest damage, including field location, should be recorded to help improve efficiency of future pest management decisions.
For additional information on identigying and managing common disease, insect and weed problems of alfalfa, see Growing Alfalfa the IPM Way and Your Pocket Guide to alfalfa and Field Corn Management, Cornell Cooperative Extension, NYS IPM Program publications 305 (1991) and 313 (1994), respectively, available from your local Cooperative Extension office and from Cornell University Resource Center, 7 Business & Technology Park, Ithaca, NY 14850.
See Table 7 and Figure 1 for suggestions on IPM activities and common pests by crop growth stage and seasonal occurrence.