Black Walnut Curculio Control, Missouri 1973-75

An experimental control program for the black walnut curculio was conducted over a three-year period in a 5-acre stand of mature black walnut located in Cedar County, Missouri. Initial spray dates for the first two years were established on adult emergence dates obtained from available literature. For the final year, the first spray date was based on emergence dates established through adult trapping. Spray dates in 1973 were May 15, May 30, and June 12; in 1974, May 30 and June 17; and in 1975, May 7, May 15, and June 11. Trees were selected and flagged to represent three spray groupings and one control group of five trees each in one block. Three such blocks were established for a total of 60 trees. The spray groups received applications of Guthion 2S, Benlate (WP), and a mixture of the two. Guthion was mixed at a rate of 24 oz/100 gal water. Benlate was mixed at 2 lb/100 gal of water. Eight tablespoons of Plyac a spreader-sticker were added to each 100 gallon formulation. Benlate was tested in an effort to reduce walnut anthracnose. When possible, spraying was done in the evening. At all times the wind was less than 10 mph with temperatures in the lower 70’s. Sprays were applied with a 150 gallon capacity Broyhill power sprayer the first year. The following two years a farm tractor carrying a 55 gallon drum with a PTO powered pump served as the spray unit. As nuts dropped they were collected and dissected for curculio larvae. Data were recorded as to presence or absence of larvae and total nuts collected per spray group.