TOWARD DEVELOPING PESTICIDE-TREATED SPHERES FOR CONTROLLING APPLE MAGGOT FLIES, RHAGOLETIS-POMONELLA (WALSH) (DIPT, TEPHRITIDAE) .1. CARBOHYDRATES AND AMINO-ACIDS AS FEEDING STIMULANTS

Contact behavioral responses of Rhagoletis pomonella (Walsh) flies to various carbohydrates, amino acids, and surface characteristics of 8-cm red spheres were examined in the laboratory for the purpose of developing spheres that could be treated with a pesticide and fly feeding stimulant to control alighting R. pomonella in commercial orchards. By the criterion of median tarsal acceptance threshold, sucrose and fructose were the most stimulating of the 5 sugars tested, whereas melezitose, glucose, and maltose were less so. R. pomonella did not respond to saccharin, which is sweet to humans. The amino acids phenylalanine, glutamine, leucine, methionine, and arginine, when mixed with water alone at 0.1 M concentration, were not phagostimulatory to R. pomonella. When mixed with 4 % sucrose in water, phenylalanine was significantly more phagostimulatory than sucrose alone, while the other 4 amino acids tested were not. R. pomonella fed significantly longer on filter paper dipped in an aqueous sucrose solution and dried than on filter paper dipped in an aqueous sucrose solution and allowed to remain wet, provided the concentration of sucrose exceeded 8 %. Covering spheres with cotton fibre, potentially useful as a method of retaining, pesticide residue, led to significant reduction in visiting and feeding times of R. pomonella compared with times on smooth-surface spheres when both types were treated with an aqueous solution of 8 % sucrose and dried before testing. The relevance of these findings to development of pesticide-treated spheres for the control of R. pomonella is discussed.