Field Evaluation of Three Baits for South American Cucurbit Fruit Fly (Diptera: Tephritidae) Using McPhail Traps

Abstract

Anastrepha grandis (Macquart), the South American cucurbit fruit fly, is a subtropical pest of cucurbits in southern Brazil. Its hosts include some varieties of pumpkin, squash and winter squash (genus Cucurbitae). Norrbom & Kim (1988) recorded A. grandis in 10 host plants (6 Cucurbitacea species). It is considered a quarantine pest by United States Department of Agriculture and cucurbits from countries where this species has been reported are not permitted entry into the United States. Little is known of the biology of the pest, except its geographical distribution. However, it is known to be genetically quite different from most common species of Anastrepha occurring in Brazil (Morgante et al. 1980). A. grandis is not widespread in Brazil like other Anastrepha species, but is present in small localized populations depending upon pumpkin availability. Although considered a quarantine species, there is only one questionable record indicating that A. grandis infests melons (Norrbom & Kim 1988), the main cucurbit produced by South American countries for exportation. A survey and monitoring program for establishment of A. grandis-free areas requires an efficient trapping system that may detect low density populations. Protein hydrolysate and torula yeast have been reported to be more effective as food bait for many tephritids including some species of Anastrepha (Lopez et al. 1968, 1971). A study showing that wild adults are attracted to McPhail traps with food baits, is desirable, to support detection programs in Latin America. We have attempted in this study to determine whether McPhail traps usually employed for Anastrepha are also effective for wild A. grandis and to determine which commonly available bait is the most attractive for this species. Since Anastrepha fraterculus, the South American fruit fly, occurs in high densities in most fruit growing areas in the southern area of Brazil (Malavasi & Morgante 1980), and is attracted to McPhail trap baited with sugar cane molasses (Malavasi & Morgante 1981), trap catches of this species were used to compare with those of A. grandis. The experiment was conducted in a non-commercial mixed fruit planting near Sao Roque, approximately 50 km west of Sao Paulo, during 7 consecutive weeks in AprilJune 1987. Collections of infested pumpkins in 1985 and 1986 revealed that A. grandis was present. We set up traps around a field that had pumpkins growing between rows of grapes. Traps were hung in host and non-host trees. We assumed that A. grandis has patterns of behavior similar to Anastrephafraterculus in that adults visit host and non-host trees for food, shelter and mating sites (Malavasi et al. 1983). Modified McPhail traps, made of polyethylene plastic, had 250 ml of bait capacity and were 20 cm high and 10 cm diameter, with a conical bottom entrance hole (2.5 cm diam) and four lateral, conical entrance holes (1.0 cm diam). Three baits were tested: 1% molasses (cane sugar syrup), 5% corn protein hydrolysate plus 3% borax (pH 9.0), and 4% torula yeast pellets (2 pellets per trap). Fifteen sets (one set = 3 traps) of traps, with the three types of bait were hung 1.7-2.3 m high. Seven sets were hung on persimmon trees, two on guavas, two on quaresmeira, one on peach, one on loquat, one on avocado, and one on pecan. All trees