Observations on the Oviposition Process of Diaprepes abbreviatus (Coleoptera: Curculionidae)

Abstract

A single adult Diaprepes abbreviatus L. was discovered in a citrus nursery in Orange County Florida (Woodruff 1964). D. abbreviatus was not collected again until 1968, when larvae were collected at the same nursery and several hundred adults and larvae were subsequently collected in and around Apopka, FL (Woodruff 1968). Since its introduction in 1964, D. abbreviatus has spread to 20 counties in Florida, where it currently infests approximately 164,000 acres (66,420 ha) (Anonymous 1997). This area contains approximately 30,000 acres (12,150 ha) of infested commercial citrus and has a limited and localized geographical distribution. D. abbreviatus is an insidious pest; tree symptoms may not appear until the larvae are well established on the tree roots (Wolcott, 1936). Adults feed on young foliage, females lay egg clusters between leaves, and the larvae feed on the roots of a host (Fennah 1942, Jones 1915, Wolcott 1936, Woodruff 1968). Oviposition by D. abbreviatus appears to be restricted to nighttime hours (Jones 1915, Schroeder 1981, Wolcott 1936). Females oviposit approximately 60 egg masses during their lifetime which may contain from 30 to 260 eggs each and an average of about 5,000 eggs over their life span (Wolcott 1936). Wolcott (1933) observed that female D. abbreviatus preferred to oviposit between paper strips compared to leaves. Neonate larvae failed to emerge from these strips (Wolcott 1933). Fennah (1942) found that D. abbreviatus preferred paper strips over tin foil strips and mature leaves which were both favored over immature leaves for oviposition. Immature leaves are preferred feeding sites (Jones 1915, Wolcott 1936). Adair et al. (1998) reported that freezer paper strips might serve as a potential oviposition trap in citrus. Adult D. abbreviatus were field collected in Vero Beach, Florida and maintained as previously described (Adair et al. 1998). Thirty females and 30 males per cage were held in 30 x 30 x 60 cm aluminum rearing cages (Bioquip Products, Gardena, CA 90248-3602) at 27 ? 2?C, 30% RH and photoperiod of 11:13 (L:D). Five 2.54 cm x 15.24 cm doubled strips of transparency film (polyester, Labelon, Canadaigua, NY 14424) were provided for oviposition sites. At 10:00 PM, transparency film strips containing an ovipositing female were removed to a microscope stage for observation and photographing. Microscopic observations were conducted with an Olympus S2-6045 zoom stereo microscope with a 100AL 0.5x objective lens, lOx eyepiece and a NFK 2.5 x LD 125 lens and Olympus S2-PT (with L-adapter) adapter for a SLR camera. An Olympus OM 2S camera with automatic shutter speed and f-stop was used with Kodak Kodacolor 400 Gold? film. The transparency film strip with an ovipositing female was placed across an open Petri dish and illuminated above and below with a tungsten halogen lamp (Olympus Highlight 3000) equipped with bifurcating cold fiber optic goose neck