Distribution. Diaprepes abbreviatus is found widely in the Caribbean Islands, and was discovered in Florida in 1964. It has since then spread slowly, but occurs throughout southern and central Florida. It is thought to have been introduced with ornamental plants shipped to Florida from Puerto Rico, and there fore has the potential to spread again by this means, particularly to other warm weather regions such as southern Texas and California. In Puerto Rico these pests are known as "vaquitas."
Host Plants. Although first reported to be a pest of sugarcane, this weevil has since been found to attack many other plants. In Florida, it is a serious pest of citrus and woody ornamentals. However, it has been known to cause serious injury to okra in the Virgin Islands, to yam, pepper and lima bean in Puerto Rico, and to potato in Florida. The adults have been found on numerous shrubs and flowers (Griffith, 1975), and sometimes trees are defoliated by adult feeding. However, adult-feeding behavior is not truly indicative of host suitability, because it gives no indication of suitability for larval development. Schroeder et al. (1979) evaluated over 70 plants for larval suitability, and indicated that in addition to citrus and sugarcane, larvae could develop on aloe, coralberry, croton, false aralia, waxplant, shore juniper, red cedar, liriope, and prayerplant. Eggs are deposited on ornamental plants such as ficus and cornplant (Abreu-Rodriguez and Perez-Escolar, 1983).
Natural Enemies. Predation rates of young larvae are quite high as they drop from their point of hatch on foliage and crawl along the surface of the soil seeking a suitable site to enter the soil. Within Florida citrus groves, several species of ants account for nearly 50% destruction of young larvae (Whitcomb et al., 1982). The ants, Pheidole dentata Mayr, P. floridana Emery, and Tetramorium similimum Roger (all Hyme-noptera: Formicidae) are most effective. The ant, Cre-matogaster ashmeadi Mayr (Hymenoptera: Formicidae) also attacks weevil egg masses on foliage. In the absence of ants, the earwig Labidura riparia (Pallas), is an important predator (Tryon, 1986).
Several egg parasitoids of D. abbreviatus are known, but Tetrastichus haitiensis Gahan (Hymenoptera: Eulo-phidae) is the most important parasitoid in the Caribbean areas and it has been introduced into new infestations in the Caribbean areas and Florida (Beavers et al., 1980). In Florida, performance has been erratic.
The larvae are affected by such fungi as Metarhizium anisopliae, Beauveria bassiana, Paecilomyces lilacinus, and Aspergillus ochraceous, and the nematodes Steinernema carpocapsae (Nematoda: Steinernematidae) and Hetero-rhabditis sp. (Nematoda: Heterorhabditidae). The nematodes cause higher levels of mortality than the fungi in Florida, often about 50% (Beavers et al., 1983).
Life Cycle and Description. A life cycle requires about a year for completion, but development time is highly variable and diapause apparently is variable. Adults can be found throughout the year, but there are two periods of peak emergence—June and September. Adult males are active for about two months, whereas females are active for four months.
Quintela et al. (1998) studied larval development on artificial diet and citrus roots. This study suggested that larvae can have 10-11 instars, though it is not clear that all larvae display this pattern of growth. Mean head capsule widths were 0.26, 0.35, 0.47, 0.65. 0.99, 1.39, 1.81, 2.22, 2.64, 3.03, and 3.31mm for instars 1-11, respectively. Mean duration of each instar was 7.9, 5.1, 4.0, 9.4, 3.7, 4.8,11.9, 11.1, 37.2, 35.1, and 18.0 days, respectively. Total larval development time, about 148 days, was relatively short in this study, probably because a period of diapause was absent. Larval growth, as reflected by head capsule width and larval weight, was rapid for the first 75 days, but there was little increase thereafter.
The West Indian sugarcane rootstalk borer weevil, including its color forms, was described by Pierce (1915). The most complete biology was given by Wolcott (1936). Methods of culture, including an artificial diet, were presented by Beavers (1982). A bibliography was published by Hall (1995).
Adults injure plants by feeding on foliage. Initially they feed along the edge, creating a notched appearance. Eventually, however, they may consume the entire leaf, even defoliating trees. The larvae feed below-ground on roots. They will consume rootlets and remove the outer layers of larger roots, often girdling them. The larvae also burrow into soft below-ground plant tissue such as the base of sugarcane stalks and the tubers of yam and potato. However, vegetable
crops are not normally injured by this weevil. Injury occurs to vegetables mostly when planted in soil previously occupied by sugarcane or ornamental crops.
Biological Control. Larvae of D. abbreviatus are susceptible to infection by Steinernema and Heterorhab-ditis spp. entomopathogenic nematodes (Nematoda: Steinernematidae and Heterorhabditidae) (Figueroa and Roman, 1990a,b, Downing et al., 1991, Shapiro et al., 1999). Under field conditions, Heterorhabditis bacteriophora significantly reduced adult emergence (Downing et al., 1991).
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