Anthonomus eugenii Cano Coleoptera Curculionidae

Natural History

Distribution. First found in the United States in Texas in 1904, pepper weevil reached California in 1923 and Florida in 1935. It is now found across the southernmost United States from Florida to California. Pepper weevil populations persist only where food plants are available throughout the year. Because transplants are shipped northward each spring, however, pepper weevil sometimes occurs in more northern locations. Pepper weevil was first observed in Hawaii in 1933 and in Puerto Rico in 1982. Although its origin is likely Mexico, it has spread throughout most of Central America and the Caribbean.

Host Plants. Pepper weevil develops only on plants in the family Solanaceae. Oviposition occurs on plants in the genera, Capsicum and Solanum, but feeding by adults extends to other Solanaceae, such as Physalis, Lycopersicon, Datura, Petunia, and Nicotiana. Among vegetables, all varieties of pepper are susceptible to attack, tomatillo is a moderately susceptible host, and eggplant grown in proximity to pepper may occasionally have the blossoms damaged. Several species of nightshade support pepper weevil oviposi-tion and development, particularly black nightshade, Solanum nigrum, but also silverleaf nightshade, S. elaeagnifolium; horsenettle, S. carolinense; buffalo bur, S. rostratum; and Jerusalem cherry, S. pseudocapsicum.

Natural Enemies. Parasitoids of pepper weevil include Catolaccus hunteri Crawford (Hymenoptera: Pteromalidae) and Bracon mellitor Say (Hymenoptera: Braconidae). Riley and Schuster (1992) reported up to 26% parasitism of pepper weevil larvae by C. hunteri.

Life Cycle and Description. In California, a complete generation is reported to require about 25 days under optimal conditions, about 33 days on average. In Florida and Puerto Rico, 20 days is about average. Under insectary conditions in California, up to eight generations have been produced in a single year. In most locations, 3-5 annual generations is probably normal, though adults are long-lived and produce overlapping generations, so it is difficult to ascertain generation numbers accurately. In central Florida, adults are common from March until June, and sometimes in the autumn months, reflecting the availability of peppers. However, a few can be found throughout the year except during inclement periods, such as

December and January. Adults overwinter, but only where food is available, because diapause does not occur in this species.

  1. Oviposition may commence within two days of mating. Eggs are white when irst deposited, but soon turn yellow. They are oval in shape and measure 0.53 mm long and 0.39 mm wide. Eggs are deposited singly beneath the surface of the bud or pod. The female creates an egg cavity with her mouthparts before depositing the egg, and seals the puncture containing the egg with a light brown fluid that hardens and darkens. Females deposit eggs at a rate of about 5-7 eggs per day, and fecundity averages 341 eggs, but is nearly 600 in some individuals. The mean incubation period is 4.3 days (range 3-5 days).
  2. Like other weevils in this genus, apparently the pepper weevil has three instars. The larvae are white to gray with a yellowish brown head. They lack thoracic legs and have few large hairs or bristles. They are aggressive, especially during the end of the larval period. Usually only a single larva survives within a bud, though more than one can occur within larger fruit. First instars measure about 1 mm long (range 0.8-1.5 mm). Second instars measure about 1.9 mm long (range 1.3-2.6mm). Third instars measure about 3.3 mm (range 2.2-5.0 mm). Mean development time of the larvae is about 1.7, 2.2, and 8.4 days for instars 1-3, respectively. The figure for third instar development time contains a prepupal period of about 4.9 days, during which time the larva creates a pupal cell from anal secretions.
  3. The pupal cell is brittle and found within the blossom or fruit. The pupa resembles the adult, except that the wings are not fully developed and large setae are found on the prothorax and abdomen. White when irst formed, the pupa eventually becomes yellowish with brown eyes. Mean duration of the pupal stage is 4.7 days (range 3-6 days).

Pepper weevil larva.

Pepper weevil pupa.

Adult. The adult emerges from the pupal case 3-4 days after being formed. A clean, round hole marks the escape of the beetle from the bud or fruit. The beetle is oval and varies from 2.0-3.5 mm long and 1.51.8 mm wide. The body is strongly arched with a long, stout beak as is typical for this genus. The thorax and elytra are mostly covered with small scales. The antennae are long and markedly expanded at the tip. The femora each bear a sharp tooth. The color is dark mahogany to nearly black. Feeding begins immediately after emergence. Males produce an aggregation pheromone that attracts both sexes (Eller et al., 1994). (See color figure 131.)

The most complete treatment of pepper weevil biology was given by Elmore et al. (1934), though Riley and King (1994) published a useful review of biology and management. Other descriptions were provided by Goff and Wilson (1937) and Gordon and Armstrong (1990). Host relations were described by Patrock and Schuster (1992).

Damage

This is the most important insect pest of pepper in the southern United States. An important form of damage is destruction of blossom buds and immature pods. On buds, adult and larval feeding cause bud drop. Adult feeding punctures appear as dark specks

Larva Curculionidae

Adult pepper weevil.

Pepper weevil larva.

Adult pepper weevil.

on the fruit, and are not very damaging. Sometimes the fruit is deformed. Fruit drop is very common, and is perhaps the most obvious sign of infestation. Larval feeding within the mature pod is another important form of damage, causing the core to become brown, and often moldy. The stem of pods infested by larvae turn yellow, and the pod turns yellow or red at the base prematurely. In the absence of pepper blossom and fruit, adults feed on leaves and pepper stems, but cause no significant damage by these habits. Puncture of peppers by pepper weevil allows penetration of the fungus Alternaría alternata, an otherwise weak pathogen, and extensive fungal growth within the pepper fruit (Bruton et al., 1989). (See color figures 24 and 30.)

Management

  1. The distribution of weevils is aggregated, especially at field margins. Adult population estimates are best obtained by visual examination and yellow sticky traps (Segarra-Carmona and Pan-toja, 1988a). Traps should be placed 10-60 cm above the soil; one 375 sq cm trap captures as many weevils as are detected by inspecting 50 buds (Riley and Schuster, 1994). If visual monitoring is preferred, terminal bud sampling is effective, though more beetles are present in the morning than evening (Riley et al., 1992a). Action thresholds of one adult per 400 terminal buds (Riley et al., 1992b) or 1% of buds infested (Cart-wright et al., 1990b) have been suggested. A sequential sampling protocol was developed by Segarra-Car-mona and Pantoja (1988b). Isolation of an aggregation pheromone may lead to improved sampling techniques (Eller et al., 1994).
  2. Insecticides are commonly applied to the foliage at short intervals once buds begin to form. Insecticidal suppression of adult weevils is feasible, but insecticides vary considerably in effectiveness, and even in the presence of chemical insecticides some loss commonly occurs (Ozaki and Genung, 1982; Schuster and Everett, 1982; Armstrong, 1994). Segarra-Carmona and Pantoja (1988b) estimated that economic damage commences with adult populations of 0.01 beetle per plant.

Cultural Practices. Cultural practices that significantly affect pepper weevil damage are limited, but campatible with other management practices including biological control. Berdegue et al. (1994), working in Texas, compared 35 varieties of jalapeno, bell, pimento, serrano, yellow, cayenne, chile, tabasco and cherry peppers, and found few differences in susceptibility. Sanitation can be important, if it can be implemented on an appropriate scale. Removal and destruction of fallen fruit, for example, will result in destruction of larvae and pupae. Similarly, a crop-free period, particularly if accompanied by destruction of alternate hosts, can disrupt the life cycle. Solanaceous weeds should not be allowed to grow in proximity to pepper as the weeds may serve as an alternate host.

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