USDA / APHIS / PPQ PEST ALERT:

Old World Bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

synonyms: Heliothis armigera, Chloridea armigera

The old world bollworm has been intercepted frequently at ports of entry on a variety of fruits, vegetables, plant cuttings and flowers. Larvae are usually intercepted, however, hitchhiking adults have been found on aircraft. Most recently, H. armigera larvae were intercepted in the U.S. on geranium cuttings originating from the Canary Islands. This species is a general feeder and is highly resistant to pesticides.

Life History

In more temperate regions of H. armigera's range (Figure 1) , it completes 2 1/2 generations per year with pupae overwintering in the soil. In more tropical areas, this species may continue to be active throughout the year with multiple overlapping generations. After a short (2-3 day) feeding and maturation period before their ovaries will mature and oviposition can begin. Adults, which are mainly nocturnal in their mating and egg laying activities, live as long as 2-3 weeks. During a life time, a single female may oviposit from 500 to 3,000 eggs, averaging close to 1,000. Ovipositional sites on a plant are highly variable. However, there is a tendency for eggs to be laid on or near flowering plant parts. Eggs hatch after only three days at 25 degrees C (9 days at 17 degrees C). Larvae are nearly omnivorous, feeding on many important crops including cotton, tobacco, corn, tomatoes, peppers, potatoes, sunflowers, soybeans, sorghum, alfalfa, beans and other Fabaceae, a number of fruit (citrus, prunus), forest trees and ornamental plants and flowers. Many mortality factors, including cannibalism in the later instars, usually limit the number of insects per plant part.

Larvae rarely move from one plant to another. Therefore, if damage is detected, the larvae are usually in close proximity. Larval development is rapid under favorable conditions lasting only 19-26 days at 25 degrees C. Fully developed larvae move to the soil where they form an earthen cell 2-10 cm below the surface. The pupal period generally lasts from 8-21 days depending on the temperature. Diapausing pupae can overwinter in the soil in more temperate areas for long periods of time (> 175 days). In tropical areas, diapause can be induced by drought.

Adults are highly migratory and can move long distances (> 100 km). During the summer, adults move north into portions of Europe where it is believed they are unable to overwinter. Overwintering survival is limited to below 40 degrees north latitude. During the cooler fall months, adults from northern European areas migrate south. Because successive generations move from one economic crop to another and thereby are exposed to many applications of pesticides, this species has become highly pesticide resistant.

Identification

This species is similar in appearance to our native H. zea and to exotic heliothine noctuids (e.g. Helicoverpa punctigera, Heliothis pelitigera). Presently, reliable identification is based on examination of the male genitalia (Hardwick, 1965). Development of molecular techniques in the near future may provide identification techniques for immature stages and adult females.

Eggs are small (approximately 0.5 mm ida.) and subspherical (dome shaped with a slightly flattened bottom) in shape. Eggs are usually laid singularly, making detection difficult near buds, flowers, fruits, or on leafy plant parts. Larvae are yellowish-white to reddish-brown in the early instars and appear spotted because of dark spiracles and tubercle bases. In later instars, the head is mottled and the body is marked with three dominant longitudinal dark bands or stripes (see Figure 2). Superimposed on the dorsal bands are numerous lighter colored wrinkled or wavy longitudinal lines. Color is extremely variable, ranging from shades of green, straw yellow, black and pinkish or reddish brown. Fully grown larvae are 30-40 mm long. Larvae may feed internally, in fruits and vegetables, making detection difficult. External feeding damage, particularly by later instars, is readily detected. Pupae are 14-18 mm in length, smooth and mahogany- brown in coloration. Larval and adult stages cannot be distinguished from our native corn earworm (syn bollworm) Helicoverpa zea (Boddie) using external characteristics. The adults have a 3.5-4 cm wing span with a 1.4-1.8 cm long, stout body (Figure 3). Coloration of forewings of both sexes have a line of 7 or 8 black spots on the margin. Hindwings of both sexes are cream color with a dark-brown outer-marginal band.

Detection

Adult males can be detected using pheromone-baited traps. Adults of both sexes can be captured in black light traps. Larvae can be located by inspecting plants for feeding damage and fruits for bore holes. Plant material needs to be inspected carefully to detect eggs because of their small size and because they are usually laid singularly. Ornamental plants, cuttings and cut flowers provide good pathways for movement of this pest in international trade. This pest has been transported on cuttings to greenhouses in northern Europe which is outside of its normal range.

We wish to acknowledge Steve Passoa for the photos and Janet Knodel for the specimens.

For more information contact: Vic Mastro, Fax: 508-564-4398

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