Effect of field infestations of immature pigeonpea (Cajanus cajan (L.) Millsp.) pods on production of active (flight) and sedentary (flightless) morphs of Callosobruchus chinensis (L.)

Abstract

A study conducted in Uganda on Callosobruchus chinensis showed that adults emerging from dry seed-infested and immature pod-infested pigeonpea diered in a number of morphological and biological characteristics in one or both sexes. Adults emerging from dry seed-infested pigeonpea were more or less uniform in a number of these characteristics; in contrast, adults emerging from green podinfested pigeonpea diered depending upon when they emerged: the dierences were greatest between those emerging during the 2nd to the 6th days from ®rst emergence, and those emerging from the 8th to the last days of emergence. In one or both sexes, these dierences were expressed in terms of elytral hue and size, body length, distance between the compound eyes, length of pygidium, body water content, pre-maturation periods, fecundity and adult longevity. We suggest that these dierences are due to polymorphism, and speci®cally the predominance of¯ight forms among late emergers from pod-infested pigeonpea. The dierences observed in the two morphs of C. chinensis and ascribed to the¯ight and ightless forms, are thought to be adaptations for survival and propagation under ®eld and storage conditions, respectively. The predominance of emerged adults of the¯ightless forms from dry seed and the¯ight forms from green pods were associated with low moisture content in dry seed and high moisture content in green pods, respectively. These observations show that bruchid control measures are needed in the ®eld as well as in storage.

Insectes ravageurs des graines de légumineuses

“…Il est en revanche absent dans les populations monovoltines se développant aux dépens des légumineuses sauvages au Japon. Nahdy et al (1999) ont analysé des populations de C. chinensis se développant en Ouganda aux dépens de Cajanus cajan et ont décrit chez cette espèce un polymorphisme proche de celui observé chez C. maculatus. Les adultes des deux morphes diffèrent par des critères morphologiques et comportementaux (aptitude ou non au vol).…”

Comparative insecticidal activity of nano and coarse silica on the Chinese beetle Callosobruchus Chinensis (L) (Coleoptera: Bruchidae)

“…Because they are known for their high protein content of good quality, they are invaded by a series of beetles and these beetles can cause serious damage and seed weight loss. Infestation commonly begins in the field, where eggs are laid on mature pods (Singh, 1997;Nahdy et al, 1999). The pulse crops are attacked by more than 150 insect pests.…”

Botanicals as eco friendly biorational alternatives of synthetic pesticides against Callosobruchus spp. (Coleoptera: Bruchidae)—a review

“…Eggs adhere on the surface of pods from where the first instar larvae bore into the seeds through the pod cover. During threshing, no clear cut evidence or symptoms of damage is visualized (Nahdy et al 1999). Infestation in the field has no serious implications as the damage in the field is low.…”

“…However, once infested seeds are stored, huge damage occurs due to rapid multiplication of insects in a very short time (Taylor 1981). Although beginning of infestation occurs from field, no one denies from the cross infestation which also occur in food commodities during storage (Nahdy et al 1999). …”

“…in response to environmental variations. They have two distinct adult morphs; a flightless, inactive, normal or sedentary morph and a flight or active morph (Nahdy et al 1999;Zannou et al 2003). This polymorphism of bruchids arises from their different ecological niches (Messina 1990).…”