The host location behaviour of two closely related bethylid parasitoids was investigated under laboratory conditions. Although both species of parasitoid attack the coffee berry borer (CBB) Hypothenemus hampei Ferrari, they differ in their diet breadth. In Y-tube olfactometer bioassays, we investigated the behavioural responses of Cephalonomia stephanoderis (Betrem), a parasitoid with a narrower diet breadth, and Cephalonomia hyalinipennis (Ashmead), a parasitoid with a wider diet breadth, to the coffee–CBB complex volatiles. The results revealed that the responses differed for the two species. In single- and dual-choice tests, C. stephanoderis was attracted to volatiles emitted by CBB-infested coffee berries, dust/frass and CBB immature stages, whereas C. hyalinipennis was not attracted to any cues from plant–host complex offered.

Bacillus sphaericus (Bs) is a potential mosquito larvicide especially against Culex quinquefasciatus (Say), the vector of bancroftian filariasis. It is a gram-positive, aerobic and endospore-forming bacterium. During sporulation, it synthesizes binary endotoxins (molecular weight 42 and 51 kDa proteins) that are highly toxic to mosquito species. The mode of action of the binary toxin of this biolarvicide in the alimentary canal and the ultrastructural events in the tissues of the affected larvae have been demonstrated. Lysosomal components are the most important organelles involved in the metabolism of the foreign molecules encountered by the cells. In this paper, we report the ultrastructural changes in the midgut epithelial cells, with special emphasis on lysosomes (L), in untreated Cx. quinquefasciatus larvae and those treated with the Bs-IAB59 bacterial strain. In the Bs-treated larvae, the size of the L gradually increased, and within 16 h, fine filaments appeared and compartmentalized into small lamellar bodies, within the L. After 36 h, these lamellar bodies appeared to be collapsed, and later disintegrated in the 48th hour. In the untreated larvae, such ultrastructural changes in the L were not seen. These observations suggested that, though the target site of action of the Bs toxin is the midgut epithelial cells, ultrastructural changes in the L compartments play a vital role in the mortality of the mosquito larvae.

The legume pod borer (Helicoverpa armigera (Hubner)) is one of the most important pests of pigeonpea. The levels of resistance to H. armigera in the cultivated germplasm are quite low, and therefore there is a need to introgress resistance genes from wild relatives into the cultigen. We evaluated a diverse array of wild relatives of pigeonpea for oviposition non-preference and antibiosis components of resistance to H. armigera. The accessions ICPW 1 (Cajanus acutifolius), ICPW 13 and 14 (C. albicans), ICPW 159 and 160 (C. sericeus), ICPW 68 (C. platycarpus), ICPW 83, 90, 94, 125, 137, 141 and 280 (C. scarabaeoides), ICPW 207 (Paracalyx scariosa) and ICPW 210 (Rhynchosia aurea) showed high levels of antixenosis for oviposition under no-choice, dual-choice and multi-choice conditions. High levels of antibiosis were observed when the larvae were reared on leaves and/or pods of C. acutifolius (ICPW 1), C. cajanifolius (ICPW 29), C. sericeus (ICPW 160), P. scariosa (ICPW 207), C. scarabaeoides and C. albicans. Lyophilized leaf or pod powder incorporated into the artificial diet can be used to assess antibiosis to H. armigera, and high levels of antibiosis to H. armigera were observed in diets with leaf and/or pod powder of some of the accessions of C. acutifolius, C. lineatus, C. sericeus, C. scarabaeoides, C. platycarpus, P. scariosa and R. aurea. Post-embryonic development period was prolonged in insects reared on leaves and pods of wild relatives of pigeonpea. The accessions showing high levels of antixenosis and antibiosis can be used to increase the levels and diversify the bases of resistance to H. armigera in pigeonpea.

Cacao genotypes of various origins were evaluated for resistance to the cocoa mirid (Sahlbergella singularis (Haglund)) based on field damage, antixenosis, antibiosis and tolerance. Field damage was assessed by scoring recent and cumulative damage by the mirid to the major genetic groups of cacao. Antixenosis assessment was based on the number of feeding lesions on twig segments using a choice test. Antibiosis was measured through survival of young mirid nymphs on shoots and pods, whereas tolerance was assessed through the reaction of the twigs to mirid feeding punctures. Among the genetic groups of cocoa, the Upper Amazon, the materials from Guiana and hybrid genotypes were the least damaged by the mirids, both for recent and cumulative damage. The Catongo group was, by far, the most susceptible group with more than 50% of the canopy showing both recent dieback and cumulative canker damage. With regard to antixenosis, antibiosis and tolerance, significant differences (P < 0.05) were found between the genotypes. The least preferred clones sustained between 2 and 3 lesions compared with the most preferred ones with 6–8 lesions per twig segment. Clones UPA402, T79/501 and IMC67 gave the lowest rate of mirid nymph survival, indicating that they exhibit antibiosis. The clones PA107, SCA6 and C151-61 sustained high numbers of mirid feeding lesions and relatively high levels of shoot death, but have a good ability for re-growth and can be considered as tolerant genotypes.

We studied the abundance and diversity of flower-visiting insects on Bt and non-Bt cotton plants in the Makhathini Flats region of South Africa during the 2003/2004 and 2004/2005 crop seasons to detect any impact of the Bt toxin (Cry1Ac). Bt cotton cultivars produced more flowers than non-Bt cultivars regardless of the cropping conditions (farmers' fields or research station), probably due to the fact that Bt cotton is not susceptible to flower bud pests. The results obtained in both crop seasons highlighted the prevalence of honeybees (Apis mellifera L.), various Nitidulidae and a unique Meloidae species (Mylabris oculata Thunberg) as flower visiting insects in this area. No impact of the Bt phenotype on insect abundance and diversity could be drawn on the basis of our comparative results on Bt and non-Bt cotton plants, and no direct effect of these transgenic plants was actually noted. The potential role of some of the inventoried insects, especially M. oculata, in the dispersal of transgenic pollen is discussed.

Studies on the larvicidal properties of extracts and fractions from Kotschya uguenensis Verdc. were done by long-term exposure of Anopheles gambiae s.s. larvae. The cumulative mean percentage mortalities and deformities at different concentrations for the extracts and fractions were recorded after every 24 h. Treatment of A. gambiae s.s. larvae with K. uguenensis extracts showed growth disruption by forming elongated guts and resulting in eventual death. Larvae treated with the methanol extracts from the stem and root barks, and fractions of the former extract attained complete mortality in 6–8 days at 50 and 100 ppm. More deformed larvae were observed from the methanol extract of the stem bark (40%) and methanol-soluble fraction (88%) than those treated with water-soluble fraction (22%) and methanol extract of the root bark (5%). The growth disruption may be associated with constituents in the plant that interfere with the normal endocrine system functions.

In Cameroon, the demand for hive products is growing. Honey and pollen yields are low in the country, partly because of the poor knowledge of the apicultural value of the flora. To determine the apicultural value of Dichrostachys cinerea (L.), Vitellaria paradoxa Gaertn. F., Persea americana Mill. and Securidaca longepedunculata Fres., Apis mellifera adansonii Latreille activity was observed on the flowers of these plants in Ngaoundéré, from December 2001 to May 2002 and from December 2002 to May 2003. The flowers of each plant species were prospected at least 4 days per month, between 0700 and 1800 h, for recording of the nectar and/or pollen foraging behaviour of A. m. adansonii workers. Results show that A. m. adansonii harvest nectar and pollen of V. paradoxa, P. americana and S. longepedunculata. The flowers of D. cinerea were visited for pollen only. The greatest number of workers foraging simultaneously on a plant varied from 34 (D. cinerea) to 1640 (P. americana). A. m. adansonii workers that visited flowers of a given plant species once remained with this nectar source throughout the observation period. Thus V. paradoxa, P. americana and S. longepedunculata could be cultivated and protected to increase honey production, whereas D. cinerea could enable bee-keepers to increase their pollen production as a hive product. During foraging, A. m. adansonii workers increased pollination possibilities of each of the plant species.