Insect pest problems on cowpeas can be reduced by use of strategies which involve ecological manipulations. These include crop diversification (mixed cropping, etc.), alteration of planting dates, crop rotation, trap-cropping and weed control. The merits of these cultural methods of pest control are discussed.

The status of biological control of cowpea pests is still low but promising. The crop is an annual and therefore offers very limited possibilities for the application of the classical biological control techniques. However, a large number of parasitic Hymenoptera, Diptera and predatory Hemiptera, notably Reduviids have been identified in the cowpea ecosystem. Ecological studies of some of these have been carried out and levels of parasitism determined in a few cases, but their significance in the dynamics of cowpea pest populations have not been fully established.

It is however known that conservation of parasites and predators in their wild environment is one of the traditional biological control methods. Therefore, a rationalized pesticide programme for the control of cowpea pests should aim at preventing hazards to their natural enemies so as to increase their biocontrol efficiency.

Glutathione S-transferases (GSTs) have been recognized as important metabolic detoxifying enzymes in many phytophagous insects. However, the contribution of GST to insecticide resistance in Zonocerus variegatus (L.) has not been studied. Therefore, we carried out an initial study on the induction and kinetics of GST in Z. variegatus exposed to pyrethroids (PYRs) and Ocimum gratissimum leaf extract. Fifth-instar nymphs of Z. variegatus collected from cassava farms (with no history of insecticide exposure) on the campus of the University of Ibadan were reared to adult stage. Adult insects were divided into four groups of two replicates, each consisting of 30 insects. The groups were exposed to 20 ml of PYR insecticide and 25 mg/dl and 250 mg/dl of O. gratissimum leaf extract, respectively, while the last group served as the control. GST was extracted from the body tissues of the insects using the Bradford method and the kinetics of the enzyme was evaluated using the Lineweaver–Burk plots. No mortality was recorded in insects exposed to 25 mg/dl of O. gratissimum leaf extract, while mortality rates of 93.3 and 43.3% were recorded in insects exposed to PYR insecticide and 250 mg/dl of O. gratissimum leaf extract, respectively. The activity of GST was higher in insects exposed to the insecticides than in the control insects, while a higher enzyme activity was recorded in insects that died after exposure to the insecticides than in insects that were alive after exposure. The GST extracted from insects that were alive after exposure to PYR insecticide and O. gratissimum leaf extract exhibited a high affinity for the glutathione substrate compared with that extracted from insects that died after exposure. Higher GST activity in insects exposed to insecticides is indicative of the role of this enzyme in the metabolic detoxification of insecticides by Z. variegatus.

Ovipositional nonpreference and larval development of stalk-borer, Chilo partellus Swin., on leaf-whorl and stem of 70 sorghums comprising of released varieties and hybrids, experimental high-yielding varieties, lines selected for stalk-borer resistance and local cultivars were studied in the laboratory. Data on oviposition of egg-masses as well as on number of eggs, larval duration, larval mortality and pupal weight on leaf-whorl and stem of individual variety were separately recorded. These characters were also correlated with number of holes, number of tunnels and per cent tunnelling observed in the field.

The egg-masses per seedling ranged from 0.32 to 2.25, while eggs per seedling varied from 2.25 to 20.80 on different varieties. These were highly correlated (0.92**) characters. The varieties SPV nos 35, 101, 110, 232, 257, 289, 291, 309 and 311, E 302, E 701, CSV nos 3, 6 and 8R and Aispuri were relatively less preferred for oviposition. Larval development took 17–32 days on leaf-whorl and 33–62 days on stem of the various varieties. The larval duration on leaf-whorl as well as on stem were more than average on SPV nos 35, 103, 107, 110 and 310, E 302, E 701, CSV-8R, IS 2312 and Aispuri. The larval mortality ranged from 1.7 to 95.0% on leaf-whorl and 13 to 95% on stem. Significantly higher larval mortality on leaf-whorl of SPV nos 35, 101, 292 and 311, E 302, CSV nos 3, 6 and 8R was recorded. It was 11.5 and 29.6% higher on SPV-35 and CSV-8R respectively than the most resistant variety, IS 2312. Larval mortality on leaf-whorl of early maturing varieties was 8.1% more than late varieties. The mean pupal weight was 65.55 ± 3.82 mg on leaf-whorl and 51.65 ± 4.93 mg on stem. The pupal weights were 47–75 mg on leaf-whorl and 33.5–47.7 mg on stem of local varieties.

Larval duration was positively correlated with larval mortality on both leaf-whorl and stem and negatively with pupal weight on leaf-whorl. Larval duration and mortality on leaf-whorl were negatively correlated with per cent ‘dead hearts’, and number of tunnels per plant. Larval duration and mortality on stem were also negatively and significantly correlated with holes per peduncle and per cent tunnelling. The magnitude of correlations of larval duration and mortality with tunnelling parameters were higher than that of oviposition. Though ovipositional nonpreference and antibiosis act together to determine the degree of resistance, antibiosis has a greater effect on Chilo resistance than the effect of ovipositional nonpreference.

The antibiosis factor(s) affecting larval development exists in leaf or in stem or in both the plant parts. Short peduncle varieties were less preferred for oviposition.

Key mortality factors of sugar-cane top borer, Scirpophaga excerptalis Wlk. during the third brood were quantified on a susceptible sugar-cane variety, Co 1148 during 1981 and on susceptible CoJ 64, resistant CoJ 67 and collateral hoste, Sorghum halepense Peru, and Saccharum spontaneum L., during 1982 in Haryana (sub-tropical India). As artificial rearing of this borer is not possible, a methodology to have uniform age group at the beginning of the study by tagging the egg masses and the freshly attacked plants was developed. Results showed that parasitization of various stages and failure of neonate larvae to enter the midribs were the key mortality factors common to all the hosts. In S. halepense there was negative trend index (0.104) due to high mortality of larvae in all the instars. This revealed that it is not a suitable host for top borer. No predators were found to feed on any of the sub-imaginal stages of the borer due to the unique habits of the borer.

In olfactometer assays, the predatory mite Amblyseius ciicumeris (Oudemans) recorded a significantly higher response to volatiles from chrysanthemum, Denranthemct morifolium plants infested with western flower thrips (WFT), Frankliniella occidentalis (Pergande) than to volatiles from healthy plants. This increased attraction was attributed to the presence of higher amounts of Germacrene-D in WFT-infested plants. In choice experiments using synthetic volatiles, the predator remained longer in the olfactometer treated with 50 ng Germacrene-D and made many entries at 500 mg.

Preferential attraction of WFT to healthy chrysanthemum flower buds was observed, and attributed to the significantly higher amounts of (E)-β-farnesene found in the buds compared to leaves and open flowers. This attraction peaked at 100 ng/μl (E)-β-famesene. In greenhouse experiments, blue sticky traps with 500 ng (E)-β-farnesene or 1000 mg p-anisaldehyde attracted 32.3% and 27.5% more WFT than the untreated controls, respectively.

The prospects of using Germacrene-D in improving the attraction of A.cucumeris to whole chrysanthemum plants and (E)-β-farnesene in monitoring WFT, are discussed.

Polyacrylamide gel disc electrophoresis of the salivary secretion from the tsetse, Glossina morsitans morsitans Westwood, showed 11 protein bands, four of which were characterized as glycoproteins. Sixteen amino acids and four sugars in the hydrolysates of saliva were identified. Thin layer chromatography showed five lipid classes and three phospholipids. The secretion is a clear, transparent, viscous fluid with a pH between 7.00 and 7.5. These findings are discussed in relation to the nutritional requirements of the metacyclic forms of trypanosomes that may be found in the salivary glands.

A new 6a-hydroxylated pterocarpan, named hildecarpin, has been isolated from the healthy roots of Tephrosia hildebrandtii. It has been assigned the structure (−)-3, 6a-dihydroxy-2-methoxy-8, 9-methylenedioxypterocarpan on the basis of its spectroscopie data, optical rotation and chemical transformations. Hildecarpin has exhibited insect antifeedant activity against the legume pod-borer Maruca testulalis, an important pest of the cowpea (Vigna unguiculata), and antifungal activity against Cladosporium cucumerinum. This finding suggests that the pterocarpan phytoalexins formed as a result of microbial infection of the cowpea plant may constitute a basis for induced resistance in the plant against M. testulalis.

Among several species of insect pests that attack the millet crop, the earhead caterpillar, Raghuva albipunctella de Joannis and Acigona ignefusalis Hmps., are considered the major pests. The constraints against the successful implementation of an integrated pest management programme of these insects are examined. The relative importance and significance of host plant resistance in such a programme is compared against other modalities.

The use of insecticides is negated by lack of cash value returns, water supply, trained personnel and poor delivery system. Cultural practices, such as the synchronisation of early planting, destruction of harvest residues and end-of-season ploughing, have the potential for reducing carry-over populations. However, the difficulties in their implementation range from farmer education and efficiency to changes in traditional practices and introduction of new labour intensive practices after harvest. While it appears that natural enemies are taking a gradual toll on R. albipunctella, they appear inefficient in controlling A. ignefusalis. A range of plant characters have been identified: tillering in certain varieties as a form of tolerance to borers; maturity cycles that result in escape (pseudo-resistance) from Raghuva infestation, hairiness in relation to preference for oviposition and head compactness in deterring larval penetration into millet heads. Most of these characters are common in landrace types. The real problem appears to be one of incorporating and utilising the identified resistance into germplasm sources which possess other desirable agronomic characters that the farmer requires. This implies multi-disciplinary effort which is the basis for integrated pest management. In most of Africa, and in the Sahel in particular, this basis is remotely present.

Field surveys along the Lake Basin and the Coastal regions of Kenya were carried out to assess the natural incidence of pathogenic microorganisms associated with the legume pod-borer, Maruca testulalis Geyer on the cowpea crop. A regular sampling regime was maintained on plots planted with four varieties of cowpea: T VX 66–2H, Vita 3 (TVU 1190), Ex-Luanda and Nyar-Milambo. Larvae of M. testulalis were recovered from the flowers and pods of the crop, and subjected to routine laboratory disease diagnosis including: tissue examination, culture incubation, microscopy and pathogen identification. The main groups of pathogenic microorganisms found to act as natural mortality factors to M. testulalis larvae include: protozoa, bacteria, fungi and a virus. A higher level of disease incidence and diversity on M. testulalis larvae occurred in the lake basin region of Kenya than the coastal part.

Trials for cold storage of the mummies of Aphis craccivora Koch parasitized by Trioxys indicus Subba Rao & Sharma were made. Newly formed mummies having fourth instar larvae of the parasitoid were put either at 20–25°C or at 12–15°C, 10 hr photoperiod for 24–72 hr before storage inside the refrigerators (4–8°C) for 10–40 days. A higher proportion of adult emergence was usually associated with the group of mummies passed at 12–15°C before storage and practically good emergence was recorded even if the mummies were stored for a month at 4°C if kept at 12–15°C for 72 hr prior to storage.

The use of pheromones to disrupt mating behaviours is perhaps the most promising method for controlling the sugarcane pest Dasylepida ishigakiensis Niijima et Kinoshita, also known as the white grub beetle. Herein, based on laboratory observations of mating, oviposition and hatching behaviours in the white grub beetle, we suggest guidelines for the timing and length of sex-pheromone release in the field. In the present study, we collected virgin female adults early in the mating season (4 February) in sugarcane fields in Okinawa, Japan and mated them in the laboratory after different time intervals with males collected at the same time. We investigated the effects of delayed mating on mating success, timing of oviposition, female longevity after mating and progeny hatchability. Mating success – defined as the proportion of mated females that produced progeny – and hatchability were not significantly affected by mating delays of less than 31 days, although further delays dramatically decreased these parameters. Female life span and the time between mating and oviposition were unaffected by mating delay. Similar results were obtained for laboratory-reared adults mated on day 45, 60 or 80 after adult emergence. Based on these findings, we propose that releasing synthetic sex pheromones between mid-January (i.e. shortly before the start of the mating season) and late March would be optimal for disrupting the mating behaviours of this beetle in the field.

Data on the populations of larval and pupal stages of Aedes africanus, an important sylvan vector of arboviruses, were collected from tree-holes which are its natural breeding sites in forests. Comparable data were also simultaneously collected from bamboo pots stationed in the Zika Forest to simulate the natural breeding sites. Survivorship curves and time-specific life-tables were constructed. It was observed that the immature stages of A. africanus in both tree-holes and bamboo pots suffered very high mortality rates (an average of 91% in tree-holes and 83.2% in bamboo pots). It was further observed that mortality rates varied monthly. The survivorship curves constructed for the immature stages collected on a daily basis tended to show that a large proportion of the mortality rate was confined to the early instar stages, but the survivorship curves based on the combined data for the 2 years indicated constant mortality rates for all the stages. The high mortality rates of the immature stages of A. africanus appear to be attributed to predation by larvae of Toxorhynchites brevipalpis, with which it shares the same breeding places.

Some aspects of flight behaviour in the triatomine bug Triatoma sordida were investigated. A strong link between flight initiation and nutritional status as expressed by weight: length ratio was shown. Flight activity was strongly nocturnal and unimodal, commencing with the onset of darkness. A capacity to lay eggs after flight initiation was noted.

Topical application of crude ethanol extracts (CEs) of the leaves of 43 of 51 Jamaican plants produced varying degrees of multiple acaricidal effects on engorged Boophilus microplus Canst., including mortality (M), inhibition of oviposition (IO) and inhibition of embryogenesis (IE). Acaricidal indices (AI) ranged from 50 to 100 for the CEs of 29 plants, 38 to 47 for 9 plants and from 0 to < 25 for 13 plants. The most active CEs, in decreasing order of activity (AI values in parentheses) were those of: Simarouba glauca (100), Symphytum officinale (99), Nicotiana tabacum (95), Hibiscus rosa-sinensis (93), Ervatamia divaricata = Ricinus communis (82), Salvia serotina (80), Stachytarpheta jamaicensis (79), Blighia sapida = Ocimum micranthum (76), Spigelia anthelmia (75), Cycloptis semicordata (74), Mormordica charantia (71), Bontia daphnoides (69), Azadirachta indica (68), Capsicum annum = Catharantus roseus = Petiveria alliacea (66), Gliricida sepium (64), Lippia alba (62), Cuscuta americana = Erythrina corallodendrum (61), Piper amalago (60), Cannabis sativa = Cecropia peltata (58), Dioscorea polygonoides (56), Artocarpus altilis (53), Crotalaria retusa (51), Citrus aurantium (50).

Floral fragrance oils related to pollination were studied in three species of Theobroma and one Herrania species (Sterculiaceae) in Costa Rica. This study was prompted by field observations that floral odours and floral visitors are markedly different between Theobroma and Herrania, as well as between species of Theobroma.

Floral fragrance in cultivated T. cacao consisted of 78 components, primarily saturated and unsaturated hydrocarbons, with 1-pentadecene the major constituent followed by n−pentadecane. The distribution of 1-pentadecene was similar at 0900 hr (43.6%), 1130 hr (52.5%) and 2000 hr (51.1%) sampling times but only 1.2% at 1600 hr. The ratio of 1-pentadecene to n−pentadecane in the 1600 hr sample, approximately 1:6, contrasted with a 3:1 ratio at 0900 and 1130 and a 6:1 ratio at 2000 hr. The greatest concentration of volatiles was found in the 1130 hr sample, with 0900 and 2000 hr concentrations being essentially equal and intermediate between the high (1130 hr) and the low (1600 hr).

Of the 58 compounds detected in T. mammosum steam distillate at 0815 hr, an array of linalool oxides accounted for 12.5% of the oil followed by isoeugenol (8.9%). Saturated hydrocarbons were also present but, unlike T. cacao, n-tricosane was the major hydrocarbon (12.2%). The major constituents of T. mammosum oil clearly distinguish this species from T. cacao.

A markedly different profile of major floral volatiles was found in T. simiarum: major constituents included the monoterpenoids citral, geraniol, nerol, and citronellol. Unlike the oily, hydrocarbon fragrance of T. cacao and T. mammosum, T. simiarum floral fragrance is citrus-like both in the field and laboratory. Our fragrance studies suggest considerable evolutionary divergence within Theobroma.

The floral fragrance of H. cuatrecasana contained volatiles characteristic of dipteran-pollinated plant species. Unusual volatiles found in Herrania fragrance included iridomyrmecin, guaiol, and other azulenic derivatives. No such monoterpenoids and bicyclic sesquiterpenoids (with the exception of longifolene, 0.1%, in T. simiarum) were found in Theobroma. The profiles of floral fragrance chemotaxonomically support the exclusion of Herrania spp. from the genus Theobroma.

Species composition and behavioural patterns were determined for anopheline mosquito samples collected between October and September 1990, from Gambella region, south west Ethiopia. At least eight anopheline species, which differed in their habits, were found to be prevalent in the region. Findings of indoor-resting collection and hut density determinations showed the relative prevalence, in decreasing order of magnitude, to be Anopheles pharoensis, A. gambiae s.l., A. nili, A. coustani, and A. ziemanni. On the other hand, the relative frequency of occurrence based on outdoor human-bait capture was A. pharoensis, A. ziemmani, A. coustani, A. squamosus, A. paludis and A. funestus, in decreasing order of importance. The rate of human feeding of A. nili, A. gambiae s.l., A.pharoensis and A. coustani were 37.5, 33.0, 22.5 and 6.7%, respectively. Among the endophilic mosquitoes assayed, the overall infectivity rate was found to be 0.56%. Sporozoite rates of 0.77% for A. gambiae s.l. and 0.47% for A. pharoensis were determined.

The quantitative and qualitative changes of bacterial flora associated with the silkworm (Bombyx mori) at different stages of its life cycle were studied. Larvae reared on mulberry leaves were dissected and their bacterial populations counted after a 3-day incubation period at 28 ± 2°C. The results showed a higher heterotrophic bacterial population in the fourth and the fifth instars, which coincide with the active feeding stage of the larvae. The similarity of the genera observed in the digestive tract and that observed on the leaves fed to the larvae suggests colonisation of food microflora in the gut following ingestion. The bacteria inhabiting the gut of silkworm were found to be elaborating amylase, caseinase, gelatinase, lipase and urease. The highest percentage of isolates were protease producers followed by lipid and polysaccharide splitters. The results indicate that the bacterial flora play an important role in the digestion of ingested food material.

The biosystematics of species in the Cotesia flavipes complex is reviewed with reference to studies conducted on their morphology, morphometrics, enzyme electrophoresis and hybridisation. A survey of 5 morphological characters scored from 17 populations indicated that the scuto-scutellar sulcus and the rugosity on the propodeum could be used to separate the species. The shape of the male genitalia was valid for separating the populations of C. flavipes from those of C. sesamiae and C. chilonis. Canonical variate analysis separated the complex into three distinct clusters with populations from Africa together, populations from Asia and the neotropics forming a second cluster, and material from China and Japan forming the third cluster. Electrophoretic studies showed that esterase, glucosephosphate isomerase, hexokinase, sorbital dehydrogenase and phosphogluconate dehydrogenase, among others, had fixed alelles and could be used to distinguish the species. Cladistic analysis of the allozyme data indicated that allopatric populations currently included in C. flavipes may not be a monophyletic group. Interspecific crosses revealed that males of C. sesamiae could mate with females of C. chilonis and produce viable females.

Literature on the distribution, biology, seasonal population fluctuations, economic importance, acaricidal susceptibility and measures for the control of the cattle ticks Boophilus microplus Canst., Amblyomma cajennense Fab., A. variegatum. Fab. in the Caribbean has been critically reviewed. The ticks, which inflict about $62 million annual loss on the region's livestock industry, are still susceptible to acaricides, despite a few populations of B. microplus showing 31- to 227-fold resistance to lindane and 15- to 67-fold resistance to carbaryl, chlorfenvinphos, dimethoate and crotoxyphos.

The screwworm, Cochliomyia hominivorax Coq. is widespread, except in Puerto Rico and Curacao, from where it has been eradicated. The annual cost of surveillance against the fly and treatment of cattle for myiasis is estimated to be about $59 million. Its eradication from the entire Caribbean region by insect sterile method is advocated.

Steam-distilled floral oils (essences) from several species of Theobroma(Sterculiaceae) (T. cacao Linneaus, T. simiarum Donn. Smith, T. mammosum Cuatr. & Leon, and T. speciosum Willd.) were tested using McPhail traps, in an abandoned Costa Rican cocoa plantation to determine their levels of attraction for flying insects. In each of the three bioassays (two successive dry seasons and one intervening rainy season), the traps were inoculated with floral scents at 1, 10, and 100 ppm, while controls were inoculated with a 10% solution of chloroform solvent in distilled water. Of a total of 223 Diptera captured in all three bioassays, only 5% were found in the controls, indicating attraction to the floral oil. About 72% of all Diptera captured were Cecidomyiidae, of which three species, Mycodiplosis ligulata Gagne, Aphodiplosis triangularas (Felt.) and Ledomyia sp., comprised 59% of the total. Eighty-eight per cent of all midges captured were females. Only 7% of the total were known cocoa-pollinating midges of Ceratopogonidae, and all of these were females. Sixteen per cent were Phoridae, known pollinators of the allied genus Herrania in Costa Rica. Although the chemical composition of floral oils varies greatly among the species of Theobroma, no discernible differences were found in the attraction of midges to floral oils tested. While floral fragrances in Theobroma species may represent a generalized adaptation for dipteran pollination, small numbers of several species of Trigona bees (Hymenoptera: Apidae: Meliponinae) were also attracted to the floral oils.