The impact of a new design of permethrin-impregnated wall cloth (“Mbu” (mosquito) cloth) on mosquito populations was assessed in Marigat area of Baringo District, Kenya. The cloth was fitted in 2000 houses. Mosquito relative density, species composition and the proportion of blood-fed females before and during the use of the Mbu cloth were monitored by hand catch, exit trap and CDC light trap catches. The common mosquito species were Culex quinquefasciatus, Mansonia uniformis, Anopheles gambiae sensu lato and An. funestus. A statistically significant decline in the mosquito population was observed following the introduction of the cloth. The decline was particularly high during the first and second six month impregnation cycles when it ranged between 43 and 94% indoors. C. quinquefasciatus was less affected by the cloth than other species, while M. uniformis apparently avoided treated houses. An. gambiae s.I. and An. funestus were collected in extremely low numbers during the post-treatment period. The Mbu cloth and other permethrin impregnated wall-hanging fabrics constitute a novel way Of controlling mosquitoes and malaria in rural communities.

—In order to evaluate the effect of permethrin-treated wall cloth against phlebotomine sandflies, a study lasting 26 months (February 1989 to March 1991) was conducted in Marigat Location of Baringo District, Kenya, an endemic focus of both visceral and cutaneous leishmaniases. In six experimental villages, a total of 2000 houses were fitted with cloth made of cotton and impregnated with permethrin EC 20% at a dosage of 0.5 g/m2 diluted in water. Houses in the two control villages were not fitted with cloths and were located 1.5 km away from the experimental area. Traps made of clear polythene sheeting were coated with castor oil and placed inside houses to collect endophilic sandflies. In the experimental villages, the permethrin-treated wall cloth (called Mbu cloth) reduced the population of sandflies found inside houses by 52–73%. Phlebotomus martini and P. duboscqi, vectors of visceral and cutaneous leishmaniases, were reduced by 76 and 85% respectively. In the experimental villages, highly significant differences were observed between the average numbers of sandflies collected before deployment of the treated wall cloth and those observed after thethird treatment of the cloth. No major sandfly reduction was observed however, in the control villages. There was also evidence of feeding reduction due to the permethrin.

Animal burrows are major habitats for both P. martini and P. duboscqi, vectors of visceral and cutaneous leishmaniases in Kenya. In burrows, both species were collected throughout the year. The highest relative abundance of P. martini and P. duboscqi was recorded in August and in April, respectively. The lowest relative abundance was observed in july for P. martini and in October for P. duboscqi. In termite mounds, P. martini was present all the year round, but P. duboscqi was absent for the greater part of the year. The highest relative abundance of P. martini was observed in November and April, while that of P. duboscqi was seen in March and April. The lowest relative abundance of P. martini was recorded in July. In termite mounds, P. duboscqi showed a significant positive correlation with rainfall, contrary to P. martini which did not afford any significant correlation with any environmental factor. Rainfall, relative humidity and ambient temperature did not correlate with relative sandfly abundance in animal burrows.

The influence of larval diet, body weight at imago, size of blood-meal and age on the fecundity of Culex quinquefasciatus was investigated. The mean weights of mosquitoes at adult emergence varied significantly with larval diet. Larvae reared on liver diet grew into heavier adults, and produced more eggs than those reared on milk. The volume of blood engorged by the female mosquitoes apparently remains constant during each gonotrophic cycle. However, the number of eggs produced is a function of both the blood-meal size and age of the mosquitoes. These results were discussed in relation to the need for full knowledge of the reproductive potential of this species of filaria vectors.

The juvenile hormone analogue (JHA) 6′, 7′,-epxy-3, 7′-dimethyl-undec-2′-enyl 6-ethyl-3-pyridyl ether at 10 ppm (v/v) applied to whole wheat grains was not toxic to adult insects, but effectively reduced the F1 generation of the lesser grain borer, Rhizopertha dominica (F.). However, topical applications of 4 ppm (v/v) of the JHA prevented normal metamorphosis of the larvae and pupae; all the test insects died due to morphogenetic abnormalities induced by treatment with the JHA.

The haemolymph of the tsetse, Glossina morsitans morsitans, contains a low molecular weight protein of very high density (1.29 g/mi). The protein was detected in the haemolymph during all developmental stages of the insect. Purification of the protein was achieved by a combination of density gradient ultracentrifugation and repeated gel permeation chromatography. Electrophoresis under non-denaturing and denaturing conditions showed the protein to be a single polypeptide chain (M,˜23,000). Amino acid analysis revealed a relatively high content of the acidic amino acids as well as serine and glycine. The protein contained lipids as shown by Sudan Black staining but was nonglycosylated. Using rabbit antiserum against the isolated protein in immunodiffusion and immunoblotting experiments, no cross-reactivity was detected with haemolymph samples from insects representing six orders. Although the function of the protein remains unknown, its uniqueness to Glossina suggests that it may have a role in the physiology of this insect.

As part of an extensive and systematic programme to find genetic sources of resistance to Aphis craccivora, a major pest of cowpea, Vigna unguiculata, a total of 181 accessions from the germpiasm collection at the International Institute of Tropical Agriculture were screened in glasshouse tests using a simple visual damage scale. Twenty-four accessions showed considerably reduced damage. To confirm these results on IS selected accessions, aphid population growth over 10 days was recorded. Zero aphids were found on three accessions (310,408-P2 and 801); another six accessions had populations of less than 30, compared with 200–400 on susceptible varieties. The other accessions showed only partial antibiosis and/or tolerance.

Light and pheromone trap networks were used to monitor and compare moth catches ofHelicoverpa (= Heliothis) armigera (Hubner) in both types of traps at many locations across India. There were obvious changes with latitude in flight patterns and in the correlation between light and pheromone trap catches. At northern locations, the correlation between light and pheromone trap catches were higher as compared to southern locations. The traps located in the central part of India showed correlations, intermediate between those of northern and southern locations. Pheromone traps were thus found suitable for monitoring at northern and central locations. At southern locations, where light and pheromone trap catches differ considerably at different times of the year, both types of traps should be operated simultaneously for better monitoring of this insect. Good correlations were found between larval population and light and pheromone trap catches of H. armigera at Patancheru, one of the southern locations in India.

Two indigenous maize cuitivars, Inbred A and Nyamula, were evaluated in a field trial for their susceptibility/resistance to Chilo partellus at the artificial infestation levels of 10 larvae/plant and 20 larvae/plant. Foliar damage was caused predominantly by C. partellus, but stem-tunnelling was caused not only by C. partellus but also by another species of borer, Eldana saccharina, which invaded the crop during the tassel emergence stage and persisted during harvest. In the 10-week old crop, the number of C. partellus recorded on Nyamula was greater than on Inbred A, but the incidence of injury to foliage and stem-tunnelling on the two cuitivars was the same. At harvest the degree of damage to the two cuitivars varied. At the infestation level of 20 larvae/plant, the cuitivars suffered equal stem-tunnelling. There was a significant negative correlation between stem-tunnelling and yield for Inbred A, but the correlation was not significant for Nyamula. At the infestation level of 10 larvae/plant, the correlation between stem-tunnelling and yield was not significant for either of the cuitivars, perhaps, due to excessive activity of E. saccharina in the stalks of Inbred A.

Sixteen taxa in the genus Vigna were compared for susceptibility to attack by Callosobruchus rhodesianus (Pic.) under laboratory conditions. Ovipositional response, adult emergence and their development periods differed significantly between the species. Although oviposition took place on all the Vigna taxa at varying levels, the bruchid was unable to develop successfully on four of the 16 taxa Investigated. V. vexillata var. angustifolia, V. vexillata var. vexillata, V. oblongifolia and V. luteola were resistant to attack.

Some properties of the gut amylase of Sophrorhinus insperatus Faust have been studied. The enzyme has maximum activity at pH 5.0 and 45°C. It is activated by C−, Ca2+ and Cd2+ tons and inhibited by Cu2+ and Hg2+ lons. Low Michaelis constants of 0.26 mg/ml and 032 mg/ml were obtained for the larva and adult gut amylases. Enzymatic activity was found to be consistently higher in the larva than in adult stage, probably suggesting the larval stage as the most destructive stage. Extracts of Cola nitida (Vent) Schott and Endlicher and C. acuminata (Pal de Beauv) Schott and Endlicher, inhibited amylase activity in vitro at varying magnitudes. The higher level of inhibitors in C. acuminata is an index of its low susceptibility to weevil attack both on the field and at storage.

A system for developmental timing for Panstrongylus megistus and Rhodnius prolixus (Hemiptera: Reduviidae) adults is presented, using as a marker, the evolution of the cuticular tanning after ecdysis. In both species the setting of the cuticular pigmentation pattern after imaginal moult is a homogeneous process in population, i.e. no individual variations were detected. The system allows one to estimate the exuvial time up to 5 or 7 hr after occurrence. A preferential exuvial period (PEP) was determined in the population under usual rearing conditions by using this system. The PEP runs from 2100 to 0500 hr for P. megistus and from 0100 to 0800 hr for R. prolixus. These data are meaningful for endocrine studies on those species. Studies on PEP under natural environmental conditions would be useful for the control of Chagas' disease vectors.

Artificial diets were formulated and evaluated for their suitability to rear the spotted bollworm, Earias vittella, a major pest of cotton and okra. The most satisfactory diet consisted of maize semolina 11%, wheat bran 4.6%, soybean powder 2.4%, yeast 1.4%, salt mixture 0.9%, ascorbic acid 0.3 %, cellulose 0.9 %, agar 1.8%, water 76.7% and preservatives. The insect was reared on this diet for 10 generations without any adverse effect on its development and reproductive potential.

The crude n-hexane and methanol extracts of the aerial parts of plant, Pimpinella monoica Dalz. (Umbelliferae) showed significant feeding deterrency to Spodoptera litura F. larvae. Phytochemical investigation of these extracts has resulted into the isolation of one furanocoumarin and five biogenetically related furanochromones. Furanocoumarin, isopimpinellin was found to be most active. Furochromones, visnagin and khellin exhibited significant activity while their hydroxymethyl analogues, khellol and ammiol showed moderate activity. α-Hydroxyisopropyldihydrofurochromone, visamminol was found to be least active.

Stability of resistance to corn planthopper, Peregrinus maid is (Ashmead), was studied over three plant growth stages in 56 sorghum germplasm accessions. Genotype x stage interactions were significant. Plant age exerted a profound influence on the rate of oviposition, establishment of nymph, macropterous and brachypterous adult populations and plant damage. Resistance to corn planthopper was stable over three growth stages in IS 18557, IS 18677 and PJ 8K(R), which also supported low colonization of nymph and adult populations; IS 12308 was unstable due to high deviation. Significantly low rate of oviposition on resistant as compared to susceptible genotypes and the positive and significant correlation between oviposition and plant damage illustrated that antixenosis for oviposition is the primary mechanism of resistance. As a consequence the genotypes preferred for oviposition showed susceptibility due to higher plant damage. Establishment of nymphs was affected on the genotypes, IS 1054, IS 1082, IS 2194, IS 3992, IS 12308, IS 18676 and IS 19349 which may be due to the factors involved either in reduced hatchability of eggs and/or deterrence or poor feeding preference of nymphs.

The fine structure of the trifoliate process of three species of Atherigona were studied. The outer surface of the lateral lobe of the process for the three species, A. bedfordi, A. hyalinipennis and A. secrecauda is covered with a dense mat of hairs. There are spine-like outgrowths on their inner surface referred to as “commasets” as well as some unusual sensilla on the rim of the lateral lobe and the section connecting the lobes to the stem. These structures showed inter-specific variation. The stem of the process is glabrous and granulate in A. bedfordi and A. secrecauda, but sparsely pilose in A. hyalinipennis.

The effects of Decis® (deltamethrin) and Systoate® (dimethoate) were assessed by the number of Megalurothrips sjostedti (Trybom) (Thysanoptera, Thripidae) recorded per cowpea plant at 40, 50, 60 and 70 days after planting (DAP), evaluated by the drop-cloth sampling method. The trial was carried out under natural infestation conditions during the 1985 early cropping season (from April to July). Systoate® was better than Decis® in controlling the flower thrips and its effect was significantly different from the unsprayed control (P = 0.01). The Decis® effect on the flower thrips was also effective in comparison with the control (P = 0.01). The effectiveness of two insecticides used in relation to pest management and the adequacy of the drop-cloth sampling method in relation to other methods are discussed.