The insecticide diflubenzuron, Dimilin, was applied topically to the eggs of Tabanus triceps and Chrysops dispar. Mean per cent hatchability of these eggs at various concentrations ranging from 1 to 150 ppm were observed. The hatchability depended upon the age of the egg and increased with age. A minimal dose of 10 ppm of diflubenzuron caused 100% mortality (no hatchability) at the age of 48 hr in both species. The per cent hatchability was inversely proportional to the concentration of Dimilin. The larvicidal effect of Dimilin was also noted. Larval mortality (100%) was observed after 60 hr treatment. The larval mortality was directly proportional to the concentration of Dimilin. The results show that Dimilin has potential for controlling Tabanid vectors.

Simple methods for production of all life stages of the banana weevil on its natural diet, banana rhizome and pseudostem are presented. Their effectiveness, labour demands and applicability for different purposes are discussed. The most effective method for the production of eggs, pupae and adults is the utilization of the rhizome part of suckers, whereas larvae are easier to recover from pseudostem. The hatchability of the eggs produced is high.

Populations of adults of Smicronyx guineanus Voss and Smicronyx umbrinus Hustache were sampled on the witchweed Striga hermonthica (Del.) Benth, in Burkina Faso. Samples were taken at four localities in 1991 and at one locality in 1992 and 1993 using a Univac portable suction sampler, beginning at emergence time of the adult weevils, to assess their dispersion patterns and the optimum sample size for Smicronyx. Sampling was done weekly by placing the 60-mm-diameter suction cone on a Striga plant until it was about 5 cm above the ground. Smicronyx adults on S. hermonthica were aggregated. A sample size of 20 and 126 units provided a 25 and 10% precision level respectively at six Smicronyx adults per sampling unit. A chart was designed which could be useful for determining the level of precision attainable at various densities of Smicronyx adults for sampling and monitoring programmes. Larval vertical distribution of Smicronyx was described. Striga plants were stratified with respect to distance from the base and categories were designated as upper, central and lower parts. Results indicated that Smicronyx larvae were located in the upper stratum of the witchweed where they made galls and destroyed large numbers of seeds.

Experiments on artificial infestation of soybean with pod-sucking bugs showed that Riptortus dentipes caused more damage to the plant than did Nezara viridula. The density of four insects per plant used was high enough to significantly damage the plant. The reproductive developmental stages of the plant defined as R3, R4 and R5 were sensitive to the pod-sucking bugs studied. Plots infested with R. dentipes adults suffered 72% pod damage compared to 44% pod damage in plots infested with N. viridula. Riptortus dentipes significantly affected the physiology of the plant and reduced grain yield and grain quality. The results also showed that there is potential for biocontrol of pod-sucking bugs.

Results of a field survey of certain host-related and off-the-shelf compounds as possible attractants for the black fly, Simulium arcticum (Malloch) (IIS-10.11) (Diptera: Simuliidae), are reported. Silhouette traps were baited with carbon dioxide and candidate attractants in an incomplete randomised block design. Carbon dioxide alone exerted a strong attractant effect on this species. Both acetone and crude whole body odour of cattle (tested in combination with carbon dioxide) were significantly more attractive than carbon dioxide alone (control). Although bovine urine produced larger catches than control (carbon dioxide only) traps, the effect was not statistically significant. Other odours tested in combination with carbon dioxide, including fractions of the crude bovine odour and l-octen-3-ol (a potent tsetse fly attractant), were without apparent attractant effect when compared to the carbon dioxide-only control.

A simple method for the insecticide bioassay of liposcelids is outlined. The contact toxicity of five organophosphorus insecticides (OPs) and two carbamate insecticides (CBMs) was ascertained for Liposcelis bostrychophila and L. entomophila. Liposcelis entomophila was more tolerant to all the insecticides tested than the other species. Malathion was the least toxic OPs to both species, while chlorpyrifos-methyl was the most toxic insecticide tested against L. bostrychophila. These findings are discussed in relation to the infestation of these liposcelids in rice storages.

Postembryonic development and adult emergence of Tribolium castaneum (Herbst) were adversely affected in varying degrees when its larval stage was reared on wheat flour treated separately (at concentrations of 0.001–1.0%) with one of the following commercially available extracts: roots of both sweet flag, Acorus calamus Linn. and Java devil pep per, Rauwolfia serpentina Benth ex Kurz, fruit cortex of soap nut, Sapindus trifoliatus Linn. and gum of Indian Myrrh Commiphora mukul Jacq. A marked decline in the reproductive potential, in terms of female fecundity and egg hatchability was observed when the extracts were applied topically or administered orally through diet.

The occurrence and distribution of Cerataphis palmae (Ghesquierei) on Raphia palms in six Southern States of Nigeria, were studied. The percentage infestation of palms in the States were 24.9% (Bendel), 41.23% (Cross River), 37.17% (Imo), 34.73% (Lagos), 11.55% (Oyo) and 28.0% (Rivers). C. palmae is found in places in Southern Nigeria where Raphia palms, particularly R. hookeri Mann & Wendl. and R. vinifera Beauv. occur. There was no significant difference in percentage aphid coverage among the six States (F = 2.013; 0.01 < P > 0.05).

Several terpenoids and oils were screened for vapour toxicity and repellency against the termite, Odontotermes brunneus. In toxicity tests, knockdown time KT50 and KT90 values were derived at 5 mg/cm2. For repellency screening, a new experimental setup was designed and effective time ET50 and ET90 values were determined at 2 mg/cm2. Among the compounds screened, eucalyptus oil produced the fastest knockdown (KT50 24.8 min) while β-ionone was found to be the least effective (KT50 536.0 min). Terpeneol (anhydrous) afforded maximum persistence of 338.0 min, whereas the least persistence was obtained from linalool (78.9 min) which prevented 50% of the population from crossing over the treated barrier (ET50).

The present study deals with the interrelationship of the neuroendocrine complex (NEC) and male accessory reproductive gland (ARG) of a cotton bug, Serinetha augur. The NEC consists of brain (cerebral ganglia), corpus cardiacam (CC) and corpus allatum (CA). Based on the staining reaction of aldehyde fuchsin (AF) and chrom alum haematoxylin-phloxin (CAHP), four types of neurosecretory cells have been identified in the brain. The neuroendocrine control over the ARG in S. augury was investigated through ARG extirpation (andgonadectomy)-induced hypertrophy of CA. The changing pattern of proteins in the brain during the pre- and post-mating periods (as judged by electrophoretic investigations) further supports the interrelationship of the NEC and ARG.

In the forest zone of Côte d'Ivoire, Vavoua's traps and supports treated with pyriproxyfen® (Sumitomo) have been tested against Glossina palpalis palpalis. The supports were impregnated one time only at the dosage of 2 mg/cm2.

This juvenile hormone mimic acting as growth regulator has a good efficacy: apparent density was reduced by 87% after 2 months and was maintained at this level for 150 days; percentage of nulliparous females was equal to 0 between 40th and 120th days.

Pyriproxyfen may be recommended for the control of animal trypanosomiasis vectors—if it costs less than the insecticides; its slow effect on tsetse population does not favour its use for the control of human African trypanosomiasis which needs a drastic and immediate reduction of Glossina densities.

Bioactivity of Melia azedarach L. was tested against diamondback moth (DBM), Plutella xylostella L. in the laboratory. The adult of DBM laid significantly lesser number (upto 71%) of eggs on the surfaces treated with methanolic extracts of M. azedarach than on those treated with solvent only. When larvae derived from above eggs were reared on fresh food, the mortality in the larval stage was upto 22.8% and that in pupal stage was upto 29.6%. The methanolic extracts also reduced feeding among the larvae significantly, when methanolic extract-treated food was offered to second instar larvae in a different set of experiment, thus, indicating an antifeedant effect.

Field experiments at the Msekera Regional Research Station during 1988–1990 and at Masumba (Luangwa Valley) Sub-station during 1989–1990 showed that six groundnut genotypes—ICG.485, ICG.2271, ICG-2306, ICG.5041, ICG.5045 and HyQ (cg) S-10 were distinctly less susceptible to the leafhopper, Empoasca dolichi (Paoli). ICG.2271 also appeared to combine low susceptibility to early leaf spot, Cercospora arachidicola Hori and good yield potential. This genotype as well as ICG.5041 and ICG.5045 also are known to be resistant to thrips and/or termites. The scope for their utilization in exploitation of leafhopper resistance in groundnut improvement programme in Zambia is indicated.

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.

Newly-deposited pupae Glossina pallidipes were incubated until emergence at constant temperature (20.5, 22.5, 25.0, 27.5, and 29.5°C) and compared with pupae held at ambient conditions (19 to 31°C). Egg follicles and enclosed oocytes of newly-emerged females were dissected and their lengths measured together with the lengths of the cutting blade of the hatchet cell of the right and left wings. Linear discriminant functions analysis showed that the mean length of egg follicle A accounted for 80% of the temperature-related variability. We therefore used a simple predictive equation for temperature experience based on mean follicle length in small batches of newly-emerged females. The equation predicted with reasonable accuracy the temperature experience of 19 monthly samples of newly-emerged G. pallidipes reared in an insectary under ambient conditions. Mean sizes of egg follicle A of the newly-emerged tsetse may therefore be of utility in estimating temperature experience of pupae.

The effect of methionine on longevity, antioxygenic enzymes and lipid peroxides in Callosobruchus maculatus was investigated using C. maculatus maintained on Vigna radiata seeds soaked in seven levels of methionine, 0, 1, 3, 5, 7, 9 and 12 mg/ml water. The life span and activities of catalase and peroxidase were higher in Callosobruchus maculatus infesting Vigna radiata seeds soaked in methionine as compared to their control cohorts. However, the lipid peroxide (malondialdehyde; MDA) levels generally remained unaltered. The present observation on the increased longevity in C. maculatus with methionine level is an extension of earlier findings on its anti-ageing effect in higher animals.

Ticks and tick-borne diseases of cattle have been and still are a threat to the development of the cattle industry in Zambia. Other control methods of ticks and tick-borne diseases appear to have been used elsewhere in the world in addition to chemical control. In Zambia, chemical control of ticks appears to have been and still remains the most practical method of controlling ticks and tickborne diseases. This paper looks at chemical control from the time it was first used to present and future.