A bioassay was developed to assess the in vitro feeding responses of Chilo partellus larvae to susceptible (Inbred A) and resistant (MP 704) maize varieties. Consumption of internode tissues from the two maize varieties differed while the reverse was true for the nodes. Aqueous extracts from the two varieties caused a decrease in feeding and weight gain, but these effects were more evident in MP 704 than in Inbred A treatments. This suggests that MP 704 has a water extractable factor affecting weight gain negatively. Dose-response curves of neural responses from the maxillary styloconica sensilla showed that aqueous extracts from the two maize varieties evoked different functional forms of impulse frequencies especially in the lateral sensilla. These observations suggest that the quality of gustatory stimuli in the two maize varieties differs.

Permethrin, deltamethrin, fenvalerate and cypermethrin were evaluated for their termiticidal efficacy in a graveyard test. Semul wood, Salmalia malabaricum veneers (size 15.00 × 6.00 × 0.06 cm) were impregnated with concentrations of 0.25, 0.50 and 0.75% aqueous solution of these chemicals. Fenvalerate provided 100% protection for 44 months at all three concentrations. Cypermethrin provided 100% protection at 0.50 and 0.75% concentrations, while permethrin and deltamethrin provided 100% protection at 0.75% concentration for 7 and 10 months, respectively.

The effect of covering post-harvest banana stumps with soil on banana weevil Cosmopolites sordidus (Germar) oviposition levels was investigated at three locations, Sendusu, Kawanda Agricultural Research Institute (KARI) and Ntungamo district of southwestern Uganda. In the first experiment oviposition levels were assessed in a banana system comprising growing plants and residues. Oviposition increased on sword suckers, reaching a peak 1–7 days after harvest and decreased thereafter. In the second experiment conducted on farmers' fields, corms received 70% of the eggs and pseudostems 30%. The area 5–10 cm below the collar received 27% of the eggs, the area 0–5 cm above the collar 30% and the area 5–10 cm above the collar 0.3%. The remaining eggs (43%) were laid 0–5 cm below the collar. The effect of stump height and covering the stumps was evaluated in both the wet and the dry seasons at Kawanda and Ntungamo. Cutting stumps to the ground level alone had no effect on oviposition. Covering post-harvest banana stumps reduced C. sordidus oviposition in the wet but not in the dry season.

The juvenoids fenoxycarb and methoprene were evaluated for morphogenetic activity on last-instar nymphs of the American bird grasshopper, Schistocerca americana (Drury) (Orthoptera: Acrididae). Topical application of fenoxycarb induced supernumerary nymphs, adultoids and adults with curled wings. Methoprene yielded similar morphogenetic effects although at reduced levels of activity. Of particular interest, however, is the discovery that, in addition to its morphogenetic activity, fenoxycarb causes significant mortality in developing fourth-, fifth- and sixth-instar nymphs.

The numbers of the separate cohorts of the cocoa shield bug Bathycoelia thalassina which were observed up to hand-height on 50 cocoa trees in a Nigerian cocoa farm were recorded. The data were analysed for any patterns of aggregation. In the egg as well as 1st to 3rd nymphal instar stages, B. thalassina was highly aggregated on individual cocoa trees and the coefficients of aggregation ranged from 2.14 to 2.77. In the 4th and 5th nymphal instar and the adult stages distribution was random and analyses of data in units of 1, 2, 4, 8 and 16 cocoa trees did not reveal any patterns of aggregation.

More egg batches were laid on stem than on pods and the least number of batches was found on the leaves. There was no significant difference in the size of batches laid on different plant parts (P < 0.05) and cocoa pods did not influence the choice of oviposition sites by B. thalassina.

The implication of this distribution pattern was discussed, and a suggestion made for spot application of insecticides on the eggs or 1st instar nymphs as a method of control that would be both economical and of ecological advantage.

Twelve models are presented to examine the feasibility of using pheromone baited traps containing chemosterilant for pest control, and to compare the efficiency of this method with the use of (i) pheromone baited traps containing insecticide, and (ii) sterile releases. It was found that the number of matings per individual has little effect on the efficiency of population control, whereas immigration of even a relatively small number of the pest species severely limits this method in its ability to control the population. The existence of density-dependent regulation on the other hand greatly enhances the effectiveness of this control method. If the birth rate greatly exceeds one young per adult per day, then the method using chemosterilants is approximately twice as efficient as either insecticides in the pheromone traps or the release of sterile males. However, if the birth rate is much less than one per day, as in tsetse, then chemosterilants are very much more efficient than either method. These differences in relative efficiency appear to depend on the frequency of mating relative to the birth and mortality rates.

A volatile female sex pheromone, secreted by the pygidial glands of Blattlla germaniea, which attracts males from a distance was studied. Ultrastructural studies showed common epidermal and canal cells associated with glandular cells, classified as class 3 secretory unit The thickness of pygidial glands from young virgin females Increased progressively and became larger, 10 to 13 days after adult emergence. It decreased markedly after mating and increased again after the release of the ootheca. Based on the morphology of the glands, it was further observed that B. germaniea young virgin females' attractiveness increased gradually, such attractiveness decreased at mating. After larval emergence, females' attractiveness wasonce more enhanced. Dkhktromethane extracts of pygidial glands attracted males from a distance. These results demonstrate the pheromone gradual secretion and similarly pygidial glands evolution during adult emergence.

Pesticides provide an important component of integrated pest management, but the timing, accuracy of dosage, and method of applying the pesticides need careful consideration to permit harmonisation with other control tactics. Concern about pesticide spray drift has led to categorising the spray quality of nozzles, which is defined by comparing the droplet spectra of selected reference nozzles measured with a laser light diffraction analyser. However, there is a conflict between a need for small droplets for increased biological efficacy and large droplets to reduce downwind drift. Registration authorities tend to favour a coarser spray with large droplets, and an untreated barrier area that can be left around a treated crop to protect sensitive crops downwind that can provide a refuge for natural enemies. In some circumstances, drift can be reduced with small droplets by electrostatically charging a spray. The charged spray needs to be released close to the crop to avoid the upward dispersion of droplets within a spray cloud due to mutual repulsion exacerbated by convective air movement. Increased deposition of charged sprays on the crop foliage is associated with less soil contamination which allows greater survival of ground-dwelling predators. This feature needs to be exploited by growing relatively narrow strips of a range of crops so that if one crop needs a pesticide treatment, natural enemies can be conserved in adjacent untreated crops. By careful selection of insecticides and dosage rates, these predators should be able to recolonise the treated area and thus integrate chemical with biological control. Application of more selective mycopesticides may require special formulations as well as particular droplet spectra. Pesticides can also be applied mixed with attractants such as pheromones, as a ‘lure and kill’ technique.

The amount of free amino acids increases during the larval development. The accumulation is greater during the later larval life followed by an abrupt decline in the defaecating larva and early prepupa. The overall decrease in the free amino acid content during the period of metamorphosis is more in case of drones in comparison to that in workers. However, the amount present in adult drones is less than that of workers. The changes in the free amino acid content during the post-embryonic development of workers and drones of Apis cerana indica seem to show sexual dimorphism.

Studies were carried out on the neonatal development of Riptortus dentipes (Fabricius) and Nezara viridula (Linnaeus) on pods of cowpea Vigna unguiculata (L.) Walp (var. VITA-3) and soybean Glycine max (L.) Merrill (TG× 536–02D). Both crops sustained nymphal development and adult reproduction of R. dentipes. Nymphal duration was 20.7 days on cowpea and 21.3 days on soybean; mean adult weight was 56.3 mg (male) and 58.3 mg (female) on cowpea and 55.8 mg (male) and 57.6 mg (female) on soybean. Adults preferred soybean to cowpea for egg laying though a substantially higher number of eggs was laid on the mesh walls of the cages indicating the somewhat suboptimal nature of both plant substrates. The nymphal period for TV. viridula was 24.4 days on cowpea and 25.4 days on soybean, and the mean adult weight for males was 139.0 mg while that for females 186.0 mg on cowpea. On soybean, the mean adult weight was 127.3 mg for males and 176.9 mg for females. Soybean leaves were preferred for oviposition. The concept of host plant suitability to the various stages of these insects with respect to host switches between cowpea and soybean.

Three aromatic juvenoids were evaluated for morphogenetic activity on Schistocerca americana. Fenoxycarb, the most active insect growth regulator examined, was found to induce a significant mortality in developing fifth stage nymphs and caused severe morphogenetic damage during ecdysis to the adult. Juvenoid treatments were also observed to increase the duration of the last nymphal stage and to induce chromotropic colour changes similar to that observed in the solitary phase of the desert locust, Schistocerca gregaria Forskal.

Laboratory and field assays carried out so far indicate that microsporidian pathogens, especially Nosema spp., may be exploited for the management of the spotted stalk borer Chilo partellus and possibly other Chilo spp. Several formulations have been tested for the application of Nosema spores in the field for borer management. Significantly high levels of control were achieved when the pathogen was sprayed on plants infested with borer larvae, compared with unsprayed plots. Sublethal dosages of Nosema spp. reduced the biological performance of C. partellus, as indicated by reduced fecundity in infected females, high mortality in pre-imagines as well as in the filial generations, and reduced lifespan. There was also a high level of deformity in the surviving adults. Such debilitating factors would subsequently result in a reduction of population levels.

In sugar-cane pests, granulosis viruses have been observed to cause high natural mortalities in C. infuscatellus and C. sacchariphagus. Field infestation has been reduced by the application of the virus. Further, the presence of polyhedrosis viruses in C. partellus, and Chilo iridiscent virus in C. suppressalis, points towards the possibility of using this group of pathogens in Chilo control.

Distinct differences in Panonychus ulmi population densities on various apple cultivars have been observed under natural field infestations. Various laboratory techniques may be used to determine the differences in susceptibility or resistance to P. ulmi of different apple cultivars. The lowest variation in P. ulmi behaviour, and fecundity between replications was observed for females reared on leaf discs 20–25 mm in diameter and for females reared in the small plastic cages placed on the leaves of potted young apple trees. The leaves used for bioassays should be collected from the same part of the trees. The density of P. ulmi populations and their fecundity should be observed on leaves growing on short spurs. Preconditioning P. ulmi on various cultivars did not influence the female's fecundity on the new plants. There is no individual, singly-acting mechanism responsible for the moderate resistance of apples to P. ulmi. The resistance is caused by a number of morphological, anatomical and biochemical leaf properties, expressed differently in different cultivars.

The rice plant is an extremely versatile crop that is grown under both tropical and sub-tropical conditions in various ecological conditions. Several insect pest species attack the rice crop at all growth stages while in the field. The nature and magnitude of crop loss due to insect pest attack in tropical and sub-tropical Africa are highlighted. Reliable evaluation techniques for establishing relation between insect pest intensity/damage and crop loss are outlined. Natural insect pest infestation in the field, manipulation of pest infestation with chemicals, caging to confine or keep out insect pests and the use of resistant varieties as methods of estimating on-farm losses due to insects are discussed. In tropical Africa, the major constraint to the determination of crop loss due to insect pests of rice is research-related.

Both sublethal and lethal doses of fenitrothion treatment caused positive temperature toxicity relationship in three lepidopteran fifth instar larvae, Achaea Janata, Mythimna separata and Bombyx mori.

The LD50 value was very low at 30°C compared to 28 and 18°C. In all the three species, the insecticide caused greater rate of regurgitation of body fluid at higher temperature. It is believed that the loss of body fluid causes desiccation and enhances the poisoning effects of fenitrothion.

The spread of human trypanosomiasis towards Central Africa from sources in the Congo at the beginning of the present century, has been linked to population changes and movements between the affected states.

The re-appearance of the disease in this part of Africa during the last 10 to 15 years raises again the question of how this disease is propagated. Although present day population movements are not so pronounced as those at the beginning of the century, these are significant population movements along major lines of communication (large rivers particularly). Of equal importance are disease foci which straddle national boundaries. Migrant populations (fishermen from Nigeria and displaced persons or refugees) also play important roles in the dispersal of the disease.

Even within certain foci, the mobility of rural populations helps to sustain the endemicity of the disease over large areas.

The risks of introducing or increasing trypanosomiasis must not be neglected when populating new areas and when developing agro-industrial complexes which require large labour forces.

Soil samples collected from six localities in Pakistan—Peshawar, Quetta, Loralai, Sibi, Lahore and Sheikhupura—were screened for insecticidal Bacillus spp. Bacillus coagulane, B. megaterium and B. alvei, which constituted 50%, 33% and 17% of the Bacillus isolates respectively, were isolated and their toxicity was evaluated against larvae of the house fly, Musca domestica (Diptera: Muscidae). The most toxic bacterial isolate of the three was B. alvei (98.7% mortality) and the least toxic was B. megaterium (89.3% mortality). Extracts of experimental larvae showed the presence of strains of the respective species of Bacillus in all cases, indicating that the observed mortality in the house flies was caused by the Bacillus species.

At 25°C and 70% r.h. larvae of Spodoptera exempta develop faster and pass through five instars on star grass, Cynodon dactylon (L.); Pers. maize, Zea mais L.; and Kikuyu grass, Pennisetum clandestinum Chiov. whereas on guinea grass, Panicum maximum Jacq.; and Setaria plicatilis (Hochst.) Hack, the development is not only slower, but the larvae pass through six and seven instars, respectively. Samples of larvae reared on the former grass species suffer high mortality only at the first and the last instar stages so that the distribution of per cent mortality is U-shaped. On the latter host plants, the mortality during the first instar stage is equally high and continues through the subsequent instars with no obvious peak towards the end of the larval life. The samples on C. dactylon and Z. mais had much higher growth indices than those on P. maximum and S. plicatilis. C. dactylon is a preferred natural food plant of S. exempta in the field, and these investigations demonstrate its value and importance.

Two monoclonal antibodies (Mabs), that react in an enzyme linked immunoabsorbant assay, were generated against Aedes aegypti vitellin. One of these Mabs, VIIG9 that reacted predominantly with a 64 kDa component of Ae. aegypti yolk protein, also recognized 68 kDa and 66 kDa components in the yolk proteins of Culex sitiens and Cx. annulirostris, respectively. Mab VIIG9 has been used to detect vitellin or vitellin precursors in gravid female and non-blood fed nulliparous female mosquitoes as a possible age grading method. The presence of polyclonal and monoclonal antibodies to vitellin in the blood meal did not affect the fecundity of Ae. aegypti.

Biochemical approaches have been used to enhance the potency of Bacillus thuringiensis against Plodia interpunctelia. Tests were made with different classes of chemical compounds, characterizedby being safe, non-toxic to man, and cheap in price. Among the tested inorganic salts, calcium carbonate, calcium oxide and zinc sulphate were found to increase the potency of B. thuringiensis δ-endotoxin by 2.5-, 1.9- and 2.7-fold, respectively. With the nitrogenous compounds, the amino acids serlne, arginine, alanine and teucine enhanced the endotoxin effect by 52-, 3.6-, 13- and 1.1-fold, respectively. Also, among the protein solubilizing agents, EDTA and sodium thloglycollate led to a 100- and 2.6-fold Increase in the potency. Formic acid was highly effective among the organic acids used in enhancing the potency, followed by malk acid, with 4.8- and 2.4-fold increase, respectively.