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.

Successive extraction of the green alga, Scenedesmus acutus 276–3a with different solvents indicated that the petroleum ether extract was the most repellent to the hatched larvae of Spodoptera littoralis. The application of spray emulsified 1 % petroleum ether extract inhibited egg laying. At 0.25% concentration the moths laid only 52.4 of their egg masses on the treated oviposition sites in comparison to the untreated control. Concentration of 1% was protective against the immature stage by hindering the third instar larvae to feed on treated leaf discs. In addition, the water emulsion of petroleum ether extract was insecticidal. The percentage mortality was directly proportional to the concentration applied and to the duration of exposure.

Studies on the effect of various diets on development, longevity and fecundity of Oxycarenus gossypinus were conducted in the laboratory at temperatures of 25–33°C. The mean periods of nymphal development when reared on seeds of okra, kenaf, roselle and cotton were 15.5, 15.7, 15.8 and 18.1 days, respectively.

Mated males lived longer and in decreasing order on okra (59.2 days), roselle (57.5 days) and kenaf (57.3 days) than on cotton (43.5 days). Mated females also lived longer on okra (41.4 days), kenaf (40.1 days) and roselle (39.3 days) than on cotton (32.5 days).

Mated females reared on okra seeds laid significantly the highest mean number of eggs per female per day (15.05 ± 0.87 eggs). But the mean number of eggs oviposited when fed on seeds of kenaf (12.9 ± 1.01 eggs) and roselle (10.9 ± 1.18 eggs) was not significant.

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 on relative susceptibility of 78 citrus varieties/hybrids to the incidence of black citrus aphid, T. aurantii under tropical humid conditions in south India revealed that none of the varieties was completely free from aphid incidence. The varieties Nagpur Mandarin and Ikeda Unshiu among mandarins; Longsport Valencia, Campbell Valencia and Washington Navel among sweet oranges; and Carrizo Citrange a hybrid and Dessert Orange, Eureka Lemon, Grape Fruit Pink and Jatti Khatti, among acid citrus group, recorded significantly least mean number of aphids per flush and can be effectively used in breeding programmes.

Antixenosis component of resistance to corn planthopper, Peregrinus maidis (Ashm.) was investigated in 10 selected sorghum genotypes at three plant growth stages (30,45 and 60 DAG) under laboratory and field (rainy and postrainy seasons) conditions. In a free-choice test, the orientationa) and settling responses of nymphs and brachypterous adults on all genotypes although influenced by the olfactory and visual responses, then- feeding was notsustained due to gustatory stimuli indicating their significant role in determining the degreeof antlxenosis. The genotypes IS 18676, IS 19349 and IS 18677 showed a high degree of antixenosls in settling fewer nymphs and adults consistently at 30,45 and 60 DAG. This finding was supported with low colonization of nymphs, and brachypterous and macropterous adults under field conditions. In addition, high degree of antixenosis for oviposition in both laboratory and field tests was evidenced on IS 18676 and IS 19349 at 30,45 and 60 DAG, but on SPV 472 and SPV 475 only at specific plant growth stages. The variability in the rate of adult colonization together with suitability of plant growth stages for oviposition has contributed to variable degrees of antixenosis for oviposition.

The number of instars in the silkworm Anaphe venata was determined using three methods namely: (1) direct observation of cast exuviae by larvae reared through the entire larval stage, (2) use of frequency distributions of head capsule lengths and widths taken from larvae representative of the entire larval stage of the species and (3) morphological observations and examinations of larval segments and anal plates. Seven instars were observed for A. venata. The most reliable method was the direct observation of cast exuviae by larvae reared through the entire larval stage. It is further suggested that either the method of histograms of head capsules or examination of larval segments and anal plates be used to supplement this method for better reliability.

Intraspecific competition in the rice weevil, Sitophilus oryzae (L.) and the angoumois grain moth, Sitotroga cerealella (Oliv.) in grain sorghum was studied in laboratory experiments. Progeny production per female of each of the two species when reared separately, decreased as the initial parent population density increased. The number of progeny produced by Sitophilus oryzae increased to a peak, and then declined sharply with a further increase in initial parent population density, characteristic of a scramble competition. In contrast, the progeny produced by Sitotroga cerealella increased with an increase in parental density to reach a fairly constant maximum (flat topped curve), characteristic of a contest competition. It is concluded that intraspecific competition will not limit the potential of the grain moth S. cerealella of becoming a major pest of stored sorghum.

The effect of potassium application to maize plants on the development, survival and fecundity as well as larval and pupal weight of Sesamia calamistis and Eldana saccharina were studied in the laboratory. Six different potassium treatments corresponding to 0, 30, 60, 60, 90, 120 and 150 kg K2O/ha were used. Potassium had no influence on larval and pupal developmental time or longevity of adult S. calamistis. The highest larval mortality was observed at 0 and at 150 kg K2O/ha. Increased doses (> 60 kg K2O/ha.) tended to reduce pupal survival. The lowest pupal weight was obtained at 150 kg/ha whereas fecundity was negatively related with potassium. The highest values of intrinsic rate of increase (rm) and net reproductive rate (Ro) were obtained with 60 kg K2O/ha and lowest with 150 kg K2O/ha. For E. saccharina, potassium had no significant effect on larval and pupal developmental time, larval survival, and pupal weight. The highest larval weight, pupal survival and fecundity as well as rm and Ro values were observed at 90 kg K2O/ha.

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.

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.

A total of 39 strains of Anopheles stephensi, an important urban malaria vector, were collected from various parts of India and maintained in the insectary for this study. Based on the egg-float ridge number, 19 strains were classified into ecological variants and 32 strains were exposed to chlorpyrifos and propoxur to investigate their resistance status. Filter paper containing freshly laid eggs was taken, the ridge numbers on the floats were counted under the microscope, and strains were classified into ecological variants. Of the 19 strains, 18 were of ‘type form’, with ridge numbers ranging from 15 to 21. The Papareddipalya (PRP) strain belonged to the ‘intermediate form’, with 14 to 17 ridge numbers. Larval bioassays were carried out according to the procedure of the WHO. For chlorpyrifos, the lowest LC50 value was 0.00107 mg/l (Padmanabhanagar strain) and the highest value was 0.0403 mg/l (GOA-A strain). Furthermore, the lowest LC90 value was 0.00368 mg/l (Delhi strain) and the highest was 0.1746 mg/l (GOA-A strain). For propoxur, the lowest LC50 value was 0.00029 mg/l (Goraguntepalya strain) and the highest value was 0.0037 mg/l (JP Nagar strain). Moreover, the lowest LC90 value was 0.00094 mg/l (Goraguntepalya strain) and the highest value was 0.0115 mg/l (JP Nagar strain). The tolerance values ranged from 1.26 to 37.68 for chlorpyrifos and from 1.34 to 12.77 for propoxur. All the type forms were from urban and semi-urban locations, and the intermediate strain was from a semi-urban location. The bioassay results indicated that the strains of An. stephensi were more susceptible to propoxur than to chlorpyrifos.

The persistence of 34 formulations in the green (G) and red (R) berries of C. arabica var. typica, infested with female adult H. hampei were assayed by a dip-technique. The 3-day LC50 values in G and R (figures in parentheses) berries for thiodan EC 35 were 0.00284 (0.00327), and the relative ratio of values for other formulations were: perfekthion 1.2 (2.1) > carbicron 1.6 (2.3) > basudin 3.5 (3.2) > actellic 4.0 (3.6) > decis 4.1 (3.7) > thiodan EC 3 4.2 (4.2) > bidrin 5.8 (5.0) > malathion 5.8 (5.1) > lindane 5.8 (5.6) > ciodrin 5.9 (5.6) > folimat 6.0 (6.0) > belmark 6.2 (6.3) > aldicarb 8.0 (9.7) > nexion 11.0 (12.0)>kelthane 13.5 (15.4) > tiovel 14.6 (16.3) > dursban 15.6 (22.0) > chlordane 17.8 (23.8) > methomyl 21.5 (24.3) > aldrin 25.1 (24.9) > supona 27.2 (26.5) > dimilin 29.0 (27.5) > methoxychlor 31.7 (92.2) > chlorfenvinphos 35.8 (92.5) > dieldrin 41.2 (93.8) > phosdrin 65.0 (94.7)>sevin 104.2 (118.0)> nexagan 106.4 (121.9) > bimarit 196.4 (301.7) > azodrin 271.2 (410.4) > fenitrothion 448.3 (417.0) > chlorpyrifos 448.8 (614.3) > gardona 514.6 (703.1), -fold more than the thiodan EC 35 values.

The 7-day LC50 values for 29 formulations were ca 10–82% less than those of the 3-day values; the decrease in the values for leading formulations being thiodan EC 35 13.4 (8.3), perfekthion 6.5 (39.9), carbicron 12.4 (10.6), thiodan EC 324.3 (16.4), malathion 35.2 (25.7), lindane 82.1 (76.9) and tiovel 59.6 (67). The values for the 17 least toxic formulations (except dimilin and bimarit) showed ca 27–88% decrease during the last 4 days of observations.

A ‘rice garden’ with monthly plantings of rice was established in an irrigated lowland area in April 1993 and continued for 3 years. Populations of the most common insects, the stalk-eyed flies, Diopsis spp., and the green leafhoppers, Nephotettix spp., and spiders and stemborer damage varied distinctly in relation to month of transplanting. Arthropod populations also exhibited distinct patterns in relation to crop growth stage. Grain yields varied with month of transplanting but there was no distinct trend from one year to the next. This study indicated that continuous cropping of the same fields over a 3-year period did not result in a build-up of insect pests or a decline in grain yield.

Herbivory by insects and mites on physic nut (Jatropha curcas L.) seedlings was investigated and compared with irrigation in the semi-arid Sahelian Niger, utilizing a randomized complete block design experiment. Three water treatment protocols were applied and the types of damage were recorded. Less than 5% of the seedlings died during the 10-month trial period with sap suckers causing the most damage on the surviving plants. Plants with high production of biomass and leaf cover (foliage) were most strongly positively correlated with irrigation and were also the plants that endured the highest degree of herbivory. The low dieback may indicate that defence mechanisms counteract seedling herbivory and that drought-stressed plants invest more in their defence mechanism system than vital plants.

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 oviposition behaviour of spotted bollworm, Earias vittella Fab. was studied on 23 cotton genotypes under field and laboratory conditions. There were substantial differences in the number of eggs laid on different genotypes. More eggs were deposited on the bolls compared to leaves and squares. The relative oviposition preference differed under the field and laboratory conditions in the case of some genotypes. Leaf hairiness was significantly and positively correlated with number of eggs laid both under field and laboratory conditions. The effect of oviposition on varietal susceptibility appeared to be modified through other factors, such as gossypol and tannins. However, oviposition non-preference was one of the important resistance mechanisms in some cotton genotypes.

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.

The fecundity and duration of oviposition in three strains of Callosobruchus rhodesianus from the highveld, middleveld and lowveld regions of Zimbabwe and a laboratory strain were recorded on cowpea and greengram. Within-legume variability for both parameters was high among the four strains. The lowveld strain was the least fecund and had the longest duration of oviposition. The middleveld strain showed the highest fecundity on cowpea, but did not differ significantly from the other three strains on greengram.

A number of resistance sources have been identified against two major pests of sorghum, viz the sorghum shootfly, Atherigona soccata Rondani, and the stem-borer, Chilo partellus (Swinhoe). These identified sources of resistance were generally tall, late maturing and poor yielders. Two of these identified sources of resistance, viz. BP 53 and M 35-I, have been utilized in the breeding programme, by crossing with dwarf exotic types, which are highly susceptible to both the pests, but are agronomically desirable varieties. The crosses thus obtained were screened for their reaction to the two pests. An extensive screening programme was carried out under heavy levels of shootfly and stem-borer infestation from 1968 to 1980, which resulted in the identification of nine advanced generation derivatives possessing moderate to high levels of resistance to both shootfly and stem-borer as well as desirable agronomic characters.

The derivatives with M 35-I, as one of the parents showed more resistance to shootfly as compared to derivatives with BP 53, as one of the parents. However, in the case of resistance to stem-borer, the reverse was true.