A function for distinguishing between the long, intermediate and short-setaed forms of Mononychellus species complex is described. The results show that the dorsal-central body setae, variable D3, with a discriminant correlation coefficient of 0.99, was the most important variable. Five other variables, lengths of dorso-central body setae Dl, D2, laterals LI, L2 and propodosomal P2, which had significant discriminant correlations (0.28 to 0.35) with the function were, however, included in the discriminant function.

Twenty isolates of Bacillus thuringiensis Berliner belonging to vars. kenyae, kurstaki, aizawai and ostriniae, were tested for their activity against first instar larvae of Boarmia selenaria Schiffermüller. Isolate 30-11 (serovar 3a3b, kurstaki) proved to be 8% more effective than the standard HD-l-S-1980 (serovar 3a3b, kurstaki). This isolate was 13% more larvicidal to third instar larvae than the standard. Significant lower mortalities than the standard were obtained with the isolates: 400-1, 400-2, 400-3, 400-4, 400-8, 400-11, 400-12, 400-14, 30-2, 30-12, 30-13, 30-15, Ser. 17 and BL8a8c. Isolates 400-5, 400-6, 400-7, 400-9 and 400-10 were similar in larvicidal effectiveness to the standard.

Pyrethrins I and II were extracted from five seasonal Compositae herbs collected from semi-arid and hilly areas of North India. The relative toxicity of natural pyrethrins were evaluated against Mesocyclops leuckarti sensu lato. Based on the LC50 values, the extract of the plants could be arranged as follows: Tagetes minuta > Pulicaria crispa > T. patuia > T. minuta > P. angustifolia.

Field screening of Lablab niger germplasm for 3 years revealed that two cultivars, PLS-24 and PLS-16-1 consistently displayed resistance to pod borer, Adisura atkinsoni Moore larval boring and egg laying. Observations at different intervals of plant growth permitted a comprehensive evaluation of cultivar response to the pod borer complex.

Preliminary tests indicated pod colour, pubescence and fragrance to be associated with the borer resistance in L. niger. However, none of the characters per se imparted resistance or susceptibility, partly or fully. Cumulative effect of the aforesaid characters appeared to impart borer resistance to Adisura. Pod wall did not form a physical barrier to Adisura larval entry. Positive relationship existed with amount of chloroplast and susceptibility, and starch grains and resistance in four cultivars studied for anatomical details. Anthocyanin pigment in the pod wall was associated with resistance in L. niger to Adisura.

Based on field and laboratory evaluations of Lablab niger cultivars to the bean aphid, Aphis craccivora damage, the “local” and H-2, rated as highly susceptible to borers, reacted as resistant and PLS-24 and PLS-16-1 rated as resistant to borers reacted as highly susceptible to the aphid attack. It is therefore imperative that promising Lablab niger cultivars be evaluated for resistance to both the sucking and chewing insect pests.

Under artificial infestation conditions the resistant cultivars exhibited susceptibility to larval boring by Adisura, but confirmed resistance to ovipositional response. Non-preference for oviposition was the most important factor in imparting resistance to the borer damage in L. niger. Factors inducing host preference for larva and for adult were different and independent. PLS-24 and PLS-16-1 contained significant degrees of antibiosis as demonstrated by reduced larval survival, larval and pupal weights, prolonged larval duration and altered sex ratio.

Cultivars that sustained low levels of seed yield loss at high infestation levels were identified as tolerant. MS-9579 and IC-661-1 exhibited low degree of tolerance. Resistant cultivars proved non-tolerant even to slight infestations (ca 10%) received under field conditions.

In the present study, we investigated the development of Leishmania donovani promastigotes in Aedes aegypti. Infection rate in the mosquito averaged 53%. Promastigotes were limited to the hindgut where they appeared on day 4 post-infection. Massive multiplication of promastigotes occurred between 6 and 17 days post-infection. The mosquito pylorus and rectum had the highest concentration of promastigotes. A maximum life span of 20 days was observed for L. donovani promastigotes in the mosquito. Morphologically intact L. donovani promastigotes were ejected with A. aegypti faeces, following a blood meal. Implications of the development of Leishmania spp. in the mosquito host are discussed.

Preliminary investigations have shown the presence of pathogenic fungi in natural populations of the cassava green spider mites. Among others, Entomopthora sp. and Hirsutella sp. were isolated from dead mites sampled from the field. Laboratory bioassays have given mite mortality of up to 60%, indicating the possibility of utilizing some of these pathogens in mite control. Tests with Beauveria bassiana, isolated from lepidopteran pests, have also shown that the mite is susceptible to this fungus.

Laboratory mice infected with a Trypanosoma congolense isolate of water-buffalo origin did not respond when treated with diminazene aceturate (Berenil, Hoechst, West Germany) at 3.5 mg/kg and 7 mg/kg body weight (b.wt.) and also isometamidium chloride (Samorin, May & Baker, Dagenham, England) at doses less than 3 mg/kg b.wt. Effective cure was achieved with isometamidium and diminazene at 3 mg/kg and 14 mg/kg b.wt. respectively; doses in excess of those recommended for use in the field to treat animal trypanosomiasis by the manufacturers. Irregular use of the two drugs on infected water-buffaloes while improperly restrained may be one of the factors responsible for the dual drug resistant T. congolense isolate emerging.

Sun-dried guava (Psidium guajava L.) and eucalyptus (Eucalyptus globulus L.) leaves were evaluated as repellent and toxic materials against the rice weevil, Sitophilus oryzae L., and the granary weevil, Sitophilus granarius L. under laboratory conditions. LC50 values of sun-dried guava and eucalyptus leaves admixed with rice grains against S. oryzae were 2.251 and 4.140g leaves/100g rice grains, respectively, while they were 2.278 and 4.857 g leaves/100 g rice grains in the case of S. granarius, respectively. Guava leaves were more toxic for both species than eucalyptus leaves. Eucalyptus leaves were more repellent than guava leaves.

Both test materials at 15 g/100 g depressed the progeny development of the test insects.

Experiments were conducted during two consecutive years (1983 and 1984) on irrigated rice, in the Southwest of Burkina Faso, in order to monitor the seasonal incidence of the rice gall midge, Orseolia oryzivora H. et G.

The damage incidence is the same whatever the date of planting within the rainy season. Attacks are low during the early growth phase of the rice plants (0 to 3% of “silver shoot”), and increase gradually to reach spectacular levels (20 to 55% of “silver shoot”) between 70 and 90 days after transplantation, after which there is decreased attack.

Parasitism is an important check on the larval population of the pest; up to 77% of parasitized larvae were observed. However, this parasitism due mainly to microhymenoptera, Platygaster diplosisae Risb. and Tetrastichus pachydiplosisae Risb., gets established late.

These results could contribute significantly in developing an IPM process on irrigated rice in Burkina Faso.

The ultrastructural changes in the ejaculatory duct epithelium in Glossina morsitans morsitans Westwood was examined for special features related to spermatophore formation; special attention was paid to the cytoplasmic organelles and the plasma membrane specializations (apical infoldings and space formation). Internally, the transportation system is characterized by a cuticle-lined lumen bordered by cuboidal cells. The endoplasmic reticulum is scarce, while mitochondria are distributed throughout the cytoplasm. At the cuticular surface of the cells, extensive apical infoldings are associated with numerous mitochondria. Glycogen granules are found only in the cytoplasm of teneral flies. Apically, adjacent cells are tightly apposed; however, prominent intercellular spaces develop (1 to 7 days), permeate most of the epithelium and connect to the basal surface of the cells. These are features characteristic of transporting cells believed to have an absorptive function. As the adult fly ages, the ultrastructural characteristics of the epithelium change and are typified by the disappearance of glycogen granules and the formation of intercellular spaces. The features of the ejaculatory duct are discussed briefly in terms of their role in spermatophore formation.

Genetic diversity analysis was conducted on a set of 20 sorghum [Sorghum bicolor (L.) Moench] cultivars having resistance to shootfly (Atherigona seccata Rond.), originating from different geographic regions, and representing different taxonomic groups. The genetic diversity for shootfly resistance was assessed using multivariate analysis (D2 statistic and canonical variate analysis), and geographic/taxonomic divergence. The grouping of cultivars based on genetic divergence was found more accurate and relevant than that based on either geographic or taxonomie divergence. Both D2 and canonical variate analyses gave very similiar clustering patterns over the years analysed. Trichome density contributed mainly toward genetic divergence in shootfly resistance, followed by glossiness. Based on the presence or absence of these traits, the cultivars resistant to shootfly were classified into four major clusters. Resistant cultivars IS 844 and IS 1054 formed separate clusters over the years. Heterosis for shootfly resistance was found associated with genetic divergence but not with geographic or taxonomie divergence.

Management programmes for the use of action thresholds to initiate insecticide treatments for controlling pod-borer, Adisura atkinsoni on field bean were evaluated in comparison with standard sprays on calendar basis. Results of three field experiments revealed that management based on initial spray at peak egg laying on tender pods, followed by sprays to maintain 1.5 flat pod damage/inflorescence realised maximum benefit: cost ratio. This management also resulted in reduced insecticide usage.

The circadian flight activity of mosquitoes breeding in septic tanks in Jos, central Nigeria, was studied using exit and entry traps. The pattern of peak activity in Culex quinquefasciatus, Culex horridus and Culex cinereus leaving septic tanks was the same between males and females. Aedes aegypti left the tanks earlier than any of the Culex species. There was a difference in time and pattern of peak activity between sexes in this species. Also, a significant difference in peak activity between females of different physiological states was noted in Cx. quinquefasciatus.

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.

Eight cultivars of the common bean (Phaseolus vulgaris L.) and the Tepary bean (Phaseolus acutifolius) were used to study the distribution of puparia of the bean fly species Ophiomyia phaseoli (Tyron) and O. spencerella (Greathead). The puparia of the two bean fly species were distributed differently in the plant, O. spencerella predominating in the root and O. phaseoli in the shoot. There were significant differences between some of the bean cultivars and the number of puparia found. Tepary had the least puparia and P. vulgaris cultivars GLP 806 and GLP 1131 the most. There was a low correlation between the number of puparia and the final yield or root dry weight.

A study of the effect of microenvironment on the pea leaf weevil's behaviour was made comparing a broad bean monoculture with a broad bean-oat crop mixture. It is observed that more weevils depart from the crop mixtures than from the monocultures. Microenvironment study in the two cropping systems show that temperature and wind speed are not significantly altered in the crop mixtures as compared to the monoculture, but beans growing in the mixtures were significantly more shaded than those in the monoculture. Evidence is given to show that this relative shading could be the main factor responsible for the observed increased weevil departure from the crop mixtures.

Studies on the spatial distribution and sampling of infestation of the blister midge, Erosomyia indica Grover, were carried out in a mango orchard at Bangalore, India. The spatial distribution of the infestation on the panicles were studied using the parameters variance-mean ratio, and Lloyd's index of patchiness. It was found that the midge infestation tended to follow a random distribution pattern. The infestation was not significantly different among the sections of the canopy delineated horizontally and vertically. However, infestations in east lower, south lower and south upper were significantly correlated to the total infestation. The sample sizes were apportioned to these sections using regression analysis, thus arriving at a sectional random sampling plan for better precision estimates. For the data on percentage infestation, angular transformation was found to be satisfactory. These results have application in field studies leading to the management of the pest on mango.

An investigation was carried out in India, to study the extent of heterosis expressed in single, three-way and double cross hybrids with respect to important economic characters. The results were discussed in terms of relative heterosis (heterosis over mid-parent value) and standard heterosis (heterosis over standard check variety). Significant negative relative heterosis was observed for total larval duration in single and majority of the three-way crosses; whereas it was positive and significant in double cross hybrids. The commercial characters like cocoon and pupal weight, shell percentage, filament length and denier, recorded positive relative heterosis in most of the single and three-way crosses; whereas they were negative and significant in most of the double crosses. In general, higher degree of heterosis was expressed in single crosses followed by three-way and double crosses for the characters studied.

Electrophoretic studies were carried out on isozymes of Glossina pallidipes to determine whether there are any genetic differences between natural populations from an area free of sleeping sickness (Nguruman) and an area where sleeping sickness is endemic (Lambwe Valley) in Kenya. Out of 12 enzymes examined, two enzymes, GPI and PGM, showed high polymorphism in the two populations, while the other 10 enzymes were all monomorphic. At the GPI locus, at least five alleles were detected, and two alleles were found at the PGM locus. There was a difference in the frequency of isozyme patterns between males and females, indicating that the PGM locus is on the sex-linked chromosome (X-chromosome). Nei's genetic distance (D) was 0.00154 between the two populations, which is the value within the range for local populations in different organisms examined so far. Some difference between the two populations was found in the level of average heterozygosity (H) and in allelic composition of the GPI locus, that is, the Lambwe Valley population is more heterogeneous than the Nguruman population.

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.