The groundnut variety ICG 2271 is the most resistant to thrips In our conditions. Despite the existence of some differences between types, the number of thrips per flower In the cowpea is negatively correlated with the total number of flowers present per plant, the rate of pod formation, the internode and pod length, the pod number per plant and grain yield. It Is positively correlated with the percentage of flowers shed per plant.

In the pigeonpea, the characters linked to the number of thrips per flower vary with varieties. However, days to maturity and height at the same stage are more consistent.

The days to 50% flowering are positively correlated with the number of thrips per flower In the cowpea and pigeonpea.

The ability of males of Ephestia cautella to mate and transfer sperms aftergamma radiation as 5–6–day old pupae was investigated. The results indicate that gamma radiation had no significant effect on mating, sperm transfer and percentage of egg hatch.

Population of Spodoptera litura F. were monitored through pheromone-baited traps during the rainy season 1988 and 1989 in groundnut fields in relation to oviposition on leaves. Four peaks of adult catches were recorded. First and second peaks were smaller and caused no threat to crop. Third peak was observed at the pegging and pod-initiation stage during first week of September and coincided with the greatest oviposition on leaves. The fourth peak was greatest and occurred between 40th and 43rd standard week. However, no oviposition was recorded on groundnut during this period. The moths possibly dispersed and/or migrated to other areas with crops at an appropriate stage of susceptibility.

A quantitative measure for assessing the level of resistance of zebu cattle to Rhipicephalas appendiculatus is discussed. Basic data for the derivation of the mathematical index were from artificial infestation of cattle to adults, nymphs and larvae ofthe Rusinga Island stock of the tick species. Observed variables were the weights and numbers of the engorged/detached instars.

The index derivation process was by the use of the stepwise discriminant function procedure and the Mahalanobis distance. These procedures led to the derivation of an index which was a function of the engorged weights of the female and nymphal instars, the numbers of detached females and the Mahalanobis distance. Variables associated with the larval instar were found to be insignificant and were therefore not included in the index function.

The derived index is capable of discriminating between susceptible and resistant cattle, and can be used to monitor changes in the resistance levels of cattle over time.

Pupation patterns, viz. larval ripening, pharate pupal and pupal formation were diurnally predominant in the silkworm, Bombyx mori L. (PM × NB4D2), under different photoperiodic conditions. Under continuous light (LL), the rhythm damped-out. Upon circular statistical treatment of the data, the peaks expressed two distinct modes short day and long day resultant groups and these phenomena are distinct for pharate pupal formation. Duration between larval ripening and pharate pupal formation, as also between pharate pupal and pupal formation was influenced by different light/dark conditions. Duration between larval ripening and pupal formation was significantly (P < 0.05) less under LD 11:13 as compared to LD 12:12.

Cutting millet stem at harvest until the end of November reduced by 76 to 92.5% the number of third generation larvae of Coniesta ignefusalis entering diapause. When harvest was done after the beginning of December, reduction of diapausing larvae in millet stems did not exceed 50%. Weekly harvests from beginning of November to the end of January 1988–1989 and 1989–1990 showed an increased percentage of larvae in diapause. The percentages of larvae in diapause reached 100% at the end of January in 1988–1989 and between the end of December and beginning of January in 1989–1990. The distribution of diapausing larvae in the stems was not regular with 60% of the larvae located between 40 and 80% of the total stem height.

The stage-specific and age-specific survivorship of the immature stages of Anopheles gambiae Giles s. l. were studied in Baringo District Kenya, using vertical life-table methods.

Survivorship from first instar to adult emergence was 0.085, giving a mortality of 91.5% during the rainy season. However, survivorship dropped to zero (100% mortality) in the dry season.

Mortality was most severe in the first and second instars in all cases. Mean life expectancy increased significantly for larvae that survived beyond the first 3 days of life. Suspected predators of mosquito pre-imagines in the breeding sites were collected and counted. From their large numbers and diversity it was inferred that predation was probablyan important mortality factor.

A series of experiments involving plots of sole cowpea and sorghum/cowpea intercrops were carried out, on-farm, in Minjibirr village, northern Nigeria between 1986 and 1988. The objectives were to:

(1) elucidate the relationships between sorghum/cowpea Intercropping, insect pest numbers and grain yield reductions in cowpea.

(2) examine the role of sorghum/cowpea intercropping alone or together with reduced Insecticide usage in the management of cowpea insect pests. Different cowpea varieties were grown under both cropping systems in sprayed and unsprayed plots.

The insecticides used were Sherpa Plus and/or Cymbush Super ED. Intercropping reduced the numbers of flower thrips and pod sucking bugs, but made no difference to the numbers of pod borers. Unprotected sole crop and Intercropped cowpea had yields reduced by 55 and 48% respectively, compared to sprayed subplots. The best results were obtained with three Insecticldal sprays, which increased grain yields 4.5-fold. Intercropping with two sprays produced lower, but comparable yields. Thus, it is suggested that intercropping can be used with reduced insecticide levels for the effective management of cowpea insect pests.

An experiment to examine the effects of four agrometeorological factors on population fluctuations in legume pod borer, Monica testulalis (Geyer) in two cowpea varieties was carried out under field conditions in Ibadan, Nigeria. Plots, 5 x 10 m each, of cowpea varieties IT84S-2246–4 and Dan ilan were planted fortnightly between 5 May and 5 October 1988 (12 plantings in all for each variety). Three peaks of the pod borer populations were observed on the cowpeas. There were smaller peaks on crops planted between 5 May and 1 June and again between 29 June and 13 July and a larger one on those planted between 24 August and 7 September. These two peaks coincided with the peaks of the rainfall.

Significant relationships were obtained between pod borer counts and (a) cumulative rainfall (R2 = 0.41; P = 0.004) (b) number of rainy days (R2 = 0.17; P = 0.04) from plant emergence to 50% flowering. These results suggest though, the distribution of rainfall over time is more crucial than the total amount in determining the fluctuations of pod borer populations. Thus, the adjustment of planting dates is suggested as an IPM tactic to avoid the development of damaging levels of pod borer infestations.

The life cycle of Cathartus quadricollis (Guerin-Meneville) was studied under ambient laboratory condition on maize, sorghum, wheat, cowpea and melon. Egg hatchability was found to be 95.5% with an incubation period of 3–7 days. Five larval instars were recorded based on head-capsule width measurements. The growth ratio of the head-capsule width ranged from 1.05–1.20 with a grand mean of 1.12. This range falls within the acceptable range in Dyar's rule. The mean growth rate of C. quadricollis after 2 weeks of rearing on maize, sorghum, melon, wheat and cowpea, ranged from 22.4 to 1.6. While the mean developmental periods of C. quadricollis on the selected food media ranged from 18.80 days on cut maize to 30.70 days on cut cowpea.

An emulsion concentrate (locust lotion) containing 20% v/v neem oil and 40% w/v aqueous extract of Tetrapleura tetraptera L. was found to be most stable when subjected to viscoslty measurement, creaming rate determination, droplet size analysis and accelerated stability tests. The emulsion supported the growth of microorganisms which was prevented by a combination of 0.2% w/v methylparaben and 0.1% w/v propylparaben. Octylgallate, 0.1% w/v was added as an antioxkiant to prevent the oxidation of neem oil in the locust lotion concentrate. The recommended use concentration for protection ot cassava Manihotesculenta Crantz from damage by grasshopper Zonocerus variegatus L. was 1.8–2.2%. At 2.5%, locust lotion was phytotoxic to cassava.

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.

Results of research on biology of Thinophilus guineensis Coul. et Neg. (Diptera, Dolichopodidae) confirm the importance of predaceous feeding behaviour of some other species of Dolichopodidae such as Medetera fisch, Hydrophorus fallen, Sciapus fatten, Diaphorus meigen, etc. Larval mortality of some pests (mosquitoes, blackflies, scolytes, etc.) reach 83 to 99%.

These species, because of their extraodinary ubiquity and their biocoenotical importance, could well be used in biological control programmes of vectors of pathogens affecting man and other animals or pests in agroforestry.

Transmission of Ife virus by Aedes aegypti mosquitoes was investigated. Mosquitoes were experimentally infected by feeding on viraemic mice or on infected mouse brain suspended in defibrinated chick blood. Normal infant mice were exposed to infected mosquitoes after predetermined extrinsic incubation period. Ife virus persisted for only 1 day in mosquitoes that fed on viraemic mice and for 5 days in those that fed on infected brain/blood suspension. Virus was not recovered in infant mice exposed to infected mosquitoes. However, there was serological evidence of virus transmission manifested as the presence of complement fixing antibody against Ife virus in mice exposed after 2 days and 2–5 days extrinsic incubation periods to mosquitoes infected by feeding on viraemic mice and by feeding on infected brain/blood suspension respectively. This transmission was considered mechanical in view of the short virus persistence and extrinsic incubation periods.

Five natural compounds possessing antiparasitic activity were isolated from East African plants and tested, together with some semisynthetic derivatives, against micro-organisms and arthropods of agricultural interest. Anonaine (1), from Annona squamosa, canthin-6-one(8) and 5-methoxycanthin-6-one (9), from Fagaropsis angolensis, showed fungicidal activity. E,Z-matricarianol (4), from Hoehnelia vernonioides was fungicidal, Insecticidal and acarlcldal. Caryophyllene oxide (12), isolated from Uvaria sp., turned out to be insecticidal and antifeedant. Canthin-6-one (8) and its dihydroderivative 11 were the most effective antimicrobial compounds tested. The possibility ofusing some of the isolated compounds as leads for new synthetic chemicals is discussed.

Malathion tolerance of the rose-grain aphid Metopolophium dirhodum (Walker) reared on the ancient wheat variety Emmer (Triticum dicoccum L.) was tested by topical bioassay and found to be lower than that of aphids reared on the modern more susceptible variety Marts Kinsman (T. aestivum L.). On both varieties, tolerance was greater at stem elongation than at the tillering stage of plant growth. All statistically significant differences when plants were treated with Cycocel and MCPA showed that the two chemicals, respectively, reduced and increased aphid tolerance to malathion, in keeping with the effects of the chemicals on induced plant resistance to aphids reported in the literature. Probit mortality slopes were not progressively altered by changes in LC50, so that similar differences in aphid tolerance to malathion were found at both LC59 and LC90 levels.

Nature of resistance against the rice leaffolder, Cnaphalocrocis medinalis (Guenee) was studied in 16 rke varieties selected on the basis of greenhouse feeding test. Resistant varieties as a group were less preferred for feeding by the larvae in a free choice test lasting 10 days. Cut leaf assay with limited choice brought out subtle differences among some of the test varieties In larval settling response. Larval preference was correlated positively with the leaf area damage noted In feeding test, per cent pupation and leaf width, and negatively with trichome density. However, oviposltton preference was neither distinct nor correlated with resistance or leaf morphology. An antibiosis component in the test varieties ARC 11128, Balam, Gorsa, ARC 7064 and Ptb 19 was distinctly manifested as reduced larval survival, lower pupation rate and pupal weights in comparison with the susceptible check. When neonate larvae were reared on the meridic diets containing the leaves of the varieties Darukasail, Balam or Ptb 12, antibiotic effects were much more pronounced in comparison with the larvae reared on the diet containing the leaves of the susceptible check TN 1.

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.