Thirty-eight Leishmania isolates from different host species (humans, mammals, reptiles and sandflies) from various parts of Kenya were compared with six World Health Organization Leishmania reference strains. Isoenzyme variations were assessed on the basis of their electrophoretic profiles on cellulose acetate membranes. Out of 18 enzymes studied, Five were selected for differentiating the Leishmania isolates. These were glucose-6-phosphate dehydrogenase (G6PD, E. C. 1. 1. 1. 49), glucose phosphate isomerase (GPI, E. C. 5. 3. 1. 9), malate dehydrogenase (MDH, E. C. 1. 1. 1. 37), mannose phosphate isomerase (MPI, E. C. 5. 3. 1. 8) and phosphoglucomutase (PGM, E. C. 2. 7. 5. 1).

Twenty-one isolates showed enzymatic patterns identical to the Leishmania reference strain Leishmania major IC-236, five isolates were similar to the Leishmania reference strain L. donovani IC-245 and three isolates were identical to the Leishmania reference strain L. aethiopica IC-228.

However, nine Leishmania isolates could not be identified by this method. They are either leishmanial species for which more Leishmania reference strains are needed for comparison or unidentified flagellates species.

The banding patterns revealed by L. major IC-235, isolated from Israel, were different from those of L. major IC-236, isolated from Kenya, with respect to G6PD; GPI; MDH; MPI and PGM.

Field studies to investigate the effect of intercropping on the relative resistance and susceptibility of cowpea cultivars to Maruca testulalis impure stands and intercropped with maize, were conducted at the International Centre of Insect Physiology and Ecology (ICIPE). It was clearly indicated that intercropping affected the relative resistance and susceptibility of cowpea cultivars. The resistance of TVU 946 to Maruca was reduced when the cultivar was under maize. This was attributed to the phenological changes observed, i.e. when planted with maize there was a significant (P = 0.05) increase in length of the pods and peduncles and significant (P = 0.05) reduction in the number of branches. Weekly mean temperatures and relative humidities indicated that there were significant differences between cropping patterns. Similarly there was a significant reduction in the photosynthetic active radiation incident on cowpea canopy in all the intercropped plots. This suggested that both intercropping and microenvironmental differences observed, reduced resistance in cultivar TVU 946 by probably acting directly on the crop, thus rendering it more susceptible.

A questionnaire survey was conducted to find out the information and knowledge of extension workers on thresholds of cotton bollworms, (Helicoverpa armigera and Diparopsis castanea). A sample of 30 extension officers was interviewed in Southern and Central provinces of Zambia. The results showed crucial deficiencies in extension worker's knowledge on thresholds of key pests and their implementation in cotton IPM. More than 60% extension officers were not aware of the basic information and knowledge such as thresholds of cotton bollworms, the recommended time to start scouting (weeks after germination of cotton) and the number of cotton plants to be examined for pest observance in each field. All extension officers indicated a desperate need for more field oriented practical training on thresholds. The recent increase in the incidence of aphids, Aphis gossypii as reported by 50% extension workers is obviously due to calendar sprays of synthetic pyrethroids and the lack of a suitable aphicide in current spray programme. Demonstrations on the practical aspects of thresholds deserve much more attention at college level and also during the in-service training. More co-operation in cotton IPM training for extension officers within Central and Southern Africa is suggested.

The composition and preparation of an artificial diet for the coffee berry borer, Hypothenemus hampei is described. Ten generations were obtained without any significant change in fecundity. Development at 25°C on this diet was similar to previously reported work using coffee berries. One female reared on this diet lived for 380 days. This diet will permit investigations into the genetics of insecticide resistance, potential biopesticides and other research, requiring a convenient laboratory rearing system.

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.

A light trap was operated in Samaru, Nigeria between 1973 and 1980 to monitor populations of Coniesta ignefusalis. Two generations of the insect/year were represented by two adult peaks in July and September. In 1974, an early peak in May resulted in three generations. In cages in the field, eggs were laid between the leaf sheath and the stem in batches of 20 to 70 with a mean of 47.5 eggs/batch. Laboratory studies conducted at 25–28°C and 75–85% r.h. showed an average developmental period of 35.5 days. The average duration of the egg, larval and pupal stages were 4.5, 21.9 and 9.2 days, respectively. Unfed adults lived for 5.3 days.

Heliothis armigera (Hubner) completed five generations in the laboratory, as well as in the field, in a year. The first generation was completed from the first week of December to the fourth week of February, the second generation from the second week of February to first week of April. The third generation from third week of August passing through the extreme summer, the fourth generation during monsoon period and the fifth last generation from the third week of September to the fourth week of November. The seasonal variation in generation time is largely due to extreme variations in ecological factors, temperature (10–45°C), photoperiod (10–14 hr), relative humidity (15–95%) and rainfall. These factors also affect the percentage of pupation, emergence and fecundity of the female moths. Males outnumbered the females in the first, second and fifth generation. The females lived longer than males in all generations.

Feeding deterrency tests by leaf disc dipping method revealed AZT-VR/K extract of azadirachtin as the most potent antifeedant against cabbage butterfly, Pieris brassicae L. larvae. The leaf damage on treatment with the extract (at 3, 2 and 1%) was minimum and ranged between 4.9 and 16.3 % as compared to 98 % in untreated check. High level of feeding deterrency was exhibited at all the concentrations of AZT-VR/K, while in neemark (at 1%) and neem oil (at 2 and 1%), the deterrent effects declined considerably on their decreased concentrations.

The anatomical and biochemical basis of resistance of Vigna vexillata (Benth) (Ace. TVNu 72) to Monica testulalis were investigated. An uncharacteristic network of fibrous structures was observed on the petal surface of TVNu 72 but not on those of the susceptible control, IT82D-716. Stems of TVNu 72 and IT82D-716 have thick and closely packed collenchyma cells. Both varieties have been identified as possessing resistance to stem feeding; however, IT82D-716 is susceptible to flower and pod damage. The distance between pod wall epicarp and mesocarp was significantly (P ≺ 0.05) smaller in IT82D-716, but cell and tissue arrangement were similar for both varieties.

Total sugar content in the pod wall and seed of TVNu 72 was higher (P ≺ 0.05) than in IT82D-716. Phenol content was lower (P ≺ 0.05) in the pod wall of TVNu 72 but the reverse was true for fresh and dry seeds. This suggests that neither phenol nor total sugar are involved in the resistance of TVNu 72 to M. testulalis. However, it seems that thick and compact collenchyma cells in the stems and Fibrous tissues on the petal surface contribute to the resistance in TVNu 72. The results are discussed in line with previous reports which indicate that trichomes are the principal factors in the resistance of TVNu 72 to M. testulalis.

In the majority of insects, migration occurs exclusively or predominantly during the pre-reproductive period (PRP) and therefore, the duration of the PRP provides a useful index of migratory potential. The present study describes a novel method for estimating the PRP of Spodoptera exempta (Walker) (Lepidoptera: Noctuidae). It relies on the fact that as the female approaches sexual maturity, there is a substantial change in the shape of her gonopore-patch (an area of black scales at the posterior of the abdomen). Gonopore-patch shape (GPS) is strongly correlated with PRP (as determined by “calling” behaviour) and may prove to be the best method for estimating migratory potential in some circumstances. A number of other species of moths also have gonopore-patches which may aid the study of their migration.

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 length of the reproduction cycle of Lasioderma serricorne (F.) under ambient laboratory conditions (temperature range 28.0–32°C and 72.5–80.5% r.h.)was shown to depend on the identity and state of division of various cereal grains, cowpeas, groundnuts and dried root crops. Cut dried yams allowed the shortest cycle andwholericethelongest.The rate of population increase by L. serricorne was also assessed and this was maximal when cut wheat and minimal when whole rice was provided. Fecundity was highest with sorghum and lowest with rice as food source. Females of the species lived longer than males.

Studies were conducted during the dry period February to May 1986 in River Shelliekha, Bahr El Arab fly belt, Sudan, to obtain baseline data on catch and age compositions, reproductive status and trypanosome infection rates of trapped and fly round samples of Glossina morsitans submorsitans. The objective was to assess the tsetse situation before the establishment of trypanosomiasis treatment stations at the northern limits of the fly belt. Trapped tsetse included significantly higher proportions of teneral and non-teneral females and a lower male:female ratio. Insemination rates were over 98% in both samples. In any one group, the frequency of pregnancy with egg predominated, followed by the second, first and lastly the third instar larva. There were significant differences between the two groups of females in the proportions of nullipars and pregnancy with any one of the larval instars. Abortion was the predominant reproductive abnormality and no relationship could be found between abortion rate and the sampling method, age or trypanosome infection rate of females. Age compositions were similar in the two samples, save for age categories 0 and 1 for females and two and four for males. Flies were infected with Trypanosoma vivax and T. congolense only, though T. brucei infections could also be diagnosed in livestock.

Lipophorin was isolated from the stalk borer, Busseolafusca, larvae by ultracentrifugation in a KBr density-gradient. The lipophorin (M, ˜ 700,000) is a high density lipoprotein (density = 1.13 g/ml) composed of 46% lipids and 4% carbohydrates. It consists of two apoproteins, apolipophorin-I (apo Lp-I, Mr ˜210,000) and apolipophorin-II (apo Lp-II, Mr ˜78,000). Both apoproteins are glycosylated as shown by periodate Schiff reagent staining and binding to the lectin, concanavalin A. Amino acid composition analysis of lipophorin showed predominance of aspartate (13%), glutamate (9%) and glycine (9%).

In an immunoblotting experiment, both apoproteins showed immunoreactivity with antiserum to B, fusca lipophorin and no cross-reactivity occurred with any other haemolvmph proteins. Immunodiffusion studies with the same antibodies showed cross-reactivity with haemolymph derived from other Lepidoptera and not from Orthoptera, Dictyoptera or Diptera.

The leaf surface treatment given to nymphal instars of Lipaphis erysimi with methoprene (1–10,000 ppm) prolonged the developmental period only in the second instar. The percentage emergence decreased significantly in the treatments of first and second instar and the alate production increased in the treatment of the latter instar only. In addition, dose-dependent morphological abnormalities were also observed. The longevity and fecundity were affected adversely when adults were given both topical and leaf surface treatments. However, these effects were not transmitted to the F1 generation.

This is a description of species area effects for Agromyzidae associated with leguminous plants. The data on geographic area was extracted from the National Museums of Kenya (Herbarium section). The geographic area species plots showed an effective partial correlation of 16%. The correlation was unfortunately low and could be attributed to inadequate botanical and agromyzid records in Kenya. Generally, geographical area explained most of the species richness in Kenya. Other variations not accounted for by the logarithmic plot of species-area effects were derived from residuals. The plots between residuals and different variables showed that leaf-form, habitat variation, altitude and taxonomic isolation also explained variation in species area plots.

Accessions of Vigna vexillata, Vigna oblongifolia, and Vigna unguiculata (subspecies unguiculata, dekindtiana, and pubescens) were evaluated under laboratory conditions to identify sources of seed and/or pod resistance to the cowpea weevil Callosobruchus maculates. TVnu 37 and TVnu 88 (V. oblongifolia) and TVnu 72 (V. vexillata) possessed high levels of seed resistance. On mature, dry pods, seventeen-fold differences in mean eggs laid/cm2 were observed, suggesting that ovipositional nonpreference could be a practical form of resistance to C. maculatus. In infested pods, pre-establishment larval mortality (mortality before larvae become established in seeds) varied among accessions, ranging from 19.3% in N1 778 (cv-gr. Biflora) to 91.3% in NI 816 (cv-gr. Textilis). The total percentage larval mortality in infested pods ranged from 34.6% in TN 88–63 (V. unguiculata) to 100% in TVnu 72 (V. vexillata) and NI 816 (cv-gr. Textilis) with the majority of accessions producing over 80% mortality. Higher levels and more durable forms of bruchid resistance might be achieved by combining seed and pod resistance.

Life-fertility tables were described for Bracon hebetor Say (Hymenoptera: Braconidae) developing on the millet head caterpillar (MUC), Heliocheilus albipunclella de Joannis (Lepidoptera: Noctuidae). Mated B. hebetor females lived an average of 24.7 days, oviposited ca. 22 days, and produced 173.7 adult progeny with a 1:1 sex ratio. The estimated innate capacity of increase (ir) and net reproductive rate (R0) were 0.26 and 86.5, respectively. The mean generation time was 1 days.

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.