The major alkanone constituents of the resin of Commiphora rostrata, 2-decanone and 2-undecanone, and a series of structural analogues were bioassayed for their repellency against the maize weevil, Sitophilus zeamais in olfactometric assays. All the aliphatic ketones and aldehydes showed comparable or greater activity than the synthetic commercial insect repellent N, N-diethyl toluamide (DEET). In the 2-alkanone series the C-8 and C-9 compounds demonstrated significantly higher activity than their shorter- and longer-chained congeners. Analogues differing in the relative positions of the carbonyl group, including aldehydes, showed a variable pattern of repellency. Alkanols appeared to be mildly attractive to the weevil. The results support our previous suggestion that the resin constituents may play an allomonal role in the ecosystem where the plant thrives.

Green marine algae (Codium sp.) was extracted sequentially with different organic solvents on cold. Lima bean leaf discs treated with the different extracts were offered to adult female T. urticae for 96 hr and the corrected percentage mortality of the females was calculated. The toxicity of the different extracts to the eggs was also recorded. Petroleum ether extract of this seaweed was highly toxic to females at 4 g/ml. At 1 g/ml ca. 48% of the individuals were killed. Chloroform and ethyl alcohol extracts were found to be poorly effective against the females even at high concentrations (4 g/ml) where less than 50% of the individuals died after 96 hr. Toxicity of crude extracts to the egg stage was less pronounced and chloroform extract was found to be more efficient than the other extracts tested.

The effects of various concentrations of Neem Azal-T and Neem Azal-T/S as natural insecticides on the biology and percentage mortality of adult Aphis craccwora Koch were studied under laboratory conditions. Both extracts had an aphicidal effect against the adults and significantly decreased their fecundities and longevities. Addition of synergists such as ethyl oleate, sesame oil and dimethyl sulphoxide (DMSO) improved the aphicidal effects of both insecticides. The biological activity of Neem Azal-T/S only could be enhanced with suitable additives as they adversely affected the fecundity and longevity in comparison to the extract alone. Addition of CaCO3 to the above extracts had no clear effect on either neem seed extract formulation.

The feeding habits and infestation of the bitterleaf weevil, Lixus camerunus Kolbe, were investigated in Rivers State, Nigeria. Vernonia amygdalina was the only species preferred for feeding and oviposition by adult L. camerunus, among the species (Talinum triangulare (Jacq.) Wild, Telfairia occidenlalis Hooker fil, Amaranthus hybridus L., Solanum melongena, Capsicum sp., Chromalaena odorata (Eupatorium odoralum) L., Emilia praetermissa L.) associated with V. amygdalina in farms, that were offered. There was a significant correlation between dry weight of foliage consumed and weight of males and females.

Initial tunnelling direction by larvae was upwards, but on the death of shoots, larvae reversed direction and moved downwards along old tunnels. However, newly-emerged larvae in leaf petioles, tunnelled downwards to the main branch, before pursuing an upward course. In addition to main tunnels, there were also branch tunnels. There was a significant negative correlation between length of tunnel and stem diameter. There was a significant negative correlation between gall/stem diameter ratio and stem diameter.

L. camerunus is widely distributed in the State.

Gravid Lucilia treated topically with ivermectin (0.05μg/g, which represented approx. 4% of the 48 hr LD50) laid fewer viable egg batches (less than 50% of controls) and more sterile ones, when compared to untreated (P = 0.019) and acetone-treated flies (P = 0.028). This effect was also seen when mature third instar larvae were dosed with 7.6 μ g ivermectin/g (P = 0.0075 and 0.016 respectively); number of viable egg batches produced were only 25% of the number laid by the progeny of untreated larvae.

Dosage with fenthion stimulated an increase in the number of viable egg batches laid when incorporated in the original larval feeding medium at 0.2 μg/g liver; fewer viable egg batches were laid by the flies which developed from mature larvae treated with 7.6 μ g fenthion/g. Acetone solvent alone had a mild stimulatory effect on topically dosed flies.

Screening of leishmanial parasites from domestic and wild animals was carried out in Kacheliba, West Pokot District. Spleens and livers of the animals were cultured in NNN diphasic medium. Thin smears of the same tissues were also made and stained with Giemsa stain and examined under microscope. Positive slide smears were obtained from goats and positive cultures obtained in four goats, one rat and two lizards.

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.

At present there are nine species of tephritid fruit flies in Mauritius and together they plague a wide range of hosts, from wild guavas to cultivated fruits and vegetables. The most destructive among them are: the natal fruit fly, Pterandrus rosa Karsh; the medfly Ceratìtis capitata Wiedemann and the melon fruit fly Dacus cucurbitae Coquillet. Studies with parapheromones indicate that trap colour has little if any effect on the efficiency of fly capture, the olfactory component completely dominating any visual effect. The efficiency of the traps with respect to height varies from species to species and with the vegetation. A height of 120 to 180 cm from the ground was found to be optimal for the natal fruit fly in wild guava zones. Traps placed at ground level on creeping plants were found to capture the highest number of the melon fruit fly. The response of the medfly in fruit tree orchards with height of traps was erratic, showing inconsistent trends with more than one peak.

Simple methods for production of all life stages of the banana weevil on its natural diet, banana rhizome and pseudostem are presented. Their effectiveness, labour demands and applicability for different purposes are discussed. The most effective method for the production of eggs, pupae and adults is the utilization of the rhizome part of suckers, whereas larvae are easier to recover from pseudostem. The hatchability of the eggs produced is high.

Epidinocarsis lopezi proved to be an efficient biological control agent of the cassava mealybug (CM), Phenacoccus manihoti, despite apparently low parasitization rates. Laboratory experiments indicated that its killing power at higher temperatures was two to three times higher than the per cent mummy formation suggested. Following an attack by an E. lopezi female some CM hosts were killed through host feeding and some through successful development of the parasitoid larva, processes which both benefit the parasitoid. If the host was found unsuitable, no egg was laid, and the CM survived the attack. Other CM died from the wasp attack without forming a mummy. This mortality is attributed to mutilation and unsuccessful larval development of E. lopezi. Most ovipositions induced a defence reaction by the host that lead to melanization. This process involved mainly wound tissue, sometimes partial encapsulation of the tail end of the parasitoid larva, and infrequently complete and fatal encapsulation of the parasitoid larva.

The relationship between seasonal numbers of outbreaks of African armyworm (Spodoptera exempta) in Kenya and Tanzania, and early season rainfall in source areas has been examined using records for 21 seasons. Significant inverse relationships were found between numbers of Kenya outbreaks and early season rains in the Kisumu area, and between numbers of Tanzania outbreaks and early season rains in the Morogoro and Mtwara areas. Total Kenya and Tanzania outbreak numbers were significantly inversely related to early season rainfall for 8 areas combined. These results suggest that early season rainfall totals, either from specific likely source areas or countrywide, could be used in January to give a seasonal forecast of likely numbers of armyworm outbreaks during the rest of the season. Seasons with more than average numbers of outbreaks often follow poor early season rains and visa versa. Further work is needed to establish biological causes of this apparent relationship.

Lepidopteran stem borers account for heavy losses in cereals in areas where they are prevalent throughout Africa. Microsporidia, especially Nosema sp. may be developed for use in the management of this group of insect pests. Studies carried out so far show that the application of Nosema spores may increase yield up to 34% in sorghum when the plants are infested with Chilo partellus eggs and sprayed with the pathogen, and up to 80% in sorghum infested with borer larvae.

The procedure for spore production is simple, and may easily be adapted for small scale industrial production by local or regional communities and organizations. In trials aimed at the mass production of Nosema sp. for the management of C. partellus, a yield of 109 spores/larva has been attained. If this production level can be maintained, then a system that produces only 6000 larvae/day would yield enough cadavers for preparation of 6000 1 daily. At the rate in which the pathogen suspension is applied as foliar sprays in the field, this would be sufficient to treat 5373 ha. If widely adopted, use of microsporidia would revolutionize cereal stem borer management in the tropics.

Regular field surveys were carried out in 2 week intervals in 1986 and 1987 to determine population density, species composition, migration activity of Cicadulina leafhoppers and their infectivity with maize streak virus (MSV) in different ecological locations of southeastern Nigeria: mangrove swamp forest (IITA and RIART station at Onne), deltaic swamp forest (RSUST, Port Harcourt), seasonal swamp forest (Iriebe) and high forest zone (NCRI, Amakama near Umuahia).

Population density was always low during dry season, significantly lower in the rain forest zone and higher in the swamp forest, rapidly rising in the second rainy season in all ecological zones and reaching its maximum before the rains finally stopped. Sharp increase in the population density in Nov. and Dec. may indicate mass migration activity of Cicadulina leafhoppers from already dry areas of adjacent Guinea savanna at that period.

Six species of Cicadulina were collected from most of sampled areas. C. ghaurii was the predominant species in 1986 and 1987, averaging 55.9% for all locations and periods. Its portion was higher in the mangrove swamp forest (Onne) than in the high forest zone (Amakama). The predominance of other species declined in the order: C. triangula (18.2%), C. mbila (17.2%), C. arachidis (5.9%), C. similis (2.8%) and C. hartmansi (0.1%). In absolute values, the portion of individuals out of the total number of leafhoppers collected was for C. triangula 53.7%, C. ghaurii 25.5%, C. mbila 17.3%, C. arachidis 2.3%, C. similis 1.1% and C. hartmansi0.1%. A high population of C. triangula occurred only in the relatively short period in Nov.-Dec, especially in Iriebe and was correlated with the rapid increase of Cicadulina densities in all sampled areas; a high migration activity of C. triangula and C. mbila was confirmed.

Incidence of MSV in the surveyed farmers' field varied between 0–22% in the first rainy season (1987) and 12–25% in the second rainy season (1986). The portion of Cicadulina adults already infected with MSV under field conditions and capable of transmitting MSV to the susceptible maize seedlings varied from 3.3 to 23.3%, with higher values for leafhoppers collected at the end of the second rainy season.

Larvae of the Caribbean fruit fly, Anastrepha suspensa Loew (Diptera: Tephritidae) parasitized by the wasp, Biosteres longicaudatus Ashmead (Hymenoptera: Braconidae), were topically treated with diflubenzuron (Dimilin®), a chitin synthesis inhibitor, at 100, 500 and 1000 ppm. Each dosage was initiated during the parasite's egg stage, each of four larval stages and the pupal stage (pharate pupa + pharate adult). Adults emerging from all immature stages treated with the two higher dosages were significantly (P < 0.05) fewer than the controls. Developmental stages, in decreasing order of susceptibility to diflubenzuron were: egg, first instar, pharate adult, pharate pupa and larval stages two to four. Abnormally developed ovipositors occurred in some adults which emerged from eggs, pharate pupa and pharate adults that were treated with the two higher concentrations. Such females were unable to successfully locate and parasitize hosts. Females with normal ovipositors which emerged from treated eggs and pharate adults were able to find and attack hosts but had significantly fewer eggs in their ovaries and oviposited less than the controls. The F1 eggs laid by these females developed normally and survived to adulthood with no apparent abnormalities.

Several mounds in western Kenya were excavated to examine their internal structure. The mounds and the soil beneath them were found to be densely packed with discrete chambers containing fungus combs. A simple system of passages opening to the exterior provided both access and ventilation to the interior of the nest. One nest was killed by fumigation and its contents extracted. The nest population was estimated to be 0.28 million adult steriles with a biomass of 462 g dry weight, and the total dry weight of fungus comb was 2.8 kg. These estimates are very low in comparison to nests of Macrotermes spp. that build mounds of comparable size. The ratio of fungus comb weight to adult biomass (6:1) is higher than that in Macrotermes spp., perhaps because the comb is constructed in a different way.

Field-trapped tsetse Glossina pallidipes, G. brevipalpis and G. austeni were dissected and the incidence of hypertrophy of the salivary glands (HSG) recorded. This condition was observed only in G. pallidipes. The highest level of infection (15.6%) was observed in July in one of the trapping sites. Both very young teneral (ovarian category 0a) and very old (ovarian category 7 + 4N) tsetse had greatly enlarged glands. The differences in bi-monthly HSG incidence for the five trapping sites were statistically significant. The level of infection in males and females did not show significant differences.

Despite the growing acceptance and adoption of the IPM concept, up until now no “optimal” or pragmatic IPM programme has been realized. This is apparently because most of these programmes are still in need of new types of pesticides, with no or negligible adverse impact on the environment including the non-target beneficial arthropods. From a practical perspective, such pesticides are still rather far reaching. Most, if not all, pesticides in current use as components of IPM programmes are so far belonging, in one way or another, to the conventional pesticides. It is admitted that in designing IPM programmes, several efforts should be made to minimize not only the frequency of pesticide applications but also their negative consequences on beneficial arthropods. Whilst the first goal has been achieved in several situations, the other one appeared hardly accessible. A number of methodologies are currently being suggested to cause conventional pesticides more selective, but apart from having many technical and other constraints, they might at best have fallen short of providing the hopeful solution. These together with other problems facing the development and practical utilization of juvenoids and related compounds are discussed mainly in view of their possible contribution to tropical pest management.

The millet stem borer, Acigona ignefusalis Hampson, can cause total crop failures when severe infestations occur such as happened in northern Nigeria in 1984. Research at the Institute for Agricultural Research at Samaru has shown that various millet types and varieties exhibit different levels of susceptibility to the stem borer, although no resistant varieties are yet available. Infestation and damage by the stem borer are strongly influenced by date of planting and rate and time of nitrogen fertilizer. The effect of mixed cropping with sorghum depends on the spatial arrangement of the component crops in the mixture as well as on the insect population pressure. Systemic insecticides, particularly granular carbofuran, have been found to control the stem borer more effectively than contact insecticides like carbaryl. Seed dressing with carbofuran has been found to be ineffective. Some natural enemies of the stem borer have been identified but their role in lowering damage to millet is minimal. The destruction of infested stems before the beginning of the rainy season is a very important control measure against the insect. The possibilities of integrating these various methods for stem borer control are discussed.

The effects of plant growth habit (erect versus spreading and flowering pattern) on the resistance of cowpea Vigna unguiculata (L.) Walp., to the legume pod borer, Maruca testulalis Geyer, were studied in Nigeria. Five cowpea cultivars of known agronomic and architectural characteristics were selected for the study: TVu 946, IT82D-716, VITA-3, Oloka local and Kamboinse local. Seed and pod damage assessment values were better in profuse flowering than in non-profuse flowering cultivars and in erect cultivars than in spreading cultivars. Best performances were obtained from TVu 946 (profuse flowering and erect resistant), and worst results from Oloka local (spreading susceptible) and VITA-3 (susceptible non-profuse) respectively. Erect and profuse flowering cowpea cultivars are proposed as having good architectural components for reducing M. testulalis damage to cowpea. The implications of architectural variations in cowpea are discussed.