The effect of light on the development of the angoumois grain moth, Sitotroga cerealella, was studied. Three different light conditions, i.e. continuous light (LL), continuous darkness (DD) and antural illumination (LD), were used.

Eggs bred under LL system showed the shortest mean incubation period, 3.27 and 4.66 days after one and four generations, respectively. The light had no effect on egg hatchability. The number of larvae that reached the adult stage under LL was less (33–36%) than under LD (37–40%) or DD (38%). The fertile females begin egg laying within 0.9 to 2.3 days after mating under all light systems. The shortest period (0.9) was shown under continuous light. The least oviposition period 4.4 and 4.5 was obtained under LL, while the longest period (6.4 and 5.7 days) was obtained under LD, after one and four generations, respectively. The light has no effect on the post-oviposition period. The longest life span of adults was recorded under LD and the shortest under LL. The females bred under LL, laid the least number of eggs (85–87 eggs), while those bred under LD and DD laid the highest number (128–130 for LD and 113–146 for DD, respectively).

The life cycle of the koinobiont endoparasitoid Platygaster diplosisae Risbec was investigated to assess its suitability as a biological control agent of the African rice gall midge Orseolia oryzivora Harris & Gagné. Screen house and laboratory experiments were conducted in 2008 under ambient conditions in Ibadan, Nigeria. Morphological characteristics of the parasitoid's immature stages were observed, and its life cycle parameters were measured. The parasitoid's average egg incubation period was 12.9 days, and on average, 67.3% of eggs hatched. Three instars occurred, with average developmental durations of 2.2, 0.5 and 2.5 days for the 1st, 2nd and 3rd instars, respectively. Pupal development took 6.7 days until adult emergence. Pre-oviposition period averaged 12.1 h, and a female laid on average 95.2 eggs, with a mean oviposition period of 3.5 days. The longevity of males and females was 3.0 and 4.1 days, respectively, without food; longevity was extended when honey and water were provided. Mating and oviposition behaviours were recorded, and a sex ratio of eight females to one male was found in parasitoid progeny. The parasitoid had a total developmental period of 27.3 days, which is about 5 days longer than that of its host. In conclusion, P. diplosisae can play an important role in the biological control of O. oryzivora on rice, and should be conserved in African rice production systems.

The stemborers Busseola fusca (Fuller) and Chilo partellus (Swinhoe) cause the highest economic damage to maize and sorghum in Zimbabwe. A number of studies on stemborer bioecology and management in Zimbabwe have been conducted, but most are still incomplete. The more important of these are studies on life history, incidence and distribution patterns, host plants, yield losses, chemical control, cultural control, host plant resistance, the use of sex pheromones, and biological control. These are discussed here in detail, and areas where further research is needed are pointed out. As part of an integrated strategy for managing stemborers in Zimbabwe, an exotic braconid larval parasitoid, Cotesia flavipes Cameron, has been released in the lowveld area and prospects for its establishment appear to be good. However, this establishment might be curtailed mainly by the inability of Co. flavipes to adapt to the seasonal carryover mechanisms utilised by the indigenous Cotesia sesamiae (Cameron).

The location of olfactory and gustatory sense organs in the larvae of the American bollworm, Heliothis armigera, have been studied using the scanning and transmission electron microscopy. The olfactory chemoreceptors of the larvae are located on the antennae, mostly on the top of the second antennal segment in the form of two trichoid sensilla, two basiconic sensilla, two styloconic sensilla, campaniform sensilla and a uniporous peg sensillum. The third antennal segment bears one basiconic sensillum and two styloconic sensilla. The gustatory sense organs are located on the mouthparts including the labrum, mandibles, hypopharynx, maxillary palps and labium. Trichoid sensilla have been located on the labrum. Epipharyngeal setae as well as long short spines are located in the epipharyngeal membrane. The basal segment of the maxillary palp bears three trichoid sensilla and one campaniform sensilla. The maxillary palp also bears four styloconic sensilla on the distal portion of the lateral protuberance and one styloconic sensillum at the apex of the medial protuberance. Close to the bases of the protuberances, there are three basiconic sensilla and one campaniform sensillum. The third apical segment of the maxillary palp carries three campaniform sensilla on its lateral side, while on its top, eight small basiconic sensilla are distributed.

Observation on the distribution and seasonal variation of riverine tsetse population at Egbe in the Derived Savanna Zone of Nigeria was made and compared with variation in other vegetation types of the country. Egbe, in a sub-humid location, was observed to have a low rainy/high dry season population density similar to what occurs in part of the Southern Guinea Savanna Zone. To the north of these areas, the less humid vegetation zones show a definite reverse pattern (high rainy/low dry season) of seasonal population density. The Rain Forest Belt, a humid zone has, surprisingly, more similarity with the less humid zones to its far north than with the sub-humid zones nearer to it Irrespective of zone and season, a favourable temperature of between 26.1 and 26.7°C appeared important towards having a high population density. Reasons were given for the low rainy season tsetse density at Egbe. Unlike zones in the less humid north where rainy season dispersal is well marked, tsetse distribution in the Derived Savanna Zone remained by the riverine vegetation almost throughout the year. The advantage of this study to a proposed ranch for the area was highlighted.

Vertical distribution of different larval instars and pupae of Culicoides oxystoma in different depths in the mud and sandflats of Hooghly estuary were studied in relation to soil temperature and moisture at three stations in and around Sagar Island during March 1983 to February 1984. Temperature recorded higher in 0–3 cm depth and gradually decreased in subsequent depths. During the last part of the pre-monsoon (May and June) season, moisture was recorded minimum in 0–3 cm depth and gradually increased in greater depths, but in other seasons (monsoon and post-monsoon) the results were just opposite. Larval and pupal population showed a peak during post-monsoon then gradually declined in pre-monsoon and early monsoon. They were mostly encountered throughout the year from 0–3 cm depth except during summer months (May, June and July). First and second instar larvae were only recorded from 0–3 cm depth. Third and fourth instar larvae were distributed in all the depths, maximum in 0–3 cm. Pupae were never encountered from deeper depth (6–9 cm). Temperature and moisture act as important factors to control the vertical distribution of larvae and pupae of this species.

Sweetpotato weevil, Cylas formicarius formicarius F is the most destructive pest of sweetpotato, Ipomoea batatas in tropical and subtropical regions. The larvae and adults feed on sweetpotato roots and crowns. For the past 12 years we have been screening sweetpotato germplasm for resistance to this pest in order to breed an agronomic cultivar with weevil resistance. Resistance screening is conducted at AVRDC and Penghu island in autumn and summer, respectively. Germplasm is planted between heavily infested source rows maintained in a weevil nursery. Roots are harvested, sliced into thin pieces, and the number of insects (larvae + pupae + adults) per unit weight, as well as the weight of damaged and healthy root slices, are recorded. The resistance rating is based mainly on the number of insects found in the root. Considerable differences in resistance rating are observed from location to location and season to season. Even at one location, tremendous differences are observed in weevil infestation of a particular entry among the replicates. Although over 1000 sweetpotato accessions have been screened, we have not found any that is consistently less damaged over several seasons at either location. Our recent screening of a population of I. trifida × I. batatas crosses show certain hybrids with high yield and low weevil infestation. These hybrids need to be evaluated further to confirm their resistance.

This paper reports the results of extensive pest surveys conducted on farmers' fields and pest population studies at two national research stations between 1979 and 1981 in Burkina Faso. Major findings indicate that, under normal planting conditions, infestation of the sorghum shootfly, Atherigona seccata is very low in farmers' fields. This pest appears to be restricted to research stations. Stem borer infestation is caused by a complex of species, and species predominance varies with rainfall. South of latitude 12°N, Busseola fusca is the predominant species but further north it is replaced by Acigona ignefusalis, which is a primary pest of pearl millet. Panicle damage caused by the sorghum midge, Contarinia sorghicola, varies with season; is usually very low in the dry northern Sahelian zone but severe south of latitude 13°N. Maximum midge populations occurred between mid-September and early October.

A South American leaf galling psyllid, Calophya schini Tuthill, has recently been discovered attacking the South American tree Schinus molle L. in Kenya and Ethiopia. This represents the first record of the psyllid in each country and the only record of C. schini in Africa outside of South Africa. In Kenya, the psyllid was parasitized by an unidentified tetrastichine (Eulophidae), probably of the genus Tamarixia, while in Ethiopia C. schini nymphs were heavily parasitized by an unidentified hymenopteran.

Role of trichome density in cassava resistance to mealybug, Phenacoccus manihoti Matile-Ferrero was evaluated on the apex, the first expanded leaf and the stem in pubescent and glabrous cassava varieties. Pubescence significantly retarded the rate of settling and establishment of P. manihoti. The weight of the developing larvae was also affected becoming more pronounced at the pre-ovipositing adult stage. However, the relationship between pubescence and P. manihoti weight was not significant. Moreover, the significant differences in weight at the preovipositing adult stage was not reflected in the corresponding fecundity on the glabrous and pubescent varieties. Pubescence accounted for only 18% of the differences in observed fecundity. There was also no significant difference in the development period of the mealybug on glabrous and pubescent varieties. Pubescence appeared to be a mechanical irritant only.

A one-year survey was carried out in two brackish water pools to study the incidence of Amblyospora sp. in field populations of Culex sitiens larvae at the Kenya coast. Salinity of the pools, water temperature, and rainfall patterns were also recorded to check their possible effects on the infection rates. Levels of infection in both pools were low, and ranged between 2 and 15%. Infections occurred in a wide range of salinity. Statistical analysis (t-test) showed no significant correlation between infection rates and neither salinity, temperature nor rainfall in the field.

The shootfly, Atherigona soccata Rondani, is a major seedling pest of sorghum in many areas of tropical Asia, Africa and Mediterranean Europe. A chronological review of the progress made in various programmes on the screening techniques (natural and artificial) with artificial diets, sources, stability and mechanisms of resistance, bases (physico-morphological and biochemical factors) of resistance, inheritance and breeding for resistance is made. Many resistant varieties have been identified and sources of resistance utilized in breeding programmes to transfer resistance in high yielding background are listed. In addition, the glossy and trichome traits identified is sorghum cultivars are also reported. Glossy leaf surface and trichomes are frequently associated with shootfly resistance.

A test with 100 nymphs of Hyalomma anatolicum anatolicum for evaluation of resistance of cattle to ticks was found to have a good potential for assessing the resistance status of cattle. Thus, 7% of nymphs engorged and moulted on a resistant host with average engorgement weight of 7.6 mg compared to 19 and 45% of engorged nymphs on two susceptible hosts with 15.8 and 13.6 mg average engorgement weights. Similarly, the number of detached fully engorged Rhipicephalus evertsi nymphs dropped from the resistant cows ranged between 14 and 57 compared with 118–124 from the two susceptible animals. The correlations between the three parameters; ranking cattle for resistance (natural tick burdens), the number of detached fully engorged R. evertsi nymphs, and the percentage survival of H. a. anatolicum nymphs after artificial infestation are discussed and found to be significant (r = +0.778; r = +0.886; r = +0.936). It is, therefore possible to assess the overall resistance status of hosts and cull the susceptible, if necessary.

Whole body tick collections, carried out at 6-day intervals for 2 months at Nisheishiba, showed significant differences in tick counts between three breeds of cattle. Crossbred (Bos taurus × B. indicus) cows carried 4.5 times more ticks (mean tick count 70.5 ± 84.8) than the B. indicus Kenana (mean tick count 16.7 ± 24.4) and Butana cows (mean tick count 15.0 ± 18.4). In all cases, the SD's were larger than the means reflecting the usual wide variability in tick numbers between individuals. Significant differences also existed in the degree of engorgement achieved by female Hyalomma anatolicum anatolicum ticks on different breeds of cattle. The weight of detaching fully engorged females feeding on Kenana and crossbred cattle was 374.8 mg and 422.0 mg respectively. This was reflected in the amounts of eggs laid by the females which were 191.3 mg for the Kenana-fed ticks and 261.1 mg for those from the crossbreds. The resulting larval challenge from the crossbred-fed ticks was 36.5% greater than from the ticks fed on Kenana cattle.

The application of nucleic acid hybridization techniques in the identification of most protozoan parasites, using species-specific DNA probes, has recently been described by several investigators. Species-specific DNA probes have been employed in the characterization of trypanosome infections in cattle and tsetse from Uganda. Most infections revealed by our DNA probes were mixed. Using these probes, a mixed infection with Trypanosoma brucei, T. vivax and both savannah and Kilifi types of T. congolense was revealed in one cow. This mixed infection could not have been detected by any of the classical parasitological methods. Isolates made from natural field infections, which had been passaged in laboratory animals, were found to consist of homogeneous trypanosome species. This was demonstrated in all of 47 stabilates which were homogeneous infections either of savannah type T. congolense or T. brucei.

The method of sample preparation for DNA probe analysis was modified to suit field conditions. The samples, which were spot-blotted onto nylon filters and either immediately denatured or left undenatured, could be kept at room temperature for 1 month with only a moderate loss of hybridization signal intensities. Although hybridization signals were visible in undenatured samples, those seen with the samples that had been denatured were clearly more intense. This approach eliminates the need for liquid nitrogen and/or an incubator in the field. The simplicity, sensitivity and specificity of this diagnostic technique using species-specific DNA probes, make it an important tool for future studies of the epidemiology of African trypanosomiases.

Scirtothrips dorsalis Hood is a polyphagous species and an important sucking pest of tea (Camellia sinensis) (Theaceae). The fitness traits of S. dorsalis on two alternative host plants: Capsicum annuum L. (chilli) (Solanaceae) and Ricinus communis (castor oil plant) (Euphorbiaceae) and on C. sinensis and corresponding levels of defence enzymes was studied. The study revealed that C. sinensis is the more suitable host of S. dorsalis based on faster development (13.6 days) compared to the alternative hosts, C. annuum (15.5 days) and R. communis (16.7 days), a higher fecundity (C. sinensis: 11.4 eggs; C. annuum: 9.7 eggs; R. communis: 8.6 eggs), and superior egg hatchability (C. sinensis, 92.6%; C. annuum: 82.5%; and R. communis: 74.6%). The host-based variation in the fitness traits of S. dorsalis corroborated in light of differential activity of three major detoxifying enzymes, such as the general esterases (GEs), glutathione S-transferases (GSTs), and cytochrome P450 mediated monooxygenases (CYPs). Densitometric analysis of GEs showed five esterase isozymes (EST I–V) with retardation factor (Rf) values of 0.17, 0.22, 0.27, 0.35 and 0.52, respectively. The pixel density, and accordingly the profile height, varied in different host-specific S. dorsalis. A significant variation of the quantity of these enzymes was also apparent in the insect when reared on the three hosts. A 2.4 and 2.7, 1.6 and 2.0, and 2.0 and 2.3-fold higher GEs, GSTs and CYPs activity on the two non-tea hosts possibly signify a predisposition of the species for higher tolerance to insecticides, enabling the pest to switch to tea where synthetic insecticides are routinely used.

Evaluations of toxicity, antifeedant, growth-regulatory activity of the methanol extract of Gliricidia sepium leaves were carried out against Dysdercus koenigii Fabr. (Heteroptera: Pyrrhocoridae), Achaea Janata Linn, and Spodoptera litura Fab., (both Lepidoptera: Noctuidae). Topical application of 100-300 μg of the extract to different stages of the test insects resulted in dose-dependent effects including larval-pupal intermediates and deformed adults. The highest tested dosage (300 μg/ μl) resulted in reduced survival rate and morphological abnormalities. At certain doses a strong antifeedant activity was evident against the lepidopteran insects.

Gorging is stimulated in some insects by plasma components alone. In other insects engorgement is maximal only when blood cell components are present in addition to the plasma. Plasma components recognized by insects are NaCl, NaHCO3 (some anopheline mosquitoes) and albumin (Anopheles dirus and Pediculus humanus). Those requiring blood cells recognize this fraction by its adenine nucleotides which, for optimal engorgement, have to be offered in the presence of isotonic NaCl solution buffered by NaHCO3 (i.e. Rhodnius, culicine mosquitoes, Simulium, tsetse and Tabanus). The presence of albumin in the feeding medium may lower the level of nucleotides required to induce gorging (i.e. Aedes).

For most haematophagous insects requiring the cellular fraction, ATP is the most effective phagostimulant. It may however be replaced quite effectively by non-hydrolyzable analogues, indicating that ATP is not essential as a source of energy for the gustatory receptors involved in blood meal recognition.

A large and varied group of insects attack crops of the tropical farmer, and carry various disease-causing organisms to him and his animals. The control of these agricultural pests, and vectors of human and animal diseases relies mostly on chemical pesticides. However, investigations show that alternative methods such as biological control and resistant crop varieties are available, which may be used in the reduction of pest infestation, resulting in an Increase in food production by the African farmer.

In this study, Coccinella septenipnnctata was efficient in controlling Aphis gossypii populations on cucumber in the greenhouse. This efficiency was a function of the predator/prey ratio and the initial aphid density at the time of release of the predator. Prey density had a large influence on the fecundity and establishment of this coccinellid in the greenhouse.