A wide variety of Hemiptera species are found on the leaves of palms in humid tropical zones. Many of them are highly polyphagous, and generally once adult, only accidentally end up on palm leaves, on which they can nevertheless feed. Other hemipterans spend the whole of their developmental cycle on palms, and some seem to live on palms alone. Most of the Hemiptera have no economic impact on their hosts, since their population levels are rarely high enough to cause significant damage. However, some Heteroptera: Coreoidea and Homoptera: Coccoidea species can be very damaging primary pests. Others amongst the Homoptera: Fulgoroidea, Cicadelloidea and Heteroptera: Pentatomoidea transmit serious diseases that have decimated oil palm and coconut plantations, for example coconut lethal yellowing in Africa and the Caribbean, and oil palm and coconut trypanosome diseases in Latin America. Lastly, some Heteroptera: Pentatomoidea and Reduvioidea species are natural enemies of lepidopteran caterpillars.

Participatory trials on the use of a mycoinsecticide based on spores of the entomopathogenic fungus Metarhizium flavoviride were carried out to control grasshoppers on farmers' plots at Gouré, Niger. The study was conducted in collaboration with the natural resources management project financed by Africare. From a fallow area of about 800 ha, six plots of 5 ha each were selected. Three of these plots were treated with M. flavoviride, strain IM 330189, while the three remaining plots served as controls. An emulsion of the fungus was prepared with 50 g of dry spores mixed with paraffin and ground oil at a ratio of 7:3. This formulation represents a concentration of 2.5 × 1012 spores per litre. The mycoinsecticide was applied at the rate of 2 litres/ha with a Micron ULVA sprayer. Immediately after spraying and three days later, two batches of 50 L4 and L5 Oedaleus senegalensis larvae were collected per plot and each batch kept in a separate cage. One of the two cages was kept in the experimental plot, whereas the second one was taken to the station, in order to follow the grasshoppers' mortality. Cages were checked daily for two weeks starting from the day of fungus application, and insect mortality recorded. Dead insects were transferred into Petri dishes with moistened filter paper to allow the fungus to sporulate from the cadavers. Grasshoppers kept in cages suffered 80% mortality, 12 days after application. Reduction in grasshopper population density between treated and untreated plots was significantly different, but did not convince farmers, as full grown L5 larvae had emerged as adults and began migrating. However, cadavers collected from cages containing insects from treated plots allowed farmers to follow how the fungus sporulates and contaminates healthy grasshoppers. Farmers were interested in the product but were reluctant to buy a slow-acting insecticide.

Cassava varieties resistant to the cassava green mite, Mononychellus tanajoa (Bondar) ( Acari:Tetranychidae) have been reported in many parts of Africa where the pest has been introduced. However, the resistance mechanisms have not been identified. Laboratory studies on biology and feeding behaviour of cassava green mite were carried out at the International Institute of Tropical Agriculture (IITA), in order to determine whether this resistance is mainly due to pubescence.

Cassava pubescence was found to have no antibiotic effect; both pubescent and non-pubescent varieties were preferred by the mite for oviposition, food and shelter. In addition, pubescence does not afford a mechanical barrier to cassava against green mite infestation.

Two types of failures of attack by the top borer, Scirpophaga excerptalis Wlk., and their relation to sugarcane resistance to deadheart formation were studied in 164 genotypes of sugarcane for three years at two locations, viz., Karnal (Haryana State) and Chakia (Bihar State) in India. Attacks were unsuccessful either because of failure of neonate larvae in the mid-rib to reach the spindle (Type 1) or failure of older larvae in the spindle to reach the meristem (Type 2). Type 1 failure was frequent (19.2 to 26.7 %) while Type 2 was rare (2.9 to 5.1 %) among the genotypes. Larval dispersal and mortality were influenced by several factors related or unrelated to resistance and occurred concurrently in the same genotypes. This led to variation in larval mortality even among genotypes with the same levels of Type 1 failure. Those genotypes (Co 1223, Co 1224, E 276, Co 7224, Co 745, E 128, Co 62235, E 132, E 50, CoS 767 and CoJ 67) that had high scores of both Type 1 failure (14 to 18) and larval mortality (13 to 17) had the lowest percentages of deadhearts (11.8 to 24.4%).

Type 2 failure was not related to resistance; the highly resistant genotypes, Co 1223, Co 1224, E 276, Co 62235, E 132, CoS 767 and F133, showed no Type 2 failure. Furthermore, genotypes IA 3017 and Co 7322 which had the highest Type 2 failure scores of 9 and 12 respectively, had 61 and 36% deadhearts respectively. It is concluded that Type 2 failure may be caused by larval mortality in the spindles due to diseases and/or asphyxiation by accumulated rain water.

Soil samples collected from six localities in Pakistan—Peshawar, Quetta, Loralai, Sibi, Lahore and Sheikhupura—were screened for insecticidal Bacillus spp. Bacillus coagulane, B. megaterium and B. alvei, which constituted 50%, 33% and 17% of the Bacillus isolates respectively, were isolated and their toxicity was evaluated against larvae of the house fly, Musca domestica (Diptera: Muscidae). The most toxic bacterial isolate of the three was B. alvei (98.7% mortality) and the least toxic was B. megaterium (89.3% mortality). Extracts of experimental larvae showed the presence of strains of the respective species of Bacillus in all cases, indicating that the observed mortality in the house flies was caused by the Bacillus species.

The effect of N, P and K fertilisers, measured as percentage leaf dry matter, was assessed on larval populations of Maruca testulalis (Geyer) (Lepidoptera: Pyralidae) recorded on cowpea, Vigna unguiculata, var. IT 82E-32 under natural infestation. The study was carried out during the 1987 long rains (March-July), at Abomey-Calavi's experimental farm. A factorial experiment with 9 completely randomised treatments in three replicates of N-P-K fertilisers was used. Phosphorus was applied at three levels (P0, P1, and P2) corresponding to 0, 40 and 80 kg of P2O5/ha respectively. Potassium was also applied at three levels (K0, K1 and K2) representing 0, 40, and 80 kg K2O/ha respectively. In all plots nitrogen was applied as 20 kg /ha of urea. All the fertilisers were spread on the soil on the day of planting. Fourteen sampling dates for flushing shoots, flower buds, flowers and pods were subsequently made 29, 33, 36, 40, 43, 47, 50, 54, 57, 61, 64, 68, 71 and 75 days after sowing (DAS) to evaluate the infestation rate by M. testulalis larvae. Sampling for. N, P and K contents in cowpea leaves was conducted 29, 47 and 61 DAS. As for interaction between P and K and the pest, only the averages of larvae from interaction P0 K0, P2 K0 and P0 K1 on the one hand, and those from the interaction of P0 K0, P0K2 and P0K2 on the other hand, were statistically, (P < 0,05) different. Multiple regression analysis showed that the content of N, P and K in cowpea leaves throughout the sampling period influenced by 40% the total variation of larval population of M. testulalis in the plant. The remaining 60% were due to other factors of experimental agrosystem. Application of N, P and K fertilisers to the cowpea and their assimilation by the plant are primarily aimed at increasing the plant vigour and grain yield. In contrast, the plant vigour induced by these nutrients leads to an increase in the larval population of M. testulalis in the plant and also to a decrease in the highest yields that can be expected from the use of these fertilisers. Therefore, an agrobiological competition takes place as a result of two inductive opposite effects inherent from fertilisation. In connection with this situation, the control of M. testulalis using fertilisers could be one option to maintain a buffer effect between the pest and the plant, thus therefore help in increasing cowpea yield.

In a study to determine the costs of tsetse trapping in terms of construction materials, labour, transport and maintenance, two hundred forty-six traps used to control Glossina pallidipes in an area of 100 square kilometres at Nguruman, Kenya were evaluated from November 1990 to July 1992. The total cost of materials, labour and servicing per trap per year, was US$ 30.6 which, at that time was equivalent to 1071 Kenya shillings.

Gas-liquid chromatography was used to analyse the saponifiable and unsaponifiable fractions of petroleum ether (PE) extracts of neem fruits and leaves. Both fractions, as well as a crude PE extract, were assayed for biological activity against third instar cotton leafworm, Spodoptera littoralis.

In neem fruits, eighty-eight percent (88%) of the saponifiable matter consisted of saturated fatty acids, while 12% was composed of unsaturated fatty acids. In the neem leaves, the corresponding proportions were 62 and 38%, respectively. Unsaponifiable matter of both fruits and leaves contained varying amounts of hydrocarbons and sterols. All the tested extracts demonstrated significant larvicidal effects against leafworm larvae. They also prolonged larval duration, caused malformations of the resulting pupae and significant adverse effects on the fecundity of resulting adults.

The effects of diet on quantitative nutritional indices were measured in fifth-instar female nymphs of the grasshopper, Euprepocnemis plorans. Analysis of the main and interactive effects of feeding on the host plants lupine (Lupinus termis), horsebean (Vicia faba) or clover (Trifolium alexandrinum) and some of the plants' allelochemicals indicated that nymph performance was adversely affected by the hydrogen cyanide (HCN) and quinolizidine in horsebean and lupine respectively. Assimilation of clover was higher than of lupine or horsebean. Relative growth rate (RGR) was significantly higher in grasshoppers fed on clover than in those fed on either lupine or horsebean. Relative consumption rate (RCR) was in the order lupine > clover > horsebean. The efficiency of the digested and ingested food conversion were significantly lower in grasshoppers fed on lupine or horsebean than those fed on clover. The duration of the fifth instar was in the order horsebean > lupine > clover. Grasshoppers fed on horsebean or lupine lost weight during the experiment, with a greater weight loss recorded in those fed on horsebean. Grasshoppers contained the highest concentration of haemolymph proteins when fed on clover. Short-term feeding on lupine and horsebean resulted in 10 and 20 % mortality respectively, and nymphs that died on a horsebean diet were malformed.

Effects of adult nutrition were investigated by measuring female longevity, body weight, fertility and ovariol yield in the grasshopper, Euprepocnemis plorans reared on 3 different host plants. Rearing the insect on lupine (Lupinus termis) and horsebean (Vicia faba) caused significant reduction in fertility and ovariol yield of its first and second pods compared with those reared on clover (Trifolium alexandrinum). Resorption bodies were significantly higher in the ovariols of females fed on L. termis and V.faba. Diet also affected longevity and body weight. Fecundity was highest in females reared on T. alexandrinum. Significant reduction in haemolymph protein was noted in females reared on L. termis and V. faba. Nitrile (allylcyanide) significantly reduced the approximate digestibility (AD), efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD), inhibited nymphal growth, increased food consumption and decreased its assimilation. Feeding grasshoppers on T. alexandrinum treated with 125–250 μ mole/g resulted in various degrees of malformation and death.

The reproductive ability of gamma-irradiated Tribolium spp. (Coleoptera: Tenebrionidae) males was determined by studying their mating competitiveness when confined in various ratios with unirradiated males and females. Irradiated males of all the species studied competed favourably with unirradiated males for females. Competitiveness was significantly greater when males were irradiated soon after emergence (1-day old) than when they were older (10 days old). Infertility percentages increased as the proportion of irradiated males increased. The highest competitiveness was found in irradiated T.freemani and the lowest in T. destructor. Competitiveness also increased as the ratio of irradiated males increased.

The chitin synthesis inhibitor lefenuron [N-{2,5-dichloro-4-(1, 1, 2, 3, 3, 3-hexafluoropropoxy)-phenylaminocarbonyl}-2, 6-difluorobenzamide] was found to have a negative effect on the encapsulation responses of Spodoptera littoralis larvae towards supernumeraries of Microplitis rufiventris parasitoid. Superparasitised hosts fed on compound-free diet showed strong encapsulation reaction (ca. 40.8%) to surplus parasitoid larvae having scars of physical combat. Treated hosts exhibited a significant reduction in either capsule thickness or encapsulation rate to the excess parasitoid larvae. Even when a capsule was formed, it had a thinner haemocy tic layer than tha t of control hosts. Studies on the differential haemocyte counts showed that failure of treated larvae to encapsulate injured surplus parasitoid larvae could be attributed to the following factors: (1) disturbance in plasmatocytes-granular cells (GR) ratio, e.g. abnormal increase in GR levels possibly causing faint haemocytic reaction to injured parasitoid larva(e); (2) the parasitoid surface becoming less attractive to the granulocytes and plasmatocytes; (3) the haemocytes involved in capsule formation (granulocytes, plasmatocytes) losing their ability to spread out over the surface of parasitoid larvae; and (4) the blood cells of the treated host failing to recognise wounded larvae as foreign bodies. Reduced encapsulation capacity might be due to a secondary effect(s) of IGR treatment inducing a suppression of adhesive activity of the plasmatocytes. These results may be useful for improving our understanding of insect immune reaction and/or manipulating parasitoids activity against nonhabitual Parasitoida.

The ecdysteroid agonist KK-42 [l-benzyl-5(E)-2,6- dimethyl-1,5-heptadienyl] imidazole adversely affected the growth of Spodoptera litura and caused a delay in pupation. The compound also caused adult deformation, increased sex ratio in favour of males, and adversely affected the fecundity and fertility of emergent females. The ecdysteroid 20-hydroxyecdysone, identified by HPLC, was present in treated and control insects. Ecdysone was also detected in only the insects treated with 1 μg/larva KK-42.

An artificial diet for rearing the spotted bollworm, Earias vittella (Fabricius) was developed under laboratory conditions (temperature 27 ± 1°C, RH 60 ± 5% and 16:8 h scoto /photophase regime). The diet ingredients consisted of wheatgerm (5 g), seeds of cotton (Gossypium hirsutum L. var. Pusa 8–6) (50 g) and chickpea (Cicer arietinitm L. var. Kabuli)(35 g) as base materials along with agar-agar (15 g), dried yeast powder (8.0 g), methyl-p-hydroxybenzoate (1.0 g), l-ascorbic acid (1.2 g), sorbic acid (1.0 g), cholesterol (0.2 g), streptomycin sulphate (0.2 g), and multivitamin multimineral and vitamin E capsules (one each). After rearing neonates on okra for 3–4 days, the diet supported the growth and development of E. vittella successfully for eight generations. Larval development on this diet was completed in 11.9 ± 0.66 days against 11.64 days on the pest's preferred natural host, okra (Abelmoschus esculentus) Moench. The growth and developmental indices on the artificial diet for the eight generations are reported.

Teneral tsetse flies, Glossina morsitans morsitans (Mall) aged less than 32 h were divided into two groups and infected initially with Trypanosoma congolense IL 1180. Flies of group A were maintained on healthy rats and those of group B fed exclusively on parasitaemic rats, to ensure regular re-infection. Flies in group A recorded mesoprocyclic, metacyclic and vectorial competence (VC) index values of 0.65 ± 0.09; 0.73 ± 0.10 and 0.47 ± 0.11, respectively. The corresponding values for group B flies were 0.76 ± 0.08; 0.79 ± 0.08 and 0.60 ± 0.10. In group A, the mesoprocyclic and the VC indexes of the females were significantly higher than those of the males. In group B, no such significant differences were registered between the sexes. For both sexes taken together, the mesoprocyclic and the VC indexes of the tsetse flies of group B were more important than those of flies of group A. Males of group B revealed a higher VC index than that of group A males; no significant differences in this index were observed in the females of both groups.

Life table statistics on the age-specific fecundity and survival of female Spilosoma obliqua Walker reared on sunflower showed a net reproductive rate of 513.6 eggs per female, with approximate generation time of 48.2 days. Its intrinsic rate of increase (rm) was 0.1295, meaning that its population could double in 5.35 days. Spilosoma obliqua on sunflower was parasitised by Apanteles obliquae, Glyptapanteles creatonoti and Carcelia sp.