Studies on critical time of insecticidal protection in relation to damage by aphid, Aphis gossipii Glover and leafhopper, Amrasca biguttula biguttula Ishida on plant growth and yield of okra revealed that 21–42 days after germination, was the most critical time prior to fruiting. Application of carbofuran at the time of sowing was redundant. Effective plant protection 21–42 days after germination resulted in lowest leafhopper and aphid infestation and subsequently the highest benefit to cost ratio.

Flight activity in strain 16cSS of Anopheles gambiae (sensu stricto) has been investigated using an acoustic actograph. The peak activity was concentrated within the first hour after light off. After recording their activity, individual mosquitoes were examined for their chromosome inversion karyotype. No significant relationship was found of any of the karyotypes to total activity over the 2 hr after light off or the time at which 50% of their activity had been completed.

The results are discussed in relation to the possible widespread introduction of mosquito bednets and the possible selection of mosquitoes biting abnormally early before people go to bed.

The temporal evolution of the populations of Megalurothrips (=Taeniothrips) sjostedti (Trybom) (Thysanoptera, Thripidae) (larvae and adults) and of Maruca testulalis (Geyer) (Lepidoptera, Pyralidae) (larvae) as well as the rate of flower infestation by these insects was carried out under Held conditions using 10 cowpea varieties (IT 82D-889, IT 82D-287, IT 82D-716, IT 82D-789, IT 82D-703, IT 82D-713, IT 82D-890, IT 82D-709, TVu 57 and “Kpodjiguegue”).

The investigation was carried out during the 1984 early cropping season (from April to July) at Abomey-Calavi. In the research station the abundance of M. sjostedti populations was observed 47 days after planting (DAP) for one variety and 68 DAP for the nine other varieties (384–634 thrips/20 flowers according to the varieties). In addition, the decline of the insect population was recorded 40 DAP for four varieties and 75 DAP for the six other varieties (88–375 thrips per 20 flowers according to the varieties). But 90–100% of the sampled flowers were infested by M. sjostedti towards 40 DAP whereas 95–100% of flowers were injured 68 DAP.

Larval populations of M. testulalis reached their maximum value 40 DAP for four varieties and 47 DAP for the six other varieties (4–17 larvae/20 flowers according to the varieties). The population declined 61 DAP for two varieties, 68 DAP for seven varieties and 75 DAP for one variety (0–3 larvae/20 flowers according to the varieties). Regarding the rate of flower infestation by M. testulalis, the highest percentages (20–70% according to the varieties) were obtained among all varieties from the same sampling dates where the larval population peak was noted for the same varieties. In the same way, lowest percentages (0–15% according to the varieties) were recorded among all varieties on the same dates where the minimum value of larval populations of the pest was obtained.

M. sjostedti and M. testulalis fluctuate in opposed phase. The peak value of M. sjostedti generally coincides with the minimum value of M. testulalis and inversely. But the peak activity period of both insects occurs between 40 and 70 DAP. The average number of insects recorded all along the sampling period has shown significant differences (P=0.05) between the various cowpea varieties for M. sjostedti and M. testulalis. The biological and nutritional factors that contribute to such population fluctuations are discussed in the light of results obtained.

The anatomy of damaged and undamaged young stem, peduncle and young pods were examined from transverse sections in three varieties of cowpea in order to evaluate the anatomical basis of resistance to the pod borer Maruca testulalis.

While tissue development in the stem, peduncle and pods of the three varieties of cowpea were similar, the relative thickness of the various tissues were different in the order Vita-1>ICV-2>TVu 946. The smaller diameter and the relative abundance of strengthening tissues in the stem and peduncle of TVu 946, by limiting total ingestible biomass, might be restricting the damage to these organs by the pod borer.

Pod damage, on the other hand, was concentrated on the parenchymatous tissue of the pod wall lining and inter-seed spaces and the sizes of this tissue were also different among the varieties in the order Vita-1>ICV-2>TVu 946, the same order of susceptibility to attack by M. testulalis.

Various neem products were compared with copra oil, palm oil and 0.25% diazinon dust for protection of stored maize against the grain weevil, Sitophilus zeamais Motsch. Maize kernels treated with neem oil or ash were damaged less than the control. Although copra and palm kernel oil reduced S. zeamais attack, these edible oils were not as effective as neem oil. Neem wood ash was however, less effective than 0.25% diazinon dust. Neem derivatives inhibited oviposition and/or deterred feeding.

There is a large knowledge base available worldwide for growing many crops according to the principles of integrated pest management (IPM). CIBA-GEIGY is active in much IPM related research. Several biological control projects are being carried out at present and include studies of Trichogramma minutum against the spruce budworm in Canada; Encarsia sp. against glasshouse white-flies in Spain; the fungus Beauveria brongniartii against cockchafers in fruit gardens and forests of Switzerland and Italy; and the protozoan (Nosema) preparations against the African desert locust. In cotton, CIBA-GEIGY is concentrating on testing pesticides for the selectivity of beneficial arthropods under practical field conditions.

Some of the most important pests in cotton, rice and vegetables are monitored regularly for the occurrence of resistance, and strategies are being developed to overcome it. A computer model has been developed for American cotton, which is now under practical evaluation and which should allow for appropriate treatment decisions based on plant phenology and regular pest scouting.

General recommendations are given as to the implementation of IPM programmes in cotton, which are based on methodologically sound monitoring of cotton arthropods, establishment of economic thresholds, use of selective compounds or the selective use of broad spectrum pesticides, rotation of pesticides of different chemical classes to avoid the build-up of resistance, and a strengthened search for biological control alternatives such as more potent strains of Bacillus thuringiensis.

—Life table studies of American bollworm Heliothis armigera Hubner on four species of cotton revealed that maximum mortality in the population occurred early in the life cycle. Predation and dispersal accounted for maximum mortality of early instars, whereas migration and unknown reasons accounted for maximum mortality of late instars. Considering the life tables on four varieties of cotton, the loss of population during the first instar was significantly high in K8 and TKHe 44 whereas in Suvin and MCU 9 the loss was less.

The influence of drought on egg development, survival and hatchling weight was studied in the solitary phase of Locusta migratoria migratorioides (Reiche and Fairmaire). There was retarding effect of drought on the rate of egg development. The level of egg survival was lowered during prolonged drought, which also led to a decline in hatchling weight. Also the rate of egg survival was lower in eggpods experiencing longer incubation period.

Eurystylus marginatus Odhiambo (Hemiptera: Miridae) was the most important and abundant insect pest of sorghum panicles in Niger in 1985 and 1986. First generation adults initially infested sorghum panicles in late August, and two succeeding generations developed on sorghum. Economic losses were manifested in yield and grain quality reduction. A commonly grown indigenous variety Mota Galmi, suffered 14% yield loss and 19% grain vitrosity reduction in field trials in which E. marginatus density averaged 80/panicle. Among 14 other sorghum varieties grown under natural conditions, vitrosity was decreased 20% on average (range 0–47%). Headcage experiments using 20 female/male pairs of E. marginatus on each of three varieties resulted in losses ranging from 19–62% of grain weight/panicle, 1000-kernel weight, per cent low density grain, and vitrosity. Damage resulted from both oviposition and feeding. Among seven panicle and glume characteristics, percentage coverage of grain surface by glumes, and the time from anthesis to opening of the glumes were significantly correlated with reduced head bug numbers. Among varieties, grain damage was not highly correlated with head bug numbers; but within varieties, increasing head bug numbersclearly caused increased damage. Measureable damage occurred with as few as five female/male head bug pairs per panicle. MostE. marginatus eggs were oviposited into exposed, apical portions of sorghum grains during the milky stage of kernel development. Grain of variety CE90 were vulnerable to oviposition for less than 1 week after glumes opened.

Insect pests and plant diseases are among the main factors limiting bean production in Tanzania. A survey of methods of pest and disease management in small-scale bean production systems was carried out in Mgeta Division.

The results revealed that small-scale farmers are well informed of the major insect pests limiting bean production. The farmers know the type of damage caused by most insect species and the time of their occurrence. Although farmers are not aware of the pathogens affecting their crops, they can distinguish damage caused by insects from those due to diseases. Farmers are also aware that diseases are associated with environmental factors which influence disease development.

Farmers use both deliberate practices and incidental practices to manage insect pests and diseases.

The most frequently used deliberate practice is avoidance. Choice of growing season and date of planting are observed closely as a means of avoiding diseases. Although beans are cultivated in both growing seasons (September–December and February–May), the first season is the best for growing beans. Rains are not very heavy, but reliable and well distributed, and the season does not end up with low temperatures and high humidity which favour development of fungal diseases. Planting commences as soon as the rains start because early planted crops suffer less from pests. Farmers do not use purchased inputs in the form of fertilizer and pesticides. Larger insects are killed mechanically.

Incidental control takes place in the form of a number of cultural practices. Intercropping with maize, potatoes, cowpeas, pigeon peas, cassava or sorghum is normal and reduces the risk of crop failure. Terracing, where crop residues and weeds are buried under soil, reduces the amount of initial inoculum of certain pathogens. Farmers use a mixture of seeds of different cultivars deliberately, some high yielding and early maturing; and some late maturing, thus ensuring the farmer of food early in the season and beans as a cash crop later. Such variety mixtures appear to provide a buffer against pests and diseases.

A breeding strategy should be developed for variety mixtures instead of pure line varieties as the productivity of pure varieties in most cases is associated with the use of purchased inputs such as fertilizers and pesticides which are beyond the reach of small-scale farmers. Variety mixtures have a greater efficiency in using environmental resources, and are less affected by pests and diseases, and thus give higher yields than pure varieties.

Steam-distilled floral oils (essences) from several species of Theobroma(Sterculiaceae) (T. cacao Linneaus, T. simiarum Donn. Smith, T. mammosum Cuatr. & Leon, and T. speciosum Willd.) were tested using McPhail traps, in an abandoned Costa Rican cocoa plantation to determine their levels of attraction for flying insects. In each of the three bioassays (two successive dry seasons and one intervening rainy season), the traps were inoculated with floral scents at 1, 10, and 100 ppm, while controls were inoculated with a 10% solution of chloroform solvent in distilled water. Of a total of 223 Diptera captured in all three bioassays, only 5% were found in the controls, indicating attraction to the floral oil. About 72% of all Diptera captured were Cecidomyiidae, of which three species, Mycodiplosis ligulata Gagne, Aphodiplosis triangularas (Felt.) and Ledomyia sp., comprised 59% of the total. Eighty-eight per cent of all midges captured were females. Only 7% of the total were known cocoa-pollinating midges of Ceratopogonidae, and all of these were females. Sixteen per cent were Phoridae, known pollinators of the allied genus Herrania in Costa Rica. Although the chemical composition of floral oils varies greatly among the species of Theobroma, no discernible differences were found in the attraction of midges to floral oils tested. While floral fragrances in Theobroma species may represent a generalized adaptation for dipteran pollination, small numbers of several species of Trigona bees (Hymenoptera: Apidae: Meliponinae) were also attracted to the floral oils.

Immune haemolymphs from the giant silkmoth, Hyalophora cecropia and, to a lesser extent, from the tsetse, Glossina morsitans morsitans possess antibacterial activities against several species of bacteria known to be pathogenic to man, animals and poultry, as demonstrated by in vitro bacterial growth inhibition assays. Cecropia immune haemolymph possesses a broader antibacterial spectrum and was found to be active against several Gram-positive and Gram-negative pathogenic bacteria. Mice injected with pre-determined lethal doses of Enterobacter cloacae, Klebsiella pneumoniae and Corynebacterium pseudotuberculosis and then treated with single intraperitoneal or subcutaneous injections of Cecropia immune haemolymph had much lower mortality than untreated controls. A possibility of developing a broad-spectrum antibiotic modelled on insect immune factors is discussed.

Blister beetles have recently become the key pests of food crops in Mali and Senegal. The endemic areas of most destructive species, Psalydolytta fusca Oliv., P. vestita Duf., are situated in Northeast Mali and Central South Senegal. Host plants of certain species were identified. Light traps were used to study population dynamics of major species at Béma and Samé (Mali), and at Bambey, Gossas, Sokone and Nioro du rup (Senegal). Abundance of P. fusca and P. vestita populations in September–October generally coincided with sorghum and pearl millet flowering. Number of P. vestita beetles trapped was higher than that of P. fusca.

Studies conducted using laboratory and field bioassays showed that cypermethrin (b = −1.691) had a significantly (P < 0.05) higher and longer residual action at 7,14,21 and 28 days after application than did fenvalerate (b = −2.28) and permethrin (b = −1.871) against Dysdercus fasciatus Sign, and D. nigrofasciatus Stal. when coefficient regression analyses were performed. Residual action of fenvalerate and permethrin was regarded as being identical over the same experimental period in the field since their regression coefficients were not significantly (P > 0.05) different from each other.

It was also shown by these studies that the effective interval between applications was 21 days for cypermethrin and 14 days when fenvalerate and permethrin were applied. This finding has important practical implications in the adoption of an integrated approach aimed at minimizing damage to cotton by D. nigrofasciatus.

Examination of Giemsa stained smears made from the peripheral blood, liver and spleen of hand-caught lizards from West Pokot area showed the presence of seven out of the nine Plasmodium species of lizards which have been previously described in Africa. These species are redescribed using a set of biological characters and procedure which enabled a large quantity of each stage of any species to be studied, measured and compared. The utilization of these characters and procedure was a reaction to the multiple infections in individual lizards and a wide host range of each species among lizard species. The adoption of the criteria is recommended for future taxonomie work on lizard Plasmodia in Africa.

A key which brings together all the previously described species of lizard Plasmodia and the new species encountered in the present investigation is presented. The key is simplified so that it can be of use to epidemiologists and pathologists who may work on saurian malaria in Africa.

Studies on the vertical distribution of phlebotomine sandflies were carried out at Marigat (Kenya) at determined heights above ground level in both wooded and open fields. Traps set up at different heights from 0–11 m (in wooded area) and 0–9 m (in open field), showed a clear vertical zonation of sandflies as large numbers were collected between 0–7 m in the first site and 0–4 m in the second ones. Among the nine sandfly species collected, Sergentomyia bedfordi Newstead and S. antennatus Newstead were the only species recorded at a height of 11 m above the ground and the commonest sandflies at all studied heights. Overall, more sandflies were collected from the wooded area than the open field. The relationships between the sandfly relative abundance and their heights of flight above the ground showed significant negative correlation coefficients.

Fourteen differential rice cultivare under four major donor groups were evaluated at 11 field locations in seven Indian states during 13 years against the rice gall midge, Orseolia oryzae (Wood-Mason) (Diptera:Cecidomyiidae). Three basic variations, which qualify to be called biotypes 1,2 and 3 could be identified based on overall reaction patterns against Eswarakora and Siam 29 differential groups. Biotype I cannot damage entries involving either Eswarakora or Siam 29. Biotype 2 is capable of damaging the group of Eswarakora and its derivatives but not able to damage the group of Siam 29. Biotype 3 can damage the Siam 29 group while being incapable of doing so with Eswarakora group.

A large number of male and female tenerals and young non-teneral female G. pallidipes were attracted to the exterior of the trap but appeared not to enter the trap readily. About 20% of tenerals of both sexes that visited the trap were captured in the retaining cage and the remaining 80% on the outside. The sex ratio of flies stuck on the outside was 1:1 whereas that of flies from the retaining cage was 1:1.5 females:males. The efficiency of the trap for non-teneral G. pallidipes was about 39%. Direct observation using binoculars from a stationary vehicle about 10–15 m from the trap showed that the catching efficiency of the biconical trap was 30% for a total of the four categories of non-teneral females and males, and teneral females and males.