Shea parklands have a great socio-economic, cultural and ecological interest but suffer pest attack, which is among the major causes for their deterioration in Africa. To establish an inventory of insects associated with shea trees, the foliage, stems and fruits were regularly examined on 180 trees randomly chosen at six sites in the central and northern regions of Benin. From June to October 2010, a total of 196 samples containing 1415 specimens were collected. These insects belong to 8 orders, 36 families and 56 genera. Forty-seven insects were identified to the species level. The defoliator Cirina forda (Westwood) and the stemborer Neoplocaedaerus spp. were the two most damaging insect species occurring on shea trees. This study stresses the need to protect the shea parklands in Benin through the implementation of integrated insect pest management strategies against shea tree pests.

There are several stem-borer species recorded on important cereals such as rice, maize and sorghum as well as on grain legumes like cowpea. Those of considerable economic importance are: Chilo partellus, Sesamia infer ens, Sesamia eretica, Busseola fusca and Eldana saccharina on maize and sorghum; Sesamia infer ens. Chilo spp., Maliarpha separatella and Tryporyza incertulas on rice; and Maruca testu-lalis on cowpea.

Chemical control of insect pests will continue to be a major component of integrated pest management. However, control of tissue borers with insecticides is relatively more difficult than control of the insect pests feeding externally on foliage, shoots and stems. The foliar application of dust and spray formulation of most of the available insecticides has generally proved to be unsatisfactory as these cannot penetrate deep inside the tissues in sufficient quantities to kill the borers.

The recent advances in pest control technology, placing greater emphasis on use of various pest management components as well as insecticide selectively based on improved application methods has now made the control of stem-borers more effective and economical. Advantage can now be taken of the knowledge of the specific habits of the pests, period of peak activity of the most vulnerable stage and the economic thresholds for determining the appropriate time of application to control these pests. The development of new systemic insecticides and their granular formulation has further contributed towards the effective control of these borers. The recent research findings and recommendations for the control of cereal stem-borers are reviewed and discussed.

Studies were conducted in Niger in 1986 and 1987 on the population dynamics and parasitism of the millet stem borer, Coniesta (= Haimbachia) ignefusalis (Hampson) (Lepidoptera:Pyralidae), Sesamia calamistis Hampson, and the millet head caterpillar, Heliocheilus albipunctella de Joannis (Lepidoptera: Noctuidae). Planting dates were assessed for effects on population densities of C. ignefusalis and H. albipunctella. Population densities of C. ignefusalis were not reduced by adjusting millet planting dates, but were affected by millet growth stage. Platytelenomus sp. (Hymenoptera: Scelionidae) was the most common parasite of C. ignefusalis on millet. Parasitism of C. ignefusalis larvae and pupae was rare. Sesamia calamistis was a minor pest of millet in Niger, and was rarely parasitized. Population densities of H. albipunctella were reduced by delaying millet planting dates. Bracon hebetor (Hymenoptera: Braconidae) was the most common parasite of H. albipunctella.

Tannin extracts of two sorghum, Sorghum bicolor (L.) Moench. cultivars, BKS5 and BTX 623 were assessed for their bioactivity against the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) and the angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae), in whole wheat flour pellets, and against the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in whole wheat flour at three treatment levels. The number of adult progeny was reduced and number of days to emergence increased by tannins extracted from both sorghum cultivars at all treatment levels. However, the effects were not significant in all cases. In a short-term (25 days) feeding test using S.oryzae adults, the presence of sorghum tannins from cv. BKS 5 in the pellets significantly reduced feeding by the insects.

Chilo species constitute one of the three major lepidopterous rice stem borers in Africa and their occurrence stretches across the different rice ecosystems; two major species, C. zacconius Bles. and C. diffusilineus (J. de Joannis) are found in West Africa, while C. partellus (Swinh.) and C. agamemnon Bles. appear to be the predominant species on rice in East and North Africa, respectively. A brief note is given on some aspects of the biology, especially the life history and behaviour of C. zacconius. Control measures are discussed as well as an integrated approach towards management based essentially on growing resistant varieties, conservation of natural enemies and adjusting planting dates.

Botanical insecticides are among the most promising alternatives to synthetic insecticides for stored product protection. Calneem oil from Ghana and local neem oils from two localities in northern Cameroon (Garoua and Maroua) were tested at 0 (untreated control), 2, 4, 6, 8 and 12 ml/kg, on the adult and immature stages of the maize weevil Sitophilus zeamais (Motschulsky), for mortality and reproduction inhibition. The neem oils from Cameroon were extracted using the traditional kneading method and a hydraulic press in the laboratory (refined). Maize grains were coated with the five neem seed oils (Calneem, Garoua traditional and refined, and Maroua traditional and refined, respectively) and adult mortality was recorded at 1, 3, 7 and 14 days after exposure. Within 1 day of exposure, the highest tested concentration (12 ml/kg) of Calneem, Garoua traditional, Garoua refined, Maroua traditional and Maroua refined oils caused similar weevil mortality of 86.3, 93.8, 93.8, 97.5 and 97.5%, respectively. The 24-h LC50values for the oils in the same order were 7.0, 6.0, 5.0, 5.0 and 4.8 ml/kg, respectively. The lowest (2 ml/kg) and highest (12 ml/kg) concentrations of the oils suppressed progeny production by over 80 and 98%, respectively. The oils arrested the development of the hidden eggs and immature stages in the maize grains. The results suggested that neem seed oils from different localities of northern Cameroon, irrespective of the method of extraction, were effective for the protection of stored maize against S. zeamais. The promotion of natural neem seed oils as stored grain protectants in Cameroon would boost food security, alleviate poverty and reduce environmental degradation.

We report here the pathological effects of a microsporidian isolate (Nosema sp.) from the lepidopteran teak defoliator Hyblaea puera Cramer. The spores were ovo-cylindrical and had a mean size of 5.1 × 2.8 μm. The midgut and fat body were the primary organs infected by the microsporidium. Subsequently, infection was observed in Malphigian tubules, tracheal epithelium and gonads. The sequence of infection observed was: midgut – fat body – tracheal membrane – Malpighian tubule – gonad. Infection of this microsporidium produced a marked negative effect on the growth and development of larvae. The weight of healthy larvae increased about 22 times from the 3rd instar to pupation while the increase was about 12 times in the infected larvae. Rearing experiments conducted in the laboratory revealed a high potential for horizontal transmission (>90%) of the microsporidium among the defoliator larvae developing together. A nearly equal degree of vertical transmission (88.7%) was also observed from the infected females to the progeny larvae. The observations reported here indicate the prospect of the microsporidium as a bio-control agent against the defoliator pest if exploited properly. Small subunit rRNA gene sequence analysis revealed that this microsporidium differed from Nosema bombycis of silk moth by only two nucleotides. The teak moth and the silk moth are not as closely related as these two parasites appear to be, implying the likelihood of host switching.

The present study investigated the incidence and effect of the Russian wheat aphid (RWA) Diuraphis noxia (Kurdjumov) on irrigated wheat yield at Debre Zeit, Ethiopia. Wheat varieties were sown at the rate of 140 kg/ha on Vertisols on plots of 3 × 3 m. Treatments were tested in a split plot with varieties as the subplot and insecticide as the main plot, and were replicated three times. RWA appeared first when the crop reached the four- to five-leaf stage (Zadoks stage 22). In 2012 season, the RWA population peaked in the last week of March, and at this peak infestation, the average number of RWA per tiller was 46.9 on Denbi, 59.6 on Kubsa, 63.6 on Millennium and 56.2 on Werer. However, there were less than three RWA per tiller on sprayed wheat. In 2013, at the peak population intensity, there were 10.1, 10.5, 9.6 and 10.2 RWA per tiller on Denbi, Kubsa, Millennium and Werer, respectively. However, on sprayed wheat, the average population was less than one per tiller. The pattern of population build-up observed in the 2014 season was similar to that in 2013. Natural enemies of RWA were only a few generalist predators and were found at an extremely low density. In the 2012 season, avoidable loss in plant height, seed weight, grain number and grain yield ranged from 3 to 10%, 32 to 47%, 12 to 25%, and 69 to 93%, respectively. In the 2013 season, avoidable loss in seed weight and grain yield varied between 14 and 20%, and 15 and 41%, respectively. Similarly, in the 2014 season, avoidable loss in seed weight ranged between 9 and 24% and in grain yield between 35 and 49%.

A network of experiments was established in three different agroecological areas at the periphery of the Central Plain of Thailand during three successive years to assess the effect of a multiple insect pest complex on cotton yield loss. A large range of combinations of jassid and bollworm injuries was achieved from the application of several insecticide treatments and sowing dates. Other pests were of minor incidence. Seed-cotton yield varied from 0 to 3600 kg/ha, and yield losses due to pests ranged between 0 and 100% of the attainable yield. Damage mechanisms were addressed through path coefficient analysis of the interaction between injuries and plant compensation. Before boll production, jassids were the most serious pests, while bollworms had a positive effect on vegetative growth. At the fructification stage, bollworms were very harmful, while sucking insects such as jassids became progressively less important. Injuries did not necessarily lead to yield losses because of the plant compensation ability. Cotton response to pest injuries depended on the development stage and crop status. Decisions made on cotton protection against pests should thus consider the development stage of the crop and interactions between injuries instead of the traditional single pest population threshold. This study of a plant–pest system exemplifies the need to incorporate plant compensation processes in the design of pest management programmes aiming at reducing insecticide use.

A field experiment was conducted to track the daily population trends and occurrence of the flower thrips Megalurothrips sjostedti Trybom and Frankliniella occidentalis (Pergande), and their indigenous natural enemies Orius spp. and Ceranisus menes (Walker), infesting French beans. French beans in monocrop or interplanted with six companion crops (Zea mays L., Coriandrum sativum L., Tagetes erecta L., Brassica oleracea var. acephala L., Daucus carota L. and Capsicum annuum L.), and two chemical insecticides, methiocarb (Mesurol 500SC) and L-cyhalothrin (Karate 1.75% EC), were evaluated for their effects on the abundance of flower thrips, throughout the day, at 1-h intervals. The average population peak of thrips was found to occur at around 1300 h, but each species had different peak periods. Adult F. occidentalis populations peaked at midday and adult M. sjostedti populations at 1500 h, while the larvae of the two thrips species peaked at around 1300 h. Orius spp. were the most abundant natural enemies and their populations peaked at around 1400 h. Ceranisus menes population also peaked at around 1400 h.

Five groups of adult Rhipicephalus appendiculatus Neumann, with an average of 98 Theileria parva-infected salivary gland acini per tick, were exposed to four different temperature conditions in the laboratory or to quasi-natural conditions in Kenya. The survival of the infected ticks and T. parva parasites in their salivary glands were determined over time. Ticks kept under quasi-natural conditions survived up to 86 weeks. This period was longer than that of ticks exposed to any of the four laboratory conditions, except the diurnal temperature rhythm of 13–23 °C and 85% relative humidity (RH) to which it was comparable. Theileria parva survived for 82 weeks in ticks exposed to quasi-natural conditions, a period which was much longer than that of the parasites in ticks maintained under any of the laboratory conditions. Survival of the infected ticks and their infections seemed to be adversely affected by higher temperatures in the laboratory or drought in the field. There was an apparent density-dependent influence in parasite survival, with a dramatic fall in infection occurring in the more highly infected ticks before stabilizing at lower levels.

Larvae of the Mediterranean flour moth (Anagasta kuehniella Zeller) cause major losses in stored grains throughout the world. In this study, pouterin, a lectin-like protein isolated from Pouteria torta (Mart.) Radlk. seeds, was tested for activity against A. kuehniella larvae. Pouterin did not produce significant effects on survival; however, at c. 1% w/w concentration in artificial diet, it produced a 71.4% reduction in average weight of the larvae. A dietary utilisation assay showed a reduction in efficiency of conversion of ingested food, efficiency of conversion of digested food and approximate digestibility, as well as an increase in metabolic cost. Pouterin increased the level of trypsin in the midgut and faeces of larvae. We conclude that pouterin possesses an insecticidal effect against A. kuehniella larvae and this effect may be mediated by the binding of pouterin to chitin components of the peritrophic membrane, or glycosylated proteins in the insect midgut.

An experiment to examine the effects of different plant spacings on cowpea insect numbers and yields was undertaken at two sites in Nigeria. Two varieties, viz. Tvx 3236 and IT84E-1-108 were planted under field conditions at three different plant spacings. Plant spacing did not affect the number of Ootheca beetles, pod-borers, flower thrips and pod sucking bugs. Yield differences were not significant for the spacing regimes and there were no interactions between spacings and insect numbers for yields. Thus, plant spacing may not be an important control tactic in the management of the key cowpea insect pests in Nigeria.

The biology of Bemisia afer (Prisner & Hosny) reared in clip cages on leaves of 15 varieties of cassava, Manihotesculenta (Crantz)(Euphorbiaceae) was studied under field conditions during the cold months of June–August and during the warm months of September–October. Both variety and time of the year significantly affected the developmental period, the rate of population increase and the mortality.

The longest mean developmental period (59.5 days) occurred on the MH108 leaves during the cold months (at 20°C and 62.9% r.h.), while the shortest (27.1 days) was on the Kithekere variety during the warm months (at 25°C and 53% r.h.).

The pest population increased most rapidly on MH84 (at 5.4 eggs per female per day) and slowest on the Nigerian 3057/1 (at 0.9 eggs per female per day). The mortality of the pest indicated that Chitembwere had the greatest killing power (K = 2.555) and Nigerian 3057/1 had the least (K = 0.0760).

The combined use of the developmental periods, rate of population Increase and mortality indicated that Gomani was the most resistant while Kithekere was the least resistant variety to B. afer. Other varieties with high resistance properties included MH108, Chitembwere and Mbundumali. Of the three biological characteristics used, the developmental period was the most powerful while the rate of population increase was the least.

Pubescence of a cassava variety was only weakly associated with resistance to B. afer (r = 0.48) suggesting that other factors are more responsible for resistance to this pest than hairiness.

Field observations on Chilo infestation of 100 promising sorghum lines showed that there are six levels of relationship affecting plant colonization and damage level by stem-borers: non-preference for oviposition (E 302, E 303, IS 1044, IS 1151, IS 2162, IS 4660, IS 17739, IS 18328, IS 18349, IS 18479, and IS 18489); feeding of the first larval instars on young leaves (reduced on E 302, E 303, IS 1044, IS 2162, IS 2209, IS 18349 and IS 18427); causing of ‘dead hearts’ by young larval instars due to extensive feeding in stems of young plants (lower for IS 2162, IS 2263, IS 18328, IS 18349); tunnelling (extent and location) of older instars in stems (low in IS 4660, IS 18427 and IS 18479); tolerance of plants to leaf damage (in spite of high damage, plants form panicles) (IS 2205); and tolerance of plants to larval feeding in stems (in spite of high tunnelling, the plants form seeds). The effect of a number of cultivars showing different levels and mechanisms of resistance on the Chilo behaviour and biology was studied in depth under field conditions.

The soybean plant introduction (PI)227687 is highly resistant to 16 different insect pests of soybean in Australia, Brazil, Taiwan and the United States. In most of the pest Lepidoptera, resistance is expressed as greatly increased mortality in the later larval instars. The soybean looper, Pseudoplusia includens (Walker) is most severely affected in the final larval instar. Antibiotic effects include reduced weight gain, growth rate and increased mortality. These effects are enhanced by mechanically wounding foliage 24 hr prior to larval consumption. Antibiosis appears to be due to the combined effects of a feeding deterrent and a growth inhibitor. Resistance is location-specific on (PI)227687 plants and occurs abruptly on the third fully-expanded leaf from the plant apex. Larval growth on leaves of the susceptible variety ‘Davis’ is similar to or greater than that of the upper, susceptible leaves of (PI)227687. Resistance appears to be chemically based, since larvae fed artificial diets containing leaf extracts exhibit antibiotic symptoms similar to those fed fresh (PI)227687 leaves.

Three cowpea cultivars, TVu 946, Ife Brown and Vita 1 were examined for resistance to the legume pod-borer, Maruca testulalis (Geyer). TVu 946 was found to be the most resistant in both the flowering and pre-flowering stages, followed by Ife Brown and Vita 1, respectively. Field and screen-house experiments show that Maruca larvae caused significantly less damage on TVu 946 than on Ife Brown and Vita 1. In addition, larval survival and development on TVu 946 was the most negatively affected. Screenhouse experiments in a choice situation clearly show non-preference of TVu 946 for oviposition by adult Maruca females, and biochemical studies show evidence of antibiosis due to nutritional and antibiotic factor(s).

The trends in flowering, podding and seed yield of four cowpea varieties planted at different times of the growing season in 1975 and 1976, were studied along with the associated pest activity. Flowering, podding and seed yield were found to decrease over the season from April to September irrespective of whether the crop was protected against insect pests or not. However, there seemed to be two peak periods of pest activity—April to July and October to December—when severe damage to the crop occurred in unprotected plots. Planting in June or July usually led to an escape from several major pests even though the cool night temperatures and incidence of overcasts at that period seem to preclude optimal reproductive performance of the crop.

The pattern of insect pest succession on the crop over the season is discussed and it is suggested that for small farm holders in Southern Nigeria, who are unlikely to apply insecticides, planting in June is advisable.

The economic injury level (EIL) of the maize stem borer, Chilo partellus (Swinhoe) was determined by artificially infesting maize (cv. Katumani) plants at three different growth stages; viz, 20, 40 and 60 days old plants with varying densities of newly hatched larvae; viz, 2, 4, 6, 8, 10 and 12 per plant constituting the borer population. The grain yield data obtained from the infested and the protected plants showed that maximum yield reduction and stalk damage occurred to the 20-day old crop, while there was insignificant larval effect on yields for the 60-day old crop. Regression analyses gave a significant linear equation (y = a + bx) which estimated the yields per plant at different infestation levels and these were used to calculate the economic injury level at each stage. The resultant EIL was 3.2 and 3.9 larvae/plant for 20- and 40-day old plants, respectively.

Studies at ICIPE's Mbita Point Field Station (site 1) and a farmer's field in Lambwe Valley (site 2) in Western Kenya, revealed the presence of at least seven parasitoids, two predators, one nematode and several microorganic pathogens attacking Maruca testulalis on cowpea crop. Some parasitoids and pathogens were also recovered from M. testulalis cadavers collected on wild host plants of the pest. A pupal endoparasitoid, Antrocephalus sp. was the most predominant, while the pathogens Nosema sp. and Bacillus sp. caused the highest natural mortality on M. testulalis in this region.

Parasitoids and pathogens contributed 40.65 and 35.6% to the total generation mortality (K) at sites 1 and 2 respectively. Observed parasitism only contributed 3.25% at site 1 and 3.8% at site 2 of the generation mortality. Mortality due to disappearance which included predation accounted for 59.35 and 64.8% of K at the respective sites. Life table data and survival curves for the pest revealed high generation mortality (ca. 98%), most of which occurred in the early life stages of the pest. The results suggest a high potential for utilizing biocontrol agents in IPM of the pest.