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%.

This study was conducted on both station and farmers' fields during the 2010 dry cropping season in the Vallée du Kou rice scheme. We investigated the effect of three rice-transplanting periods (8–10 days) on the population dynamics, damage and parasitism associated with rice stem borers. The on-station experiment was designed as a randomized complete block with three treatments (planting dates) and four replications. Regular intervals of 14 days were observed between subsequent planting dates. Weekly agronomic and entomological assessments were performed from the 21st day after transplanting (DAT) to the 84th DAT. The on-farm experiment covered 1200 ha divided into two zones in which 48 farmers' fields were selected according to the periods of rice transplanting (resulting in 16 fields per period). On-station results indicated 10.1% of deadhearts and 7.5% of whiteheads due to stem borers in the first transplanting period, resulting in the lowest yield (2 metric tons/ha). In farmers' fields, the genus Chilo was found to be the most injurious rice stem borer in Vallée du Kou. The highest larval parasitism (38.5%) was recorded in the third treatment. These results provide important data that can be used in the development of an integrated management strategy for rice insect pests in Vallée du Kou.

The effects of sowing date, host plant and insecticidal control of the stemborer Busseola fusca Fuller were studied in the highlands of Eritrea at Halhal Begos in 2003–2005. Sowing date had a significant effect on stemborer incidence and damage levels. Early sowing dates (April 1 and 15) had significantly lower numbers of larvae, percent infestation and deadhearts, and produced higher yields compared with later sowing dates. In the host preference experiment, Sudangrass (Sorghum× drummondii (Steud.) Millsp. & Chase) had the highest infestation (91%), and it was the most preferred host for oviposition among the tested plants. All the chemical treatments significantly reduced stemborer infestation and damage levels compared with untreated plots. Furadan and Cymbush significantly lowered infestation and larval damage. There were significant differences in days to heading, maturity, plant height and yield. In general, the study showed that early planting coupled with host preference and insecticides reduced the infestation of stemborers and significantly increased the yield of sorghum in the highlands of Eritrea.

Glutathione S-transferases (GSTs) have been recognized as important metabolic detoxifying enzymes in many phytophagous insects. However, the contribution of GST to insecticide resistance in Zonocerus variegatus (L.) has not been studied. Therefore, we carried out an initial study on the induction and kinetics of GST in Z. variegatus exposed to pyrethroids (PYRs) and Ocimum gratissimum leaf extract. Fifth-instar nymphs of Z. variegatus collected from cassava farms (with no history of insecticide exposure) on the campus of the University of Ibadan were reared to adult stage. Adult insects were divided into four groups of two replicates, each consisting of 30 insects. The groups were exposed to 20 ml of PYR insecticide and 25 mg/dl and 250 mg/dl of O. gratissimum leaf extract, respectively, while the last group served as the control. GST was extracted from the body tissues of the insects using the Bradford method and the kinetics of the enzyme was evaluated using the Lineweaver–Burk plots. No mortality was recorded in insects exposed to 25 mg/dl of O. gratissimum leaf extract, while mortality rates of 93.3 and 43.3% were recorded in insects exposed to PYR insecticide and 250 mg/dl of O. gratissimum leaf extract, respectively. The activity of GST was higher in insects exposed to the insecticides than in the control insects, while a higher enzyme activity was recorded in insects that died after exposure to the insecticides than in insects that were alive after exposure. The GST extracted from insects that were alive after exposure to PYR insecticide and O. gratissimum leaf extract exhibited a high affinity for the glutathione substrate compared with that extracted from insects that died after exposure. Higher GST activity in insects exposed to insecticides is indicative of the role of this enzyme in the metabolic detoxification of insecticides by Z. variegatus.

The aim of this study was to identify and develop entomopathogenic fungi as biopesticides for management of Maruca vitrata (Fabricius). Fourteen isolates of Metarhizium anisopliae (Metchnikoff) Sorokin and six of Beauveria bassiana (Bals.-Criv.) Vuill. were screened against first instar larvae of M. vitrata. The two most virulent isolates were selected and further tested for production in four liquid media. Different formulations of one isolate were evaluated against different developmental stages. Metarhizium anisopliae ICIPE 18 and ICIPE 69 caused highest larval mortality of 91 and 81%, with lethal time to 50% mortality (LT50) values of 1.8 and 1.7 days and LC50 of 1.07 × 107 and 3.01 × 106conidia/ml, respectively. ICIPE 69 yielded more biomass and propagules in two liquid media than ICIPE 18. All developmental stages and adult moths were susceptible to fungal infection and horizontal transmission caused a significant reduction in fecundity. Isolate ICIPE 69 was identified as the most potent isolate for managing M. vitrata based on demonstrated efficacy against different developmental stages and amenability to production in liquid media and could be utilized as an alternative to pesticides in cowpea IPM.

House flies (Musca domestica L.) are key pests of poultry and are managed worldwide with a variety of insecticides. However, extensive and injudicious use of insecticides has led to the development of resistance in many insect pests. Insecticide mixtures can increase the efficacy of the product and/or delay the development of resistance, thus making them a useful tool for pest control. In addition to their efficacy when used alone, mixtures of emamectin benzoate, spinosad or nitenpyram with either lambda-cyhalothrin or profenofos were assessed against a susceptible strain of house flies collected from poultry farms. The analysis revealed that combination indices for lambda-cyhalothrin/emamectin benzoate and lambda-cyhalothrin/spinosad mixtures were significantly >1, indicating an antagonistic effect. In contrast, the indices for all the tested ratios of lambda-cyhalothrin/nitenpyram were significantly < 1, suggesting a synergistic effect. For mixtures containing profenofos, combination indices varied significantly. For example, synergism was observed in a 1:1 mixture containing lambda-cyhalothrin and emamectin benzoate, but antagonism occurred when a higher proportion of the latter insecticide was used. Conversely, synergism in a mixture containing profenofos and nitenpyram was observed only when a lower proportion of the second insecticide was used. The present results suggest that ideal insecticide mixtures must be empirically determined and alternative strategies such as mosaics, rotations and cultural control should be considered for the management of the house fly.

Insect species can respond adaptively to stress temperature conditions including both thermal limits and reaction norms. In this study, we considered two populations of the whitefly Bemisia tabaci (Gennadius), in which adaptive differentiation was detected for tolerance to upper thermal limits. These two populations are found in two regions of Colombia with climatic differences: the Caribbean region with high environmental temperatures and the Southwest region with lower temperature regimens. We assessed the thermal responses to a range of 1 h heat shocks (37, 39, 41, 43 and 44 °C) performed below the thermal limits for this species. Thermal responses were measured using three life-history traits involved in fitness: survival, fecundity and viability of the offspring after heat shocks. Survival or fecundity as a response to heat shocks did not differ among populations; however, there were significantly different responses for viability between populations. The Southwestern population showed higher viability responses to low heat shocks than the Caribbean population. This relationship suggests a potential trade-off, which appears to be associated with climatic regions. In addition, these results suggest that adaptation under thermal limits does not necessarily involve similar responses throughout the reaction norm. A potential ongoing evolutionary response is taking place through the thermal reaction norms for viability after the invasion by this pest in Colombia.