Maize (Zea mays L.) is Kenya's most important staple crop with annual production fluctuating between 2.6 and 3.1 million tons in 2012 and 2011, respectively. However, frequent food shortages are still experienced in the country. These have been attributed to pests and diseases and post-harvest constraints. The dominant post-harvest pest of maize is Sitophilus zeamais (Motsch.), which causes losses between 10 and 20% of harvested grain. The objective of this study was to establish the repellent activity of essential oils extracted from selected eucalyptus species against S. zeamais. Essential oils were extracted from the fresh leaves of Eucalyptus saligna Sm., Eucalyptus globulus Labill., Eucalyptus camaldulensis Schlecht and Eucalyptus citriodora Hook by steam distillation using a Clevenger-type apparatus. A repellency bioassay, with varying concentrations (0.002, 0.02, 0.2 and 2 μl/μl) of the oils, was carried out against the maize weevils using a Y-shaped olfactometer. Repeated measures of analysis of variance were applied to test the different doses and repellents, and their interactions against S. zeamais. The essential oils of E. camaldulensis and E. citriodora presented better repellent activity at the 2 μl/μl concentration (74.35 and 69.15%, respectively) followed by those of E. globulus (53.68%) and E. saligna (40.5%). Gas chromatography (GC)–mass spectrometry and GC co-injections with authentic samples showed the presence of the following major constituents in: (i) E. camaldulensis oil: 1,8-cineole (18.9%), α-cardinol (6.4%) and β-phellandrene (2.6%); (ii) E. citriodora oil: 1,8-cineole (11.2%), β-pinene (3.2%) and 4-terpineol (3.1%); and (iii) E. globulus oil: 1,8-cineol (17.2%), α-pinene (7.1%) and spathulenol (6.5%). The results provide a scientific rationale for the use of eucalyptus oils in the protection of maize against weevils.

The efficacy of different aqueous dilutions of crude seed extract of Millettia ferruginea (Hochst.) Baker (1, 3, 5 and 10%) was evaluated under field conditions in terms of the level of damage and yield loss of maize caused by the maize stemborer Busseola fusca (Fuller) in Hawassa, southern Ethiopia. The insecticide lambda-cyhalothrin 5EC, applied at a rate of 16 g active ingredient/hectare, was used as the reference product. The experiment was carried out in a randomized complete block design with four replications. The maize variety A511 was planted in individual plots of 60 m2. Data on stand count, leaf infestation, bored stem and dead heart were collected weekly. Plots sprayed with the 5% concentration of Millettia showed low levels of damage (9–11% leaf infestation, 0.4% dead heart, 14–17% bored stem and < 0.2% bored ear), compared with plots sprayed with lambda-cyhalothrin. The treatments with 1 and 3% concentrations of Millettia were inferior to those with lambda-cyhalothrin and 5 and 10% concentrations of Millettia. In contrast, the treatment with the 10% concentration of Millettia led to the death of plants, thereby lowering the yield. About 80% of the total length of individual maize stalks from the untreated plots was internally tunnelled by the feeding larvae, while the internal stem tunnelling was low ( < 7%) in plants treated with Millettia at concentrations of 3, 5 and 10%. Among the treatments with Millettia, higher yields (37–48 decitonnes/hectare) were obtained from maize plots treated with 5% concentration. The use of the aqueous crude seed extract of M. ferruginea at a concentration of 5% applied two to three times is recommended for the control of B. fusca in maize.

Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae, Aphidiinae) is a newly discovered species alien to Benin (West Africa) and the dominating aphid primary parasitoid in vegetable agroecosystems. A study on the preference of this parasitic hymenopteran for three key aphid pests of vegetables (Aphis craccivora Koch, Aphis gossypii Glover and Lipaphis erysimi (Kaltenbach) (Homoptera: Aphididae)) was carried out under choice and no-choice conditions at 26 ± 1 °C in both Petri dishes and cages. The aphidiine rejected L. erysimi and did not oviposit in this aphid species in any of the trials. In all tests, A. gossypii proved to be the aphid host preferred most frequently by L. testaceipes. This study contributes to the fundamental knowledge on the oviposition behaviour of L. testaceipes and provides information for use in the development of sustainable aphid pest management strategies in Benin.

Tea is prepared from the tender leaves and buds of Camellia sinensis (L.). In sub-Himalayan tea plantations of North-East India, different management practices are followed to protect the tea crop against different sucking insect pests such as Helopeltis theivora (Hemiptera: Miridae), Empoasca flavescens (Homoptera: Cicadellidae) and Scirtothrips dorsalis (Thysanoptera: Thripidae). Most plantations are managed conventionally through the use of different organo-synthetic insecticides, whereas some are managed organically by using herbal and microbial insecticides. In conventional tea plantations, organo-synthetic insecticides of different functional groups (organochlorines, organophosphates, synthetic pyrethroids and neonicotinoids) are routinely applied round the year to keep the sucking insect pest populations under control. A variety of defence mechanisms, including enzymatic detoxification systems (carboxylesterases, glutathione S-transferases and cytochrome P450 monooxygenases), physiological tolerance and behavioural avoidance, protect insect herbivores from these hazardous compounds. Insect pests have evolved mechanisms to degrade metabolically (enzymatically) or otherwise circumvent the toxic effect of many types of chemicals synthesized as modern insecticides. The extent to which insects can metabolize and thereby degrade these toxic or otherwise detrimental chemicals is of considerable importance for their survival in an unfriendly chemical environment. These mechanisms continue to evolve as insects attempt to colonize new plant species or encounter newer molecules of synthetic insecticides. The level and type of detoxifying mechanisms differs greatly, which, therefore, results in varying toxicity among different stages, species and populations. Variation in detoxifying enzyme activity is responsible, in part, at least for the selective toxicity of different insecticides, the development of resistance to insecticides and the selection of host plants. Overexpression of these detoxifying enzymes, capable of metabolizing insecticides, can result in higher levels of metabolic tolerance/resistance to synthetic insecticides.

The storability of five new different formulations of Metarhizium acridum (two oil, one paste, one semi-solid and one powder) was investigated under ambient and low temperatures. Fourth-instar nymphs of the desert locust Schistocerca gregaria (Forskål) were used to evaluate their virulence. Under ambient conditions (23–38°C), all the formulations maintained acceptable viability (66.1 ± 2.30 to 71.8 ± 0.88% germination) after 6 months of storage. After 10 months, only conidia from the powder formulation remained viable. In contrast, samples of the formulations kept under low temperatures ( − 1.2 to 15°C) did not show significant loss of viability after 30 months of storage despite repeated power cuts, lasting sometimes several days. During this period, M. acridum conidia remained virulent to nymphs with 100% mortality 5 to 7 days after the treatment. These results show that all the formulations have greater stability when stored under low and even fluctuant temperature changes. Under ambient conditions, the formulations could remain effective for at least 6 months of storage.

Maize was artificially infested with either 10 or 25 individual Prostephanus truncatus (Horn) and Sitophilus zeamais (Motschulsky) or a mixture of both, and stored in a hermetic grain bag (HGB) or a woven polypropylene bag (WPB) for 150 days. Population growth of P. truncatus and S. zeamais during storage was low in HGB, while in WPB, the insect population increased significantly with storage duration. Mortality rate during storage was significantly higher in HGB than in WPB. After 60 days of storage, the average mortality rate of 99.50% was observed in HGB infested with 25 P. truncatus, and 100% for S. zeamais at the same infestation density after 90 days of storage. Grain losses were significantly lower in HGB compared with WPB. Less than 0.5 and 6.0% losses were obtained, respectively, for S. zeamais and P. truncatus in HGB infested with 25 individual insects after 150 days of storage, whereas losses of 19.2% (infestation with S. zeamais) and 27.1% (infestation with P. truncatus) were observed in WPB. HGB seems to be resistant to the perforation of S. zeamais, but not to P. truncatus. The moisture content of maize grains stored in HGB remained practically the same during storage, compared with the levels in WPB, which reduced with storage time. WPB could be used for maize storage, protecting it against insect infestation without the need for insecticide use.

The fitness of Helicoverpa armigera (Hübner) was determined using demographic studies on the F1 generation that survived after exposure to four sublethal doses (LC50, LC30, LC20 and LC10) of imidacloprid. The effects were assessed on the surviving individuals emerged from sixth-instar larvae that had ingested imidacloprid-treated chickpea pods. Age-specific parameters were found to be highest with the commencement of age and gradually decreased with the progression of age in both the treated and non-treated groups. Survivorship was reduced to 37 days after exposure to the sublethal dose of LC50 when compared with 42 days in groups not exposed to the insecticide. The highest number (17%) of unhatched eggs was recorded in insects treated with the LC50 dose of imidacloprid, whereas 98% of the eggs hatched in the unexposed group. The potential fecundity of the F1 generation females was reduced to 330 eggs/female/generation when treated with the LC50 dose compared with that of the unexposed females. The intrinsic rate of increase was found to be least in insects exposed to the LC20 dose (0.0355 females/female/day) and highest (0.0470) in the unexposed group. It took 38.83 days for H. armigera to complete one generation in the unexposed population, while this was reduced to 33.94 days after exposure to the sublethal dose of LC50. The longevity of adults decreased when the larvae were exposed to the sublethal dose of imidacloprid. The developmental time of pre-pupae and pupae significantly decreased and was least when exposed to the highest sublethal dose of the insecticide. Thus, at sublethal doses, imidacloprid caused a significant reduction in the survival and fecundity as well as increased mortality of H. armigera in the subsequent generation after exposure to the insecticide. In conclusion, imidacloprid can be successfully incorporated into integrated pest management of H. armigera.

Experiments were conducted in the laboratory to screen the leaf extract of Dracaena arborea (Willd.) Link for the presence of chemical groups with insecticidal activity against Sitophilus zeamais (Motsch.) and Callosobruchus maculatus (Fab.). The plant materials were collected, dried, ground to fine powder and extracted with 90% ethanol. Phytochemical screening involved the use of thin layer chromatography analysis for chemical compounds such as alkaloids, tannins, saponins, anthraquinones, flavonoids and terpenes. Partitioning of the extract was carried out by dissolving the extract in water to obtain the aqueous phase, which was partitioned between equal volumes of chloroform, n-hexane, n-butanol and ethyl acetate. The different fractions were screened for insecticidal activity against S. zeamais and C. maculatus. Some fractions of the leaf extract such as ethyl acetate and aqueous fractions demonstrated 100% mortality, offered protection to grains, reduced progeny development and repelled the insects compared with the control. Based on the activity of some fractions, the leaf extract of D.arborea has the potential for development as a botanical insecticide against S. zeamais and C. maculatus.

The noctuid moth Helicoverpa armigera (Hubner) is the most damaging pest of chickpea worldwide. Plant resistance is an important component for the management of this pest. To develop cultivars with resistance to insects, it is important to understand the role of different components associated with resistance to insects. Therefore, we characterized a diverse array of chickpea genotypes for organic acid profiles in the leaf exudates that are associated with resistance to H. armigera. Chickpea leaf exudates contained five major organic acids that were identified as malic, oxalic, acetic, citric and fumaric acids. High-performance liquid chromatography (HPLC) profiles of the leaf exudates of nine chickpea genotypes showed that amounts of malic acid were negatively correlated with leaf feeding by H. armigera larvae at flowering and maturity, and with pod damage. Oxalic acid showed a negative association with leaf damage in the detached leaf assay. Additionally, the amounts of acetic acid were negatively correlated with larval weights and damage rating at the flowering and maturity stages. Citric acid levels were negatively associated with damage rating at the flowering stage. Implications of using the HPLC profiles of organic acids in the leaf exudates of chickpea to breed for resistance to H. armigera are discussed.

Plant protease inhibitors (PI) constitute a major class of defence proteins being selected as an important strategy towards insect herbivory. With the objective of assessing the effect of PI towards larval growth and development, an artificial diet bioassay using partially purified PI obtained from peas was performed on the melon fruit fly Bactrocera cucurbitae (Coquillett). Larval growth and developmental parameters were assessed at different concentrations (namely 12.5, 25, 50, 100, 200 and 400 μg/ml) on the second-instar larvae of B. cucurbitae. Growth and survival responses determined the anti-insect potential of this PI even in its partially purified state. Larval and total development periods were found to be significantly prolonged for the larvae fed on an artificial diet incorporated with pea PI when compared with those fed with a control diet. Furthermore, when compared with the effect of the control diet (no inhibitor), the partially purified pea PI in the diet reduced larval weight gain, mean larval growth rate and food assimilated with respect to the control of the second-instar larvae tested at the same range of concentrations. The relative effectiveness of pea PI on these parameters is in agreement with the results obtained for percentage of pupation and percentage of adult emergence, as these parameters were significantly affected by the increase in the PI concentration in the artificial diet. Feeding the second-instar larvae a diet containing a range of concentrations (50, 100, 200 and 400 μg/ml) of partially purified pea PI significantly reduced the activities of digestive enzymes (trypsin, chymotrypsin, elastase and leucine aminopeptidase) and significantly affected the activities of other non-digestive enzymes (esterase, acid and alkaline phosphatases, glutathione S-transferase, superoxide dismutase and catalase).

Trapping of adult red palm weevil (RPW) Rhynchophorus ferrugineus Olivier using food-baited pheromone traps is a major component of the integrated pest management strategy currently adopted against the RPW in the United Arab Emirates (UAE). Field trials were carried out in RPW-infested date plantations of Al-Rahba, Abu Dhabi, UAE from January to December 2010 to ascertain the combined influence of ethyl acetate (EA) and trap colours on weevil captures in RPW pheromone traps. Weevil captures were recorded throughout the experimental period with a sex ratio (male:female) of 1:2.2 and capture rates of 25.13 and 15.14 weevils/trap/month in traps with and without EA, respectively. Furthermore, treatments with black-coloured traps recorded significantly higher weevil captures.

In this study, the effect of the application of three powdery mildew fungicides, namely triadimenol, triadimefon and sulphur, on the African weaver ant (AWA), Oecophylla longinoda Latreille, was evaluated for two seasons in two cashew fields, one each in the Bagamoyo and Mkuranga districts, Coast region, Tanzania. The fungicides were applied at monthly intervals, and the dynamics of AWA were monitored monthly by counting the number of leaf nests per tree and trails on main branches. There were no significant differences among the treatments on AWA at different observation dates in terms of the number of leaf nests and colonization of AWA trails per tree in the two cashew fields studied. In August 2011, for example, the number of leaf nests before application ranged from 7.8 to 9.0 and 13.6 to 14.6 in Bagamoyo and Mkuranga, respectively, and after application, it ranged from 7.8 to 10.0 and 12.4 to 15.2 in Bagamoyo and Mkuranga, respectively. The three powdery mildew fungicides did not have detrimental effects on the abundance of AWA in cashew fields and can, therefore, be used together with AWA as important components of an integrated pest and disease management programme for cashew crops in Tanzania.

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.

Triatoma virus (TrV) is a small, non-enveloped virus that has a+ssRNA genome and is currently classified under the Cripavirus genus of the Dicistroviridae family. TrV infects haematophagous triatomine insects (Hemiptera: Reduviidae), which are vectors of American trypanosomosis (Chagas disease). TrV can be transmitted through the horizontal faecal–oral route, and causes either deleterious sublethal effects or even the death of laboratory insect colonies. Various species of triatomines from different regions of Latin America are currently being reared in research laboratories, with little or no awareness of the presence of TrV; therefore, any biological conclusion drawn from experiments on insects infected with this virus is inherently affected by the side effects of its infection. In this study, we developed a mathematical model to estimate the sample size required for detecting a TrV infection. We applied this model to screen the infection in the faeces of triatomines belonging to insectaries from 13 Latin American countries, carrying out the identification of TrV by using RT-PCR. TrV was detected in samples coming from Argentina, which is where the virus was first isolated from Triatoma infestans (Hemiptera: Reduviidae) several years ago. Interestingly, several colonies from Brazil were also found infected with the virus. This positive result widens the TrV's host range to a total of 14 triatomine species. Our findings suggest that many triatomine species distributed over a large region of South America may be naturally infected with TrV.