Short and long dry spells occur throughout the year and limit the access of gravid mosquitoes to oviposition sites. Using simulations in laboratory conditions, we explored the possible consequences of a long duration of egg retention on reproductive capacity, trophic behaviour, life expectancy and gonotrophic cycle in a context of breeding-site absence. KISUMU and wild gravid females of Anopheles gambiae were subjected to a delay in egg-laying following the preset modalities as immediate egg-laying versus retention for 5, 10 and 15 days. The egg batch size and the hatching rate were measured. In addition, blood-feeding patterns and life expectancy were investigated. Our study showed that oviposition occurs much faster in the standard susceptible laboratory strain An. gambiae KISUMU with a lapse of 2.2 days than in the wild females of An. gambiae with an average of 5 days between the second blood meal and egg-laying. In this experiment, the egg-retention time did not significantly affect the number of eggs laid. In the absence of breeding sites, the rate of egg-hatching decreased in proportion as the retention time became longer. The study also showed that gravid females deprived of oviposition sites continue to take blood meals. The average longevity of non-gravid females was estimated to be lower than that of gravid females. The oviposition-site deprivation has no impact on female fecundity and blood feeding, but influences egg-hatching.

Dengue has become the fastest-growing mosquito-borne disease in Sri Lanka and the control of the vectors, Aedes aegypti Linnaeus and Ae. albopictus Skuse, is the most effective way of controlling the disease. A detailed study on vector prevalence has not been recorded from Sri Lanka. Therefore, the present study was undertaken to study the prevalence of both vectors in four semi-urban study sites in two of the most affected districts, namely Kandy (wet zone) and Kurunegala (intermediate zone), by conducting egg surveys (using ovitraps) and larval surveys from June 2007 to May 2008. A total of 82,524 eggs and 2658 larvae of Ae. aegypti and Ae. albopictus were collected. A total of 3699 potential breeding habitats were examined. Ovitrap and larval indices (house, container and Breteau) showed that all four areas are at epidemic risk, especially due to a high abundance of Ae. albopictus. The highest numbers for both the species were from the Kandy sites where dense vegetation, high rainfall and low temperature prevailed. The results showed a high mortality rate during the egg-to-larva transition, suggesting that conducting an egg survey alone would overestimate the vector abundance and the disease risk. For Ae. albopictus, the monthly mean number of eggs showed positive relationships with relative humidity in both districts and with rainfall in the Kandy District. The number of dengue cases in the area had no positive relationships with the abundance of eggs or larval density indices. Discarded receptacles were the most preferred breeding habitat for these dengue vectors. Since the attractiveness (inferred by the calculated risk factors) of most of the breeding habitats was very high, elimination of these breeding sites is essential for the success of dengue control programmes.

The sugarcane aphid Melanaphis sacchari (Zehnt.) has become a serious pest of sorghum, particularly during the post-rainy season in India and East and Southern Africa. Therefore, we tested a number of techniques to screen sorghum genotypes for their resistance to M. sacchari. Infesting the plants with aphid-infested leaf cuttings and covering with a nylon net was effective in screening sorghum genotypes for their resistance to M. sacchari. Sprinkling the plants with aphids (filled in an 0.5 ml eppendorf tube) in the greenhouse was also used to confirm whether the resistance of genotypes selected is less susceptible to the aphids under natural infestation. Nine genotypes (Line 61510, ICSV 12001, ICSV 12002, ICSV 12003, ICSV 12004, ICSV 12005, SLR 41, PU 10-1 and DJ 6514) exhibited moderate levels of resistance to M. sacchari. These genotypes also exhibited a lower rate of aphid multiplication in the clip cage and leaf disc assays. The rates of aphid multiplication were lower on the genotypes IS 21807, IS 40615, IS 40616 and IS 40618 than on the susceptible check, Swarna in the clip cage assay under the field conditions. Also, lower rates of aphid increase were also recorded on IS 21807 and IS 40615 in the leaf disc assay under laboratory conditions. Some of the genotypes that exhibited resistance to aphid damage under field conditions showed comparatively higher rates of aphid increase than the susceptible check, Swarna in the clip cage assay, indicating that antixenosis could be one of the components of resistance to M. sacchari in these genotypes. Therefore, the clip cage assay could be used to gain further understanding of the mechanisms of resistance to M. sacchari. There is a need to assess the role of antixenosis and colonization in genotypic reaction against M. sacchari to identify the lines with different mechanisms of resistance to this pest. The results suggested that the nylon net technique could be used to screen sorghum genotypes for resistance to M. sacchari. The genotypes exhibiting resistance to M. sacchari can be used to develop aphid-resistant sorghums for sustainable crop production.

Pestalotiopsis is a disease that causes damage to the leaves of Elaeis guineensis Jacquin and defoliation in commercial plantations. Lepidoptera larvae are the main insects that spread the disease. The aim of this paper is to report for the first time the insects found in oil palm plantations in Colombia. Lepidoptera larvae were collected from cultures in the presence of Pestalotiopsis and were identified to species level. Severity and duration of the symptoms of Pestalotiopsis were evaluated from the damage caused by the insects of each species. Eighteen species of the families Dalceridae (one), Elachistidae (four), Limacodidae (eight), Megalopygidae (two), Nymphalidae (one), Psychidae (one) and Saturniidae (one) confirmed assistance and disease transmission. Increased severity of Pestalotiopsis damage was induced by Acharia hyperoche, Acraga ochracea, Durrantia arcanella, Euclea diversa, Euprosterna elaeasa and Stenoma impressella. The development of Pestalotiopsis on the leaves of E. guineensis and its symptoms were observed between 16.8 and 72.9 days. The damage caused by these insects on the leaves of E. guineensis was the main entrance of the virulent fungal spores. The results of this study contribute to the knowledge of Lepidoptera that attend and spread the Pestalotiopsis fungus on leaves in oil palm plantations. To our knowledge, no previous records of this disease on the plant are found in Colombia.

In the present study, four methods of rice crop establishment, viz. conventional transplantation, bed transplantation (BT), furrow transplantation (FT) and puddled direct seeding (PDS), were evaluated during two wet seasons to determine their influence on the incidence of insect pests and grain yield. Observations were recorded starting from 40 days after transplanting (DAT) and seeding (DAS) to 110 DAT and DAS. The interaction between crop establishment methods and observation days was significant in the case of folded leaves by Cnaphalocrocis medinalis (Guenée), deadhearts by Scirpophaga incertulas (Walker) and the Sogatella furcifera (Horvath) population. The number of folded leaves in the bed-transplanted crop (8.87%) and puddle direct seeded crop (10.62%) was significantly higher than that in crop grown using the other crop establishment methods. The incidence of deadheart damage was significantly higher in the PDS plots (5.85%), while that of whitehead damage was higher in the BT (5.89%) and PDS (6.54%) plots than in the plots managed by the other methods. The S. furcifera population build-up was significantly higher in the FT (1.98 hoppers/hill) and PDS (2.24 hoppers/hill) plots than in the plots managed by the other crop establishment methods. Paddy yield was significantly higher in the conventionally transplanted crops followed by the furrow- and bed-transplanted crops.

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.

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.

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.

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.