The host location behaviour of two closely related bethylid parasitoids was investigated under laboratory conditions. Although both species of parasitoid attack the coffee berry borer (CBB) Hypothenemus hampei Ferrari, they differ in their diet breadth. In Y-tube olfactometer bioassays, we investigated the behavioural responses of Cephalonomia stephanoderis (Betrem), a parasitoid with a narrower diet breadth, and Cephalonomia hyalinipennis (Ashmead), a parasitoid with a wider diet breadth, to the coffee–CBB complex volatiles. The results revealed that the responses differed for the two species. In single- and dual-choice tests, C. stephanoderis was attracted to volatiles emitted by CBB-infested coffee berries, dust/frass and CBB immature stages, whereas C. hyalinipennis was not attracted to any cues from plant–host complex offered.

A survey was conducted in Ibadan, Nigeria, between 1 November and 30 December 2000 to examine the mango mealybug Rastrococcus invadens Williams infestation. Results obtained prompted another study in which the population of R. invadens and its parasitism were monitored from January 2001 to December 2005 on smoke-polluted infested mango trees after relocation of smoke sources. A third study was conducted between January and April 2007 in Ibadan, Nigeria, where mealybug-infested mango trees were searched for and the levels of pollution around them characterized using a derived rating scale. The survey results showed that only 7.5% of a total of 489 mango trees examined in 2001 were infested with mango mealybug and were located in exhaust, car park, motorway or converging environments. In study 2, the mango mealybug population significantly (P < 0.05) declined, and parasitism significantly increased on trees from where pollution sources were relocated. All the 86 mango mealybug-infested trees scouted for in study 3 were located in smoke-polluted areas. Significantly higher numbers of infested trees and mealybug population, and significantly lower parasitism levels were found on mango trees in exhaust areas, compared with others. Pollution level was correlated with mealybug population (positively) and parasitism (negatively) in 2000 and 2007. Whereas mealybug population gradually built up on hitherto clean trees where pollution sources were relocated, parasitoid activity seemed to be enhanced by the relocation of smoke sources. The effectiveness and conservation of the parasitoids may therefore depend on the air quality around the infested trees.

The exact taxonomic identity of members of the Simulium damnosum Theobald complex in Ethiopia was not known until recently. A cytotaxonomic analysis of larval chromosomes from the Kulfo River area in southern Ethiopia, from where the ‘Kulfo’ form was reported, and from the Awash River at Sodere in central Ethiopia has revealed the existence of two newly recognized species, namely Simulium kulfoense and Simulium soderense. Although three fixed and 11 floating inversions in the chromosomes of the ‘Kulfo’ form were described in an idiogram, in the present study four fixed and 17 floating inversions were observed, out of which only seven floating inversions were the same as Dunbar's, indicating that the remaining 10 inversions were either missed or misinterpreted. Though both species share many inversions, S. kulfoense sp. nov. has a diagnostic inversion on chromosome II, IIL-E6, with no sex-linked chromosomal arrangement, while S. soderense sp. nov. has a sex-linked inversion, IIS-3, which warrants it as a distinct species. Both of these new species also share many inversions with the recently described new species from south-western Ethiopia, Simulium kaffaense, including the fixed inversions IIL-E1 and E3. Since both the study sites are known to be free of onchocerciasis, and the flies are not anthropophilic, both the species are not presumed to be vectors of human onchocerciasis. The presence of IS-1 and a complex inversion possibly involving IL-3 strongly indicates that the two species belong to the ‘Nile’ phylogenetic group of S. damnosum s.l.

Bacillus sphaericus (Bs) is a potential mosquito larvicide especially against Culex quinquefasciatus (Say), the vector of bancroftian filariasis. It is a gram-positive, aerobic and endospore-forming bacterium. During sporulation, it synthesizes binary endotoxins (molecular weight 42 and 51 kDa proteins) that are highly toxic to mosquito species. The mode of action of the binary toxin of this biolarvicide in the alimentary canal and the ultrastructural events in the tissues of the affected larvae have been demonstrated. Lysosomal components are the most important organelles involved in the metabolism of the foreign molecules encountered by the cells. In this paper, we report the ultrastructural changes in the midgut epithelial cells, with special emphasis on lysosomes (L), in untreated Cx. quinquefasciatus larvae and those treated with the Bs-IAB59 bacterial strain. In the Bs-treated larvae, the size of the L gradually increased, and within 16 h, fine filaments appeared and compartmentalized into small lamellar bodies, within the L. After 36 h, these lamellar bodies appeared to be collapsed, and later disintegrated in the 48th hour. In the untreated larvae, such ultrastructural changes in the L were not seen. These observations suggested that, though the target site of action of the Bs toxin is the midgut epithelial cells, ultrastructural changes in the L compartments play a vital role in the mortality of the mosquito larvae.

The larvicidal activity of 13 essential oils, 14 major monoterpenoids and 9 N-methyl carbamates based on these monoterpenoids was tested according to the recommendations of the WHO against fourth instar larvae of Culex pipiens L. The results of the larvicidal assays after 24 hr revealed a high potential for the essential oils, such as cinnamon, chenopodium and eucalyptus. Of the monoterpenoids, chlorothymol was found to be the most effective followed by thymol, carvacrol and cinnamaldehyde. Conversion of the most active monoterpenoids into their N-methyl carbamate derivatives resulted in higher larvicidal activities than those of the corresponding monoterpenoids. The use of piperonyl butoxide (PBO) to improve the efficacy of the most active monoterpenoids resulted in higher larvicidal activity. Also, all N-methyl carbamate derivatives were synergized by PBO. Carvacrol derivative, which was strongly synergized by PBO, was comparable with the standard synthetic insecticide malathion.

The fall armyworm (FAW) Spodoptera frugiperda J. E. Smith is the most noxious insect to maize and sorghum in the state of Colima, Mexico. In this work, two maize landraces (‘blanco’ and ‘aperlado’), native to Colima, were grown in Tecomán, Colima, to determine the FAW population behaviour under natural conditions. The spatial distribution of the FAW larvae was random, and natural infestations were strongly associated with the maize phenological stages. The relationship between FAW and plant phenology was explained by non-linear regression models.

Diapause hormone (DH) and pheromone biosynthesis-activating neuropeptide (PBAN) code for the diapause gene (DH-PBAN) of Bombyx mori Linnaeus. The DH-PBAN gene sequence from the BLAST database was searched against B. mori genomic gene sequences for similarity. Results showed maximum homology with a genomic contig (accession no. D16230). Primers were designed for the intron, exon and promoter regions of the DH-PBAN gene sequence. The corresponding regions were amplified using genomic DNA as template and products of diapause and non-diapause silkworm races were compared. There was no variation in the 425 bp intron and 254 bp exon regions. However, 1.3% nucleotide sequence variation was observed in selected silkworm races. The promoter region showed 4.2% single nucleotide variation in the diapause and non-diapause silkworm races. The promoter region of the diapause gene showed variations in the sequence of the POU (Pit 1, Oct 1 and Unc-86)-binding site of non-diapause and diapause races of B. mori. In phylogenetic analysis, B. mori formed a cluster with other silkworms of the Bombycidae family, whereas the Noctuidae family formed a separate cluster, indicating that the diapause gene is conserved across the insect taxa.

The effect of different constant temperatures (20, 25, 27, 30 and 35 °C) on life history stages of the Mexican chrysomelid beetle, Zygogramma bicolorata Pallister, fed on the weed Parthenium hysterophorus Linnaeus was investigated to analyse the development and survival of different life stages and the adult sex ratio. Fastest development and maximum survival were recorded at 27 °C. The first instar was the most vulnerable, while the pupa was least vulnerable. For complete development, the lower temperature threshold (t°C) was 18.5 °C and the thermal constant (K) was 480.8 day-degrees. A higher percentage of females was obtained at all temperatures; however, this was unaffected by the temperature regime. This study established that the percentage life span spent by immature stages was similar across all five temperatures, indicating developmental rate isomorphy. 27 °C was the most suitable temperature under controlled abiotic conditions for the propagation of Z. bicolorata, a bioagent for parthenium weed.

The legume pod borer (Helicoverpa armigera (Hubner)) is one of the most important pests of pigeonpea. The levels of resistance to H. armigera in the cultivated germplasm are quite low, and therefore there is a need to introgress resistance genes from wild relatives into the cultigen. We evaluated a diverse array of wild relatives of pigeonpea for oviposition non-preference and antibiosis components of resistance to H. armigera. The accessions ICPW 1 (Cajanus acutifolius), ICPW 13 and 14 (C. albicans), ICPW 159 and 160 (C. sericeus), ICPW 68 (C. platycarpus), ICPW 83, 90, 94, 125, 137, 141 and 280 (C. scarabaeoides), ICPW 207 (Paracalyx scariosa) and ICPW 210 (Rhynchosia aurea) showed high levels of antixenosis for oviposition under no-choice, dual-choice and multi-choice conditions. High levels of antibiosis were observed when the larvae were reared on leaves and/or pods of C. acutifolius (ICPW 1), C. cajanifolius (ICPW 29), C. sericeus (ICPW 160), P. scariosa (ICPW 207), C. scarabaeoides and C. albicans. Lyophilized leaf or pod powder incorporated into the artificial diet can be used to assess antibiosis to H. armigera, and high levels of antibiosis to H. armigera were observed in diets with leaf and/or pod powder of some of the accessions of C. acutifolius, C. lineatus, C. sericeus, C. scarabaeoides, C. platycarpus, P. scariosa and R. aurea. Post-embryonic development period was prolonged in insects reared on leaves and pods of wild relatives of pigeonpea. The accessions showing high levels of antixenosis and antibiosis can be used to increase the levels and diversify the bases of resistance to H. armigera in pigeonpea.

Bactrocera latifrons (Hendel) is a tephritid fruit fly of primarily Asian distribution that became established in Hawaii in 1983 and recently invaded Africa, being detected in Tanzania in 2006 and in Kenya in 2007. Although males of the majority of dacine fruit flies respond to either methyl eugenol or cuelure, B. latifrons shows little to no response to these lures. Instead, B. latifrons males respond to α-ionol+cade oil. Male age-related responsiveness to α-ionol+cade oil (using wind tunnel bioassays) relative to the age of sexual maturity (assessed through spermathecal dissections) was documented using wild B. latifrons adults. Relative to the peak response observed at day 28, males exceeded 50, 75 and 90% of the peak response at days 7, 14 and 21, respectively. No females younger than 16 days old were mated. Based on a sigmoidal regression of the percentage of inseminated females versus age, 50% of females were inseminated when 18.8 days old, with the percentage increasing to 75 and 90% at 19.8 and 20.9 days of age, respectively. At 24 days and older, 100% of females were mated. The observation that no female B. latifrons were mated by day 14, while 14-day-old male flies achieved over 75% of the peak response to α-ionol+cade oil, suggests that α-ionol+cade oil mass trapping has some potential to remove males from the field before they can contribute to increasing field populations through matings, as previously found with the oriental fruit fly, B. dorsalis (Hendel), and its respective male lure, methyl eugenol. The effectiveness of the removal of males before they mate, though, would be expected to be less for B. latifrons than the male annihilation achieved in the use of methyl eugenol with B. dorsalis because the male lure for B. latifrons is weaker overall.

The transformation from larval caterpillar to non-feeding pupa and adult moth involves a complete remodelling and restructuring of an insect and its organs. In the groundnut pest Amsacta albistriga Walker, the female sex-specific storage protein 1 (SP1) was monitored from last larval instars, during pupal development to the adult stage. Staining intensity of SP1 (which resolved at 82 kDa) in the peripheral fat body (PF) tissues subjected to 10% SDS-PAGE was maximum at mid-stage last larval instars and declined subsequently. However, in perivisceral fat body (PVF) tissues, the staining intensity of SP1 increased significantly from mid-stage final instar. The presence of SP1 during pupal ovary and adult ovariole development and its availability during egg development was confirmed by immunoblot analysis. Electron microscopy data revealed that the decline of biosynthesis of SP1 in PF tissues and its disintegration were associated with the appearance of irregular nucleus and autophagic vacuoles during transformation of larva to pupa. In vitro and in vivo studies using [35S]-methionine-labelled storage proteins showed that, unlike PF tissues, PVF tissue sequestered a significant amount of labelled SP1. During this transformation, SP1 was mainly sequestered as storage protein granules until they served as sources of amino acids for the production of egg yolk proteins. Localization of clathrin-coated pits and crystalline storage proteins was confirmed by immunogold tracer techniques.

Cacao genotypes of various origins were evaluated for resistance to the cocoa mirid (Sahlbergella singularis (Haglund)) based on field damage, antixenosis, antibiosis and tolerance. Field damage was assessed by scoring recent and cumulative damage by the mirid to the major genetic groups of cacao. Antixenosis assessment was based on the number of feeding lesions on twig segments using a choice test. Antibiosis was measured through survival of young mirid nymphs on shoots and pods, whereas tolerance was assessed through the reaction of the twigs to mirid feeding punctures. Among the genetic groups of cocoa, the Upper Amazon, the materials from Guiana and hybrid genotypes were the least damaged by the mirids, both for recent and cumulative damage. The Catongo group was, by far, the most susceptible group with more than 50% of the canopy showing both recent dieback and cumulative canker damage. With regard to antixenosis, antibiosis and tolerance, significant differences (P < 0.05) were found between the genotypes. The least preferred clones sustained between 2 and 3 lesions compared with the most preferred ones with 6–8 lesions per twig segment. Clones UPA402, T79/501 and IMC67 gave the lowest rate of mirid nymph survival, indicating that they exhibit antibiosis. The clones PA107, SCA6 and C151-61 sustained high numbers of mirid feeding lesions and relatively high levels of shoot death, but have a good ability for re-growth and can be considered as tolerant genotypes.

From 2002 to 2004, three field trials were conducted in Senegal to compare the efficacy of a new biopesticide for grasshopper control, based on the entomopathogenic fungus Metarhizium anisopliae var. acridum Driver & Milner, with mixtures of this biopesticide and cyhalothrin, a widely used pyrethroid insecticide to control the Senegalese grasshopper Oedaleus senegalensis Krauss. The aim of these trials was to obtain a knockdown effect without compromising the environmental credentials of the biopesticide too much. During the first two trials, 50 ha (2002) and 25 ha (2003) plots were treated with Metarhizium at a rate of 50 g/ha, cyhalothrin at a rate of 40 g/ha, a mixture of Metarhizium at a rate of 25 g/ha and cyhalothrin at a rate of 20 g/ha. For the third trial in 2004, several mixtures of cyhalothrin at a rate of 10 g/ha and Metarhizium at dose rates of 6.25, 12.5 and 25 g/ha were prepared. These mixtures were compared with 50 g/ha of Metarhizium, 40 g/ha of cyhalothrin and 10 g/ha of cyhalothrin on 25 ha experimental plots. The volume application rate for all trials was 1 l/ha. The Metarhizium applications resulted in a slow but long-lasting reduction of grasshopper numbers. By contrast, cyhalothrin produced a rapid reduction, but grasshopper numbers re-increased a few days after application, except in 2003, when grasshopper densities in the surrounding areas were low. The mixtures caused a similarly fast reduction in grasshopper numbers, but this lasted throughout the 3 week post-application assessment period. These trials demonstrated that adding a low dose of a pyrethroid insecticide to a slow-acting biopesticide can increase the speed of population reduction, while retaining the latter's long-lasting effect. A bonus is that the price of the combination is lower than that of each product at the recommended dose rates. Since the insecticide is added at a low dose, its environmental impact is reduced compared with the full-dose insecticide only treatment.

The development, survival and reproductive potential of diamondback moth Plutella xylostella (Linnaeus) were studied at 25 ± 1 °C in the laboratory in response to two cultivated Brassica oleracea cultivars (cabbage B. oleracea var. capitata and kale B. oleracea var. acephala) and four wild crucifer species Erucastrum arabicum, Raphanus raphanistrum, Rorippa nudiuscula and Rorippa micrantha. Rorippa micrantha was the most preferred species in oviposition choice tests, while cabbage and kale were least preferred. First instar larval mining period differed significantly between plant species with the longest period recorded on cabbage (3.0 days) and the shortest on R. micrantha (0.4 days). Pupal weight was significantly lower for larvae reared on R. nudiuscula, while those of the others were similar. The developmental period from first instar to adult was the shortest on R. micrantha (14.1 days) and the longest on R. raphanistrum (15.6 days). Survival to adult was not statistically affected by the host plant species. Adult longevity ranged between 18.2 days on R. raphanistrum and 24.7 days on R. nudiuscula. The females were significantly heavier than the males on all plant species. However, males lived longer than females. Moths reared on R. nudiuscula recorded the highest fecundity (326 eggs), while moths reared on cabbage had the lowest fecundity (262 eggs). Kale and R. nudiuscula recorded the longest generation time of 31.7 days, while E. arabicum had the highest net reproductive rate (126.4 eggs per day). The highest intrinsic rate of increase was calculated for R. micrantha (0.179) and the lowest for kale (0.147). This study shows the suitability of wild crucifers as hosts for P. xylostella and indicates that they may play a major role as reservoir for the pest during the absence of cultivated host plants.

Perovskia abrotanoides Karel is a wild growing plant in Iran and has been used in traditional Iranian herbal medicine. The present study was conducted to investigate chemical composition and fumigant toxicity of the essential oil from P. abrotanoides against Sitophilus oryzae (L.) and Tribolium castaneum (Herbst). Dry flowering aerial parts of the plant were subjected to hydrodistillation using a modified Clevenger-type apparatus. The composition of the essential oil was analysed by gas chromatography (GC) and GC mass spectrophotometry. Twenty-four compounds representing 98.8% of total oil were identified. The predominant components in the oil were camphor (28.38%) and 1,8-cineole (23.18%). Fumigant toxicity was tested against 1- to 7-day-old adults of S. oryzae and T. castaneum with five replications at 25 ± 1 °C and 65 ± 5% relative humidity in dark conditions. The mortality was increased with concentrations of 32, 161, 322, 483 and 645 μl/l air and with exposure time from 2 to 15 h. The lowest concentration (32 μl/l air) of the oil induced 100% mortality of S. oryzae and T. castaneum after 15 and 8 h exposure, respectively. The oil at 322 μl/l air caused 100% mortality for S. oryzae and T. castaneum within 13 and 7 h exposure, respectively. At 645 μl/l air, the LT50 values (lethal time for 50% mortality) were 8 and 2.84 h for S. oryzae and T. castaneum, respectively. In the probit analysis, LC50 values (lethal concentration for 50% mortality) showed that T. castaneum (LC50 = 11.39 μl/l) was more susceptible than S. oryzae (LC50 = 18.75 μl/l). The essential oil of P. abrotanoides can play an important role in stored grain protection and reduce the need for the same, and also the risks associated with the use of synthetic insecticides.

We studied the abundance and diversity of flower-visiting insects on Bt and non-Bt cotton plants in the Makhathini Flats region of South Africa during the 2003/2004 and 2004/2005 crop seasons to detect any impact of the Bt toxin (Cry1Ac). Bt cotton cultivars produced more flowers than non-Bt cultivars regardless of the cropping conditions (farmers' fields or research station), probably due to the fact that Bt cotton is not susceptible to flower bud pests. The results obtained in both crop seasons highlighted the prevalence of honeybees (Apis mellifera L.), various Nitidulidae and a unique Meloidae species (Mylabris oculata Thunberg) as flower visiting insects in this area. No impact of the Bt phenotype on insect abundance and diversity could be drawn on the basis of our comparative results on Bt and non-Bt cotton plants, and no direct effect of these transgenic plants was actually noted. The potential role of some of the inventoried insects, especially M. oculata, in the dispersal of transgenic pollen is discussed.

Morphology of haemocytes of healthy and Beauveria bassiana (Bals.) Vuill.-infected Dicladispa armigera (Olivier) adults was examined in a phase contrast microscope to characterize them into different types. The total haemocyte count (THC) and the differential haemocyte count (DHC) were also estimated. Four types of haemocytes were identified: prohaemocyte, plasmatocyte, granulocyte and spherulocyte. In the healthy adults, the THC varied between 5055 and 5950/mm3, out of which 85% were composed of granulocytes and plasmatocytes. As B. bassiana infection time increased, THC decreased and was associated with a significant concomitant increase in granulocytes and a decrease in prohaemocytes. Granulocytes reacted in various ways, including disintegration of the plasma membrane, formation of fine pseudopod-like cytoplasmic extensions and finally, clumping of cells. Granulocytes and plasmatocytes were the predominant haemocytes involved in all the cell-mediated defence reactions.

Lepidopteran stemborers (Chilo zacconius Bleszynski, Chilo diffusilineus de Joannis and Maliarpha separatella Ragonot) and diopsid flies (Diopsis spp.) are economically significant insect pests of rice in Burkina Faso. The objective of this study was to monitor damage trends and the pre-imaginal populations of these insects on two host plants, cultivated (Oryza sativa L.) and wild rice (Oryza longistaminata Chev and Roehr). The study was conducted over four consecutive rice crop seasons from 1999 to 2001 in three irrigated rice-growing locations in western Burkina Faso. Sampling of cultivated rice was conducted monthly in 1 m2 quadrates in 100 randomly selected farmers' fields. Data on wild rice were collected monthly from each of the three locations using 500 tillers that were plucked at random and dissected. Results showed that in the absence of a rice crop lepidopteran stemborers and diopsid flies are able to survive on O. longistaminata, which can host the pre-imaginal populations of these insects throughout the year. Damage caused on cultivated rice varied across farmers' fields, seasons and phenological stages of the plants. With 8% the highest average extent of ‘whiteheads’ was recorded during the dry season. These results are important elements in the design of a sustainable management strategy for these insect pests.