A 2-year study in a vegetable-growing area (Tori, Hla Avamé) in Benin has shown that the invasive aphid parasitoid Lysiphlebus testaceipes (Cresson) was attacked by three species of native hyperparasitoids. On several occasions, hyperparasitoids emerged from more than 90% of the mummies collected. The dominating hyperparasitoid was Syrphophagus africanus (Gahan). Two species in the genera Pachyneuron (Pteromalidae) and Aphanogmus (Ceraphronidae), respectively, were also recorded as hyperparasitoids. Charipinae hyperparasitoids were lacking. The only aphid host present at Hla Avamé was Aphis gossypii Glover, a dominating species in vegetable agroecosystems in Benin.

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.

To determine species composition of fruit flies on six cultivated varieties of citrus (Late Valencia orange, Pineapple orange, Ovaleto, Mediterranean sweet lemon, Satsuma tangerine and Ortanique orange), a study was conducted at the Agricultural Research Centre, Kade, Ghana. Improvised Lynfield baited traps (methyl eugenol (ME) and citrus juice (CJ)) and McPhail baited traps (trimedlure (TML)) were used. Ripe infested fruits from the selected varieties were also collected and incubated. Tephritid fruit fly species from trapping were identified as Bactrocerainvadens Drew, Tsuruta & White, Bactroceracucurbitae (Coquillet), Ceratitisditissima Munro, C. anonae Graham, C. capitata (Wiedemann), C. bremii Guerin-Meneville, Dacusbivittatus (Bigot), D. punctatifrons Karsch and Trirhithrum Bezzi. A total of 35,247 fruit flies were collected from the traps, with densities of 10.38, 1.00 and 0.27 flies/trap/day for ME, CJ and TML traps, respectively. All incubated fruit varieties showed co-habitation of three different species (C. ditissima, C. anonae and B. invadens) in each of them. In addition, one Dacus vertebratus was obtained from dropped Late Valencia fruits. Moreover, three individual Fopius caudatus (Szèpligeti) parasitoids were recorded from the infested incubated fruits. Ranking of the different fruit fly species from infested incubated host fruits was as follows: C. ditissima (476) >C. anonae (74) > B. invadens (71) and D. vertebratus (1). Competitive ability among the invasive flies in their process to infest the six citrus varieties was observed. These findings could serve as a useful starting point for the development of a reliable catalogue of host diversity, fruit fly species diversity and associated natural enemy records in Ghana.

Protease inhibitors (PIs) retard growth and development and cause mortality in a range of insect pests belonging to various orders. Some transgenic plants expressing PI genes have also been effective against insect pest attack. The effects of two purified soybean PIs, i.e. trypsin inhibitor (Kunitz type; SBTI) and trypsin–chymotrypsin inhibitor (Bowman-Birk type; SBBI), were investigated on first and third instar larvae of the melon fruit fly Bactrocera cucurbitae (Coquillett) in laboratory feeding bioassays. The larval period of both the first and third instar larvae was prolonged when the larvae were treated with various concentrations of SBTI and SBBI. The total development period prolonged significantly in both the instars of larvae treated with SBTI, but in SBBI-treated larvae, the development period was delayed significantly only in the third instar larvae. A decrease in percentage pupation and adult emergence was observed in the first and third instar larvae treated with different concentrations of both SBTI and SBBI. The present studies showed that SBTI and SBBI have a potential in inhibiting the growth and development of melon fruit fly, but further detailed and molecular level studies are required before their use in transgenics.

Lepidopteran pests have occurred in eucalyptus plantations in Brazil since 1948, reaching high population levels, reducing tree growth and causing considerable losses in wood production. The control of defoliating caterpillars in eucalyptus forests is complex, mainly due to the large extent of forest plantations and tree height, necessitating the aerial application of chemical or biological insecticides. Due to this complexity, alternative control methods have been proposed, for instance biological control through the use of parasitoids. Trichospilus diatraeae Cherian & Margabandhu, 1942 is a gregarious pupal parasitoid that preferentially attacks species of the order Lepidoptera. This is the first report of T. diatraeae parasitizing pupae of the eucalyptus defoliator Euselasia eucerus Hewitson in Brazil. This parasitoid offers new perspectives for the biological control programmes of this species in eucalyptus plantations in Brazil.

Bioactivity of Melia azedarach L. was tested against diamondback moth (DBM), Plutella xylostella L. in the laboratory. The adult of DBM laid significantly lesser number (upto 71%) of eggs on the surfaces treated with methanolic extracts of M. azedarach than on those treated with solvent only. When larvae derived from above eggs were reared on fresh food, the mortality in the larval stage was upto 22.8% and that in pupal stage was upto 29.6%. The methanolic extracts also reduced feeding among the larvae significantly, when methanolic extract-treated food was offered to second instar larvae in a different set of experiment, thus, indicating an antifeedant effect.

The sweetpotato weevil (SPW), Cylas formicarius elegantulus (Summer), is the most destructive insect pest of sweetpotatoes throughout the world. Losses due to direct damage, cost of control and regulatory action conservatively exceed $7 m annually in the USA. First reported in New Orleans in 1875, SPW has infested 11 states over time. Studies in Louisiana indicate SPW control by leaving postharvest residue on the soil surface, by applying a protectant to roots going into storage, spraying plant beds, and by using cut plants. SPW quarantine has effectively reduced detections in Alabama. In North Carolina (NC), a restriction on potato growing in a small infested area isolated from commercial production has proven effective. The NC Extension Service initiated a multimedia programme on SPW. A resource notebook containing a slide set/script, coloured flyer, photograph, plastic embedded SPW stages, insect note and suggested news releases was shared during a 1-day-workshop. Television, an exhibit, oral presentations and newsletters were used to disseminate information. Promising SPW control tactics and management strategies were shared via a workshop and proceedings. Interest is high and traditional and innovative extension and regulatory activities have intensified, and the SPW remains in abeyance.

The movement of Cicadulina storeyi China (Homoptera: Cicadellidae), vector of maize streak geminivirus, within maize (Zea mays L.) fields was studied using mark, release and recapture experiments. Cicadulina storeyi, marked with fluorescent dye, were released at dusk and monitored for 14 days using yellow sticky traps placed at different distances (5–160 m) and directions from the release point. The suitability of maize growth stage for settling by C. storeyi was also investigated. Catches decreased steadily with distance from the release point and exponentially with time following the release. The mean leafhopper dispersal rate varied between 2.6 and 2.8 m/day for dry season and rainy season tests, respectively. The dispersal rate increased with distance from 1.4 m/day at 5 m to 13.6 m/day at 160 m. Wind was a major factor affecting direction of leafhopper movement with the largest proportion of C. storeyi collected downwind. Investigations on the suitability of maize growth stage for settling by C. storeyi revealed that the leafhopper preferred young plants (2–6 weeks after planting) to old ones.

Molecular clocks based on sequence change in mitochondrial (mt) DNA have been useful for placing molecular phytogenies in their historical context, thereby enhancing evolutionary insight. Nonetheless, despite their importance to phylogeographers, the methodology is controversial. Here we report on two mitochondrial clocks for the butterfly genus Danaus based on sequences from the cytochrome c oxidase subunit I (COI) and small subunit 12S rRNA (12S) genes. Both clocks are, within the context of Danaus, reliable time-keepers, mutually consistent and, respectively, in agreement with a crustacean COI clock and a molluscan 12S clock. Though we have no fossils with which directly to calibrate sequence divergence rates for Danaus, the 12S molluscan and COI crustacean clocks chosen for comparison were calibrated to radiometrically dated geomorphological events. Our results indicate that the Danaus COI clock evolves approximately four times faster than the 12S clock. Differences between rates of sequence change in terminal sister-taxa are small and likelihood ratio tests do not reject a hypothesis that evolution has been clock-like. The species Danaus chrysippus is paraphyletic and, therefore, invalid. Danaus probably split from its sister-genus Tirumala around 4.9 ± 0.3 million years ago in the early Pliocene.

The paper which covers a two season study from 1981 through 1982, major and minor cropping seasons, describes an improved methodology of sampling for stem-/pod-borer pests within an intercropping farming system involving maize, cowpea and sorghum as target crops. The authors' approach to the intercropping study has been from a holistic angle in an attempt to gain an understanding of the processes which lead to intercropping advantages under the different cropping patterns. The target pests reported were categorized into three trophic levels: firstly, specialist feeders which were Maruca testulalis (Geyer) on cowpea and Atherigona seccata (Rondani) on sorghum; secondly, the relative specialist feeders as Chilo partelhts (Swinh.), Busseola fusca (Fuller), Eldana saccharina (Wlk.) and Sesamia calamistis (Hmps.) on maize and sorghum; and thirdly the generalist feeders represented by Heliothis armigera (Hbn.) which subsists on cowpea, maize and sorghum plants respectively. The entomological data assayed included levels of borer attack on plant spatial and temporal patterns. The population of C. partellus, the dominant stem-borer within the study area was significantly regulated within the intercropping systems. The borer incidence on the maize and sorghum monocrops and the maize/sorghum dicrop was earlier (>14 days after germination, DAG) and accentuated with time, whereas intercropping of the cereals with non cereals caused significant delay (>42 DAG) in the borer colonisation and establishment within the intercropping systems. Incidence of ‘dead hearts’ caused by the borers was significantly higher (P < 0.05) within sorghum than maize stands; a factor related to the significantly higher borer attacks on late tillers which suggest that plant ventrical heights within stands influenced borer attacks. Sorghum shootfly was restricted to within 42 DAG and very much regulated by intercropping. Maruca testulalis attack on cowpea plants was confined between 30 through 60 DAG of cowpeas. Presence or absence of non-preferred cereal hosts within the cropping patterns did not seem to interfere with the M. testulalis colonisation and establishment processes within the cropping patterns. Pod damages resulting from Maruca attack were however influenced by the cropping patterns with mixed maize–cowpea–sorghum intercrop, producing significantly higher healthier pods. The paper concludes that some intercropping patterns have many advantages over monocropping patterns with respect to pest colonisation and establishment.

In a series of field experiments conducted since 1977, various cultural pest management techniques have been tested to reduce damage by the sweetpotato weevil, Cylas formicarius formicarius F. Planting rice after harvest of the weevil-infested crop does not reduce weevil damage in the ensuing sweetpotato crop if the source of weevil is present in the vicinity. Rice rotation initiated away from the weevil source, coupled with removal of the common wild-host Ipomoea sp., can reduce weevil infestation and maximize the effectiveness of carbofuran transplant dip treatment. In order to reduce the weevil source from the weevil-infested sweetpotato of the previous season, a 2-week flooding of the field soon after harvest practically eliminated the number of volunteer sweetpotato plants and the weevil. Covering the planted area with rice straw or plastic mulch reduced weevil infestation.

The spatial distribution, pupation behaviour and natural enemies of Cirina forda in the soil around its host, the sheanut tree, Vitellaria paradoxa were investigated in the field. Results indicated that final instars pupated within a 6–15 cm depth of soil located within a 90-cm radius around the host tree. Pupal density was significantly higher (P < 0.05) in soils on the north and west axes than on the south and east axes around the host tree. Pupal mortality was significantly higher within the top 5 cm and beyond a 16 cm depth of soil around the host tree. Four fungal pathogens, Trichoderma sp., Aspergillus nigers, A. flaus and Fusarium solarti isolated from diseased larvae were implicated in the significantly high larval and pupal mortality that occurred within a 90-cm radius of the host tree trunk. Percentage field parasitism of the eggs by a parasitic wasp Entedon sp. (Hymenoptera: Eulophiidae) averaged 18%. Investigation on the potential of these microorganisms for biological control of C. forda is ongoing. An integration of effective biocontrol agent(s) with a slow release insecticide with a penetration depth of 15–20 cm could form part of an integrated management plan for the pest.

Three generations of the maize stalk borer, Busseola fusca (Fuller) per year were observed in maize fields in Southern Ethiopia. However, the third generation was not important on maize. The first generation developed on young maize plants during the wet season (April–July). The second generation occurred in July and majority of larvae went into diapause from September to February while a small proportion pupated in the months of September and October and gave rise to a third generation. Pupation of the diapause larvae was observed in April.

Female moths from the first (non-diapause) generation laid significantly more eggs than those coming from a diapause generation. Longevity of these moths was also significantly longer than the diapause generation. Despite the indicated differences, female moths from both generations laid most of their eggs between the second and fifth nights after emergence. The number of eggs laid and rates of hatching declined with age of moths irrespective of generations.

Lepidopterous stem borers constitute one of the major constraints to cereal crop production in southern Africa. Chilo partellus Swinhoe, is an economically important stem borer of maize and sorghum. Current research status on C. partellus is reviewed and substantial advances in the distribution, bioecology and control strategies are discussed. Present work on the assessment of crop losses, elucidation of mechanisms of resistance, development of resistant crop cultivare, feasibility of biological control measures and the implementation of other stem borer management methods are reported. Further areas of research into the management of C. partellus are identified.

Inheritance of resistance to sorghum midge, Contarinia sorghicola Coq. was studied on a set of 21 diallel crosses involving four midge-resistant and three susceptible sorghum, Sorghum bicolor (L.) Moench cultivars under natural midge infestation at Dharwad during the late rainy season (August to November) 1983. Both additive and nonadditive genetic variances were important for midge resistance. The parents, DJ 6514 and TAM 2566, proved as better general combiners. Mean performance of the parents and their general combining ability (GCA) effects were strongly correlated. Crosses with positive specific combining ability (SCA) effects in both F1 and F2 generations had at least one parent with high GCA effects and better per se midge resistance. Midge-resistant parents, DJ 6514 and TAM 2566, with high per se resistance and GCA effects should be utilized in breeding for midge resistance.

In two study seasons, viz. summer (March to May) and “kharlf” (August to October) 1984 at Bangalore, India, populations of Aphis craccivora Koch on cowpea increased rapidly with crop growth and their peak coincided with peak pod formation. The activity of predatory coccinellids started 1 to 3 weeks after the appearance of aphids. The peak predator population more or less coincided with the peak aphid population. Highly significant positive correlations were found between weekly aphid and predator populations in the two seasons. The prey to predator ratio reached higher values 2 weeks after the incidence of the aphid, during peak pod formation stage and at the time of harvest. Amongst the predatory coccinellids, Menochilus sexmaculatus (F.) was predominant in both seasons constituting 77–88% and 83–95% of total predator population during summer and “kharif”, respectively. The study demonstrated a prey-dependent predator growth, often lagging behind that of the prey, pressing the need for alternate control methods that can be integrated into the management strategy considering the weather factors such as rainfall.

Nature of resistance against the rice leaffolder, Cnaphalocrocis medinalis (Guenee) was studied in 16 rke varieties selected on the basis of greenhouse feeding test. Resistant varieties as a group were less preferred for feeding by the larvae in a free choice test lasting 10 days. Cut leaf assay with limited choice brought out subtle differences among some of the test varieties In larval settling response. Larval preference was correlated positively with the leaf area damage noted In feeding test, per cent pupation and leaf width, and negatively with trichome density. However, oviposltton preference was neither distinct nor correlated with resistance or leaf morphology. An antibiosis component in the test varieties ARC 11128, Balam, Gorsa, ARC 7064 and Ptb 19 was distinctly manifested as reduced larval survival, lower pupation rate and pupal weights in comparison with the susceptible check. When neonate larvae were reared on the meridic diets containing the leaves of the varieties Darukasail, Balam or Ptb 12, antibiotic effects were much more pronounced in comparison with the larvae reared on the diet containing the leaves of the susceptible check TN 1.

Understanding the impact of altitude and ecological heterogeneity at a fine scale on the populations of malaria vectors is essential to better understand and anticipate eventual epidemiological changes. It could help to evaluate the spread of alleles conferring resistance to insecticides and also determine any increased entomological risk of transmission in highlands due to global warming. We used microsatellite markers to measure the effect of altitude and distance on the population genetic structure of Anopheles funestus and Anopheles gambiae s.s. in the Muheza area in the north-eastern part of Tanzania (seven loci for each species). Our analysis reveals strong gene flow between the different populations of An. funestus from lowland and highland areas, as well as between populations of An. gambiae sampled in the lowland area. These results highlight for An. funestus the absence of a significant spatial subpopulation structuring at small-scale, despite a steep ecological and altitudinal cline. Our findings are important in the understanding of the possible spread of alleles conferring insecticide resistance through mosquito populations. Such information is essential for vector control programmes to avoid the rapid spread and fixation of resistance in mosquito populations.

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.

The oviposition behaviour of the cowpea weevils, Callosobruchus rhodesianus (Pic.) and Callosobruchus maculatus (F.) on clean and egg-laden adzuki beans was examined in choice and no-choice experiments. The oviposition rate of C. maculatus was greater than C. rhodesianus in both experiments. Both weevil species were able to distinguish between clean and egg-laden beans. Discrimination by both species was greater against seeds with 12 eggs than with 6, regardless of which species had previously laid eggs. There was a weak indication that the presence of C. maculatus eggs at high densities might reduce the oviposition rate of C. rhodesianus.