International Journal of Tropical Insect Science

The purpose of this study was to investigate nutritional and phytochemical composition of Henicus whellani Chopard, a seasonally occurring ground-dwelling cricket consumed in south-eastern Zimbabwe. Insects were sampled from four quadrants (approximately 100 m2) in one representative site (approximately 3000 m2) in Bikita District, and were hand-picked or dug out from burrows in a manner similar to traditional insect-harvesting practices. Proximate composition using whole-dried insects and bioactive components using dried pulverized material were analysed using standard procedures. The proportional nutrient composition was 53.6% crude protein, 4.3% fat, 13.4% ash, 10.6% crude fibre, 4.0% carbohydrate and 268.3 kcal/100 g energy. Phenolics, tannins, alkaloids, cyanogenic glycosides, oxalates, saponins and flavonoids were present in the extracts of insects. The quantities of saponins (53.3 mg/g) and alkaloids (52.3 mg/g) were higher than those of other phytochemicals, with the quantity of tannins (0.168 mg/g) being the lowest. Radical-scavenging capacity determined using di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium (or 2,2-diphenylpicrylhydrazyl) and methanol extracts was 42%, which is lower than those of the standards. This study shows that H. whellani provides potential nutritional benefits in terms of protein, fibre and flavonoid contents. The relatively high ash content compared with that from other edible insects indicates a rich source of minerals such as calcium, iron, magnesium, phosphorus and potassium. However, the presence of saponins, oxalates and tannins could be a limitation and requires further studies. There is a need to evaluate the bioaccessibility of the nutrients and the safety of bioactive compounds in relation to human consumption.

The papers presented in this special issue are focused on developing and validating procedures for artificial rearing of selected fruit fly species of economic importance for use in area-wide integrated pest programmes with a sterile insect technique (SIT) component. They are the result of a 5-year coordinated research project (CRP) on ‘Development and Improvement of Rearing Techniques for Anastrepha and Bactrocera Fruit Flies’ that was coordinated by the Joint FAO/IAEA Programme of Nuclear Techniques in Food and Agriculture. Twenty-two CRP participants from 18 countries worked on both basic and advanced rearing procedures of different fruit fly species to overcome technical bottlenecks and to develop appropriate and relevant procedures for use in mass-rearing facilities. A variety of studies were undertaken for three groups of tephritid species: (1) those for which mass-rearing for SIT application was available, but further refinement would be useful; (2) those for which mass-rearing for SIT application was under development in the laboratory, but that had not reached mass-rearing status; and (3) those for which research to develop colonization and rearing methods was needed. Many of the protocols developed or improved during the CRP have been transferred to the different fruit fly mass-rearing facilities worldwide.

Iris yellow spot virus (IYSV) vectored by Thrips tabaci threatens profitable onion production in eastern Africa. Host plant resistance is considered to be the first line of defence against insect-transmitted virus diseases. Hence, information on resistance to IYSV and T. tabaci among common onion cultivars in Kenya is crucial for the development of integrated pest management strategies. This study evaluated the resistance to thrips and IYSV among widely grown onion cultivars in Kenya, viz. Red Pinoy, Red Creole, Bombay Red, Green Bunching and Texas Grano, over two growing seasons. Straw-coloured, diamond-shaped necrotic lesions typical of IYSV infection were observed 2 weeks after transplantation. Observations on thrips numbers per plant, IYSV disease incidence and severity, and virus intensity were undertaken to assess the resistance. Varieties differed significantly with respect to both IYSV disease incidence and thrips numbers per plant from fourth week to physiological maturity. Red Pinoy, Green Bunching and Red Creole were highly susceptible to the virus and thrips, while Texas Grano and Bombay Red were moderately resistant. There were significant differences among the varieties with regard to IYSV intensity, with the highest and the least virus intensity positively correlated with disease severity being recorded in Red Pinoy and Texas Grano, respectively. Among the varieties, Texas Grano produced the highest yield in both seasons, while Red Pinoy produced the least. Hence, Texas Grano and Bombay Red could be recommended as moderately resistant cultivars to thrips and IYSV to be grown in Kenya for markets where pungency is not preferred and preferred, respectively. Regions with high levels of thrips population and IYSV infestation are not suitable for the cultivation of Red Pinoy.

In the present study, body length and dispersal ability were examined in carabid beetles (Coleoptera: Carabidae) sampled in the Peruvian Andes along two altitudinal gradients: old-growth forest and anthropogenically disturbed region. Dispersal ability was estimated by the flight-wing condition (i.e. macropterous or brachypterous) and the cuticular length of the flight muscle (medial length of the metasternum). The relationship between body length and altitude for combined gradients varied by tribe; all possible relationships were found: positive; negative; no relationship. At the family level, a negative relationship between altitude and insect body length was found; this was predicted because of a decrease in the diversity of resources, habitat area and primary productivity, and the increase in the unfavourable environment observed at high altitudes. Flight muscle length was also highly variable among tribes; however, for combined gradients, a negative correlation with altitude was found at the family level. Some tribes were either completely macropterous or brachypterous, but at the family level, the percentage of brachyptery increased with altitude. We suggest two hypotheses that may explain the increased incidence of flightlessness observed with increasing altitude: constraints of energy use and reduced need for dispersal potential. At the family level, carabid beetles tended to have a greater body length and decreased brachyptery in disturbed regions compared with old-growth forests. Increased dispersal ability was expected because of the need to find a suitable habitat in disturbed areas. Observed relationships may depend upon which tribes are examined and whether the forest on an altitudinal gradient has been disturbed.

Pest control strategies against Helicoverpa armigera (Hübner) using protease inhibitors have relied on the gut protease profile of the later larval stages of the insect, with serine proteases being considered predominant. Little is known about the gut protease profile of early larval instars. Therefore, the aim of the present study was to detect the levels of gut protease activities in the third-, fourth-, fifth- and late fifth-instar larvae of H. armigera reared on an artificial diet using specific substrates and inhibitors. The analysis of the gut protease profiles of different instars revealed different levels of protease activities at different instar stages. Significant variations were also observed in the specific activities of trypsin, chymotrypsin, cysteine protease, carboxypeptidase-A and aminopeptidase-N across the instars. In general, the activities of the proteases increased from the third to the fifth instar and then decreased at the onset of pupation in the late fifth instar. Proteolytic activity was optimal at pH 12 for gut extracts from the third-, fourth- and fifth-instar larvae. Bioassays with phenylmethylsulphonyl fluoride (PMSF), a serine–cysteine protease inhibitor, revealed high mortality, and that with sodium ethylenediaminetetraacetic acid (EDTA-Na), a metalloprotease inhibitor, also showed retarded larval growth. The inhibition induced by 0.05% PMSF and 0.05% EDTA-Na in combination was similar to that induced by 0.1% PMSF alone.

The egg parasitoid Telenomus busseolae Gahan is the most important parasitoid of sugarcane pink borers and plays an important role in the suppression of their populations in Iran. To understand the efficiency of T. busseolae parasitizing Sesamia cretica Lederer, in this study, the functional response of the parasitoid was investigated at different temperatures (20, 25, 30 and 35 °C). The results of logistic regression indicated a type III functional response at all the temperatures. Roger's random parasite equation fitted the observed data at 30 and 35 °C, but Holling's disc equation fitted the data better at 20 and 25 °C. The attack rate of T. busseolae ranged from 0.0036 to 0.2148, 0.00017 to 0.1031, 0.0049 to 0.2952 and 0.0006 to 0.0382 per h, and the estimated handling time was 0.80, 0.48, 0.32 and 0.13 h at 20, 25, 30 and 35 °C, respectively.

Maruca vitrata Fabricius (legume pod borer, LPB), the most serious economic pest of legume crops in the tropics, is primarily controlled by chemical pesticide application with serious consequences for the ecosystem and human health. In this study, various concentrations of three commercial biopesticides, NeemBaan®, Bactospeine® (Bacillusthuringiensis (Bt) subsp. kurstaki) and Florbac® (Btaizawai), were tested either in the field or laboratory or in both conditions. In the laboratory experiments, different concentrations of NeemBaan® exhibited significant effects on the mortality of all the tested larval instars and a mortality rate of over 80% was recorded at a dose of 3000 ppm. Bactospeine® was found to be more effective against M. vitrata than Florbac®. Bactospeine® applied at a lower dose of 500 ppm caused 100% mortality in the first-instar and second-instar larvae; however, at the same dose, Florbac® caused mortality of only 26.67% (first instar) and 20% (second instar). In the field experiments, a higher dose of NeemBaan® (6000 ppm) significantly reduced pod damage to approximately 20% in both the first and second cropping seasons. In conclusion, neem- and Bt-based biopesticide products have insecticidal potential to be used in an integrated pest management strategy for controlling M. vitrata in Thailand.

The objective of this study was to determine whether a generic diet could be developed for three species of Anastrepha: A. ludens, A. obliqua and A.serpentina. Laboratory and mass-rearing tests to assess the suitability of the A. ludens (Loew) (ALU) diet, normally used for rearing A. ludens, indicated that it was also suitable for rearing A. obliqua (Macquart) and A. serpentina (Wiedemann). Therefore, this diet appeared to be a suitable generic diet for the three species based on quality control parameters. In comparison with those observed when rearing larvae on the commonly used A. obliqua diet, the number of A. obliqua larvae recovered per g diet increased from 4.2 to 5.1, larval weight increased from 17 to 18.2 mg, pupation after 24 h from 89.3 to 96.9%, adult emergence from 91.5 to 93.7% and flight ability (% of fliers) from 86.1 to 90.4% when reared on the ALU diet. Usually, A. serpentina larvae are reared on the A. serpentina diet, but when reared on the ALU diet, larval recovery increased from 61.8 to 69.8%, number of larvae recovered per g diet from 3.7 to 4.4, larval weight from 21.7 to 23.8 mg and flight ability from 64.6 to 70.2%. These results show that the nutritional requirements of the three Anastrepha species are similar. The use of a generic diet for rearing the three species requires only one line to prepare the diet, reducing time and labour costs.

The tea (Camellia sinensis (L.) Kuntze) industry is the backbone of the agroeconomy of the North Bengal region located at the foothills of the Himalayas in North-East (NE) India. This region accounts for about 25% of the total tea production in India. The tea mosquito bug, Helopeltis theivora Waterhouse, is one of the most devastating sucking pests of tea in this region. Various kinds of synthetic insecticides are continuously sprayed to control this bug. The lynx spider Oxyopes javanus Thorell has been found to remain associated with tea plants and feed on H. theivora. The present study investigated the predation potential and efficacy of the O. javanus spider against one of its most common prey species, H. theivora. In the laboratory, with an increase in H. theivora density, the predation rate of both male and female O. javanus increased. Per capita predation rates exhibited by male and female O. javanus per day against adult H. theivora were 3.67 ± 1.52 and 11.67 ± 1.53 (mean ± standard deviation), respectively. At a reasonably small prey density, the prey consumption rate was highest, reaching up to 100%, indicating that the spider predator has the potential to eliminate smaller populations of the pest. The predation effectiveness calculated using Holling's disc equation was 6.08 and 356.58 for male and female O. javanus, respectively. The prey handling time was 0.138 day for male O. javanus and 0.012 day for female O. javanus. Female O. javanus exhibited about fivefold higher searching efficacy than male O. javanus. It appears that the conservation or augmentation of O. javanus in the tea ecosystem can provide effective biological management of the major tea pest, H. theivora, in sub-Himalayan foothills and plains of NE India.

Leptocybe invasa Fisher & La Salle was first recorded several years ago in Sri Lanka in the Eucalyptus camaldulensis Dehnh. plantation in Maragamuwa. Recent observations have revealed a decrease in gall infestation, and the present study was conducted to investigate the biology of L. invasa, its damage to E. camaldulensis and the presence of any natural enemies. Life-cycle duration, developmental stages and activity patterns were investigated. The abundance of gall wasps was monitored using sticky traps. Damage caused to different stages of coppices was also assessed. The damage index was calculated from the percentage of leaves affected in each coppice. Insects were reared from the galled coppices, brought to the laboratory, identified and counted. The life-cycle duration of L. invasa was 132 days on average. The damage index was low throughout the study period. Leptocybe invasa attacked the coppices of E. camaldulensis when they turned green in colour; damage increased as the coppices developed until maturity. Four species of parasitoid wasps were reared from the leaf and shoot galls. Megastigmus sp. was the most abundant parasitoid; the mean percentage of parasitization was 67.00 ± 8.00. Natural enemies of L. invasa might have contributed to the decrease in gall infestation observed recently in the coppices of E. camaldulensis in the study site.

The present study was undertaken to determine the nutritional value of the fifth instar larva of Bombyx mori, locally referred to as ‘Niang ryndai’, which is a popular edible silkworm among the local inhabitants of East and West Khasi Hills and Ri-Bhoi district. Larvae were collected from the Iewduh market of Shillong in the months of October and November as these larvae are available during these months. The composition of lipids, amino acids and the fat-soluble vitamins A and E in the frozen and oven-dried samples of B. mori was estimated and compared with that of conventional food items. The detection of the fatty acids eicosapentaenoic acid and docosahexaenoic acid in the larva indicates its potential to support a healthy cardiovascular function. Because of their use for the production of silk yarn, silkworms have economic potential for the people of the State and north-eastern region of India. Increased appreciation of this insect as an alternative and cheap source of nutrition would contribute to the socio-economic development of the indigenous people.

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.

In this study, the effects of relaxed mass-rearing conditions on Anastrepha obliqua (Macquart) production and quality were determined. Relaxed rearing conditions were defined by a reduction in the density of adult flies, from 80,000 to 60,000 flies per mass-rearing cage, and a reduction in the density of larvae, from 6.18 to 3.70 eggs/g of diet. In the parental generation, flies reared under relaxed conditions exhibited significant and a few non-significant changes – increased daily fecundity from 37 to 42 eggs per female, larval recovery from 80 to 91%, larval weight from 18.5 to 19.5 mg, pupation at 24 h from 92 to 96%, pupal weight from 13.5 to 14.3 mg, adult emergence from 92 to 94% and percentage of fliers from 89 to 90%. During the following 12 generations, non-significant differences were observed, but comparisons between relaxed and non-relaxed colonies were significant. The sexual competitiveness of males produced under relaxed conditions was similar to that of wild males.

Vegetable legumes are important crops in tropical agriculture, but they are susceptible to a substantial number of arthropod pests and diseases. Using farm-level survey data for 240 farm households growing yard-long bean (Vigna unguiculata subsp. sesquipedalis) in Thailand and Vietnam, this study shows that the farmers' main problem is the legume pod borer (Maruca vitrata). Farmers rely exclusively on the use of synthetic pesticides to manage this pest, and no other control methods are generally applied. Small cultivated areas for growing yard-long bean (particularly in Vietnam), a high level of satisfaction with the use of pesticides and a lack of market demand for pesticide-free produce are formidable challenges to the introduction of integrated pest management (IPM). It is important to ensure that IPM methods, if adopted, do not reduce profits and that farmers are allowed to experiment with these methods while raising awareness in the general population about the risk resulting from pesticide exposure.

In the present study, the susceptibility of different developmental stages (eggs, larvae, protonymphs, deutonymphs and adults) of Tetranychus urticae Koch to the entomopathogenic fungi Beauveria bassiana (Balsamo-Crivelli) Vuillemin and Metarhizium anisopliae (Metchnikoff) Sorokin was evaluated in the laboratory. At each developmental stage, four concentrations (3 × 105, 1 × 106, 3 × 106 and 1 × 107 conidia/ml) of both fungi were sprayed. Egg viability and motile-stage mortality varied among the fungal isolates and conidial concentrations. The highest conidial concentration (1 × 107 conidia/ml) significantly reduced the viability of eggs and increased the mortality of motile stages. However, deutonymphs and adults were more susceptible to fungal infection than larvae and protonymphs. The lethal concentration values to 50% (LC50) and 90% mortality (LC90) varied with the fungal isolates and developmental stages. The results show the prospects of B. bassiana and M. anisopliae for the control of T. urticae.

In this study, the effect of exposing entomopathogenic bacteria isolated from macerated termite cadavers to varying intensities of a magnetic field for different periods of time on their pathogenic potential was examined; pathogenicity tests were carried out for each of the bacterial species. Two of the bacteria, Bacillus subtilis (Ehrenberg) Cohn and Serratia marcescens Bizio, were able to induce morbid effects on termites and both were re-isolated from the resulting cadavers. Reinfection using different concentrations of both bacteria was carried out on termites to determine the minimum lethal concentration required for pathogenicity. Bacillus subtilis was able to degenerate the termites at concentration values of 108 colony-forming units (cfu)/ml and S. marcescens at 107cfu/ml. Both bacteria were then exposed to magnetic fields of different intensities for different periods of time, after which they were used for reinfection of healthy termites. Post-infection study after the exposure of termites to magnetic field-treated bacterial cells revealed no reduction in the entomopathogenic potency of S. marcescens. As the extensive use of chemicals to control insect pests has been found to have detrimental effects on people and the environment, there is a pressing need to discover and develop new entomopathogens to control these insects biologically. Therefore, bacteria discovered in this study to have entomopathogenic potency against termites may be further studied and formulated into either powdery forms or suspensions to be applied to infested wood or wood products.

In the present study, the synergistic effects of Beauveria bassiana (Bals.-Criv. Vuill.) (isolate Bb11) and Bacillus thuringiensis var. kurstaki (Berliner) with neem oil were evaluated in three agroecological zones in Bénin. Four bioinsecticide treatments (neem oil, neem oil and B. bassiana used separately for different target pests, neem oil mixed with B. bassiana and neem oil mixed with B. thuringiensis) were compared with a calendar-based treatment using synthetic insecticides and a control without insecticides. The bioinsecticide treatments were less effective than the calendar-based treatment at controlling cotton pests. There was no difference in yields and the number of damaged bolls in plots under treatments with the four bioinsecticide formulations, suggesting an absence of synergy between neem oil and B. bassiana and neem oil and B. thuringiensis. The numbers of natural enemies in all the bioinsecticide treatment plots and the control plots were similar and higher than those in the calendar-based treatment plots. The highest yield and profitability were obtained with the calendar-based treatment. Screening the compatibility of plant-based products and biopesticides through bioassays is essential for a successful application of their combinations in any integrated pest management strategy.

The homopteran bug Cofanaspectra (Distant), also known as the white leafhopper, is abundant in rice-growing areas of India (West Bengal, Northeast and southern states) and considered as a minor pest of paddy. The proportion of Cofanaspectra and the endoparasitoid Halictophagus australensis Perkins varied between months and demonstrated peak abundance during March to May and October to December, which corresponded with the rice cropping periods boro (winter crop) and aman (monsoon crop), respectively. There was a negative correlation between the influence of environmental factors (air temperature, rainfall and relative humidity) and the abundance of normal and parasitized C. spectra. The proportion of parasitization by H. australensis varied with the relative abundance of C. spectra. The effect of stylopization on C.spectra by the Strepsiptera may be one of the factors attributable to the suppression of the population levels of the paddy pest.

In this study, laboratory and field cage experiments were conducted to assess the performance of sterile mass-reared Mexican fruit fly Anastrepha ludens (Loew) irradiated at various doses. In small laboratory cages, the radiation dose was found to have no effect on adult emergence, flying adults or survival at 25 days. In field cages, non-irradiated males and males irradiated at 20 and 40 Gy were found to exhibit greater mating propensity than males irradiated at 60 and 80 Gy. In large field cages in competition with wild males, cohorts of flies (male and female) irradiated at the low dose of 40 Gy and wild non-irradiated flies mated randomly, while flies irradiated at the high standard dose of 80 Gy mated assortatively. Irrespective of the radiation dose, laboratory flies courted and attempted copulation significantly earlier in the day than wild flies. In large field cages, cohorts of flies irradiated at low doses, e.g. 40 Gy, tended to induce greater sterility into a cohort of wild flies than those irradiated at 80 Gy, but the difference was not significant. Our results suggest that lowering the radiation dose currently applied to mass-reared flies in the Mexican fruit fly eradication campaign would substantially improve male mating performance. This could result in greater sterility induction without posing a risk in areas where target pest populations naturally prevail and are under suppression during the early stages of eradication programmes.