Termite workers, Macrotermes subhyalinus (Rambur), produced two cellulase-free xylanases, namely Xyl A and Xyl B. DEAE-Sepharose CL-6B, Sephacryl S-200 HR, CM-Sepharose CL-6B and Phenyl-Sepharose CL-4B chromatographies purified these enzymes. They exhibited molecular masses of 63–66.1 (Xyl A) and 60.7–62.4 (Xyl B) kDa. Both enzymes appeared to be endo-xylanases, which produced oligomers of xylose from xylan and did not hydrolyse them to xylose. They had different optimum pH (pH 4.6–5.0 for Xyl A and pH 5.0 for Xyl B) and different optimum temperatures (60 °C for Xyl A and 55 °C for Xyl B). However, they had the same pH stability (4.0–5.6). Both enzymes were stable at 50 °C for more than 4 h. At a pH ranging from 4.6–5.0 and 60 °C, Xyl A and Xyl B possessed the half-life of 115 and 60 min, respectively. The xylanase activities were stimulated by Na+, Mn2+ and dithiol-reducing agents and were sensitive to Cu2+ and detergent agents. Their enzymatic activity was slightly reduced by the presence of urea at 1% (w/v) concentration. The two enzymes could be used in the presence of organic solvents such as acetone (up to 10% v/v) without loss of activity.

Rearing temperature has an important influence on the efficiency of food utilization by larvae of the silkworm Bombyx mori L. To assess food intake and utilization efficiency in B. mori reared at different temperature combinations, larvae of Pure Mysore race were fed ad libitum on M5 mulberry leaves and reared at four different constant temperatures, viz. 26, 28, 30 and 32°C during instars I to III and combinations of these temperatures during later instars (IV and V). The larvae reared at 28°C (T2) when young and combinations of temperatures 26–26, 28–26, 30–26 and 32–26°C later were taken as controls. The amount of dry food consumed was significantly higher, but a significant decrease in conversion efficiencies (K1 and K2) was noticed in silkworms reared young at 28°C than at the other temperatures. However, the dry food consumed, food converted, assimilation rate and assimilation efficiency increased with the increasing temperature, and larval duration and conversion efficiency decreased significantly with the rise in temperature during both young- and late-instar rearing. Comparisons between these two ages with regard to food utilization parameters were carried out and the factors responsible for these changes are discussed.

The damage potential of the spider mite Tetranychus ludeni Zacher was studied on 20–65-day-old seedlings of four eggplant Solanum melongena varieties: Madurai (MDU1), Coimbatore (CO1), Annamalai and Panruti at introduction levels of 2, 5, 10 and 15 mites/leaf. The average seedling mortality among varieties was lowest at the introduction level of two mites and maximum at the introduction level of 15 mites/leaf. The overall seedling mortality was 23% when the four levels of mite population were introduced on 20-day-old seedlings, and only 14% on 30-day-old seedlings. Among the different varieties, the MDU1 seedlings recorded higher mortality (1.6%) and Panruti the lowest (0.3%). The percentage losses in total plant height, number of leaves, number of flowers and fruits and fruit weight due to mite attack were highest (37–50%) in MDU1 and lowest (7–11%) in the variety Panruti. The other two varieties CO1 and Annamalai were found to be intermediate between Panruti and MDU1. The inoculated mites at different levels multiplied greatly on the variety MDU1 followed by CO1, Annamalai and Panruti. The extent of damage was higher in 35-day-old plants, when mites were introduced on 35- and 65-day-old seedlings. Therefore, the variety Panruti is recommended for cultivation in the study area in view of its resistance to T. ludeni.

An inventory of arthropods was carried out at locations in the desert area of Touggourt, southeast Algeria. Samples were collected from two diverse habitats, a palm grove (agricultural habitat) and dunes (natural habitat). Using the Barber pitfall trap, 1100 specimens, divided into four classes, 15 orders, 44 families and 99 species were obtained. In the palm grove, 660 arthropods were trapped, belonging to four classes and 12 orders. Of these four classes, Insecta dominated followed by Crustacea, Arachnida and Entognata. Insecta accounted for 59.49% of the total capture and was dominated by two orders: Hymenoptera (41.81%) and Amphipoda (34.55%). In the Hymenoptera, Cataglyphis sp. was the most abundant (38.2%), followed by Pheidole pallidula (2.3%). In the dunes, 440 individuals were trapped. Insecta was the most abundant (90.69%), and Crustacea and Arachnida were scarce. Of the dominance by insects, Hymenoptera was most abundant (68.15%), and within that order, Cataglyphis bombycina (35.5%) was the most abundant followed by Monomorium subopacum (8.9%). In the palm grove, 42 species were recorded, compared to 57 in the dunes. The Shannon–Weaver index and equitability varied in both stations. In the palm grove, the diversity was 2.6, and the equitability was 0.5. By contrast in the dunes, the diversity was equal to 4 and the Equitability equal to 0.7. The differences in vegetation between the two sites reflect the differences in species diversity.

Inhibition of okra growth in response to flea beetle injury was studied in both the screen house and field. In the screen house or field, 0, 5, 10, 20, 30 and 40 pairs of Podagrica uniforma (Jacoby), representing six treatments, were introduced into different cages containing five 3-week-old okra plants, replicated three times. Data were collected on the number of flowers and branches, plant height, stem girth and functional leaf area in both experiments. With increasing densities of P. uniforma, days to 50% flowering and fruit initiation were prolonged by 1–13 days and 2–15 days, respectively. The beetle did not exhibit florivory but caused distortion of okra fruits, i.e. bending of fruit tips at the point of flea beetle-induced damage. From the 20-pair level (eight beetles per plant), there were significant reductions in plant height (up to 50%) and stem girth (up to 43%) in both the screen house and field. The number of distorted fruits showing bent tips was significantly higher relative to the control from the 5-pair level, and was more than 90% at the 40-pair level. Regression analysis indicated that plant height was a linear function of flea beetle population. Third-degree polynomial models best described the relationship between insect density and the number of bent fruits. χ2 analysis showed that these models derived from the screen house data were not significantly different from the field data models.

Investigations into the vectorial capacity of wild caught Phlebotomus pedifer by feeding them on volunteer patients were carried out inside one of the caves of Mt Elgon. Female P. pedifer were fed on lesions of cutaneous leishmaniasis patients to determine the route of infection and infection rates in the flies and hence their vectorial capacity. The flies were kept for periods of 3–8 and 9–13 days before dissections were carried out. The results indicate that the longer period (9–13 days) yielded a higher infection rate. All parasite isolations from flies which were injected subcutaneously caused cutaneous lesions in the nose of the experimental hamsters. All infections were concentrated in the anterior stations of the gut of the experimental sandfly species P. pedifer.

This paper briefly discusses insect pest responses in mixed crop stands, their peculiarities and possible crop protection advantages. Results on the effects of a bean–oat diculture on the movements and feeding activity of the adult pea leaf weevil, Sitona lineatus L. are presented and discussed. Mixtures of these crops were found to significantly reduce the amount of notching of the bean leaflets by the weevil and weevil relative populations are compared to the sole bean crops, and to increase emigration from the more diverse plots.

Ovlposition and development of the ichneumonid Trathala flavoorbitalis (Cam.) a parasitoid of the brinjal shoot and fruit borer, Leucinodes orbonalis Guen., was investigated. The parasitoid responded to a host larva by inserting its ovipositor (stinging) into the larva, whichever instar (first to fifth) it was. All the first and about 50% of the second instars that were stung and oviposited in, were mutilated and died as a result. Successful parasitization and parasitoid development up to adult emergence occurred in 53% of the third, 57% of the fourth and 41% of the fifth instar host larvae. When given a choice of instars for oviposition, the parasitoid avoided all first instar and most second instar larvae, while third to fifth instars were equally accepted. The total developmental time of the parasitoid was much the same (about 20–24 days) whichever larval instar (second to fifth) was parasitized. The parasitized host at pupation contained different developmental stages of the parasitoid, differing in this respect from most other species of larval-pupal parasitoids.

Semi-quantitative biochemical analyses by paper chromatography–densitometry and pH determinations of honeydew excreted by Nephotettix virescens (Distant) feeding on rice plants revealed higher free amino compound and sugar concentrations in honeydew excreted on the susceptible variety TN1 than on resistant ASD7 or P203. Furthermore, sap exudates from these three varieties, presumed to be mainly from xylem, as well as honeydew excreted on the resistant varieties were acidic, whereas honeydew from TN1 was predominantly basic. Since phloem sap in herbaceous plants usually gives an alkaline reaction whereas xylem sap is acidic, and because the former contains much higher concentrations of sugars and free amino acids than the latter, the biochemical evidence strongly suggests that Nephotettix virescens is primarily a xylem feeder on the resistant plants tested, but feeds predominantly on phloem sap in susceptible TNI.

Nineteen accessions from seven Lycopersicon species were bioassayed for their resistance to Heliothis armigera (Hübner) (Lepidoptera: Noctuidae) in laboratory tests at 29 ± 1°C and 65 ± 2% r.h. Data on larval developmental duration (days), survival (%) and pupal weights (mg) revealed that maximum resistance to H. armigera occurred in accessions of L. hirsutum f. glabratum and L. hirsutum. When the larvae were fed on the foliage of PI 134417 and PI 126449 accessions (L. hirsutum f. glabratum), the developmental time was longer, and survival rate and pupal weights were lower than when the larvae were fed on cultivars of L. esculentum. Rearing of H. armigera larvae through third instar is sufficient to evaluate the resistance of wild tomato foliage since most of the larval mortality occurs prior to this stage. Accessions of L. peruvianum, L. chilense, L. cheesmanii and L. pimpinellifolium proved less resistant than L. hirsutum f. glabratum and L. hirsutum but significantly more resistant than L. esculentum. Thus, among the various Lycopersicon spp. bioassayed, accessions of L. hirsutum f. glabratum seem to have most potential for breeding H. armigera resistant cultivars.

Callosobruchus maculatus (Coleoptera: Bruchidae), commonly known as the cowpea seed beetle, is the most important pest of stored cowpea in tropical Africa. In rural area where preservation techniques and facilities are limited, it causes post-harvest weight and quality losses. The importance of damages which can reach 100% in a few months justifies the development of effective and appropriate control methods in the villages. All these control methods and their applications are discussed in this paper. Chemical control is inappropriate at farm level, because of its cost and hazards. The many studies conducted on varietal resistance have enabled identification of varieties that are more or less resistant to this pest; however, the varieties are often of little interest from the agronomic point of view. The incorporation of that resistance in cultivated varieties is in progress. The physical control methods are inadequate because their application requires equipment and technical knowledge which are not found in rural areas. Biological control is an attractive alternative but is still at an experimental stage. All these limitations support promotion of traditional control methods. Among them, the use of inert substances as well as indigenous plants or their by-products have given, in many cases, a satisfactory control of C. maculatus.

Studies on the peridomestic resting sites of Glossina f. fuscipes were carried out at night and during the day. Flies were caught, marked with fluorescent powders and then released in coffee and banana plantations, Lantana camara thicket and adjoining forest habitat and the potential resting sites subsequently searched.

Leaves, twigs and branches between 0.5 and 1 cm in dia. are the preferred resting sites of G.f. fuscipes. The resting heights ranged from 0 to 3.66 m. Results are discussed in relation to tsetse control in the Busoga sleeping sickness epidemic area.

In choice tests with well-established natural trails and glandular extract trails, allopatric populations of Trinervitermes bettonianus Sjöst followed alien colonies' trails with the same degree of motivation as their own trails. The five Trinervitermes spp. tested readily followed each other's trail. Chromatographs of natural trail extracts showed that the main component of the T. bettonianus trail pheromone also occurs in trails of T. gratiosus (and presumably in the other species); this would account for the observed cross-following of trails among these species.

The effects of temperature on the life history of Spilostethus pandurus (Scopoli) were examined by determining the different developmental and reproductive parameters with respect to days of hatching, oviposition, and adult emergence of insects reared in field cages at Giza, Egypt. Hatching, oviposition, and adult emergence continued all year round; the average daily temperature in the coldest month (January) seemed to be above developmental thresholds for different stages. This lygaeid completed six overlapping generations in 1 year. The basic population parameters, i.e. net reproductive rate (R0), gross reproductive rate (GRR), instantaneous rate of natural increase (r), finite rate of natural increase (λ), and mean generation time (T) exhibited a more or less cyclic pattern in successive generations. The highest value of r (rmax) was considered as the intrinsic rate of natural increase of this species.

Ground spraying trials with different dosages of deltamethrin wettable poweder (NRDC 161) were carried out against G. palpalis (s.l.), vector of sleeping sickness, in January and November 1981 in the Bouaflé human trypanosomiasis focus, Ivory Coast. Three dosages have been tested: 60 g of active ingredient (a.i.) per ha at a concentration of 0.08% in January; and 20 and 12 g of active ingredient per ha in November at 0.027 and 0.016%, respectively. Each dosage has been applied once as a residual spray; spraying apparatus used was the atomiser Solo Port 423. The knock-down and short-term effects of the insecticide were very satisfactory: 90–98% reduction in apparent density of the vector was obtained during the first 2 months after treatment with all the three dosages applied. In the long term, 2–4 months after spraying, more than 95% reduction in apparent density of G. palpalis (s.l.) was achieved even with the lowest dosage of 12 g (a.i.)/ha. The highest dosage of 60 g (a.i.)/ha does not seem to increase significantly the persistence of the insecticide nor the mortality rate of the vector in the study area. In order to reduce the cost of a tsetse control programme and also to minimise insecticide impact on non-target organisms, it is therefore recommended that deltamethrin w.p. be applied at the lower dosage of 12 g (a.i.)/ha in residual ground spraying.

Genetic analyses were carried out to determine inheritance of resistance, heterotic effects and reciprocal effects for resistance to the spotted stem borer, Chilo partellus in three maize crosses. Resistance was found dominant over susceptibility. Highly significant heterosis was detected for percentage dead hearts. Both additive and nonadditive gene effects were important in the inheritance of resistance to C. partellus in all crosses. Additive gene effects were highly significant for all the three resistance parameters: leaf-feeding, dead hearts and stem tunnelling. However, a high magnitude of nonadditive (dominance and epistatic) gene effects were detected for dead hearts. No cytoplasmic effects were detected in reciprocal crosses between resistant and susceptible maize lines, suggesting that the resistance to C. partellus is conferred only by nuclear genes. Recurrent selection methods should be used to accumulate alleles for resistance. Resistant F1 hybrids could be developed between resistant and susceptible lines in reciprocal combinations.

In this study, the effects of yeast protein hydrolysate (YPH): sucrose proportions in the adult diet of the Ethiopian fruit fly Dacus ciliatus Loew on survival, pupal production, and endogenous lipid and protein contents were investigated. Small populations of the fly were fed diets containing various proportions of YPH and sucrose under low-humidity and high-humidity conditions. The YPH: sucrose proportions ranged from 20 to 50%. We monitored the patterns of survival, pupal production, and individual endogenous protein and lipid loads (only under high-humidity conditions) in flies maintained on various adult diets. The survival patterns of both males and females under high-humidity conditions were inversely proportional to the proportion of YPH in the diet. Mortality of some adult flies was related to the stickiness of the highly hygroscopic adult food mix. By contrast, the survival patterns of males and females maintained under low-humidity conditions were directly proportional to the proportion of YPH in the diet. Apparently, there was no effect of diet type on the number of pupae produced; on the sucrose-only diet, flies produced significantly fewer pupae. Protein content in the flies increased significantly as the proportion of protein in the diet increased, but lipid content was clearly not related to food constitution. Based on these results and recent evidence from studies in other fruit fly species, we concluded that a large amount of protein is deleterious to the fruit flies. Workers in rearing facilities should investigate and tailor different food-delivery systems, e.g. separate dishes for carbohydrates and the food mix, and reduce the amount of YPH used in industrial adult diets.

Use of host plant resistance for the management of the banana weevil Cosmopolites sordidus (Germar) requires development of rapid cultivar screening methods. A previous study showed prolonged development of larvae feeding on excised plant material of resistant cultivars and suggested partial breakdown of resistance in such plant material. In the current study, development and survivorship of larvae feeding on potted plants of banana cultivars with differing levels of resistance were evaluated. Weevil performance was evaluated on one susceptible (Atwalira), one intermediate (Kabula) and four resistant cultivars (FHIA 17, Kayinja, Kisubi and Yangambi Km5). Differences in development of larvae feeding on the susceptible Atwalira and intermediate/resistant cultivars became apparent at 15 days after infestation of plants. Differences in survivorship of larvae feeding on different cultivars were not statistically significant. Results of this study show that experiments using potted plants can be used to screen for resistance to banana weevil based on the development of larvae. The influence of previous feeding damage to banana plants on larval development and survivorship in a susceptible (Atwalira), an intermediate (Kabula) and a resistant cultivar (Kisubi) was also examined. While no effects on larval development rate were apparent, survivorship was reduced in previously attacked plants for the intermediate cultivar, indicating that resistance may be induced by previous weevil attack of plants.

Chilo spp. are among the most important stem borers of sugar-cane in the Old World. Chemical control is not very effective mainly because of the concealed habit of the borer larvae. Efforts have therefore mostly been directed to alternative methods of control such as cultural practices, varietal resistance, biological control and the use of sex pheromones. Varieties are not normally bred for borer resistance but very susceptible ones tend to eliminate themselves at the early stages of selection. Susceptibility is normally assessed on promising and released varieties. Classical introduction of exotic parasites has more or less reached a saturation point and biological control tends to be oriented towards the possible use of new or cross-bred strains. The importance of entomopathogens as a control component against Chilo spp. needs further studies. A great potential exists in the use of sex pheromones mainly as a means to disrupt mating, as shown by the promising results obtained through trials carried out in various countries. It is very important that the various methods of pest control available be used in combination with one another, taking into account the natural limiting factors of the environment. This would be an important contributing factor towards an objective of optimum yield at minimum cost in the management of Chilo spp. on sugarcane.

In this study, rearing systems for, and the quality and demographic parameters of, a wild strain (WS) and two laboratory strains (LSs; one maintained on a torula yeast-casein diet and the other on a starter-gel diet) were determined for the American guava fruit fly Anastrepha striata (Schiner). No differences were observed between the LSs, but there were significant differences between the LSs and WSs. The LSs had the highest values for larval recovery, pupal weight, egg hatch, number of eggs/female per day, net reproductive rate and intrinsic rate of increase. Therefore, during a short oviposition period, the LSs had a high fecundity. There were no differences in pupation at 24 h and larval weight between the WS and LS. However, the values of parameters, adult emergence, female and male life expectancies, age at first oviposition, oviposition and post-oviposition periods and mean generation time were the highest in the WS.