For the last three years, CIRAD (Centre de Coopération Internationale en Recherche Agronomique pour le Développement, France) and the University of Pretoria led field research to evaluate the impact of transgenic Bt cotton, expressing the Cry1Ac toxin, on arthropod biodiversity in South Africa. The diversity and the density of insect populations were estimated at different crop development stages using traps, sweep-nets, and direct observations on the cotton plants. In untreated plots, the insect diversity in Bt cotton did not show major changes. The toxin was efficient in controlling one of the major bollworm species, Helicoverpa armigera (Hübner), and reduced the population density of specific larval parasitoids. Predators were present in comparable numbers in both cotton types, except for ladybirds. The toxin did not affect pollinators. In small-scale farming fields, where pesticides are still sprayed for controlling sucking insects, the introduction of Bt cotton did not help meet the expected reduction in insecticide use.

Life table studies of Earias vittella (Fabricius) on different hosts in the Insect Biotech Laboratory, Department of Entomology, Dr PDKV Akola, revealed that survival (lx) of immature stages of E. vittella on different hosts was 0.65 on okra, 0.56 on cotton, 0.54 on semi-synthetic diet and 0.51 on mesta. The net reproductive rate (Ro), at the end of each generation, of E. vittella was 81.91 on okra, 56.70 on cotton, 53.02 on semi-synthetic diet and 36.63 on mesta (Hibiscus cannabinus L.). The net reproductive rate (Ro) followed the same order as the survival rate (lx) on the different hosts. The innate capacity for increase in numbers (rm) ranged between 0.0888 and 0.1334 females/female/day. In descending order, the rm values on different hosts were okra (0.1334), cotton (0.1111), semi-synthetic diet (0.1029) and mesta (0.0888).

Aspidiotus destructor Signoret (coconut scale) occurs on bananas in Hawaii, infesting leaves and fruit. Seasonal population fluctuations on two banana varieties and a preliminary sampling plan for management decision making are described. There were distinct seasonal variations in A. destructor numbers on bananas in Hawaii and varietal differences in population densities and proportions of plants infested, with cv. Cavendish incurring highest A. destructor populations. An aggregated dispersion was found for A. destructor. A preliminary sequential sampling plan based on a nominal threshold is provided.

Studies were conducted at Mtwapa, in the coastal area of Kenya, during the long and short rains of 1999 and 2000 to evaluate interaction of mortality factors in lowering Chilo partellus (Swinhoe) populations in diverse agroecosystems. Treatments consisted of hedgerows of leucaena only, gliricidia only, alternating rows of leucaena and gliricidia, and three plots without trees. During the cropping seasons, maize was planted between the hedgerows while a row of cowpea was planted between the rows of maize. One of the plots without trees was planted to an intercrop of maize and cowpea. The remaining two plots without trees were planted to maize alone, one of which was mulched. The treatments were laid out in a randomized complete block design with four replications. There was no evidence of enhanced mortality in the more diverse systems indicating that the vegetation structure and cultural treatments studied did not enhance activity levels of C. partellus mortality factors. The highest mortality occurred in the early and medium larval stages in all treatments. This mortality was attributable to ‘disappearance’, which represented mortality from sources other than parasitism. The total real generation mortality showed that from the initial cohort of first and second instar larvae, less than 10% of C. partellus survived to adult stage under field conditions in all the treatments. Mortality by Cotesia sesamiae Cameron and Cotesia flavipes (Cameron) was very minimal, indicating the parasitoids were not important mortality factors of C. partellus under the cropping systems studied. Their effects were also not influenced by the cropping systems studied.

Two β-glycosidases were purified from the termite Macrotermes subhyalinus (Rambur) workers by chromatography on gel filtration, ion exchange and hydrophobic interaction columns. The preparations were shown to be homogeneous on polyacrylamide gel. Both enzymes have a similar molecular mass (68 KDa) and optimum pH (5.4) but differ in optimal temperature and thermal stability. The β-glycosidases preferred β-fucosides to β-glucosides, β-galactosides and β-xylosides, and hydrolysed glucose-glucose-β-(1–4) linkages better than β-(1–3), β-(1–2) and β-(1–6) linkages. They did not hydrolyse saccharides such as melibiose, sucrose, lactose, xylobiose, melizitose, stachyose, lactose, raffinose, laminarin, arabinogalactan, carboxymethylcellulose, inulin, lichenan and starch. β-Glycosidase A and β-glycosidase B of M. subhyalinus workers are capable of catalysing transglucosylation reactions. The yields of glucosylation of hydroxyamino acid derivatives and phenylethanol, catalysed by the two enzymes in the presence of cellobiose as glucosyl donor, were lower than those reported previously with conventional sources of β-glycosidases. In addition, the optimum pH is different for the hydrolysis and transglucosylation reactions. On the basis of this work, it is proposed that the physiological role of β-glycosidase A and β-glycosidase B of M. subhyalinus workers is the digestion of di- and oligosaccharides derived from hemicelluloses and celluloses.

Six field pea Pisum sativum (L.), lines (Holetta Local-90, 305PS210687, 061K-2P-2/9/2, 061K-2P-14/7/1, JI-898 and 304WA1101937) were screened in a greenhouse for their resistance to the pea aphid Acyrthosiphon pisum (Harris) and compared to NEP874UK line (control). The total number of progeny and the average and maximum number of nymphs produced per female during a 24-h period were significantly lower in the six lines compared to the control. The intrinsic rate of increase was also significantly higher in the control than in the other lines (except Holetta Local-90). The aphid preferred to feed on the control than on the tested lines. Line 061K-2P2/9/2 was the most resistant genotype as its height and weight were less affected by aphid attack. Based on antibiosis, antixenosis and tolerance effects, lines 061K-2P2/9/2, JI-896 and 304WA1101937T performed better against A. pisum.

Essential oils of three genotypes of Tagetes minuta, six of Tagetes patula and 15 of Tagetes erecta were screened for potential fumigant and contact toxicity against three stored product beetle species, Callosobruchus maculatus (Fabricius), Sitophilus oryzae (Linnaeus) and Tribolium castaneum (Herbst). Genotype 1 of T. minuta (TM-1), genotype 2 of T. patula (TP-2) and genotype 13 of T. erecta (TE-13) were the most toxic. These three genotypes were then evaluated for adult toxicity, oviposition deterrence, and ovicidal and population reduction activities. Essential oils of genotypes TM-1 and TP-2 induced 100% adult mortality for all three insect species at dosages of 50,000 ppm and 500 μg/insect in fumigant and contact toxicity bioassays, respectively. Adults of C. maculatus and S. oryzae were highly susceptible to the essential oils of the three genotypes in both fumigant and contact toxicity bioassays. The essential oil of genotype TM-1 deterred oviposition in T. castaneum by 81% and suppressed its egg hatchability by 91% when applied at a dosage of 70,000 ppm on filter paper.

Essential oils were extracted by steam distillation from Cymbopogon nardus, Cymbopogon schoenanthus and Ocimum basilicum. They were used in fumigation to investigate their absorption by cowpea, Vigna unguiculata seeds during treatment and their residual effects on adult Callosobruchus maculatus (Fabricius) survival and female reproduction, and seed germination. During the treatment, seeds absorbed the essential oil compounds differently. Treated seeds dried for 24 h and then maintained at 20, 30 and 50°C for degassing continued releasing terpenic compounds. After a 72-h exposure, adult C. maculatus mortality was less than 50% in the presence of treated and degassed seeds. The treated seeds did not affect reproduction in female C. maculatus nor seed germination.

An artificial diet was developed for mass rearing of the spotted bollworm Earias vittella (Fabricius) in environmentally controlled conditions (27±1°C, 65±5% R. H. and 16:8 h scoto/photophase). The ingredients for 1 l of diet consisted of soybean (Glycine max) flour (60.0 g), chickpea (Cicer arietinum var. kabuli) flour (58.0 g), wheatgerm (16.0 g), dried yeast powder (16.0 g), casein (8.0 g), l-ascorbic acid (2.4 g), cholesterol (0.4 g), methyl-p-hydroxybenzoate (0.4 g), sorbic acid (2.4 g), streptomycin sulphate (0.4 g), agar–agar (16.0 g) and distilled water (820 ml). The artificial diet developed showed a higher development index (3.58) and a higher survival rate (83.4%) compared to the most preferred natural food (okra pods), for which these parameters were 3.09 and 65.0%, respectively. All the ingredients of the diet are easily available and inexpensive. The cost of 1 l of the diet, on which 400 larvae can be reared, is approximately US$ 2.00.

Two new cost-effective trap designs for capturing arthropod flower visitors are described. Small flower visitors such as Thysanoptera and Diptera, hardly noticeable during direct flower observations, were dominant in trap catches. These trapping techniques combined with direct observations allow a more comprehensive picture of the flower visitors.

The nature, number, structure and behaviour of chromosomes during the meiotic and mitotic sequences in the armoured ground cricket, Acanthoplus speiseri Brancsik, were investigated from testicular and ovariole material. The karyotype of A. speiseri is 2n ♂=25 (24 autosomes + XO) and 2n ♀=26 (24 autosomes + XX). The species exhibits the primitive XO ♂ /XX ♀ type of sex determination mechanism. All chromosomes in the cell complement (including the X sex chromosome), in both sexes, are acrocentric in shape. The X sex chromosome is the largest element in the karyotype while the autosomes comprise three large, four medium and five small pairs. The behaviour of the chromosomes during the meiotic and mitotic processes is normal and typically orthopteran. The study discusses the important role that karyology and cytogenetics can play for species diagnostics in the subfamily Hetrodinae.