A field experiment was conducted to track the daily population trends and occurrence of the flower thrips Megalurothrips sjostedti Trybom and Frankliniella occidentalis (Pergande), and their indigenous natural enemies Orius spp. and Ceranisus menes (Walker), infesting French beans. French beans in monocrop or interplanted with six companion crops (Zea mays L., Coriandrum sativum L., Tagetes erecta L., Brassica oleracea var. acephala L., Daucus carota L. and Capsicum annuum L.), and two chemical insecticides, methiocarb (Mesurol 500SC) and L-cyhalothrin (Karate 1.75% EC), were evaluated for their effects on the abundance of flower thrips, throughout the day, at 1-h intervals. The average population peak of thrips was found to occur at around 1300 h, but each species had different peak periods. Adult F. occidentalis populations peaked at midday and adult M. sjostedti populations at 1500 h, while the larvae of the two thrips species peaked at around 1300 h. Orius spp. were the most abundant natural enemies and their populations peaked at around 1400 h. Ceranisus menes population also peaked at around 1400 h.

Preliminary screening of germplasm from the International Institute of Tropical Agriculture (IITA) showed that a number of cowpea Vigna unguiculata (L). Walp. cultivars have potential for resistance to the flower bud thrips, Megalurothrips sjostedti (Trybom). In an earlier study, 10 cultivars from this germplasm were selected and the mechanisms of resistance determined. Therefore, in this study, the basis of resistance operating in the cultivars was elucidated during the first and second planting seasons of 1998. Cowpea cultivars were analysed for primary metabolites (total protein content and glucose contents) to study their relationship with resistance parameters of M. sjostedti under field conditions. Total protein and glucose contents varied significantly (P<0.01) in floral buds and flowers of the different cultivars, while in racemes there were little or no significant differences. Highly significant negative correlation coefficients were obtained between total protein contents in reproductive structures and resistance parameters, especially during the second season, regardless of cowpea cultivar, indicating that quality of total protein content plays a significant role in cowpea resistance to M. sjostedti. Significant (P<0.05) correlation between damage indices and glucose content in Vita 7 and Kpodjiguegue is responsible for their susceptibility to M. sjostedti damage. Furthermore, presence of a unique protein band (20.1 kDa) in Moussa local, Sanzibanili and Sewe cultivars could be associated with resistance to flower bud thrips, regardless of quantity of total protein content in these and other test cultivars. Similarly, the specific band just above the 94 kDa in Vita 7 could be responsible for its susceptibility to M. sjostedti.

Neem (Azadirachta indica A. Juss.) has been demonstrated to reduce insect populations in stored products through its toxic and growth-disrupting and other effects on the pests. Grain movement and percussion also help to kill pests in grain. The combination of neem and grain movement on population growth and development of four insect pests is reported in this study. Dried whole neem leaves, neem leaf powder and neem seed kernel oil were combined individually with dried beans and rice in separate experiments, and subjected to varying degrees of gentle grain tumbling. The results showed that the combined treatments were more effective in reducing populations and disturbing growth and development of Acanthoscelides obtectus (Say) (Bruchidae), Sitophilusoryzae (Linnaeus) (Curculionidae), Oryzaephilus surinamensis (Linnaeus) (Silvanidae) and Cryptolestes ferrugineus (Stephens) (Cucujidae) compared to the untreated control or the neem or tumbling treatments alone. This study demonstrates the potential of a simple, effective and cheap method of protecting stored seed or food grain in small-scale storage for resource-poor farmers who do not have access to sophisticated control methods, entoleters or other mechanical devices for grain protection.

The penetration of adult Sitophilus zeamais Motschulsky through maize grain bulks (0.75 m deep), treated with Protect-It®, a diatomaceous earth (DE) at 0, 0.05, 0.1 and 0.2% (w/w), was determined 12 weeks after weevils were released at the upper surface of the grain. Maize was stored in columns in polyvinyl chloride (PVC) pipes, under controlled conditions of 26±2°C and 70±10% RH. Grain samples were collected from various pre-determined depths and the numbers of S. zeamais adults counted. Differences in insect numbers between treatments and at different depths from which samples were collected were highly significant (P<0.001). The bottom 2–3 layers (0.65–0.75 m deep) had significantly more insects than the upper layers for all the DE concentrations. No significant differences in total insect numbers (live+dead) were found between the DE concentrations. Dead S. zeamais weevils were found at the bottom of grain treated with Protect-It®, indicating that insects can penetrate through DE-treated grain 0.75 m deep but then subsequently die. There was no strong evidence that DEs admixed with bulk grain restrict S. zeamais movement within the grain.

A water–oil based pheromone trap was used to monitor seasonal population changes of Coniesta ignefusalis Hampson in millet-based cropping systems at Samaru, Zaria, Nigeria for three consecutive seasons (1997, 1998 and 1999). Daily meteorological data were obtained from the Meteorological Unit of the Institute for Agricultural Research, Samaru, Zaria, for the monitoring period. Two population peaks were observed in early August and September in 1997 and 1998. The first population peak in August 1997 was earlier and bigger than the one in 1998. A delayed emergence of the insects was observed in 1999 when only one population peak occurred and this was smaller than those in 1997 and 1998. Using step-wise multiple regression analyses, the relationship between pheromone trap catches of male moths and weather factors was assessed separately for each year to determine which of the weather factors contributed most to the insect population changes. Solar radiation in the preceding 10 days and minimum air temperature in the preceding 40 and 50 days explained 84.9% of the variance in population changes and flight activity of male moths in 1997. Wind direction and speed in the preceding 20 and 60 days respectively accounted for 80.6% of the variance in 1998, while maximum air temperature and relative humidity in the preceding 40 and 20 days respectively explained 99.9% of the variance in 1999. The functional regression equations developed involving these weather factors adequately predicted the changes in each year.

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.

The parasitism of Bemisia tabaci (Gennadius) was evaluated on three horticultural crops in the Nicaraguan dry tropic: tomato, Lycopersicon esculentum Mill; squash, Cucurbita argyrosperma (Huber); and sweet pepper, Capsicum annuum L. Parasitoid species were identified and their abundance recorded on the three crops. The study was carried out during both the rainy and dry seasons between 2001 and 2002. The nymphs of B. tabaci were counted weekly and parasitism rates evaluated. During the rainy season, the predominant parasitoids in squash and tomato crops were Encarsia pergandiella Howard and E. nigricephala Dozier. Parasitism rates of 17 and 10% were recorded for squash and tomato, respectively. In sweet pepper, the parasitoid species were E. pergandiella, E. nigricephala, E. desantisi Viggiani and Amitus sp. with a parasitism rate of 12%. During the dry season, the parasitoids in squash were E. pergandiella and E. nigricephala with a parasitism rate of 57%. Encarsia pergandiella was the only species noted in tomato with a parasitism rate of 58%, while in sweet pepper the species noted were E. pergandiella and E. nigricephala, with a 42% rate of parasitism. The abundance of parasitoids remained stable during both sampling seasons. Our results suggest that the parasitism rate is independent of B. tabaci densities. This is the first mention of E. pergandiella, E. nigricephala, E. desantisi and Amitus sp. as parasitoids of B. tabaci in Nicaragua.

Citrus orchards in the Nile Delta and middle Egypt were surveyed for predacious soil mites and parasitic nematodes. There were 16 species of predacious mites and the citrus parasitic nematode, Tylenchulus semipenetrans Cobb. was recorded everywhere. In the medium-heavy soil of the Nile Delta orchards, the general predators or decomposer mites like uropodids were most common. In the light-medium soil of El-Fayoum in middle Egypt, the specialized predator mites like gamasids were most common. In localities where gamasids were common, negligible infestations of citrus parasitic nematodes were reported. Regarding Egypt as a whole, the uropodid mites Uroobovella krantzi (Zaher & Afifi) and Nenteria hypotrichus (El-Borolossy & El-Banhawy) represented about 50% of the sampled mites. The remaining mites were represented by 14 mesostigmatid species, the most common being Gamasiphis pulchellus (Berlese). At least 6% of orchards suffered injurious nematode infestations, 13% critical infestations and 22% moderate infestations, and the remaining 59% were free or with negligible infestations.