A strain of diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), adapted to peas was detected in 1999 in the export vegetable growing area south of Lake Naivasha in the Rift Valley Province of Kenya. The pea strain (DBM-P) was compared in laboratory studies to the normal crucifer strain (DBM-C). Whereas DBM-P performed comparably well on kales and peas, the cabbage strain (DBM-C) suffered heavy mortality on peas. Out of the 250 DBM-C first instars, only six reached adult stage on pea. In addition, larval development was prolonged by five days on peas as compared to kale, and larval growth was greatly reduced. Pupal weights of DBM-C survivors on pea were significantly lower (3.8 mg) than of DBM-P (4.6 mg) and those of both strains on kale (5.7 and 5.3 mg, respectively). Neonate larvae of the pea strain mined on both kale and pea but both the proportion of larvae mining and the number of mining days were lower than for DBM-C on kale. The latter failed completely to mine on pea.

A laboratory culture was started with the DBM-C survivors on pea and the performance of the progeny compared on kale and pea in three additional generations of selection. Larval survival increased from 2.4% in the first generation to 28.6%, 41.3% and 49.7% in the second, third and fourth generation, respectively. Pupal weight of larvae reared on pea increased with each generation of selection, but it remained significantly lower than of larvae reared on kale. In spite of the large differences in larval mining on the two host plants, performance on peas was not related to the ability of DBM-C to mine on pea but rather to the ability to initiate feeding without the normal stimuli present in crucifers. Pupal mortality for larvae from both hosts was similar when larvae of equal weight were compared, suggesting acceptable suitability of pea for larval development once the new host is accepted. The implications of these findings on adaptability of DBM to plants beyond its normal host range are discussed.

The demographic statistics of the ladybird Exochomus flaviventris Mader (Coleoptera: Coccinellidae) were investigated under laboratory conditions on the cassava mealybug, Phenacoccus manihoti Matile-Ferrero (Homoptera: Pseudococcidae), reared on four host plants with different levels of antibiotic resistance to the mealybug: two cassava (Manihot esculenta Crantz, Euphorbiaceae) varieties, Incoza and Zanaga, Faux-Caoutchouc (FC) (hybrid of M. esculenta × M. glaziovii Muel. Arg.) and water weed (Talinum triangulare Jack, Portulacacae). Preimaginal mortality, mean oviposition time and total fecundity of female ladybirds were strongly affected by the host plant even though there was no linkage with antibiotic resistance. The net reproduction rates R0 of the predator were 1.5,1.7 and 2.4 times higher on Zanaga than on water weed, Incoza and FC respectively, and the generation time (T) was significantly longer on Zanaga than on the other three plants. The intrinsic rate of increase rm was not modified by the antibiotic resistance of the host plants. With the two cassava varieties, Incoza and Zanaga, it was found that antibiosis significantly affected the life history parameters of the ladybird without modifying its fitness, and provided better cassava mealybug control.

The effect of infestation of lepidopteran borers on yield of maize was assessed at three locations in the forest and forest/savanna transition zones of Cameroon, during the first and second season of 1992. Maize was treated once or twice with the systemic carbofuran at different developmental stages. The species encountered were the stem-boring noctuids Busseola fusca and Sesamia calamistis, which oviposit on and attack pre-tasseling stages of maize; the stem-boring pyralid Eldana saccharina, which attacks plants at and after tasseling; and two ear borers, namely the pyralid Mussidia nigrivenella and the tortricid Cryptophlebia leucotreta. Generally, carbofuran reduced infestations by B. fusca and S. calamistis but had little or no effect on species attacking the plant's later stages. Thus early treatments with granules into the whorl were more efficient than late treatments as a side dressing, and a second late treatment had little effect. During the first season, late-attacking species were predominant and grain yield losses of 17–44 % were found in one location only. During the second season, species attacking young plants (mainly B. fusca) became predominant in all three locations and yield losses of 30 to 41 % were found in two of the three locations. The percentage of ears with damage was especially high during the second season. As green maize is an important source of cash income in the area and damaged ears cannot be sold, the economic loss was likely considerable.

The termite species Macrotermes bellicosus has a vast geographical distribution, which can produce genetic divergence in populations that evolve in its different environments. Experiments carried out on digestive oxidases in two populations of M. bellicosus originating from Chad and from Côte d'lvoire showed differences in the rate of their enzymatic activities. Populations from Côte d'lvoire showed significantly higher degradation activity against fresh vegetal matter than populations from Chad.

Field experiments were conducted to investigate the attractiveness of fish bones to predatory ants in a maize agroecosystem. The fish bones were applied crushed in shallow furrows together with dry maize stalks, or broadcast on the soil surface at 3 application rates: 0, 40 and 80 kg/ha; subsequent reduction in termite attack on maize plants was then assessed. Burying the fish bone powder caused higher ant nesting (10–78 %) than surface broadcasting (12–39 %). Attractiveness of the fish bones and the predatory efficiency of the ants against termites in maize was also highest with a dose of 80 kg/ha (1.0 kg/plot) causing higher nesting of ants (>90 %) and 54 % lower termite damage to maize plants compared to control plots. Dose responses indicated significant relationships between amount of fish bone powder applied and termite activity and also between termite damage and maize yield. The mechanism by which the ants are able to protect maize against termite damage may be twofold: direct kill as a result of their predatory action and termite avoidance of maize plants with ant nests. Further studies are required to assess the potential benefits of an integrated use of this technique with other non-chemical options for termite control in maize, such as intercropping.

The influence of banana weevil, Cosmopolites sordidus (Germar)(Coleoptera: Curculionidae), population density on oviposition rates and larval survivorship was studied in the laboratory at the Kawanda Agricultural Research Institute in Uganda. This study was undertaken to elucidate the relationship between density-dependent factors and rates of banana weevil increase in the field. Oviposition substrates (corm pieces) were offered to a range of densities of weevils maintained in buckets. Mean oviposition rates per female at densities of 10, 20 and 40 females per bucket were 29, 37 and 53%, respectively, lower than that at a density of 5 females. Nevertheless, total oviposition for the same groups was 1.4, 2.5 and 3.7 times higher than that of the 5-female group. Providing fresh corms daily instead of every five days did not increase oviposition. Larval survivorship was slightly higher at lower densities of immatures following insertion of different densities of eggs or first instars into banana corms. The results suggest that density-dependent factors can influence oviposition rates of individual weevils and survivorship of immatures, but appear to exert only modest influence in reducing banana weevil population growth. More likely, high mortality of weevil immatures under field conditions and/or higher rates of adult mortality and emigration than previously postulated contribute to the slow population build-up of this pest.

The effects of temperature on the development of Orius albidipennis (Reuter) (Hemiptera: Anthocoridae), reared on its prey, Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), were studied in the laboratory. Nymphal mortality was 87, 48 and 38 % at 20, 25 and 30 °C, respectively. With the exception of first-instar nymphs, percentage mortality was lowest at 25 °C. Pre-oviposition period and longevity decreased with an increase in temperature. Mean daily and total fecundity were 2.1 and 76.4 respectively at 25 CC. The mean developmental period from oviposition to adult eclosion was 27.7, 14.1 and 10.9 days at 20, 25 and 30 °C respectively. There was a linear relationship between temperature and developmental rate (1/day) of O. albidipennis. Lower thermal thresholds were 13.8, 13.5, 12.7, 15.0, 13.8 and 12.5 °C for eggs and nymphal stages 1 to 5, respectively, with the corresponding average degree-day requirement of 46.9, 42.6, 33.3, 29.2, 26.1 and 51.4 days, respectively. The implications of these results for biological control of thrips are discussed.

A commercially produced palm oil brand, Palmin oil, was evaluated for its effect on eggs and larvae of Callosobruchus maculatus (F.) (Coleoptera: Bruchidae) on cowpea (Vigna unguiculata) (L.) Walp. Application of 1 μ1 of the oil on eggs deposited on 10 cowpea seeds, or directly on larvae growing inside seeds resulted in their death. Embryo mortality occurred only when the oil was placed at the anterior end of the egg. The nutritive content of cowpea seeds treated with Palmin oil remained unchanged. Furthermore, the oil did not go rancid following six months of storage.

Spodoptera litura (F.) (Lepidoptera: Noctuidae) is a serious pest of several crops in India and other countries. Prothoracicotropic hormone (PTTH) release from the brain of penultimate fifth instars of the noctuid was followed in the laboratory and a spiracle index developed to assess PTTH action. PTTH release from the brain occurred during the scotophase at 4.30 h of day 1 (AZT). Ecdysone secreted in the prothoracic gland was released from the 7th hour of day 1 (AZT), reaching a maximum in the haemolymph on the 9th hour of day 1 (AZT). The prothoracic gland showed three distinct phases, namely growth, synthesis and release. Injected PTTH of 5th instar brain extract induced larval moulting in head-ligated larvae. Partially purified PTTH from 6th-instar S. litura brain induced moulting in 6th instars. Abdomen-ligated penultimate instars administered β-ecdysone showed variable moulting response. The phenomenon of hormonal interaction with development of the penultimate instar of S. litura is discussed.

A study was conducted in Muswishi area, Zambia, with the objective of assessing indigenous technical knowledge (ITK) and relating this knowledge to integrated pest management (IPM) in maize production. The methods used included surveys, participatory rural appraisal (PRA), transect walks and semi-structured interviews (SSI). It was found that ITK does exist among some Muswishi smallholder farmers. Eighty-nine percent of respondent farmers never used any chemical pesticides. However, 22% used natural products to manage insect pests. The most widely used natural plant products were Swartzia madascariensis Desv, Tephrosia vogelli Hook.f, Euphorbia tirucalli L, wood ash and cow dung. Farmer's own assessment indicated that the integration of ITK into IPM technology led to increased maize yields (> 37.5%). This study demonstrated the continuing need for integrating ITK into IPM technology. Such an approach could ensure household food security and enhance sustainable livelihoods of rural smallholder farmers.

In issue 1 of this Volume (22), the headers for the article titled “Managing termites in maize with the entomopathogenic fungus Metarhizium anisopliae” by N.K. Maniania, S. Ekesi and J. M. Songa, were inaccurate