Lipaphis erysimi pseudobrassicae (Davis) and Myzus persicae (Sulzer) are important pests of brassica crops, causing significant yield losses on cabbage in Ghana. To inform the development of ecologically sound and sustainable pest management strategies for these pests, their biological and population growth parameters were studied on three cabbage varieties (Oxylus, Fortune, and Leadercross). The study was conducted in a screen house under ambient conditions at 30 ± 1°C and 75 ± 5% RH and 12:12 h photoperiod from September to November 2020. The parameters of the preadult developmental period, survival rates, longevity, reproduction, and life table were evaluated following the female age-specific life table. There were significant differences in the nymphal developmental time, longevity, and fecundity on the cabbage varieties for both aphid species. The highest population growth parameters, net reproductive rate (R0), intrinsic rate of increase r, and finite rate of increase (λ) were recorded on Oxylus variety for both L. e. pseudobrassicae and M. persicae. The lowest was recorded on Leadercross variety for L.e pseudobrassicae and Fortune for M. persicae. The results from this study suggest that Leadercross is a less suitable host for L. e. pseudobrassicae and Fortune for M. persicae, thus, should be considered as less susceptible varieties for use in primary pest management by small-scale farmers or as a component of an integrated pest management strategy for these pests on cabbage.

Laboratory and field trials were conducted to evaluate the effect of plant species (maize, sorghum), plant age (young, middle, old) and four different nitrogen fertilization levels (N0–N3) on the bionomics of the invasive crambid Chilo partellus and the performance of its braconid larval parasitoid Cotesia flavipes. Plant N varied significantly between N0 and N1–N3, but the differences among the latter were not significant. Intrinsic rates of increase and net-reproductive rates of C. partellus followed the same trends: they were lowest with N0 and similar among the other treatments. On maize only, mortality of C. partellus and parasitism by C. flavipes tended to decrease with age of the plant while the percentage of borers reaching adulthood (i.e. pupation) increased. Borer mortality and parasitism was lower and pupation higher on sorghum than on maize. On both host plants, percent dry matter content of frass, which could affect ingress of the parasitoid into the borer tunnel, did not vary with nitrogen level but varied with age of the host plants: on maize, it was highest on young plants and on sorghum on old plants. Tunnels were shorter on young maize and sorghum plants; longer tunnels on older plants indicated compensatory feeding by the larva as a result of lower nutritive value of the food source. Consequently, larval weight was lower on older than younger plants. The level of nitrogen fertilization had no effect on food conversion efficiency of C. partellus. Nitrogen did not affect number of C. flavipes progeny while egg load of progeny increased significantly with nitrogen level, on both plant species. Differences in egg load between sorghum and maize were mostly not significant. It was concluded that on depleted soils only, an increase in nitrogen via mulching, rotation with a leguminous crop or fertilization would increase survival of C. partellus on both maize and sorghum and an increase in acreage of maize and in application of nitrogen fertilizer in an area would also increase the parasitism of C. flavipes.

Comparative field studies were conducted during the rainy and dry seasons at the Mbita Point Field Station of ICIPE in southwestern Kenya, to investigate the pattern and rate of dispersal of Aphis craccivora on aphid-resistant (ICV-12) and aphid-susceptible (ICV-1) cowpea cultivars in relation to key weather factors. The effects of the dispersal trends on crop performance and aphid population dynamics were analysed. Treatments consisted of initial aphid releases at the north, south, west, east and centre of test plots and uninfested controls maintained on plants for 22 days. Parameters recorded included: pattern (direction of spread of aphids) and rate (number of aphid-infested plants at a given time) in test plots; crop growth and yields and associated factors such as incidence of sooty mould and plant mortality, and aphid density and associated factors, including the incidence of natural enemy species, particularly coccinellids. Dispersal was fastest when releases were made in the west, north and centre of plots, and resulted in adveVse effects on ICV-1 growth and yields. Infestations of ICV-12 did not significantly affect crop performance. There was an apparent direct, positive relationship between wind direction and pattern of spread of aphid infestations, but this pattern was more apparent during the rainy season, when wind speeds were higher, than during the dry season. The incidence of natural enemy species correlated with the spread of aphid infestations, while the abundance of coccinellids correlated with aphid density.

The host plant range of two ricefield caseworms, Parapoynx fluctuosalis (Zeller) and P. diminutalis Snellen (Lepidoptera: Pyralidae), was determined from screening rice and 61 weeds in the Philippines. Both species developed best on the aquatic weed Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae). Parapoynx fluctuosalis also completed a full generation from egg to egg on Cyperus brevifolius (Rottb.) Hassk. (Cyperaceae), Commelina diffusa Burm. f. (Commelinaceae), Leptochloa chinensis (L.) Nees, and Paspalum conjugatum Berg (Poaceae). Parapoynx diminutalis completed a generation on Chara vulgaris L. (Characeae), Ottelia alismoides (L.) Vahl and Blyxa auberti Rich. (Hydrocharitaceae), and Cyperus rotundus L. (Cyperaceae).