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.

Four maize varieties, 8321–21-W, DMR-LSR-W, ACR-83TZUT-W and TZB were simultaneously fed to Sitophilus zeamais in a completely randomized design. Susceptibility was assessed on such parameters as weight loss of grains caused by the weevil infestation, number of progenies at 42 days after infestation and the percentage of damaged kernels. The least susceptible in terms of loss of weight of grains was TZB. Losses in the other three were not significantly different at 5% level (P ≻ 0.05).

The least percentage mortality of adult weevils and the highest number of punctured kernels were observed in var. 8321–21-W (48%), 27 kernels respectively while var. DMR-LSR-W had the highest mortality score (80%) and ranked second in the total number of kernels punctured (13). Details of the description of maize varieties used and the analysis of damage caused by the weevil are discussed in the paper.

The paper reviews the work done on the population patterns of Chilo spp. in relation to the phenological stages of sorghum, maize and millets. The stem borer Chilo partellus entered sorghum and maize crops at 2–3 weeks after emergence and continued till harvest. There were 3–4 peaks of larval population during a cropping season. Such studies not only reveal the relationship between the larval population density and the phenological stage of the plants at infestation time, but are also helpful in scheduling and timing pest management strategies.

Lepidopterous stem borers constitute one of the major constraints to cereal crop production in southern Africa. Chilo partellus Swinhoe, is an economically important stem borer of maize and sorghum. Current research status on C. partellus is reviewed and substantial advances in the distribution, bioecology and control strategies are discussed. Present work on the assessment of crop losses, elucidation of mechanisms of resistance, development of resistant crop cultivare, feasibility of biological control measures and the implementation of other stem borer management methods are reported. Further areas of research into the management of C. partellus are identified.

Maize is the single most important food cereal in eastern and southern Africa. Yield levels, however, are among the lowest in the world. Among the major constraints limiting production are the insect pests. Objective assessment of damage and losses caused by these pests are lacking in several countries within the region. This paper discusses some of the methodologies available, and how they can be used to estimate the losses caused by insect pests under different situations. It emphasizes the need for standardization of the methodologies, so that information generated from different countries can be compared. This will promote collective action to combat the pest menace and increase food security.