Insecticide protection at the vegetative, reproductive or both vegetative and reproductive (complete) crop growth stages and untreated control was used to assess yield loss due to insect pests at the different growth stages of soybean in Ghana from 2007-2009. The objectives were to determine the economic importance of the two major insect pest guilds in soybean, viz. defoliators and pod feeders, and when to apply control measures for maximum benefit. The defoliators recorded were Podagrica spp., Ootheca mutabilis (Shalberg), Zonocerus variegatus L., Sylepta derogata F., Spodoptera littoralis Boisduval, Amsacta spp. and Helicoverpa armigera Hu¨bner. The pod feeders recorded were the pod-sucking bugs (PSBs) Riptortus dentipes F., Thyanta sp. Aspavia armigera F., Nezara viridula L. and Dysdercus vo¨lkeri Schmidt. Generally, insect densities, pod and seed damage were lower while seed yields were significantly greater and similar in plots that were protected at the reproductive stage against PSBs and those protected at both vegetative and reproductive stages. Yield loss ranged between 25.8 and 42.8% in untreated plots, 11.1 and 34.3% in plots that were protected at the vegetative stage, and 5.2 and 11.3% in plots that were protected at the reproductive stage. There was a consistent negative correlation between yield and numbers of PSBs as well as pod and seed damage. These results showed that PSBs that attack soybean at the reproductive stage were the most important insect pests limiting soybean yield in Ghana.

Soil arthropod pests are important constraints to peanut production in Ghana. Surveys of peanut fields were conducted from 2003-2005 to identify and estimate densities of key soil arthropod pests, and also to quantify their damage to peanut in the three regions (Northern, Upper East and Upper West) of northern Ghana. The main soil pests were termites (Isoptera: Termitidae), millipedes (Myriapoda: Odontopygidae), white grubs (Coleoptera: Scarabaeidae) and wireworms (Coleoptera: Elateridae). Across regions, termites and millipedes were the most abundant while wireworms were the least recorded. Significantly higher pest densities and pod damage by scarification and penetration were generally recorded in the Northern Region than in the Upper East and Upper West Regions. A checklist administered to farmers during the survey showed that no control practices were carried out for the pests though farmers generally were aware of the damaging effects of these pests on peanut. Field studies also were conducted at Nyankpala and Bagurugu in the Northern Region during 2005 and 2006 to determine the effects of insecticide (chlorpyrifos or carbofuran) applications to peanut at planting, pegging or at both planting and pegging on control of soil arthropod pests and on yield. Results showed that the insecticides used were similar in their efficacy against the pests. Generally, insecticide treatment lowered pest densities and pod damage resulting in increased yield over the untreated control. Yield losses in untreated plots ranged between 23 and 39%. Treatment at planting or pegging did not differ in the level of control compared with treatment at both planting and pegging. Yield was negatively correlated with pest densities and pod damage. These findings are discussed in the context of control of soil pests of peanut in Ghana.

Field efficacy of neem (Azadirachta indica A. Juss) for managing soil arthropods and Cercospora leaf spots damage to peanut was studied in Ghana from 2008 to 2010. Treatments consisted of neem kernel water extract (NKWE) and neem kernel powder (NKP) applied separately as soil drench at the rates of 10.5 and 21.0 kg/ha at either planting or pegging. Untreated control and chlorpyrifos treatment at pegging were included as checks. Results showed generally that the neem products at the concentrations tested were efficacious and comparable to chlorpyrifos in lowering populations of soil arthropods and severity of leaf spot diseases, leaf defoliation, and scarified and bored pod damage, resulting in increased pod yield in 2008 and 2009.