Farmers in the groundnut belts of Mali, Burkina Faso, Niger, Nigeria and Benin in West Africa were interviewed for their ability to identify economically importanct soil pests infesting their groundnut (Arachis hypogaea L.) crops, and to obtain information on farm histories and cultural practices which may influence soil pest infestation and spread in a field. Termites, whitegrubs and millipedes were recognised by the farmers as being the most important soil pests, with termites being the most damaging group. A negative correlation (P < 0.05) was found between the number of years a farm was cultivated and the frequency of termite occurrence in it. Information on cultural practices obtained from interviews and field visits indicated that practices such as late harvesting and the leaving behind of residues of previous sorghum, millet and maize crops increased termite infestation. The cutting down and burning of the vegetation in a farm before planting significantly (P < 0.05) reduced the percentage of plants attacked by termites. The cultivation of short-duration (< 100 days) varieties to escape drought at the end of the cropping season did not significantly reduce termite damage, due to late harvest. Other farmers' practices which are likely to have contributed to soil pest damage are also discussed.

Starch gel electrophoresis was used to compare eight loci in six enzymatic systems of 17 samples of the groundnut seed-beetle, Caryedon serratus (Ol.) (Coleoptera: Bruchidae) bred on five different host-plant species: Arachis hypogaea, Bauhinia rufescens, Cassia sieberiana, Piliostigma reticulatum and Tamarindus indica. The rate of polymorphism was 44.8%. The average genetic diversity (Hw) was 0.184. Allozyme variability analysis indicated that seed-beetles associated with P. reticulatum and groundnut, Arachis hypogaea were genetically similar, whereas other samples clustered according to their host plant species. Geographical distances less than 400 km were not decisive for the genetic structuring of samples associated with a given host plant.

The impact of larval defoliation by Aproaerema modicella (Deventer) on the growth, development and yield of two groundnut cultivars (Kadiri 3 and NC Ac 17090) was studied under a naturally occurring, high density infestation. Defoliation by leaf-mining larvae did not increase plant mortality in either cultivar. In both cultivars, leaf and stem production were significantly lower in untreated plots than in the treated plots. Unsprayed plants of both cultivars produced fewer flowers, pegs, and pods per plant compared to plants of the same cultivar protected with monocrotophos. Fruit growth rates, however, were marginally higher in control plots than in treated plots. Pod yields were 35 and 44% lower, and haulm yields 25 and 20% lower, in Kadiri 3 and NC Ac 17090, respectively in untreated control plots compared to plots treated with insecticide. A linear relationship between leafminer density and pod and haulm yields was observed, and differences between cultivars were not significant.

In a comparative situation, the moths Plodia interpunctella (Hubn.) and Ephestia cautella (Wlk.) caused more damage in groundnuts (41.85% for P. interpunctella; 29.21% for E. cautella) than in maize, when these commodities were stored for 1 month in plastic jars. For maize stored for 3 months in plastic and traditional storage gourds, the weight losses caused by the moths were: P. interpunctella—15.48% in jars; 4.53% in gourds; E. cautella—20.68% in jars; 4.12% in gourds. Orange peel suppressed two-thirds of the populations of P. interpunctella and E. cautella at a dosage of 20.0g/100g maize. Neem leaves caused 100% mortality of P. interpunctella at 15.0g/100g groundnut and suppressed more than half the population of E. cautella at 5g/100g groundnut. The results show that the plant materials utilised have some insecticidal properties against P. interpunctella and E. cautella over a short period.

Field experiments at the Msekera Regional Research Station during 1988–1990 and at Masumba (Luangwa Valley) Sub-station during 1989–1990 showed that six groundnut genotypes—ICG.485, ICG.2271, ICG-2306, ICG.5041, ICG.5045 and HyQ (cg) S-10 were distinctly less susceptible to the leafhopper, Empoasca dolichi (Paoli). ICG.2271 also appeared to combine low susceptibility to early leaf spot, Cercospora arachidicola Hori and good yield potential. This genotype as well as ICG.5041 and ICG.5045 also are known to be resistant to thrips and/or termites. The scope for their utilization in exploitation of leafhopper resistance in groundnut improvement programme in Zambia is indicated.

Population of Spodoptera litura F. were monitored through pheromone-baited traps during the rainy season 1988 and 1989 in groundnut fields in relation to oviposition on leaves. Four peaks of adult catches were recorded. First and second peaks were smaller and caused no threat to crop. Third peak was observed at the pegging and pod-initiation stage during first week of September and coincided with the greatest oviposition on leaves. The fourth peak was greatest and occurred between 40th and 43rd standard week. However, no oviposition was recorded on groundnut during this period. The moths possibly dispersed and/or migrated to other areas with crops at an appropriate stage of susceptibility.

The groundnut variety ICG 2271 is the most resistant to thrips In our conditions. Despite the existence of some differences between types, the number of thrips per flower In the cowpea is negatively correlated with the total number of flowers present per plant, the rate of pod formation, the internode and pod length, the pod number per plant and grain yield. It Is positively correlated with the percentage of flowers shed per plant.

In the pigeonpea, the characters linked to the number of thrips per flower vary with varieties. However, days to maturity and height at the same stage are more consistent.

The days to 50% flowering are positively correlated with the number of thrips per flower In the cowpea and pigeonpea.

Termites are important agricultural pests in the semi-arid tropics. Conventional methods of control have relied on persistent organochloride insecticides with accompanying health and environmental problems. In contrast, cultural control methods provide untested, but environmentally sound options to farmers. This study reports results from three experiments on the use of mulches to reduce Microtermes obesi and Odontotermes spp. damage with relevance to groundnut production in India.

Termites scarification of groundnut was 80–90% lower for pods dried in neem cake or Ipomoea fistulosa mulches than for pods dried directly on the soil. Similarly, subterranean attack by termites on bamboo baits was 20–40% lower in mulched plots than in controls. However, mulches were ineffective in protecting bullock manure from removal by termites.

Successful use of mulches in termite control may be related to food source concentration. Termite location of concentrated food sources, such as bullock manure, was followed by recruitment of workers and construction of protected runways. In contrast, termites foraging on limited food sources, such as groundnut pods, did not construct runways and had greater exposure to mulches.

The effects of intercropping groundnut with sunnhemp on termite incidence and damage were studied in the rainy and post-rainy season at ICRISAT Center in central India. Termite incidence in different cropping systems was determined by baiting with bamboo stakes. Damage to groundnut plants and pods was evaluated at harvest.

Intercropping groundnut with sunnhemp did not affect termite abundance or damage to groundnut. These results contrast with a Colombian intercropping study in which sunnhemp exudates repelled cassava burrowing bugs. Termite biology, including recruitment of foragers and construction of protected runways, may have reduced exposure to sunnhemp, thereby minimizing effects.

Several insects attack the groundnut, which is a major crop in Senegal. Sporadic attacks of Heliothis ( = Helicoverpa) armigera Hbn. and other insects have been recently noted. In order to reduce the pest attack, neem cake extract (1 and 3%) was compared with cypermethrin and a mixture of dimethoate and deltamethrin and gave satisfactory results. However, yield was not significantly increased.