The biological effects of affinity purified seed lectin from African yam bean, Sphenostylis stenocarpa (Harms), were tested on Clavigralla tomentosicollis (Stål) in an artificial seed system. S. stenocarpa was extracted from two African yam bean accessions: Enugu 95-3 and Enugu 98-2. Lectins from both accessions were highly toxic to the insect at 1.0% dry weight. For nymphs feeding on Enugu 95-3 and Enugu 98-2, survival ranged from 16.0 to 24.0% and 4.0 to 16.0% at 1.0 and 2.0% dry weight dietary ...

An experiment was conducted over the period 1995–96 in a warm‐temperate environment in Nepal to investigate the effect of cutting frequency on forage yields of three temperate legume species, grown during the winter season, and the residual treatment effects on a subsequent upland rice crop. The three species, Persian clover (Trifolium resupinatum), white clover (Trifolium repens) and vetch (Vicia benghalensis), proved to be well adapted to the winter growing conditions and produced cumulative ...

Geminivirus defective interfering DNAs arise spontaneously in mechanically inoculated test plants, and have previously been found with DNA‐B of the bipartite cassava mosaic geminiviruses, but not DNA‐A. Reported here for the first time is the cloning and characterization of a naturally occurring truncated form of cassava mosaic geminivirus DNA‐A, which at 1525 nt is around half the expected full size. Sequence analysis has shown it to be a defective (df) form of East African cassava mosaic virus ...

In many countries in West Africa, the pyralid ear borer Mussidia nigrivenella Ragonot occasionally causes severe damage to pre- and postharvest maize. Between 1992 and 1995, the distribution of and damage caused by M. nigrivenella were studied in Benin using survey data and an on-station field experiment. The borer was distributed across the whole country, and at maturity an average 25% of the ears sampled in maize fields were infested. Damage levels varied with agro-ecological zones and were ...

Seed coat texture is an important trait in determining the acceptability of cowpea varieties in different regions. A rough seed coat is preferred in western and central Africa, since it permits easy removal of the seed coat which is essential for indigenous food preparations. On the other hand, a smooth seed coat is preferred in eastern and southern Africa as well as in parts of South America where cowpea is consumed as boiled beans without removing the seed coats. This study was undertaken to ...

Yam (Dioscorea spp., family Dioscoreaceae) is one of the most important food crops cultivated in the West African yam zone comprising the forest and savannah areas of Nigeria, Ghana, Cote d'Ivoire, Republic of Benin, and Togo, which account for more than 90% of the 4.59 million ha of yam cultivation worldwide (1). A survey was conducted in 2005 to document viruses in yams in Ghana, Togo, and the Republic of Benin. Samples (1,405) from five species of yam showing mosaic, chlorosis, and stunting as ...

In Africa, sorghum downy mildew (SDM), caused by Peronosclerospora sorghi, infects both sorghum and maize. Systemic infection can result in severe yield loss. The effects of seed treatments and foliar sprays of metalaxyl on the disease were determined on maize in Nigeria (1992) and sorghum in Zimbabwe (1993/4). Seed treatment at 1.0 g a.i/kg or a foliar spray at 0.96 g a.i./l significantly reduced the incidence of the disease, although the latter was less consistent. The effect on yield was less ...

Field surveys were conducted on cowpea and pigeon pea in 1995 and 1996 to assess the effect of indigenous egg parasitoids on populations of Clavigralla tomentosicollis Stål in northern Nigeria. From the egg masses of C. tomentosicollis, three species of Hymenoptera belonging to three families, namel Anastatus sp. (Eupelmidae), Ooencyrtus utetheisae (Risbec) (Encyrtidae), and Gryon fulviventris (Crawford) (Scelionidae), were recorded. Among them, G. fulviventris was found to be the most abundant ...

1 Thermal behaviour of the variegated grasshopper, Zonocerus variegatus, was investigated in the humid tropical zone of southern Benin, west Africa, in the dry seasons of 1996 and 1998. In 1998, investigations included studies of a population of grasshoppers sprayed with an oil‐based formulation of the entomopathogenic fungus Metarhizium anisopliae var acridum. 2 Body temperature measurements and observations of thermal behaviour both in the field and on thermal gradients in the laboratory, suggest ...

Consecutive outbreaks of acute aflatoxicosis in Kenya in 2004 and 2005 caused > 150 deaths. In response, the Centers for Disease Control and Prevention and the World Health Organization convened a workgroup of international experts and health officials in Geneva, Switzerland, in July 2005. After discussions concerning what is known about aflatoxins, the workgroup identified gaps in current knowledge about acute and chronic human health effects of aflatoxins, surveillance and food monitoring, ...