Yam as an important staple food and major source of energy in the diet of most people in the tropics, belongs to the genius and family Diocoreaceae. It is a monocot crop. Important species mostly grown and cultivated in Nigeria are:(white guinea yam), (water yam or winged yam) and (yellow yam). Species with less economic importance but are cultivated in Nigeria include:(bitter or trifoliate yam), (Chinese yam) and (aerial yam). Global yam output was estimated at 32.9 million metric tones in which Nigeria alone produces 23.9 million metric tones equivalent to 71% of the total world production. (FAOSTAT 1997; FAO, 1998; IITA, 1995). Yam is reputed for the high prices it commands as a result of its socio-cultural values (Chukwu and Chukwu, 2002; Agbaje ; 2002).Many factors limit yam production in Nigeria which include high labour demand for most cultural operations; high cost of labour and other inputs such as planting materials; declining soil fertility, pests and diseases (Onwueme, 1978). Yams are attacked by several insects both in the field and during storage. Foliar insect pests are less serious compared to tuber pests. The yam leaf beetles (Dalm) and (Fab.) both occur together in yam farm but has been reported to be the dominant species in Nigeria (Onwueme, 1978). Mealybug species known to attack yam include , Ezat McConnel (Akinlosotu, 1984). Other insects that attack yam include yam cricket with species such as , , all belong to (Orthoptera:Gryllidae). Other minor field insect pests of yam include leaf miner spp (Cecidomiidae) which induces galls on yam leaves while termite (Isoptera) with species like , and are widely distributed in West Africa.

The potential sources and abundance of naturally occurring entomopathogenic fungi with bio-control potential against the cowpea pod borer, Maruca vitrata, were investigated by adapting the Galleria bait method. Soil samples from five sites: Cow-stead, Piggery and Poultry sites as well as Crops Research Garden (CRG) and Practical Year Training Programme (PYTP) farm for arable crops of the University of Ibadan were used in the study. Soil samples from the different sites and 2 nd instar larvae that were exposed to the samples of the different soils were assessed for occurrence and abundance of the fungi following standard procedures. Results show nine fungi species from soil samples and seven fungi species to be associated with dead larvae of M. vitrata. The most abundant fungi in the soil and dead larvae were Rhizopus sp. and Fusarium sp. while the most abundant fungus with known entomopathogenic potential was Beauveria bassiana followed by Trichoderma and Penicillium spp. The best sources for collection of the entomopathogenic fungi were the arable crop farms of the PYTP and the CRG sites where active farming activities carried out.

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The effects of plastic mulch on damage and yield of yam tuber by yam beetles were investigated at two locations in 2005 and 2006 cropping seasons in Delta State. Trials were laid out in Randomized Complete Block Design with three treatments: black plastic mulch, white plastic mulch and as unprotected control plot which were replicated three times. Data collected were, the number, depth and diameter of feeding holes on yam tuber (Dioscorea rotundata cv adaka), tuber yield and percentage yield increase over control as well as percentage tuber attacked and damage scores. The plastic mulch protected plots had positive impact on tuber yields as indicated by the relatively high percentage yield increase over control which ranged from 23%-66%. It was generally observed that plastic mulch protected plots were significantly different (P< 0.05) from the control in all the locations and year of cropping. Investigation revealed that white and black plastic mulches were not very effective against the beetle devastation but offered some protection.

Investigations were carried out in the rainforest ecological zones of Anwai and Ugbolu in Upper Niger Delta to evaluate ten plant materials as organic mulch for the control of yam tuber beetles in 2004/2005 cropping seasons. Field experiments were laid out in randomized complete block design (RBCD) and replicated three times. Results indicated that the ten plants materials applied at 20 tons per hectare caused varied differences in the feeding activities of the beetle. Across locations and planting seasons, Cymbopogun citrates L. and Ocimum viride L. were superior as repellant or antifeedant botanicals to the beetle than others evaluated. Plots with these treatments had significantly higher (p<0.05) tuber yields and less beetle damages but none caused beetle mortality.

Studies conducted in 2004/2005 in the rainforest ecological zone of Anwai-Asaba in the Upper Niger Delta, Nigeria, examined the occurrence and seasonal variation in the population of yam tuber beetles (Heteroligus spp). The beetle population started building up in May with the peak occurrence as determined by the light traps occurring in July-August. The population trend is climate dependent and the peak was unimodal. Correlation analysis was negative for temperature (b= -0.662) while it was positively correlated with rainfall (b=0.552) and relative humidity (b=0.543). Based on the coefficient of determination (R 2 ), beetle occurrence can be predicted on weather elements studied to about 52% for rainfall 29% relative humidity and 44% for temperature. The best predictive tools for monitoring the commencement of occurrence of the yam beetle are the three major weather parameters, namely temperature, relative humidity, rainfall but the later was more critical according to this study.

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