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 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.

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The effect of different weights of seed yam (250g, 300g and 350g) on growth and tuber yield of white yam were evaluated. The results showed a significant differences (P<0.05) among the three seed weight yam weights in vine length, number and basal diameter, and leaf number measured at 8, 10 and 12 weeks after planting respectively. There were gradual increases in vine length and basal diameter, and leaf number as the seed yam weight increased throughout (he sampling period. The highest mean values of 4.5, 175cm, 8mm and 69.8 were recorded for vine number, length and basal diameter, and leaf number respectively, at 12 weeks after planting. The results showed that there were no significant differences (P<0.05) between seed yam weight of 300g and 350g but they were significantly higher than seed yam weight of 250g for vine number, and basal diameter and leaf number. The results on yield parameters revealed that the tuber number, length and fresh weight increased. The results showed that there were no significant differences (I'<0.05) between seed yam weight of 300g and 350g but they were significantly higher than seed yam weight of 250g for fresh tuber weight, number and length. However, the highest values were recorded in seed yam weight of 350g. There were no significant differences between 300g and 350g. Thus, this study seed yam weight of 300g could be the ideal size for farmers growing white yam in acidic soils of Anwai, Delta State.