Materials and Methods

Post-harvested studies were conducted on yam tubers (Dioscorearotundata cv abii) pretreated at cultivation in the field with Azadirachta indica and Piper guineense (fruit powder). Minisett dust (NRCRI) (from National Root Crops Research Institute, Umudike and Apronplus 50DS (a standard insecticide/fungicides) to control soil pestsand pathogen. The treatments were applied as seed dressing duston Minisetts yam tuber at 2.7kg/ha. And were replicated four timeswith 20 minisetts per replicate. The field was arranged in four fully randomized blocks with one replicate of each treatment per block.Each block measured 6 x 5m (made up of 5 ridges 6m in length with1m between blocks). Discard ridges surrounded the experimental netplots. After normal cultural practices (staking weeding and fertilizerapplication at the appropriate times) the yam tubers were harvestedafter 28 weeks.

The harvested tubers were stored in an improvised wellventilatedbarn where the yams were placed on horizontal racks.The temperature in the barn was monitored with a maximum andminimum thermometer and relative humidity measurements takenusing a whirling hygrometer. The minimum temperature duringthe period of study ranged from 22.7-28.7 °C, while the maximumtemperature ranged from 30.7-36.6 °C the relative humidity at 9.00-1.000h ranged between 78 and 85% and at 15.00-16.00 between 50and 75%.

The investigation was conducted after 16 weeks in storage on theeffect of treatments on yam tubers in parameter:

i. Weight Loss of yam tubers.

ii. Sprouting/Germination of yam tubers.

iii. Pests and pathogens infestation and yam rot.

iv. Nutrient/Composition of yam tubers.

i. Total weight loss of yam tubers (Table 1): Y a m tubers for the study were randomly selected from each treatment anduntreated control. (Each replicate of 10 yam tubers) After 16 weeksin storage, the yam tubers from each treatment and untreated controlwere weighed and the percentage weight loss calculated.

Table 1: Effect of bio - pesticide treatments at cultivation on weight loss of yam tubers after 16 (sixteen weeks) in storage.

Wt of yam tubers at harvest - Wt of yam tubers after 16weeks X 100, Weight of yams at harvest

ii. Sprouting/Germination (Table 2))

Four replicates of five tubers (4x5 = 20 ) were randomly selectedfrom each treatment and the untreated control. Sprouting of the yamtubers were taken after 14 weeks in storage when dormancy musthave been broken.

Table 2: Effect of bio and synthetic pesticide treatments on the sprouting/germination of D. rotundata cv abii after 14 (fourteen) weeks in storage.

iii. Pests infestation and rot diseases in storage (Table 3)

a. Nematode infestation at harvest was not apparent. After 16weeks in storage, galls were apparent indicating rook-knot nematodeinfestation. The galled tubers were counted and recorded for eachtreatment and the untreated control.

Table 3: Effects of bio and synthetic pesticide treatments on: pests, pathogens and rot/bio deterioration of D. rotundata CV abii in storage, after 16 weeks.

b. Insect infestation

The total numbers of adult insects found on the yam tuberswere counted after 16 weeks and recorded for each treatmentand untreated control. The main insects found were identified asAraecerus fasciculatus Degeer (Coleoptera: Anthribidae). (A yamstorage insect).

c. Yam rot (complex disease syndrome of micro-organisms).Total number of yam tubers affected by rot disease were counted foreach treatment and the untreated control and recorded.

(iv). Yam tuber composition (Table 4)

Analysis of yam composition of treated and untreated yam tuber sample were conducted for protein, carbohydrate, fat, ash and fibercontents at the Food Science/Biochemistry Laboratory at NationalRoot Crop Research Institute (NRCRI) Umudike.

Table 4: Effect of bio and synthetic bio pesticide treatments on yam D. rotundata cv abii composition after 16 (sixteen) weeks storage.