Abstract
The population dynamics of the potato tuber moth (PTM) Phthorimaea operculella (Zeller) and the influence of potato cultivar, planting date, planting depth, hilling-up, irrigation intervals and mulching on insect infestation and on the greening of tubers in the field were studied at Shambat, Khartoum North, Sudan in the 1987/88 and 1988/89 winter seasons. The insect population initially increased slowly, then more rapidly after crop establishment and throughout the harvest period, after which it declined sharply. Tuber shape and skin characteristics had no effect on the degree of PTM infestation. Planting in the second week of November resulted in less insect damage and a significantly greater total yield compared with crops planted 3 weeks later. Greater depth of planting and more frequent hilling-up significantly lowered infestation levels and reduced the greening of tubers; for example, insect damage in early planted crops ranged from 3·3% (planting 10 cm deep and hilling-up thrice) to 16% (planting at 5 cm depth and hilling-up once). Irrigation and mulching both significantly reduced PTM damage and the greening of tubers. Light irrigation every 4 days and mulching with neem (Azadirachta indica) leaves during the last 4 weeks before harvest were the most effective treatments. Significant reductions in losses inflicted by PTM and by the greening of tubers were therefore achieved by the manipulation of crop husbandry practices.