TUBER INFESTATION BY POTATO TUBERMOTH, PHTHORIMAEA-OPERCULELLA (ZELLER), AT POTATO HARVEST IN RELATION TO FARMERS PRACTICES

Cultural practices which reduce tuber infestation by the potato tubermoth (PTM) Phthorimaea operculella (Zeller) in potato fields are conditioning an integrated control approach in low-cost, unrefrigerated potato stores. At harvest time on-farm research was conducted in Tunisia to record farmers production methods and to assess tuber infestation. The relationship between infestation and production methods was analysed by multiple regression using two different functional response models. Both models explained the tuber damage significantly, i.e. R2 = 0.58 (P = 0.0003) and R2 = 0.48 (P = 0.0035). Tubers were significantly more vulnerable to PTM attack in a region with milder climatic conditions, if harvest was delayed after final irrigation, in dry and cracking soils, and if the crop maturity was too much advanced. Compared with gravity irrigation, sprinkler irrigation apparently reduced tuber infestations. Wealthier farmers tended to have less damage. Insecticide applications in the field tended to increase tuber infestations. © 1990.