Management of tomato late blight disease using reduced fungicide spray regimes in Morogoro, Tanzania

Tanzania Journal of Agricultural Sciences 2015, Vol. 13(2) : 8-17Tomato (Solanum lycopersicum L.) production in Tanzania is affected by late blight disease caused by Phytophthora infestans (Mont.) de Bary. Currently, farmers spray more than 12 per crop per season to control diseases by weekly spraying. Field experiments were conducted at Morogoro to evaluate the performance of three tomato varieties subjected to different fungicide chemistries and reduced fungicide spray intervals. The treatment factors were tomato varieties Meru, Cal-J and Tanya as main plots; fungicides Ivory 72 WP, Volar MZ 690 WP and Topsin-M 70 WP as sub plots; and reduced number (4, 6, 8 and no-spray) of sprays per crop at a spray intervals of 14-, 10-, 7-days respectively as sub-sub plots. Variety Meru showed low tomato late blight incidence (1.4%) and severity (1.0) (P≤0.001) followed by Tanya (81.2%, 4.0) and Cal-J (82.6%, 4.0) respectively. Results show that plots sprayed with Topsin M-70 WP had significantly (P≤0.001) higher disease incidence and severity (66.2%, 3) compared to Ivory 72 WP (42.5%, 2) and Volar MZ 690 WP (44.5%, 2). The no-spraying regime (control) had highly significant (P≤0.001) disease incidence and severity than other spray regimes. Although there was no significant (P≤0.05) difference among the spray regimes plots sprayed 8 times had lowest disease incidence and severity (47.9%, 2) while, unsprayed plots had highest disease incidence and severity (66.3%, 4) followed by plots sprayed 6 times and 4 times (53.9%, 2) and (52.1%, 2) respectively. There were significant differences (P