ABSTRACT

This study is aimed at investigating the effect of pre-infection and post-infection treatments with selected plant extracts on Phytopthora leaf blight of Colocasia esculenta under screen house condition. The research was carried out in the screen house of National Root Crop Research Institute (NRCR1), Lmudike. The study was carried out with two Colocasia esculenta varieties, inoculums of Phytopthora colocasia isolated from infected taro leaf and four plants extracts which include Neem {Azadirachta indica), Bush candle {Senna alata), Eucalyptus {Eucalyptus globules) and Mexican sunflower {Tithonia diversifolia). The experiment was laid in complete randomized design and replicated three times. The disease severity and diameter oflesion oftwo varieties of Colocasia esculenta showed no significant difference due to varieties. When the treatments were compared, there was a significant difference in the four treatment regime subjected to the varieties. The mean value of NCE 01 \-Akinnbgawa was slightly higher than NCE 0\2-Akpahuru both on Disease severity and Diameter of lesion. This had no effect when compared with the LSD <o.os) value (0.57). The mean value oftreatment was highest in the control followed by treatment 1 {Eucalyptus). Treatment 4 {Tithonia diversifolia) had the least mean value on disease severity (1.92) while treatment 2 {Senna alata) had the least mean value on Diameter of Lesion (4.11). The control showed significant difference with treatment values when compared with LSD (o.O5) values (0.91 and 0.84) for disease severity and diameter of lesion respectively. There was a significant difference P (<0.05) in the disease severity as a result of the method of treatment. The mean value of Pre-infection is higher than Post-infection in both disease severity and diameter of lesion (3.08 and 4.70). Values range from 2.37 - 3.08 for disease severity and 4.70 - 4.69 for diameter of lesion. Based on these results, it is apparent that both varieties are highly susceptible to P.colocasiae, but the first variety of cocoyam NCE 012- Akpahuru should be cultivated more than the second variety of C. esculenta NCE 011- Akinngbawa, Mexican sunflower Tithonia diversifolia extract should be used for inhibition of P. colocasiae (TLB) and post-infection method should be adopted over pre-infection method