Row covers for management of insect-vectored viral diseases of tomato in Uganda

Tomato production in Uganda is constrained by among others use of low quality planting materials, non-availability of inputs, sub-optimum agronomic practices, pests and diseases. Studies have shown that viral diseases have quickly become a major threat to tomato production in Uganda. The objective of this study was to develop safe, easy to use and effective management strategies for the rampant insect vectored viral diseases of tomato (Solanum lycopersicum). The study was conducted at Makerere University Agricultural Research Institute Kabanyolo (MUARIK). In a Randomized Complete Block Design with three replications; four treatments: (i) Insect proof plastic row covers applied from transplanting to 14 days after transplanting (DAT), (ii) ) Insect proof plastic row covers applied from transplanting to 28 DAT, (iii) Insect proof plastic row covers applied from transplanting to 36 DAT, (iv) the uncovered control were considered. Tomato variety MT-56 was used. Results over two growing seasons in 2013 showed that for the duration of the application, the insect proof plastic row covers kept aphids and white flies off the protected plants but were encountered on unprotected plants. Treatments significantly affected incidence and severity of Cucumber Mosaic Virus (CMV) and Tomato Yellow Leaf Curl Virus (TYLCV). Mean disease severity for TYLCV was 0.29, 0.317, 0.097 and 0.38 for treatments (i), (ii),(iii) and (iv) respectively. Mean disease severity for CMV was 0.407,0.413, 0.043 and 0.603 for treatments (i), (ii),(iii) and (iv) respectively. In the second season mean disease severity for TYLCV was 0.353, 0.300, 0.157 and 0.450 for treatments (i),(ii),(iii) and (iv) respectively. Mean disease severity for CMV was 0.443,0.437,0.103 and 0.677 for treatments (i),(ii),(iii)and (iv) respectively. Plants protected for 36 DAT had the lowest disease severity. Despite the low disease rates on plants protected for 28 and 36 DAT, there was yield penalty in these treatments with average yields of 4 and 2 fruits respectively compared to average yields of 7 for plants protected for 14 days and the uncovered plants. Plants protected for only 14 DAT had the highest yield, followed by the untreated ones.