MANAGEMENT OF LEAF CURL DISEASE OF TOMATO
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Date
2002
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Abstract
To evaluate the influence of various phytoextracts, chemicals and other substances against Tomato Leaf Curl Virus (ToLCV) disease and the cultural management practices viz., barriers and mulching, present investigation was carried out during the year 2000-2001 at B. A. College of Agriculture, Gujarat Agricultural University, Anand. The study on evaluation of various plant extracts against ToLCV indicated that pre-inoculation spray of phytoextract was more effective as compared to their application after ToLCV inoculation (Post-inoculation treatment). Among the plant species tested 10% aqueous leaf extract of Mirabilis jalapa and Catharanthus roseus as pre-inoculation spray were the best and recorded an inhibition of 93.33% while the same when applied after inoculation could exert an inhibition of 73.33% which was highest among its post-inoculation counterparts. The effect of pre- and post-inoculation treatment of chemicals and other substances didn't have much of a variation in case of growth regulators. The difference in ToLCV inhibition by pre- and post-inoculation treatment with gibberellic acid was not as large as seen in the case of phytoextracts. Although, gibberellic acid didn't inhibit or inactivate the leaf curl virus its pre- and post-inoculation spray resulted in least ToLCV infection (6.67 to 13.30%) followed by Guanidine hydrochloride (0.2%)) and Guanidine carbonate (0.2%). None of the different concentrations of cow urine could exert any inhibition of ToLCV. Moreover, the concentrations of cow urine that exceeded 20% caused phytotoxic effect at the true leaf stage of the tomato test plants. Whitefly count recorded at weekly interval from the yellow sticky traps installed in all the unsprayed plots of barriers indicated that the yellow sticky traps in grey cloth and nylon net barriers plots recorded least number of white flies as compared to those recorded in the rest of the traps throughout the season. Further, the numbers of white flies on the traps were as high as 29 in control where as grey and nylon net recorded only 15-18 whiteflies at 11 weeks after tomato transplanting. Among the different treatment combinations of barrier and insecticide spray, grey cloth barrier along with four sprays of triazophos @ 0.04% was at par with nylon net and superior to sunnhemp and rest of the treatment combinations. Grey cloth and nylon net emerged as significantly superior to rest of the treatments in preventing the immigrant whiteflies from entering the tomato plots thus reducing the ToLCV incidence (21.67% and 27.61% respectively) which in turn reflected in the tomato fruit yield (57.50 and 54.50 t/ha). The next best treatment was sunnhemp. From the two years of periodical observation and that of pooled it can be inferred that among the variety of mulches tested, the silver and grey mulches could maintain the ToLCV disease incidence below 10% even till 75 days after transplanting. Where as, at this period the incidence in control was 45.97% about four times of that recorded in the former cases (9.67 and 9.77% respectively). Pooled analysis of two years of mulch experiment data revealed that significantly least incidence was recorded at harvest jn silver and grey mulch plots due to corresponding least whitefly population. The next best treatment was "triazophos @ 0.04%. The black and silver mulch could also suppress the weed population significantly. Fruit yield was also highest in silver and grey (58.55 and 56.32 t/ha respectively) followed by triazophos. The ICBR computed for mulching as a management practice in tomato revealed that silver and grey gave maximum additional income (73,620 Rs/ha). The ICBR for silver and grey mulches were 1:2.77 and 1:2.60 respectively. Although triazophos @ 0.04% gave a very high ICBR of 1:19.73 but the ecofriendly nature of the management through mulching puts it at an advantage over the insecticide application. Hence, it can be concluded that, silver and grey mulching in tomato field can be practiced to keep the whitefly population at a low level thereby reducing ToLCV incidence.
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AAU, Anand, A Management