4.9.12
INTEGRATED CONTROL OF ALTERNARIA BLIGHT OF OILSEED RAPE AND MUSTARD: ROLE OF PLANT NUTRIENTS AND JUDICIOUS USE OF FUNGICIDES

SJ KOLTE, SR SHARMA, RP AWASTIU and VISHWANATI

Department of Plant Pathology, GB Pant University of Agriculture and Technology, Pantnagar-263 145, India

Background and objectives
Oilseed rape (Brassica campestris) and mustard (B. juncea) are very important cruciferous oilseed crops in northen states of India. The crop usually escapes the severe occurrence of Alternaria blight disease (A. brassicae), if planted early between the second fortnight of September and the first week of October [1]. But because of the intensive cropping patterns followed these days, the crop may be sown as late as the third week of October, and later becomes very susceptible to the pod-infection phase of Altemaria, resulting in heavy yield losses. The effect of potassium application in reducing the severity of Alternaria and increasing the seed yield has been demonstrated [2]. The present studies were therefore undertaken to explore the possibility of using plant nutrients such as potassium, sulphur, zinc and boron to control the disease through inbuilt host resistance, and of integrating its usefulness with fungicides, thus minimizing the number of sprays and the recommended concentrations of fungicides.

Results and conclusions
The results of the pot experiments revealed that plant nutrients differentially altered the efficacy of the foliar fungicide mancozeb (0.2%) in controlling Altemaria blight. A combination of boron at 0.53% spray, boric acid or zinc at 0.22% spray through zinc oxide showed synergistic effect in the effectiveness of mancozeb and brought about a 16-20% improvement in disease control in comparison with such treatments used separately. Similarly, plants raised in soil supplied with sulphur (40 kg/ha) and sprayed with mancozeb (0.2%) showed increased disease severity; and adverse effect was also seen in the efficacy of zinc or boron or potassium in controlling the disease. The present studies indicate the importance of integrating plant nutrients such as boron, potassium and zinc with foliar sprays of fungicides for management of the Alternaria disease problem in oilseed rape.

References
1. Kolte SJ, 1985. Diseases of Annual Edible Oilseed Crops. Volume II: Rapeseed-Mustard and Sesame Diseases. CRC Press, Boca Raton, Florida, p. 135.
2. Sharma SR, Kolte SJ, 1994. Plant and Soil 167, 315-320.