1. Fnngal Diseases
-----------------------
WOt (Fusarium oxysporum f. sp. niveum (Smith) Snyder and Hansen): The plants are prone to attack at all stages of growth. Definite wilt symptoms are visible on old plants with drooping leaves. Affected plants turn yellow and are stunted. On nursery seedlings, "damping off" symptoms appear and the seedling dies.
Control Measures: Since the pathogen is soil borne, crop rotation is advisable for the control. Seed infection may be avoided by treatment with benlate or Bavistin (3 g/kg seed). Seed treatment with hot water (55 °C) for 15 minutes kills seed borne infection.
2. Viral Diseases
-----------------------
Watermelon Mosaic Virus: The disease was first recorded in the USA in 1932. Later on, this was reported from various countries. In India, Bhargava and Joshi (1960) first reported this disease. Diseased vines are conspicuous because the tips of the runners and a proliferation of shoots from around the crown protrude stiffly above the general level of the vines, giving a “petunia-like" appearance. The tips and shoots have shorter than normal internode which produce crowding of the young leaves, which are stunted and rolled. Mottling may or may not be present, marked or diffuse, consisting of irregular yellow areas only slightly lighter than normal green of the young melon leaves. Leaves of the infected plants also show various deformations, blistering and remain in size. Flower on severely infected plants show abnormalities of the petals, which are of unequal size and greenish colour. Stamens are distorted and unevenly developed and the flower may fall prematurely. Melons produced on diseased veins are mottled and also sometimes mis-shappen. Diseased veins bear few fruits of small size.
Control Measures: (i) Roguing of infected plants from the field as soon as they are noticed, (ii) Control of weed host Melothris pendula, which acts as a source of inoculum, (in) Control of aphid vectors through insecticides, (iv) Sources of resistant of tolerance to WMV-1 have been described for melon. Cucumis metuliferus, Cucurbitae cuadorensis and C.foetidissima are highly resistant -to WMV-1. A non specific resistance to WMV-1 transmission by A. gossypii has been found in melon line PI 161375. (v) Spread of watermelon mosaic virus (WMV-1) can be significantly reduced by mineral oil spray. JMS-stylet oil has been recommended. Summer oil at 0.2 per cent concentration has been found to encounter very less number of aphid vectors (A. gossypii) and very low incidence of WMV-1.
Yield and Storage Management:
The crop will be ready for harvest in 75-100 days after sowing depending upon cultivars and season. The fruit becomes fît for consumption in about 30-40 days after anthesis. Maturity in watermelon can be judged from withering of tendril, change in belly colour or ground spot to yellow and thumping test On thumping the fruit, die mature fruit will give dull sound. There is another test on pressing the fruit, the ripe fruit will gave a crisp, cracking noise but this test should not be followed as it may damage the fruits. The fruit should be separated from the vine with the help of knife. A well-maintained crop can yield 400-600 q/ha. Watermelon requires careful handling as they are easily damaged and they can not be stored more than 2 to 3 weeks.
