Management of Diseases in Watermelon
Watermelon is one of the most popular vegetable crops of India which is vulnerable to major diseases which needs to managed regularly for getting quality and good crop. The major diseases of watermelon and their management is discussed below.
1. Downy mildew - PSEUDOPERONOSPORA CUBENSIS
The disease symptoms start with development of chlorotic pale green to yellow or brown lesions/spot on upper surface of leaves, which later spreads to the lower surface covering violet/gray/white downy patches of mildew.
Under severe conditions leaves start to wilt, wither, die early and shed from the plants leading stunted growth of plants and reduces yields.
Sometimes infection even appears on stems, flowers and fruits, causing significant loss of fruit quality and yield.
The following chemicals can be used to control Downy mildew in watermelon
2. Powdery mildew - ERYSIPHE CICHORACEARUM
The symptoms appear with light green to bright yellow spots/lesions on the upper surface of leaf, which enlarge and become necrotic tissues.
Under severe conditions dense whitish powdery fungal growth appear on underside as well as upper side of leaves causing distortions.
Ultimately the entire leaves will wither and die, but remain attached to the stem. Under severe conditions with favorable conditions disease may also appear on the fruits which affects the quality of fruits with lack of flavor and normal taste.
The following chemicals can be used to control Powdery mildew in watermelon
3. Anthracnose - COLLETOTRICHUM ORBICULARE COLLECTOTRICHUM LAGENARIUM
Symptoms appear with water soaked sunken irregular blackish brown spots appearing first on foliage, then on stem and fruits.
The spots increase in size leading the stem girdling and wilting of vines.
It may also affect fruits with sunken spots brown spots, under severe conditions leads to rotting of fruits with secondary infections.
The following chemicals can be used to control Anthracnose in watermelon
4. Alternaria leaf spot - ALTERNARIA CUCUMERINA
Small light green to yellow concentric rings on the older leaves which later turn grey to brown. As the size increases become more darker giving bulls-eye appearance of lesions.
Infected leaves wilt and curl upward like cup and wither off from the plant. Leaf damage leads to development of brown to gray sunken lesions on fruits.
The following chemicals can be used to control Alternaria leaf spot in watermelon
5. Fusarium wilt - FUSARIUM OXYSPORUM F.SP. NIVEUM
Yellowing of the leaves occurs initially later the whole plant starts to wilt from top to bottom.
There will the brown vascular discoloration of infected stem and roots which leads to death of plants.
The following chemicals can be used to control Fusarium Wilt in watermelon
6. Gummy stem blight (DIDYMELLA BRYONIAE)
Light brown to chocolate brown lesions surrounded by yellow tissue develop initially in the margin of leaves and cover the entire leaf.
The lesions may also develop on stem, causing cankers and brown gummy ooze secrete from cankers.
The symptoms even occur on young seedlings as water-soaked regions on hypocotyls which leads to splitting of stem with brown gummy exudate.
Small water-soaked spots appear on fruits that turn into large brown spots along with gummy secretions sometimes as in case of stem causing rotting of fruits.
The following chemicals can be used to control Gummy Stem blight in watermelon
7. Bud necrosis disease - (TOSPO VIRUS)
Chlorotic rings appear on leaves initially, which turn brownish black causing complete browning of leaves and distortion of leaves.
The mottling and crinkling of leaves take place leading to stunted plant growth. On fruits surface pale ring spots appear which turn to necrotic or scab like lesions.
8. Cucumber Mosaic virus - CUCUMBER MOSAIC VIRUS
Mosaic symptoms appear on younger leaves causes downward curling of leaves. The affected leaves look mottled, distorted, wrinkled and reduced in size. The plant looks bushy/bunchy because of reduced internodal length.
If infected at early stage of crop, fruiting will be reduced, and the fruits developed from affected plants will be often misshaped, mottled with reduced size.
This viral disease is transmitted by aphids (Aphis craccivora, Myzus persicae).
9. Watermelon leaf curl virus
The affected plants show crumbled leaves with yellow, and mottled areas. The reduced leaf petioles make plants to look bushy around the vines. If disease occurs at early crop stage, it significantly affects yield.
This viral disease is transmitted by whiteflies.
The following products can be used to control all types of Viral diseases in watermelon
Note: To manage viral diseases
1. To avoid all types of viral diseases don’t use more of ammoniacal form of nitrogen fertilizers like Urea, Ammonium sulphate, 19:19:19, 28:28:0 and improperly decomposed poultry, sheet & goat manures.
2. Use only required quantities of ammoniacal fertilizers and use only completely decomposed manures from poultry, sheet and goat.
3. Use Manganese and other micronutrient mixtures to manage with viral diseases.
10. Root knot nematode - MELOIDOGYNE SP
Nematodes living in soil infest and feed the roots causing swelling and galls, which reduces the ability of roots to absorb water and nutrients.
As a result, we can observe the nutrient deficiency symptoms on the foliage of plants. It leads to stunted growth, yellowing and wilting of whole plant.
Before sowing: Multiplex Safe root @ 2kg/acre with organic manure
The following products can be used to control Root knot nematodes infestation in watermelon
Dr. Asha, K.M.,
Subject Matter Expert, BigHaat.
Disclaimer: The performance of the product(s) is subject to usage as per manufacturer guidelines. Read enclosed leaflet of the product(s) carefully before use. The use of this product(s) /information is at the discretion of user.
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