Watermelon Diseases Pictures and Pesticide Control

Watermelon is a common fruit in daily life and is very popular among consumers. However, at different stages of watermelon growth, it will be infected with different diseases, which will affect its yield and quality and require timely prevention and control. Here we talk about the complete picture of watermelon diseases and pesticide prevention.

1. Cataplexy

The pathogens are mostly fungi of the genus Pythium, which mainly harm unemerged and newly emerged seedlings.

In the early stage of the disease, yellow to yellowish brown water-soaked constriction spots appear at the base of the stems of the seedlings near the ground. The cotyledons do not wilt, but the seedlings have already fallen off suddenly. In severe cases, the base of the stem will rot, and white mycelium will be produced when the humidity is high.

The control agents include oxadiazine·mancozeb, cyathiacarb hydrochloride, cyazolin, meconium-methyl, myclobutanil, oxadiazine·mancozeb, oxadiazine·mancozeb, etc.

2. Anthrax

The pathogen is Colletotrichum spp. of the Cucurbitaceae family, which can occur throughout the entire growing period of watermelon and can infect all above-ground parts.

Circular brown spots appear on the cotyledons with light green halos on the edges; circular or irregular water-soaked spots begin to appear on the true leaves, which then turn into dark brown with purple-black halos on the edges and obvious whorls.

When the petioles or stems are infected, water-soaked, pale yellow circular spots initially appear, which later develop into slightly sunken dark brown spindle-shaped spots. When the fruit is infected, water-soaked, sunken brown spots appear, and cracks often appear. Under high humidity conditions, a pink sticky substance forms in the middle of the spots.

The control agents include Yingji (oxime·tebuconazole dry suspension), fenpropimorph, silazole·myclobutanil, myclobutanil, pyraclostrobin, etc.

3. Disease

The pathogen is Phytophthora melonensis, which can cause damage to watermelon throughout its entire growth period, but the disease is more serious during the adult plant stage.

The affected leaves develop water-soaked spots on the edges. The disease progresses very quickly, and the edges are not obvious. The leaves may rot when the humidity is high, and become brittle and easy to crack when dry.

In the early stage of the disease, the fruit has dark green water-soaked spots, and then soft rot and depressions are obvious. In humid conditions, a large amount of white mold grows on the surface of the diseased part.

The control agents include metalaxyl·mancozeb, oxazolidinone, methocarb·mancozeb, copper oxychloride·metalaxyl, oxazolidinone·metalaxyl, etc.

4. Vine blight

The pathogen is Mycosphaeria cucurbitae, which mainly harms the leaves, vines and fruits of watermelon, with the leaves and vines being more seriously affected.

After the leaves are infected, lesions mostly appear on the leaf edges, with yellow halos around the lesions and small black spots scattered on the diseased parts, which will dry up and crack in the later stage.

The most obvious feature of stem and vine damage is the outflow of amber-colored gelatinous substances, which may form longitudinal cracks after drying.

The control agents include pyraclostrobin, Yingji (oxathiapiprolin·tebuconazole dry suspension), fenpropimorph, carbendazim·thiophanate-methyl, mancozeb, etc.

5. Fusarium wilt

The pathogen is Fusarium oxysporum, which can occur throughout the growing period of watermelon.

After the disease occurs in the seedling stage, the number of fibrous roots decreases, and the plants quickly wither, turn yellow, and fall over; the disease occurs in the adult stage, and the aboveground parts wilt severely. They can recover in the early stage, but die in the later stage. The base of the stem does not constrict or rot, and the vascular bundles of the stems and vines change color and grow upward.

The control agents include Bacillus subtilis, carbendazim-methyl, thiram-methyl, and sinocycline.

6. Leaf blight

The pathogen is Alternaria cucurbitacis, and the disease is more serious in the middle and late stages of watermelon growth.

In the early stage of the disease, leaves produce brown spots that turn green, and then expand to form brown to dark brown. The spots are mainly concentrated on the leaf edges and veins. When the field is dry, they are mostly small round brown spots. If the humidity is high, they can merge into large spots, accompanied by a withering appearance.

The control agents include manganese zinc, manganese sulfamethoxam, tebuconazole, chlorpyrifos, and pyraclostrobin.

7. Bacterial fruit spot

The pathogen is Acidovorax avenae subspecies citrullus, a bacterial disease that can harm watermelon leaves, fruits, etc.

When the leaves become diseased, there are water-like spots near the veins. The spots grow along the veins and are long and narrow. When the fruits become diseased, there are large, irregular olive-colored water-soaked patches. In the later stage, the fruit skin cracks and is easily mixed with other diseases.

The control agents include spring thunder·copper king, chlorothiazide, chlorobromoisocyanuric acid, copper hydroxide, thiophanate-copper, etc.

8. Green mottle mosaic

The virus belongs to the tobacco mosaic virus genus and its symptoms are obvious on watermelon leaves and fruits.

When the disease occurs, the leaves fade and become slightly yellow with mottled spots and raised bumps; dark green spots appear on the surface of the diseased fruit, the inside rots into a gourd-shaped cavity, and the flesh turns dark red.

Since viral diseases cannot be cured, you can try using guanidine hydrochloride + Sea Elf biostimulant foliar type to relieve the symptoms in the early stages of the disease.

That’s it