Melon
Cottony Leak
Pythium aphanidermatum
Fungus
In a Nutshell
- Brown, soft, rotted areas on fruit.
- White, cotton-like growth on fruit.
- Death of newly germinated seedlings.
Melon
Symptoms
The symptoms begin as brown areas that develop into soft, rotted areas on fruits that are in direct contact with the soil. During humid conditions, white, cottony growth appears and covers this rotten area of the fruit. In the nursery, the same pathogen can damage young and old seedlings causing their death. The pathogen can also damage roots, causing them to rot: leaves then turn yellow because the plant can't take up nutrients. Fruit rot caused by Pythium can look like fruit rot caused by Phytophthora and Sclerotinia. To tell them apart, remember: Pythium looks like cotton or shaving cream. Phytophthora looks like flour or powder. Sclerotinia has thick white cottony growth with black, hard spots that also affect the stem.
Recommendations
Organic Control
There is no certified and applicable biological control.
Chemical Control
Once symptoms appear, affected seedlings or fruits can't be saved. To prevent infection, apply chemical treatments to seeds and seedlings. Treat seeds before planting and dip seedlings in the recommended concentration. Additionally, use surface soil treatments. The effectiveness of these treatments depends on the fungicide moving into the top inch of soil through irrigation or rainfall.
What caused it?
The pathogen causing Cottony Leak lives in the soil! It is favored by hot, humid weather and loves stagnant water. It spreads with irrigation water. It enters the plant’s cells easily stopping the plant from nutrient uptake and decaying affected parts. Wounds from pruning, thinning or removing leaves make plants more susceptible, allowing the pathogen to spread easily.
Preventive Measures
- Ensure proper soil drainage.
- If possible use raised beds and drip irrigation.
- Rotate with non-host plants like grasses and grains.
- Plant on cool days.
- Space plants widely to avoid dense vine-matting.
- Create barriers between fruits and soil, which is practical for small growers.
- Place fruits on wire, wood, or top of vines.
- Use plastic mulch with drip irrigation in dry areas, but be cautious in rainy areas as it can hold water and cause decay.
- Regularly clean and disinfect your tools, pots, and trays with a bleach solution, and avoid using contaminated soil.
- Do not harvest and pack harvested fruits in wet weather.
- Harvest and pack only the healthy-looking ones.
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