Pythium fruit rot (also called Pythium cottony leak) of cucurbits is caused by several fungus-like organism of the genus Pythium. The disease is most severe on cucumber, but watermelon, pumpkin, and melon can also be affected. Pythium spp. are found in most, if not all soils, of the world. Fruit infection occurs through wounds or where fruit touches wet soil. The pathogens grow quickly through diseased tissues. The Pythium fruit rot pathogens are readily disseminated within and among fields in irrigation water and on contaminated equipment. Pythium spp. survive between cucurbit crops as pathogens on many crops and weeds, and as dormant resting structures in soil.
Pythium fruit rot symptoms begin as brownish, water-soaked lesions that quickly become large, watery, soft, and rotten. The rot generally begins on the parts of fruit in contact with the soil. In cucumber, a brown to dark green blister often is apparent on fruit before they become watery and rot. White cottony mycelium is apparent on rotten tissues, especially during humid weather. Pythium fruit rot is most severe in poorly-drained fields during wet weather. The disease can render fruit unmarketable.
No biological control strategies have been developed for Pythium fruit rot.
Cucurbits should be planted on sandy, well-drained soils to allow rapid drainage after rain or irrigation. Avoid dense plant populations and narrow row spacing that leads to dense vine matting. Plastic mulch can provide some disease reduction in semi-arid production environments, but should not be used with overhead irrigation or in high rainfall production areas because water accumulates on the plastic and promotes fruit decay.
Chemical controls should be used in combination with cultural controls to be most effective.
Product List for Pythium Fruit Rot:
Pesticide |
Product per acre |
Application Frequency
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Remarks |
Mefenoxam |
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Ridomil 2E |
4-8 pt |
Preplant-broadcast |
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The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality. |
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Categories: Cucurbits, Disease, Pythium Fruit Rot, Cucumber, Melon, Pumpkin, Squash, Zucchini
Date: 04/01/2007