The Q&A Archives: Browning leaves

Question: Every year for the last three years my cucumber plants start off good but toward the middle to end of the summer the leaves start turning brown and the fruits turn yellow and die. Is this a mold or fungus and what is the remedy?

Answer: It sounds like bacterial wilt. Adult cucumber beetles and some other plant-wounding insects can transmit bacterial wilt to cucurbits. Wilt is caused by a slimy ooze which plugs the entire water-conducting tissue of the plant. The wilted plant will not recover, even if water is adequate in the soil. Other pathogens cause wilt, but bacterial wilt is distinguished by stick sap. Try cutting a severely wilted stem at the base of a lateral branch or just above ground level and squeezing the cut end. Ooze will exude from the water-conducting tissue. By touching the ooze with your finger then slowly drawing your finger away, the milky, sticky ooze will string out into fine strands up to one-fourth inch long. The most effective control is to cover your cucumber plants to exclude the insects. Since you need insect activity for pollination this becomes a real challenge! Instead, try scouting the plants for beetle activity on a daily basis and hand pick any you find. Or you can use an organic control such as Rotenone (Rotenone Garden Dust by Bonide) or a Neem oil based vegetable garden insecticide. Good luck with your garden.

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