Can Chlorine Turn Squash Leaves Yellow When You Water Them?

Chlorinated Water

• Municipal water contains chlorine, but usually not in large enough amounts to cause damage to squash plants. However, chlorine bleach in gray water, which is household water such as laundry water that is reused, may have enough chlorine to injure squash plants.

Symptoms and Solutions

• Squash plants that have been damaged by chlorine may show burned tips around the leaf edges or new growth may appear light yellow or white. Do not use laundry water for plants if you added chlorine bleach products to the wash cycle. Or, allow the water to sit overnight before applying it to plants so the chlorine dissipates. Avoid wetting the plants' leaves when watering with gray water.

Disease

• Consider disease rather than chlorinated water as a possible cause of yellowing leaves in squash. Squash plants are susceptible to many diseases, such as mosaic virus, anthracnose or bacterial wilt. These diseases usually cause spots to develop on the leaves or fruit before the entire leaves yellow or wilt. Some diseases are treatable through applications of fungicides, but a better strategy is to prevent them in the first place. Rotate crops every year and remove garden debris at the end of the season. Plant squash plants in full sun and water them in the morning so leaves dry off quickly.

Insects

• Several insects can cause squash leaves to turn yellow. Spider mites leaves a stippled, yellowed appearance, while squash vine borers cause the leaves and stems to wilt, turn yellow and collapse. Aphids suck the juices from squash plants, causing them to wilt and yellow. Look for other signs of insect infestation, such as holes in the stems and leaves, black or sawdustlike flecks or a sticky substance known as honeydew. Consult a county extension office for advice on the appropriate treatment after identifying the pest.