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WHAT’S WRONG WITH MY CUCURBIT?

written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA
published- JUNE 27, 2014

WHAT’S WRONG WITH MY CUCURBIT?

Cucurbits (squash, cukes, and melons) are popular garden veggies. That is probably why questions about cucurbits are second only to tomatoes when it comes to problems that gardeners encounter in their vegetable gardens.

A common question is, ‘why aren’t I getting any squash even though my plants have a lot of flowers?’ To understand the answer it is important to know that cucurbits have separate male and female flowers. Only the female flowers can produce fruit and only the males produce the pollen needed for pollination and fruit development. The cucurbits depend primarily on honeybees to transfer the pollen from the male flowers to the females.

In order for pollination to occur, both male and female flowers must be open at the same time. Typically, cucurbits produce all male flowers at the start of flowering and a little later also produce female flowers. Conversely, plants of hybrid cucurbits generally produce female flowers first and male flowers second. However, before long both sexes of flowers are open at the same time and then the bees must go to work.

Once male and female flowers are blooming at the same time, there are several reasons that fruit still may not develop. Lack of honeybees or low bee activity due to hot weather, wind, or rain can hamper successful pollination.

If the honeybee population is low or nonexistent, you can assume the duties of a honeybee. Do this by picking a freshly open male flower (they have pollen in the center) and removing the petals, leaving the center portion (anthers) with the pollen. Insert this into the center of a newly open female flower (has a baby fruit at its base). Gently move the anthers around to transfer the pollen from the anthers to the center structure (stigma) in the female flower.

Another common cucurbit question comes from area gardeners when they discover small to large dry whitish or tan spots on the leaves of squash, melons, or cukes. It is typically most severe on the plant’s larger, older leaves and not evident on the youngest leaves. It looks like a disease problem, but it usually is wind injury. This occurs when the winds buffets the leaves about, causing the spiny surfaces of the leaves and stems to wound themselves. Badly injured leaves will be very brittle and often tear after additional windy weather. Placing a garden in a less exposed spot or shielding the plants from wind in some way might help.

Area gardeners also wonder why the leaves of squash wilt during the day and then perk back up in the evening. Is it a wilt disease or squash bugs? No, this daytime wilting indicates that the leaves are not being supplied with enough water to keep up with the amount of water they are losing through their leaves during the heat of the day. This ‘lack’ of water may be caused by too little soil moisture, a poorly developed root system, root rot from too much water or poor drainage, or root damage from enthusiastic weed cultivation. Consider the situation and try to remedy it for a healthier, more productive plant that does not wilt during the day.

Other common problems to look for on cucurbits are squash bugs and powdery mildew. You can find out more about these on the WSU website called ‘Hortsense,’ short for Horticultural Sense. You can find Hortsense at http://pep.wsu.edu/hortsense/. Start looking for squash bugs now.

Published: 6/27/2014 11:40 AM

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