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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

IS SOMETHING BUGGING YOU? – BUGS IN THE VEGGIE GARDEN

written by Marianne C. Ophardt WSU Extension Faculty for the Tri-City Herald, Kennewick, WA Is something bugging you? Did you know all bugs are insects, but not all insects are bugs? A ‘true bug’ is a certain kind of insect that belongs to the Hemiptera order of insects. This means they have two pairs of wings that are thick and leathery at the base and membranous at the tips. When at rest, the wings overlap and lay flat against a bug’s body, resembling a shield. Their hypodermic-like beak allows them to pierce and suck up juices. There are good bugs and bad bugs. The squash bug, one of the bad bugs, is currently wreaking havoc in some area veggie patches. Because the squash bugs are sneaky and tend to hide under debris and dirt when disturbed, many gardeners fail to recognize their presence. One good way to tell if squash bugs are at fault for failing squash plants is to hunt for them. I’ve found the best time to see squash bugs scurrying about is in the evening, just before dark. Look for the bugs on the ground at the base of plants and vines. Mature adult squash bugs are elongated, dark brown to gray and three-quarters inch in length with the ‘true bug’ characteristic shield marking on their backs. Nymphs (youngsters) can look quite different with the youngest nymphs having red heads and legs on greenish bodies. Older nymphs have light gray bodies and black legs. The squash bug (Anasa tristis) attacks not only squash, but may also feed on other members of the cucurbit (squash, cucumber, and melon) family. Both the adult bugs and younger nymphs feed on leaves causing yellow spots that turn brown with time. However, the more significant damage they cause is from the toxin they inject into vines and leaf stems when they feed. This toxin results in the wilting of vines and leaves and dieback to the point of where the toxin was injected. Small plants are likely to be killed by squash bug feeding. On larger plants, several runners or more may be lost. Squash bug eggs are also a telltale sign of this pest’s presence. They lay their eggs on the undersides of the leaves, near the veins, in small groups of a dozen or so. These eggs are yellow-orange at first, later turning a bronze-brown. Squash bugs are so stealthy, many gardeners are surprised to find them on their plants. Where did they come from? In the spring after the weather warmed up and the squash plants started to grow, unmated adults emerged. They had spent the winter sheltered under garden debris, boards, or in building walls. Once the adults emerged, they started to feed on the plants and mate. Not long after, they start laying eggs and will continue until the middle of summer. Only one generation occurs during the season. In the fall, unmated adults will find a quiet, protected place to spend the winter. There is one main chemical control of squash bugs. Carbaryl (Sevin) dust is applied to the soil around the base of the plant. Care must be taken to not get the carbaryl dust near the flowers, as it’s highly toxic to the bees needed to pollinate the plant. Repeat applications of carbaryl are usually needed. It’s extremely difficult to manage a squash bug infestation without the use of chemicals. If you are a vigilant gardener you can watch over your plants and crush egg clusters as they appear. You can also collect and destroy any bugs moving about. Research indicates that the use of light-weight row-cover fabric can also help. The fabric is placed over the garden row right after the seeds or transplants are planted in the spring, leaving enough slack for the plants to grow. The fabric is then anchored tightly to the ground along the edges. It’s removed right before the female blossoms start to open. The effectiveness of using row-cover fabric for squash bug control is dependent on rotating crops in the garden each year. The stink bug is another ‘bad bug’ that will make it’s presence apparent when garden tomatoes start to ripen. How did these true bugs get their negative name? They stink! To fend off predators, stink bugs secrete a bad-smelling and bad-tasting liquid from their body. There are actually a number of different types of stink bugs. Stink bugs have broad shield-shaped bodies. The two most common stink bugs in the Northwest are the consperse stink bug, (Euschistus conspersus), which is light brown in color and the Say stink bug, (Chlorochroa sayi) which is bright green. These two stink bugs are wedge-shaped (broader in front than in the rear) and about one-half inch in length when mature. Remember that true bugs don’t have chewing mouthparts, just sucking mouthparts. When they pierce and suck up tomato ‘juice’ they inject toxins along with their saliva. This causes the cells in that area to become corky and not develop their normal color. This is what’s called ‘cloudy spot’ in tomatoes, a whitish blemish beneath the skin. If one looks very closely at the spots, you can see the tiny hole where the bug punctured the skin. It doesn’t take very long for a few bugs to significantly impair the beauty of a nice red ripe tomato. Stink bugs also attack other types of fruit including peaches, pears, and raspberries. On peaches and pears, the fruit becomes lumpy from their feeding. On raspberries their stinky body fluids leave a bad taste and odor to the berries. While the cloudy spots on tomatoes impair their luscious appearance and make them more difficult to peel, the fruit are safe to eat or can. Because the stink bugs feed for such a short time and because their damage isn’t usually noticed until after they’ve fed on the fruit, management is difficult. Your best bet is to control weeds around the vegetable garden in the fall, spring, and summer. Weeds provide habitat and overwintering spots for the bugs. It’s especially important to get rid of legumes, blackberries, Russian thistle, mustards, and mallow. Gardeners can also slow down the build up of a population in their garden by looking for and destroying stink bug eggs, nymphs, and adults. The eggs vary in color, but are barrel shaped and laid in groups. Lest you think all true bugs are bad bugs… there are also some good bugs. ‘Good bugs’ include big-eyed bugs, minute pirate bugs, soldier bugs, ambush bugs, and assassin bugs. They feed on other insects by capturing them and then using their beak to pierce and suck out the body fluids of their prey. They may also inject a small amount of paralyzing poison to make the victims easier to handle while they sip out the juices. It’s not very appetizing to us, but it’s effective for the bugs. Is something bugging you? Check things out in the garden.

Published: 7/30/2005 11:43 AM

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