Ron Kujawski | Garden Journal: Why is my zucchini squash wilting?

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After wilting in the heat and humidity of July, most of us who spend much of our day outdoors are feeling a bit of relief with the less oppressive weather of late. Yet, I do see some wilting, but it is not gardeners who are wilting. It is some of our summer squash. In my garden, the wilting of a few zucchini squash came on quite suddenly. Though it has been rather dry in recent weeks, this wilting is not weather related. Rather, it is the result of a critter called the squash vine borer.

The adult stage of this pest is a moth that at first glance resembles a large wasp with a bright orange abdomen zooming about in daylight among squash plants. Typically, the moths emerge from late June into July and lay eggs at the base of thick-stemmed squash. Most often it is summer squash but some thick-stemmed winter squash such acorn squash and pumpkins are also targets of the squash vine borer. While the sudden collapse of a squash plant may be the first visible symptom of borer intrusion, the appearance of wet sawdust-like frass on the lower portion of the plant stem verifies the presence of borer.

The best management strategy for squash vine borer is prevention. This is accomplished by application of an organic spray such as spinosad or Bt (Bacillus thuringiensis) to the lower portions of squash stems. The adults are still flying and laying their eggs at this time, so it is not too late to treat squash now. If borers are already present, a plant may be saved by slicing along the middle of the lower stem portion with a sharp knife. Eventually, you'll come across the cream-colored larvae, at which point your knife can then dispatch the critter. After the borers are killed, pile some moist soil over the cut portion of stem and keep the soil moist with frequent application of water. With a bit of luck, the plant will produce new roots from the cut stem, though I won't guarantee successful salvage of the plant.

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You may be able to salvage the rest of your gardens and yourself with these tips of the week:

- Wait until leaves and stems of potato plants have died back completely before digging. The dug potatoes may be left on the ground for a few hours to allow soil on the spuds to dry. Then gently rub off the dry soil by hand being careful not to damage the potato skin. Never wash potatoes that are to be stored. Store the plants in the dark in the coolest corner of your basement. I store potatoes in burlap lined baskets with additional layers of burlap over the top. The burlap allows for air movement around the potatoes. Never store potatoes in closed containers such as plastic bags or coolers.

- Though onions may be harvested at any stage when needed in the kitchen, wait until the tops have flopped and the shoots have dried before digging up those to be stored long term.

- Prevent cracking of tomato fruit by watering tomatoes as needed to maintain even moisture in the soil. Cracking occurs when the fruit grows faster than the skin. This typically occurs when rainy weather follows a dry spell — something which happened this past week. Cracked tomatoes are still edible but should not be stored for any length of time.

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- Take advantage of plant sales at local and mail-order nurseries now going on as businesses are reducing their inventory. I've noticed that fruit plants such as red and black raspberries, and blueberries are commonly on sale and with adequate watering this would be a good time to plant these.

- Get out the notebook and record your observations, problems, and ideas for changes to be made in your gardens. Many changes, such as additions to the landscape of plants favored by beneficial insects can be made during these last few months of this gardening season.

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"Why isn't my Hydrangea macrophylla blooming?" That is a question I was asked by a friend this past week. It was a good question since the failure to bloom is not an unusual occurrence with this species of hydrangea, commonly called bigleaf hydrangea. However, coming up with a specific answer is not easy since there are many factors which can effect flowering of the macrophyllas. For one, it is a marginally hardy hydrangea for the Berkshires. Extremes of winter temperatures (Remember the bitter sub-zero cold spells of this past January and February?) and early spring cold snaps can kill their flower buds. Old cultivars (cultivated varieties) of this species bloom on old wood, meaning that the flower buds were formed the previous summer, while new cultivars typically bloom on both old and new wood. Pruning back hydrangeas in spring will either eliminate flower buds or reduce the number of flower buds.

Other factors that influence flowering include:

- Age of the plant: It sometimes takes a few years for newly planted macrophyllas to begin flowering.

- Location: Bigleaf hydrangeas prefer morning sun and light shade in the afternoon.

- Too much fertilizer: High nitrogen fertilizers stimulate vegetative growth at the expense of flower bud development.


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