Powdery Mildew in the Garden

The July 5, 2012 issue of the UMass Vegetable Notes reports that powdery mildew has reached Central MA and you should check your summer squash for symptoms. Sure enough, we can report that powdery mildew (PM) is now affecting at least zucchini in the Bolton Community Garden. Here are some pictures of what it looks like on summer squash. PM will affect any of the cucurbits and a lot of other garden plants including beans, peas, and broccoli.

The best solution to powdery mildew is to prevent it from appearing. First of all, select varieties that are described as being resistant to powdery mildew, such as cucumber Diva and yellow squash Success, Sunray or Sunglo. Make sure plants have adequate spacing for good airflow. When powdery mildew is reported in the area, spray plants to prevent infection. It is easier to prevent infection than cure it. If plants are heavily infected, remove the most affected leaves and dispose of them in the trash, NOT in the compost bin. Spray with a fungicide.

An organic solution that is reported to be effective in preventing PM is easy to mix up. For a quart of spray, add milk (any kind) to water at a ratio of one part milk to nine parts water (4 ounces milk to 28 ounces water). Don’t use higher concentrations because it can cause the growth of other diseases. To the solution, add a tablespoon of baking soda and a couple of drops of dish soap. If you have it, add a teaspoon of neem oil, which has fungicidal properties. Spray this mixture on plants in the morning so it can dry adequately before nightfall. Repeat spray weekly. This is a preventative method, so spray now even if you are not currently affected by mildew Spray at least squash, pumpkins, melons and cucumbers now and monitor other susceptible plants.

Squash Vine Borers

Squash vine borers (SVB) are maggots of the SVB moth that bore into the stems of cucurbits (squash, cucumbers) and work their way up the stem. You can tell you have borers when your plant suddenly wilts. Check the stem about an inch and a half up from the ground and you will see a small hole with sawdust around it where the borer entered.

Once the borer is in the squash, the plant is at great risk. If you catch it early enough, you can slit the stem with a razor knife from the entrance hole up to where the borer is and destroy the borer with the knife blade or a wire. Then bury the slit stem under soil to keep it covered. This may or not be successful, but if you do nothing, the plant will die. If the plant can’t be saved, pull it and destroy it. You can replant squash in early July after the SVB threat is over.

The best method is to prevent the SVB from laying eggs near your squash, or provide a physical or biological barrier. If you can cover your plants with floating row cover, that keeps the moths away from laying eggs near or on the plant. But the cover has to be removed when the plant starts flowering so pollinators can get to the flowers.

The SVB moth does not look like a moth but more like a wasp or bug. It emerges from a cocoon in the soil the end of June or beginning of July (but remember we are way ahead of average on degree days because of the mild winter and spring). These moths fly during the day and are very good fliers like a wasp. They stand out because of their coloring so keep a lookout for them and let others know if you see one in the garden (squish it first, then let us know).

The borer itself is a big, fat, ugly thing, shown here in this cross-section. These pictures are courtesy of the University of Minnesota Extension (see http://www.extension.umn.edu/distribution/horticulture/M1209.html for their advice on SVB management).

Here is a video that suggests using cardboard tubes to prevent the borers from physically reaching the stem and boring into the plant.

Other suggestions are to wrap aluminum foil around the stems at the soil level and several inches up. Another, more elaborate technique is to inject the squash stems with a BT solution, inoculating the insides of the stems with BT, which will kill the borers when they try to enter the stem.

Update on Garden Pests - 30 May 2012

It’s the end of May and according to the UMass Extension Vegetable Program, we are facing Armageddon as a huge swarm of insects start to emerge early because of the warm Spring that we had. Already doing their work in the Bolton Community Garden are cabbage caterpillars, flea beetles and a new, surprise pest, the Tortoise Beetle!

You should be aware that flea beetles are back now in large numbers and are attacking eggplants (their favorite), mustard family plants (mustard, radish, turnip, etc.) and any other plants if they feel like it. For info on flea beetles, see this post. Eggplants should be checked now or you risk having your plants stunted or killed.

Cabbage caterpillars are the larvae of the cabbage moth, the white “butterflies” you will see fluttering around the garden. I have seen only a few moths so far , but I found a caterpillar chewing up a Brussels spout that was under the floating row cover. They are not bad yet but be aware they are here. Check your cabbage-family plants or risk losing them.

Finally, a new pest, as if we need another! While squishing flea beetles on my new eggplant transplants, I noticed a spot that looked a little like bird poo. I made a mental note to check it out and went off to talk to Pequita and warn her of the arrival of the flea beetles. We found flea beetles all over her potatoes. While squishing beetles (successful technique is to quickly pick the beetle off the leaf and then roll it between your fingertips until it disintegrates) and enjoying this sport, Pequita noticed several weird things on the potato leaves. She picked one off the leaf and flipped it over. It had little legs and after squirming for a few seconds, it flipped itself back on its feet!

What we were looking at turns out to be the Mottled Tortoise Beetle. I didn’t take a camera to the garden so unfortunately I don’t have a picture to post  See this link for a good picture. These beetles overwinter as adults. They feed on weeds until sweet potatoes emerge, then feed on those. In our garden we found them on potatoes and eggplant. They also like morning glories. These beetles and their larva (spiny green blobs) eat holes in plants. They are not considered a serious threat but I plan to see if they like the garlic and chili pepper enema I’m about to give the flea beetles.

UPDATE June 8, 2012: Here’s a photo of the mottled tortoise beetle found on a potato plant in plot 8.

Garden Opening Day, April 14, 2012

Saturday was the official Opening Day for the Bolton Community Garden. Members gathered to clean up the garden and ready it for the new gardening season. The garden plots were measured and staked, garden paths were repaired, fencing was mended, and some sub-standard plots were cleaned up and fortified with soil and compost. Let the gardening season begin.

Below are some photos taken during Opening Day by Joan Finger,