August 2021 Gardening Advice

This Eastern Tiger Swallowtail butterfly was really enjoying a beautiful hanging basket combination of calibrachoa!

submitted by Jennifer Fairfield, Garden Mill and Manchester Community & School Gardens

The weather in July certainly made gardening challenging. I don't know what I liked the least — the heat, the humidity, the rain, or the mosquitoes! I'm glad things seem to be settling down a bit, at least for a little while, anyway. It makes it easier to get things done in my gardens — and there's lots to do.

In the vegetable garden:

Last month, I gave lots of information about insect pests in the garden, so I thought I’d continue that theme this month, but with diseases, since there are lots of them out there right now.

• With all the rain we’ve been getting, plus all the humidity when it’s not raining, diseases are really causing lots of issues in vegetable gardens right now. Below are some of the more common problems people seem to be facing, along with information on what to do about them. Keep in mind – it’s a lot easier to prevent diseases than to cure them once they have gotten going, so regular applications of fungicide are important.
  • Blossom End Rot is a very common problem for tomatoes, squash, eggplant, melons, and peppers when we are getting as much rain as we have seen this summer. It also happens when plants aren’t getting enough water. As I mentioned last month, the problem is a lack of calcium that is generally because the plants aren’t able to take up the calcium in the soil, not necessarily because of a calcium deficiency in the soil itself. It’s best to check your soil for calcium levels before you do anything to add calcium. Adding calcium to soil that already has sufficient levels won’t help your plants. You can get a soil test that will help you determine the levels of lots of different minerals (including calcium) from MSU Extension Service. Fungicides and pesticides will do nothing to solve blossom end rot. If your soil has sufficient calcium, then ensuring consistent moisture levels in your soil is the best way to prevent this problem. That can be tricky when we’re getting torrential downpours like the one we saw last weekend, and really only well-drained soil can help in that situation. One other thing to mention on this topic: something that looks like blossom end rot can be caused by a lack of pollination, especially in cucurbits. I suspect that is the cause of the problem I’ve been having with my zucchini this year (pictured at left). My raised bed gardens are very well drained, so I don’t think the problem with my zucchini is related to watering. One key indicator that it is probably a pollination issue, and not a watering/calcium issue, is that it’s happening when the fruit is very small. Zucchini (as well as other cucurbits) needs the bees (or the gardener) to pollinate the flowers on the fruit — without that, zucchini fruit will wither and die, starting at the flower end, when the fruit is still very small. Pollination issues show up when the fruit is small. If it’s fully formed, and then shows these symptoms, it’s blossom end rot, not poor pollination.
  • Bacterial Speck on Tomatoes shows up as small black spots on leaves (⅛ to ¼ inch in diameter) that are usually more prominent on the undersides of leaves. As the spots age, a yellow halo often develops around the edge. Symptoms can also appear on the fruit as small, black spots. Copper-based treatments can help to slow the problem down, but there is no cure. If it’s late enough in the season, you can simply let the plants continue to grow, and hope to salvage any unblemished fruits. Do not eat fruits that show signs of the disease. The most effective way to prevent bacterial diseases is to start a regular schedule of spraying your plants with a fungicide, beginning as soon as you plant them.
  • Bacterial Spot on Tomatoes can show on any part of the plant (leaves, stems, fruit), and can lead to plant death. It is very difficult to tell the difference between bacterial speck and bacterial spot, but if left in the garden, bacterial spot can infect all tomato plants, and ruin your entire crop. Prevention is key — avoid overhead watering, use preventive sprays from the time you plant, don’t work with your plants when their leaves are wet, and always clean your tools with a 10% bleach solution or rubbing alcohol after every cut. Unfortunately, warm, wet weather (such as what we experienced all last month) is the perfect environment for this disease.
  • Early Blight can affect tomatoes, potatoes, eggplant, and peppers. Early blight generally first appears on the stem and leaves near the base of plants, as somewhat circular brown spots. As these spots enlarge, concentric rings appear, giving the areas a target-like appearance, often with a yellow halo. Eventually multiple spots on a single leaf will merge, causing the entire leaf to die. Early blight can lead to a total loss of lower leaves and even the death of an infected plant. This disease thrives in hot, humid weather, but can be prevented by keeping plants somewhat thinned, and well-spaced, to allow for good air flow and faster drying of foliage. Copper-based fungicides can help to slow down the disease, but again, prevention is best, and begins with a regular application of fungicide from the time of planting.
  • Late Blight is a very destructive disease that mostly affects tomatoes and potatoes, but can also sometimes infect peppers and eggplant. Late blight begins as pale-green or olive-green areas that quickly enlarge to become brown-black, water-soaked, and oily-looking. Dark-brown to black areas can also appear on stems. Affected parts of the plant develop a white-gray fuzzy appearance as the disease grows. This disease thrives in cool, wet conditions, and can kill a plant in a matter of days from the first appearance of symptoms. If late blight infects your plants, pull them immediately (removing all roots as well). Place all of the debris in a tightly closed plastic trash bag, set the bag in the sun for a few days to help kill the disease, and then dispose of it in the trash. Late blight is a soil-born disease that can overwinter in plant material left in the soil, below the frost line, so leaving even the smallest amount of debris could mean you’ll be dealing with it the following year. The best prevention for late blight is to plant disease-resistant varieties, rotate crops in the Solanaceae family (tomatoes, potatoes, peppers, eggplant) to different parts of the garden each year, and start a regular fungicide application at the time of planting.
  • Powdery Mildew is a disease that occurs on the leaves, branches, vines, and stems of many plants in the vegetable garden, including cucumbers, squash, beans, beets, eggplant, melons, carrots, lettuce, peas, pumpkins — you get the idea: pretty much everything. Here’s an interesting thing though — every plant species has its own type of powdery mildew fungus, so the fungus that affects cucumbers is not the same one that affects lettuce, etc. Regardless of what plant is affected, symptoms typically start with a white, powdery-looking coating on the leaves of the plant (though tomatoes, peppers, and onions usually only show yellow patches). This disease thrives in hot, somewhat humid conditions, especially where air circulation is poor, and in shady spots of the garden. Not to sound a like a broken record, but again, prevention is best. Spacing plants to allow good air flow, watering at the soil (as opposed to overhead), and applying fungicide on a regular schedule will help to keep the disease from taking hold. If you do end up with powdery mildew, Neem oil can help to eradicate it in early stages, but once your plants have a severe infection, there isn’t really anything you can do, but pull them — they won’t be producing much edible fruit at that point.
  • Downy Mildew, like powdery mildew, is a soil-borne disease that can affect many plants, but each plant family is only infected by a it’s own type of the disease. The plants most often affected in home gardens tend to be those in the cucurbit family (cucumbers, melons, squash, pumpkins, watermelon, and gourds). Basil, grapes, hops, soybeans, and spinach are also susceptible to downy mildew. In cucurbits, it appears as green to yellow spots on the tops of leaves that later turn brown. The undersides of the leaves may show a gray fuzz. Unfortunately, once this disease sets in, there is nothing you can do to stop it, and you should immediately pull the plants and dispose of them. Humid, wet conditions are perfect for downy mildew, and it has already been found here in Michigan this season. If you haven’t already begun a regular fungicide spraying program (neem oil and copper-based fungicides are generally the most effective for this disease), you should start now, to help slow down the progress of the disease in the state. Keeping plants well-spaced, and branches thinned and up, off the soil can help to deter the disease. I like to grow my cucumbers on trellises for that reason.
  • Cucumber Mosaic Disease is a virus that actually affects hundreds of different plants, including flowers, herbs, shrubs, and weeds. Symptoms, which vary by plant and plant development stage, can include stunting of entire plants, mosaic or mottling (blotchy light-and-dark-green or yellow-and-green areas) and ring spots (ring-like areas of discolored tissue) on leaves and fruits, along with a variety of growth distortions on leaves, such as cupping (or curling inward), puckering, and strapping (elongation and thinning). Severe infection can kill plants. This disease can overwinter in perennial shrubs, plants, and weeds, and is often transmitted to garden plants by aphids. Planting disease-resistant varieties of crops, mulching well around your crops to prevent disease-carrying weeds, and controlling aphids with floating row covers in your garden are your best defenses against this disease. Insecticides sprayed on aphids are not very helpful, as by the time you see them on your plants, they have likely already spread the infection to your plants. Once your plants are infected, there is no cure.
  • Bean Common Mosaic Virus and Bean Common Mosaic Necrosis Virus are diseases that affect snap and dry beans. The viruses are often already in the bean seeds, so planting resistant varieties is important. Aphids can also transmit the disease. Plants grown from infected seed are almost always stunted and unproductive. Yields are generally not as affected in plants infected by aphids later in the growing season. Symptoms of both diseases include a light green or yellow and dark green mosaic pattern on leaves, often along with leaf puckering, distortion, or rolling. This disease has no cure, and there are no preventive measures, other than planting resistant varieties.
  • As with insect pests, there are many different diseases that could be affecting your plants — far more than I can cover here. I have tried to outline some of the most common ones we tend to see in Michigan gardens, but if you think your plants have a disease, and you can’t determine what it is, you can submit digital pictures to the MSU Extension Service’s Plant Diagnostic Lab for diagnosis, or mail or drop off samples of your plants for diagnosis. I can try to help with identification of disease, but it is not my area of expertise, and many diseases have similar symptoms, so I highly recommend turning to the experts on this.
• Be sure to harvest cucumbers, beans, and zucchini regularly (I’m picking beans daily right now). Many plants will stop producing if you don’t keep harvesting. The reason for this is that they start to concentrate on maturing the fruits they have, in order to produce seeds. By constantly harvesting, you are basically tricking the plant into producing more fruit so that it can produce and mature seeds (that being the whole goal of the plant).
• If you haven’t yet harvested your garlic, it’s probably getting to be time, as leaving it too long can cause it to rot in the ground – especially with how wet the ground has been. Get tips on harvesting, curing, and storing your garlic here. Onions are also usually ready to harvest in July and August. Once those are out, you can put in some “succession” plants. Beets, radishes, lettuces, spinach, Swiss chard, kale, and peas all can be planted in August for harvest into the early fall. Take a look at the seed packet for the “days to maturity” to determine how late you can plant and still harvest before frost (and some things, like kale, are even better after a light frost). To figure out your safe planting timeframe, just count backwards from your average first date of frost (usually early October for our area, but you can get detailed information for your zip code here). So, if your packet says that the days to maturity is 45 and it takes 5 to 10 days to germinate, then you need to make sure that you have your seeds in by about August 10.
• It looks like (according to the latest weather forecasts) we are heading into a drier period than we’ve seen in a while, so make sure that you keep your garden watered. All that rain that we got in July doesn’t mean that your garden doesn’t need to continue to get at least an inch of water per week. When vegetable plants are at their peak of production, keeping them properly hydrated is key to making sure you get good quality harvests. Raised beds and container plantings dry out even faster than in-ground gardens, so it’s really important to pay attention to soil moisture in those. When it’s hot and sunny, you may need to water raised beds and containers daily.
• Keep your garden weed free by doing a little bit every day. The rain and heat we’ve had this summer are really helping the weeds proliferate. Don’t let them take over, or you may not get as good a harvest from your plants!

Flowers:

• Diseases are also a problem for flower gardens, and the same rules apply to flowers as vegetables — prevention is key: plant disease resistant varieties when possible; allow ample space for airflow around plants; water at soil level, rather than overhead; clean up and remove infected plant material; for plants that are very susceptible to diseases such as powdery mildew and leaf spot, early and often fungicide application can help ward off problems before they begin.
• Deadhead both annuals and perennials throughout the rest of the season. Deadheading is simply the act of removing spent blooms. For some plants, this is done simply to improve appearance, but for others, it’s necessary to encourage more blooms. I find this article from Fine Gardening to be very helpful in understanding the how and why of deadheading perennials. For information on deadheading annuals, Proven Winners offers lots of information.
• Keep an eye out for insect pests that are still working their way through your plants. There’s a really great web page, from The Ecological Landscape Alliance, that offers an immense amount of information on lots of insect pests found in gardens (even more than I included in last month’s newsletter). There’s probably far more information than most of us care about, but if you scroll through, you can find out a great deal about what might be eating your plants, and understanding what is doing the damage is key to controlling it. If you can identify the problem, I can probably help you decide what to do about it.
• As with veggies, make sure your flowers are getting the water they need. August tends to be a pretty dry, hot month, so be sure to supplement whatever water Mother Nature is providing, whenever we’re not getting enough rain.
• Regular weeding of your flower beds, just like with your vegetable garden, will help keep your gardens looking great, along with helping to keep your plants healthy. Weeds can harm your plants in a few ways — they rob your plants of water and nutrients, they can help to spread disease, and taller weeds can block sunlight from reaching your plants.

Birds:

• I have had a number of people ask about the disease that is affecting songbirds in many parts of the country. So far, Michigan does not seem to have as much of a problem with this, but the experts think it’s likely just a matter of time. To help keep our feathered friends healthy, please keep your feeders clean. Cleaning feeders on a regular basis can mean the difference between life and death for the birds visiting your yard. The Michigan DNR has a video explaining how to properly clean your feeders. This video was done a year ago, and under normal circumstance, the DNR recommends cleaning feeders once per month. However, with the disease issues that are causing so much concern these days, more frequent cleaning is being recommended — at least twice per month, or even weekly. If you observe diseased birds in your yard, please report your sightings to the DNR at their “Eyes in the Field” page. This will help track any spread of disease in our state. Learn more about the disease from Audubon Great Lakes here.
• As always, if you are feeding hummingbirds, clean out and replace the sugar-water in the feeders regularly. The Audubon Society recommends cleaning feeders twice per week during hot weather, and once per week when the weather is cooler. They also have lots of other great information about attracting hummers to your yard at their Hummingbird FAQ page.
• Offering birds a source of water for drinking and bathing is a great way to attract them to your yard, and can provide you with lots of entertainment. Just be sure to clean out and fill your birdbaths daily to help keep the birds healthy, and to keep mosquitoes under control (or at least give them one less place to multiply!). I have been making this a morning ritual, right before I leave for work. I keep a scrub brush handy to give the baths a good scrubbing before filling them up every day. Using a solution of vinegar and water weekly will help to keep bacteria from building up. Again, the Audubon Society offers good tips for providing clean water for birds in your yard at their website.

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by Marsha Chartrand

Marsha Johnson Chartrand, a founder, writer, and copy editor with the Manchester Mirror, is a 50-year resident of Manchester. She has a long history of volunteer and community involvement.