Drought, Disease & Blight

Powder fungus on my mustard wiped out all the greens this season.

What a wonderful summer it has been! Hot as ever, with long sunny days and a nice cool rain in the afternoon to ease the heat into the night. As the days shorten, subtle influences of fall begin to creep into each dusk and dawn, combining with the sweltering summer heat to make ideal conditions for diseases, mold, and fungi to spread.

Throughout each growing season and the lifetime of each crop there are numerous opportunities for diseases to enter a garden. It can be caused by outside influences from store-bought soils and plants, or simply from the weakening of plants due to improper care. Let us look at my garden over this growing season and some of the issues I’ve had, to see if we can find helpful solutions.

More likely than not, my gardening problems stem from the gardener. My indoor crops are more sensitive to their environment as they cannot dig their roots deeper to strengthen themselves in times of stress. As a busy woman, I can get forgetful, and my routine may be disrupted. My plants often oscillate between chronic over- and underwatering as a result. My mint and scented geraniums are always leggy (classic sign of overwatering) with dried and yellow leaves (signs of underwatering). The aloe is quite happy as I never neglect her for more than a week, and I prune from her daily for remedies.

Signs of slight nitrogen burn are coupled with underwatering in an indoor system.

Having a ready aquaponics system presents its challenges as well. What to do with the wastewater? The obvious solution is to water the plants with it, but a few months later we see some negative results, or at least I did. Fish waste is full of nitrogen, which even in the right form can lower the soil’s pH and weaken the root structures, making room for fungi to enter.

This is an issue for those using common fertilizers and certain composts, which all tend to have large amounts of nitrogen. Inside the tent, both the basil and the cabbage showed signs that they were getting a little too much love from the fish. More crops in the plant bed would have helped, but the heat made it impossible to keep seedlings alive long enough to be planted.

Outside, the effects of overfertilization are different. A few tomatoes and some summer squash experienced blossom rot this year. That’s a phenomenon in which the bottom of the fruit, at the blossom point, turns black and sunken and begins to rot. It is caused by rapid growth or calcium deficiency in the soil. Rapid fruit growth generally occurs during times of drought. I noticed only a couple of tomatoes had this problem and they grew during that dry spell in early/mid-July. Calcium deficiency can be treated with oyster shell, gypsum, or a calcium supplement. The good news is that it’s not a virus or fungus and will not spread from plant to plant. It will affect tomatoes, squash, peppers, and eggplant, so be watchful and water selectively if needed during dry spells. Count your blessings, compost the rotted fruit, and keep it moving.

Fusarium wilt certainly took hold of my tomatoes this year, what a shame. Two of my largest have been wilting from the bottom up, one never produced fruit, and the other is producing slow as ever. Identify it by older leaves drying up and dying later in the season. Pull up the entire plant when this is spotted. The disease can be spread by local pests and can manifest on dirty shears, so be sure to sanitize them between uses to reduce the exposure risk. The disease lives in the soil and can remain for years if untreated. Solarize it by covering the soil in clear plastic during the hottest time of year to “bake” out the disease. This will also remove weed seeds and other contaminants.

Club rot got into my indoor system.

In tandem with the white flies that ate at my mustard greens from below, powder mildew ate at them from the top. This thick white fungus grows on the top of the leaves and tends to attack all of a single crop family, meaning my kale, cabbage, and collards all suffered due to this brassica-loving fungus taking over my mustard while the tomatoes were spared. Like the fusarium wilt, this disease needs to be baked out of your soil using clear plastic and lots of heat. How to prevent it? Keep your shears clean, prune wild brush, and keep airflow in your garden space. This condition can also be triggered by excess nitrogen in the soil. Be sure to use slow-release fertilizers and have the dogs do their business elsewhere.

Club rot is the last nasty fungus that has affected my brassicas inside and out. It infects the roots, causing them to become misshapen. This is noticeable when the leaves are curled up at the edges and yellow prematurely. Prevent it by keeping your soil’s pH in balance and rotating your crops. Solarizing may be required as this fungus can last over 10 years.

This year, I may need to pull the crop and solarize while the weather is still warm. Don’t be afraid to pull up today’s crop for a larger harvest tomorrow. We are fortunate to have (limited) food access in our community and usually don’t have to rely on our gardens for most of our food. Summer is almost over and harvest time is here. Next month we will learn more about harvesting techniques as we tidy up the main growing season and move into the fall and winter crop rotation. Enjoy your August!


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