those spot There may be a little rash-inducing on the foliage of your beloved tomato plants, and recently humid, wet weather is not helping. and misshapen or otherwise defaced fruit Can also be disappointing.
“If you can learn to recognize certain diseases and pests this year,” says C., an extension specialist in botanical pathology at the Rutgers New Jersey Agricultural Experiment Station. “You can make better decisions next year and have better results,” says Andrew Weinand.
Tomato School, here we come.
The lesson plan includes diseases that are biological in nature – caused by a fungus, bacterium or virus. Disorders of an abiotic nature are also covered – where environmental stresses cause an abnormal reaction on the fruit, cases where the fruit fails to set (usually because the temperature drops above 32C or falls below 13C, interferes with pollination, although over-fertilizing can also be a cause).
Oh, and pests.
Some, like the vengeful tomato and tobacco hornworms – native insect caterpillars that feed on solitary crops – make themselves known dramatically, eating leaves from entire stems in no time, leaving behind droppings for good measure. give.
Often the stress of developing heavy fruit loads can be the tipping point, says Kristian Holmstrom, who runs Rutgers’ Vegetable Integrated Pest Management Program for northern New Jersey, which may dispose of a growing plant vigorously for fungal leaf issues. could.
The two most common fungal diseases may, at first glance, look similar—and you could have both: alternaria, or early blight, and septoria leaf location. This is where the hand lens comes in useful again to differentiate between the two.
Early blight progresses from the bottom up, starting with the lower or oldest leaves, which first show dark lesions and then may turn yellow, dropping prematurely. As the spots enlarge, distinctive concentric rings develop within them. Eventually, early blight can infect plant stems and fruit shoulders.
“Don’t be alarmed if you see this,” Holmstrom says. “It happens; it’s common. Your job is to try to minimize it so that your plants remain healthy and productive for as long as possible.”
septoria Begins by infecting the lower leaves as well. Its small, circular spots—often in multiples, each with a dark brown edge and gray or tan center—may coalesce, causing the areas around them to turn yellow and the leaves to drop.
both early blight and septoria Leaf spot is a soil-borne fungus that overwinter in affected soil. They are likely to exist where tomatoes or their relatives have been grown in previous years. They’re also polycyclic, Weinand says, with multiple disease cycles possible throughout the growing season, as long as the weather cooperates.
“You can see some disease on the lower leaves,” he said. “And then it rains, sprays spores all over the plant, and then goes even higher. This goes on as long as the weather is conducive to disease.”
Both are also difficult to control. Good practices such as adding a layer of mulch at planting are needed to reduce the spraying of spores on leaves. And the same measures apply to both, starting with a commitment to the most powerful strategy: crop rotation.
Avoid planting tomatoes and their relatives – eggplants, potatoes or peppers – in the same place year after year. A rotation of at least three years is recommended, perhaps the biggest challenge for gardeners with limited space. (Next year, maybe try growing bags or bales of straw?)
At the end of the season, remove all tomato debris in a sharp cleanup, and compost or bury it. Otherwise, material that hasn’t decomposed can become a substrate for pathogens, Holmstrom says.
terrible late blight
The good news about late blight in tomatoes is that the disease, known to be the cause of the Irish potato famine of the 19th century, does not occur every year. What causes late blight Phytophthora infestans, a fungus-like organism called an oomycete (pronounced oh-oh-my-sit) that requires a living host to overwinter. Often, the culprit is a potato tuber that has been left in the ground or compost pile. The weather should cooperate, too: High humidity and cool, moist conditions are ideal incubators.
Symptoms of infected tomatoes and potatoes include roundish black, greasy spots on foliage, and green and ripe tomato fruits during prolonged hot, humid, rainy weather. Under ideal conditions, white fungal growths appear on the lesions. Plants that drop rapidly, upon diagnosis, should be pulled up and destroyed immediately.
Misshapen fruit and other juicy mishaps
Although many fruit issues are abiotic—not caused by disease, but by disorders resulting from stress such as nutrient imbalances, poor soil conditions, and uneven watering—anthracnose fruit rot is an exception. You’ve probably seen the telltale round, sunken patches from this common soil-borne fungus on ripe fruit. As the spore-containing bodies develop, the centers of the patches darken.
like early frost and septoria Leaf spot, anthracnose can also overwinter, so good garden hygiene and crop rotation are essential – as well as picking them before the fruits are overripe.
No hand lenses are needed to diagnose anthracnose, or the most common abiotic disorders. Are the undersides of some fruits shriveled, leathery, black? Then blossom-end rot is at work, technically caused by a calcium deficiency. But it is often not a lack of calcium in the soil; Rather, the plant is not getting enough water to carry calcium to the fruit, a condition that results from prolonged periods of drought.
Are there concentric rings around the stem end of the fruit, or running radially down from there? Cracking, as it’s called, usually also follows dry-then-wet weather.
Follow a regular watering schedule to balance that provided by the season, to help prevent cracking and blossom-end rot, and for overall productivity. A cheap rain gauge will remind you when it’s fallen.
Another condition that causes funky but edible fruit: catfacing. This results in severely deformed tomatoes, and is more common in large-fruited and early varieties.
Sunscald is what it sounds like: too much light on the developing fruit, which causes yellow spots. The fall can expose tomatoes to disease, as can overzealous pruning, especially above. Or unfertilized plants may flop, depriving the fruit of the necessary shading from leaves.
Next time around…
And so goes our plant-care checklist for growing better tomatoes—starting with tomato bed rotation, mulching, and frequent watering. Also remember to regularly inspect plants and remove infected parts. Then, at the end of the season, clean thoroughly.
This article originally appeared in the new York Times