Problems Growing Vegetables: Common Vegetable Plant Diseases And Pests
By: Amy Grant
Growing a vegetable garden is a rewarding and fun project but unlikely to be free from one or more common veggie problems. Try as you might, your garden is likely to be afflicted with any number of vegetable garden pests or plant diseases.
Common Veggie Problems
Problems growing vegetables may run the gamut from the more obvious vegetable garden pests or plant diseases to issues related to the environment like weather conditions, nutrition, and even those caused by people or animals. Proper irrigation, fertilization, location, and when possible, the choice to plant disease-resistant varieties can aid in creating your own little Garden of Eden.
Vegetable Plant Diseases
There are a plethora of plant diseases that may afflict the veggie garden. These are merely a handful that are commonly found in gardens.
Clubroot – Clubroot is caused by the pathogen Plasmodiophora brassicae. Vegetables affected by this common disease include:
Damping off – Damping off, or seedling blight, is another common disease seen in most veggies. Its source may be Aphanomyces, Fusarium, Pythium, or Rhizoctonia in origin.
Verticillium wilt – Verticillium wilt may afflict any number of veggies from any of the Brassicae (except broccoli) family to:
White mold – White mold is another common disease found in many crops and is inflicted by the pathogen Sclerotinia sclerotiorum. These include:
- Some Brassicae veggies
Other diseases such as cucumber mosaic virus, root rot, and bacterial wilt may cause wilting of foliage with dead areas apparent and mottled fruit.
Vegetable Garden Pests
Other problems one may encounter when growing vegetables are caused by insect infestations. Some of the most common invaders that can be found in the vegetable garden include:
- Aphids (feed on almost any type of crop)
- Stinkbugs (damage foliage on veggies as well as fruit and nut trees)
- Spider mites
- Squash bugs
- Seedcorn maggots
- Nematodes, or root knot disease (causes galls to form on carrots and stunt coriander, onion, and potato crops)
Environmental Vegetable Garden Issues
Beyond diseases and pests, gardens are susceptible to problems caused by temperatures, drought or over-irrigation, and nutrient deficiencies.
- The end result of all of the previously mentioned, blossom end rot (common in tomatoes, squash, and peppers) is a calcium deficiency caused by moisture fluxes in the soil or the application of too much nitrogen fertilizer. Avoid over-fertilization and use mulch to retain soil moisture and water during periods of drought.
- Edema is a common physiological problem found when the ambient temps are cooler than soil temps, and soil moisture is high with high relative humidity. Leaves often look as if they have “warts” and afflict lower, older leaf surfaces.
- A plant going to seed, otherwise known as bolting, is extremely common. Plants prematurely flower and elongate as temperatures rise and the days get longer. To avoid this, be sure to plant bolt resistant varieties in the early spring.
- If plants fail to set fruit or drop blossoms, temperature variables are also most likely the culprit. Snap beans may fail to flower if temperatures are over 90 F. (32 C.) but may resume blooming if temps cool down. Tomatoes, peppers, or eggplant are also affected by temperature fluctuations which can inhibit blooming or production.
- Low temps of between 50-60 F. (10-15 C.) may cause the fruit to become misshapen. Cool temps or low soil moisture may cause cucumbers to grow crooked or oddly shaped.
- Poor pollination may also cause irregularly shaped kernels to form on sweet corn. To encourage pollination, plant the corn in blocks of multiple short rows rather than one long row.
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Read more about General Vegetable Garden Care
Caterpillars are soft, segmented larvae with distinct, harder head capsule with six legs in the front and fleshy false legs on rear segments. They can be found on many fruits and vegetables, ornamentals, and shade trees. Caterpillars chew on leaves or along margins some tunnel into fruits. To deter them:
- Encourage native predators and parasites
- Hand-pick your harvest
- Apply floating row covers
How much damage am I willing to tolerate? Don’t overreact. One hornworm should not send you to the shed for the sprayer. Consider these questions:
- Is the insect making the leaves ugly, but not harming the vegetable?
- Will the problem be gone before any real damage is done?
- Is this an isolated problem that will clear up when the weather changes or the insect moves on?
- Am I willing to sacrifice some dill to have swallowtail butterflies?
Pests and diseases can ruin an onion crop. Here are ways to avoid these problems.
Onions in the North aren't usually bothered by insects like onion thrips or onion maggots, but if you live in the South you'll have to deal with them.
Thrips are very tiny insects that feed on the leaves of the onion plant. The plants weaken, and the yield of the crop can be reduced quite a bit. Spraying or dusting with insecticidal soap and hanging yellow sticky traps around the plantings is usually all it takes to control thrips. Follow spray directions on all sprays carefully when you use them.
The onion maggot is the offspring of a small fly that lays its eggs near the base of the plant, or late in the season right on the bulb itself. The small maggots kill the plant by burrowing into the stem and the bulb. Pull up and destroy any plants with maggots before the maggots mature into flies.
There are some insecticides that can handle a bad case of onion maggots, but an easier control is to cover the newly set out plantings with a floating row cover to prevent the adult fly from laying eggs on your onions.
Neck rot is probably the most common onion disease. It often hits just after the harvest or while the bulbs are in storage. All onion varieties can develop neck rot, but the mild-flavored, thick-necked Bermuda-type onions are especially susceptible. Drying the onions at warm temperatures with good ventilation can help prevent this disease.
There are some fungus diseases such as pink root, mildew, and bottom rot that are carried in the soil itself, but rotating the onion plot and growing resistant varieties are just about all a home gardener has to do to avoid these.
It's a good idea to spread out your onions, planting them in several sections of the garden. You not only reduce the chance of onion disease, but, because onions repel many insects, you create a kind of defense network that protects your other vegetables.