Vegetable garden troubleshooting: common problems, and solutions

You've worked hard on your vegetable garden; reap

You've worked hard on your vegetable garden; reap the rewards with preventative measures against pests and disease. (Credit: AP)

Jessica Damiano

Jessica Damiano, Newsday columnist Jessica Damiano

Jessica Damiano is a master gardener and journalist with more

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Home gardeners growing vegetables are by now knee-deep in their routines: weeding, watering, fertilizing and, hopefully, monitoring closely for insects, diseases and critter activity. Here's a little help for identifying some common harmful pests before they have a chance to destroy your crops -- and all your hard work, plus a few preventive measures.

CALCIUM DEFICIENCY

Telltale sign Mushy, black spots on the undersides of tomatoes, peppers and eggplants.

Cause Calcium deficiency, which usually can be traced to uneven watering (heavy rains after drought or vice versa, or neglect followed by overcompensation). Using too much nitrogen fertilizer also can cause the disease, as can injured roots or improper soil pH.

Prevention Test soil before planting to ensure pH is neutral and add dolomitic lime if soil tests lower than 6.5. Do not plant near a lawn that will be fertilized. Install stakes or cages around tomatoes at planting time -- not when plants grow bigger -- and avoid digging, hoeing or cultivating soil around roots.

Remedy If fruit is already showing symptoms, drench foliage with a calcium spray like Enz-rot or Rot-Stop, according to package directions. Affected fruit will not be "cured" but can be eaten (just cut away affected parts). Fruit that is produced after treatment should not develop symptoms. FYI: Stock up on this product early in the season; by the time you realize you need it, stores and catalogs may be sold out.

FUNGAL DISEASE

Telltale sign Beginning as small, cream-colored lesions on leaves, spots enlarge and darken rather quickly and run into one another, sometimes covering the entire leaf. On cucumbers, leaves can drop and entire vines can die back. Tomato and pepper fruit becomes marred with sunken circular depressions that darken and become more visible as fruit ages; harvested tomatoes may even appear fine, with symptoms becoming apparent during storage. Fruit is safe to eat, just cut away affected parts.

Cause Fungal disease caused by one of a number of species of the fungus Colletotrichum, affecting beans, cucumbers, peppers, pumpkins, squash, corn and tomatoes.

Prevention Select resistant varieties, rotate crops, enrich soil with plenty of compost at planting time and apply mulch.

Remedy Fungicides containing chlorothalonil, such as Fung-onil and Daconil, or copper (if growing organically) can be applied. (Be sure to follow package directions carefully and heed precautions on product label.)

BLIGHT

Telltale sign Elongated lesions on stems and large grayish-green to brown spots on leaves that cause plants to blacken, wilt and die. White mold full of spores encircles spots visible on the undersides of leaves.

Cause This disease -- caused by a pathogen capable of releasing millions of spores per plant per day that can travel long distances, especially during wet weather -- was responsible for the great Irish Potato Famine in the 1840s. Since 2009 it has been making an unusually early seasonal appearance on Long Island, and has the potential to destroy entire farm crops.

Prevention Preventive applications of a fungicide containing chlorothalonil (Fung-onil and Daconil) can stave off disease. Gardeners growing organically can use a copper fungicide alternated with applications of Actinovate and Regalia, a regimen recommended by Meg McGrath, plant pathologist with Cornell University at the Long Island Horticultural Research & Extension Center in Riverhead who has been monitoring the region's late blight occurrences for several years. Fungicides should be applied vigilantly and regularly every 7-10 days. Follow the package directions and heed precautions on the product label.

Remedy There is no cure for late blight. Inspect tomato and potato plants for symptoms at least once a week. If late blight is detected, plants should immediately be bagged tightly in plastic and set in the sun for a few days until they die, then disposed of only in the trash (never composted or left on the ground in piles, as spores will continue to form and spread until the plant dries up).

SQUASH VINE BORES

Telltale sign Small puncture holes in the bottom portion of the stalk and stems of zucchini, squash, cucumber and muskmelon plants, where you'll also find frass, or caterpillar excrement, which resembles sawdust. Plants flower, then simply die, seemingly without cause.

Cause Squash vine borers, pests that lay their tiny eggs along the lower portions of stalks and stem, and then morph into inch-long, thick white caterpillars with brown heads that bore into stalks and kill the plant while chewing their way out. They cocoon in the soil, where they survive winter and re-emerge in late spring as orange-and-black moths ready to repeat the cycle. Sometimes there's even a second generation in August.

Prevention Keep a close eye out for the red, flattened-oval eggs and pick them off as soon as you find them. You'll need to be vigilant and hunt at least once a week to avoid damage.

Remedy Slit punctured stems open lengthwise near holes using a razor blade, and pick out the borers. Then mound soil around the base of the plants to cover the injured portion of the stem. This will encourage new roots to grow. If all else fails, use a product labeled for use against squash borers, such as all-natural Btk, and be sure to follow directions precisely.

SLUGS

Telltale signs Irregularly shaped holes chewed into plant foliage.

Cause Slugs thrive in moist conditions and feed on leaves and fruit, leaving a slimy trail in their wake.

Prevention Raking and thoroughly cleaning up the garden in early spring will remove not only leaves and debris, but slug eggs as well. Be careful not to apply mulch any thicker than 3 inches, or it may become home not only to slugs, but rodents as well. After ensuring slugs aren't present in beds or containers (or removing them if found), surround the planting zone (or pots) with copper tape, which slugs will not cross.

Remedy Sluggo and Escar-go! are two products that are quite effective in eliminating most slug problems, and both are natural and safe to use around pets. But I'm a big fan of the old beer-in-a-tuna-can trick: Fill a small, clean can, such as from tuna or cat food, halfway with beer and set into the soil around affected plants (under foliage for long-leaved plants like hostas). Slugs will be lured in for a drink and then drown in a drunken stupor.

Salt also is quite deadly to slugs: When it comes into contact with their bodies, slugs automatically release moisture to their outer surface in an attempt to dilute the irritating substance. As a result, they become dehydrated and die. The problem is that unless you're planning to sit up all night in your garden with a salt shaker and apply to each pest individually, you'll need to sprinkle salt around your plants, and that can be harmful to soil.

RABBITS

Telltale signs Chewed-up leaves and even completely eaten plants. Targets include tulips, clematis, roses, blackberries, raspberries, apple trees, rhodendron, junipers, yews, grass, carrots, lettuce, cabbage and many others.

Cause Hunger, plain and simple. Warm winters lead to an increased rabbit population in spring and, therefore, even more hungry rabbits eager to feast on what you've planted.

Prevention Repellents, like cayenne pepper, blood meal, bone meal, Liquid Fence and Messina Rabbit Stopper offer some benefit, but they need to be reapplied, especially after rainfall. Human hair stuffed into old nylon stockings and hung around the garden at rabbit-eye level also can serve as somewhat of a deterrent, as rabbits will sense a human presence nearby.

But the most effective weapon against rabbit damage is a chicken-wire fence installed around garden beds, which admittedly is unattractive. However, nearly foolproof, a 30- to 36-inch fence with mesh openings of an inch or smaller is your best bet. Rabbits do like to dig, so the fence should penetrate 8 inches below the soil line.

Remedy Live traps set around the garden are quite effective for smaller rabbit populations, but figuring out where to release them poses a challenge.