Time Your Plantings to Avoid Pests

Out-smart common garden pests by strategically timing your planting.

June 29, 2011

You can prevent many pest problems by timing your plantings carefully. Here are 10 pernicious pests that can be foiled just by changing the planting time of their veggie targets.



Aphids suck the life out of many garden plants with their piercing mouth parts and often transmit viruses. Plants that have curled, distorted leaves or that are covered with sticky honeydew are likely aphid infested.

If these tiny, pear-shaped pests have plagued cool-season crops like lettuce and broccoli in the past, start them indoors early so you can set out good-sized transplants 4 to 5 weeks before your last frost date. In other words, start lettuce and other quick-growers indoors 8 weeks before your last frost. Start broccoli, cauliflower, and other slower-growers indoors 12 weeks before your last frost date. Early planting will help to minimize the aphid-caused virus problems. And don't let cool-season crops linger as the weather warms up—pull them up and replace them before they bolt and become an aphid breeding ground.

Here's a fall-planting tip for gardeners in the South: Wait 2 to 4 weeks after most of the cotton is harvested before you plant your fall crops of lettuce and spinach. Aphids love to feed on cotton and they will search for their next meal right after the crop is harvested. By setting out fall transplants after the cotton is harvested, your crops will be less likely to be troubled by hungry aphids.

Cabbage Looper

To prevent these light green caterpillars from chewing up your cabbage and other brassicas, choose quick-to-mature varieties that you can harvest by late spring or early summer—before the first wave of loopers hits. Start the seeds indoors, 12 weeks before the last frost date, then transplant them to the garden when they are 7 to 8 weeks old.

To avoid fall crop damage, start transplants indoors about 18 weeks before your first fall frost so you can put 7-to 8-week-old plants in the garden about 10 weeks before your first fall frost.

Prevent Damage from Aphids, Cucumber Beetles and More with this Shiny Cure! Learn more.

Cabbage Maggot

When brassica crops wilt unexplainably, the most likely cause is cabbage maggots. The first wave of these little root and stem feeders in early spring usually is the most destructive. By delaying planting until after yellow rocket (wild mustard) has bloomed, you can avoid these maggots.

If there are no brassicas (such as the yellow rocket) in the garden for the adult flies to lay their eggs around (which eventually hatch into those root-eating maggots), they'll move on. If you're direct-seeding your crops, wait a week after the peak of yellow rocket's bloom to sow. Wait about two weeks if you're putting out transplants.

Corn Earworm

One of the most destructive sweet corn pests in North America, corn earworms chew through the silks and into the tips of the ears, making an unattractive mess. Plant early maturing varieties as early as possible to avoid sharing your sweet corn. Corn planted much after that will probably be silking just as the corn earworm moths are looking to lay their eggs.

Consider starting your corn indoors in peat pots and then transplanting, pots and all. Corn won't germinate in cool soil, but it grows just fine in it.

Colorado Potato Beetle

Simply delay planting your potatoes for 7 to 14 days after the usual planting date in your area and you could defeat this defoliating pest! Adult Colorado potato beetles (CPBs) emerge from the soil in early spring. If they don't find any potato plants, they move on.

Just be sure you plant fast-maturing varieties so the tubers will be a good size when the second generation of beetles comes around in midsummer. A little leaf chewing by the beetles (who only eat the above-ground growth) at that point won't hurt your harvest.

To further protect your late-planted potatoes, build a trench trap when you plant your potatoes. Surround the bed with a 16-inch-deep vertical-sided trench lined with black plastic—the beetles will crawl to get to the potatoes, fall into the trench, and won't be able to escape.

Prevent Damage from Aphids, Cucumber Beetles and More with this Shiny Cure! Learn more.

European Corn Borer

Another sweet corn menace that can be outwitted by planting time! This caterpillar is a pest in northern and central United States and southern Canada. Bent tassels or broken, chewed leaves and ears with holes in them are the signs of European corn borer damage.

To combat this corn pest, you must avoid very early and very late corn plantings. For most, that means planting corn about 2 weeks after the last frost date (or as close as possible to the midpoint of your corn-planting season). If your corn usually suffers from both of these pests, choose the timing that will beat your most troublesome pest.

Flea Beetles

These jumpy little black beetles chew small, rounded holes in the leaves of many vegetables (such as brassicas, eggplant, potatoes, and tomatoes). They sometimes kill seedlings. If you've had flea beetle problems in previous years, avoid them by delaying the planting of susceptible crops by a week or two beyond normal planting times for your region.

Because flea beetles overwinter as adults, full-size adult beetles appear in your garden very early in the season. If food isn't there when the adults emerge, they won't lay their eggs in the garden, which means fewer problems later in the season. When you do plant, use transplants rather than direct-seeding your crops whenever possible—transplants can withstand flea beetle damage much better than young sprouts.

Mix Up Flea Beetles: Timing planting right helps prevent flea beetle problems, and so can interplanting, says Sally Cunningham, author of Great Garden Companions. "One year I planted eggplants all alone in one area, and in another place, I interspersed eggplants with marigolds and basil," Sally says. "Guess what? The solo eggplants were full of holes, but the other ones were camouflaged enough that they squeaked through the season undiscovered! Flea beetles are easily confused."

Pepper Weevil

Found across the south from California to Florida, these weevils puncture immature peppers with their sharp snouts and lay eggs in the peppers. The eggs hatch and the larvae feed on the peppers, causing them to turn yellow, get misshapen, and/or drop from the plant.

But you won't witness such horrors in your garden if you start your peppers indoors and plant them outside as early as possible (about 2 weeks after the last frost), before the weevil population builds up. At the end of the season, get your peppers out of the garden as fast as possible, too—allowing the plants to linger will invite future weevil problems.

Root Knot Nematodes

These tiny, eel-like creatures feed on the roots of almost all veggies and are especially problematic in the warm, sandy soils of southern and coastal regions. Affected plants look weak and sickly. Their roots are covered with galls (knobby, abnormal growths).

Early spring planting (at least 4 weeks before the last frost) is the key to getting a good harvest of crops like lettuce, broccoli, and cauliflower, because nematodes don't become active until soil temperatures are fairly warm. Start your broccoli and cauliflower indoors about 12 weeks before the last frost and plant them outdoors when they are 7 to 8 weeks old. Lettuce and other greens should be started 8 weeks before the last frost and planted outside when the seedlings are 4 weeks old.

In fall, reverse this timing: Delay lettuce, spinach, and other cool-season plantings until the soil temperature drops below 64ºF. Choose nematode-resistant varieties when you can.

Sweet Potato Whitefly

These tiny, sap-sucking insects attack vegetables just about everywhere in North America. When infested plants are disturbed, clouds of adult whiteflies fly into the air. The greatest damage to plants is done by the viruses they transmit.

Allowing 2 weeks between crops is an effective way to control whiteflies. After you harvest one crop, clean up and allow a 2-week fallow period before planting the next. Sweet potato whiteflies will have nothing to feed on during those 2 weeks and will either die off or move on.

In the fall, a simple delay in planting will help. In the South, wait about 2 weeks after the late summer cotton harvest to avoid the masses of whiteflies that were feeding on the cotton.

Prevent Damage from Aphids, Cucumber Beetles and More with this Shiny Cure! Learn more.

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