Home & Garden

Take these steps to prevent garden insect infestations

Caterpillars are larvae that live to eat and can do serious damage overnight, so keep a sharp eye out for new hatchlings.
Caterpillars are larvae that live to eat and can do serious damage overnight, so keep a sharp eye out for new hatchlings. TNS

Insect infestations thoroughly creep me out. I can handle a few grasshoppers and other bugs in my vegetable garden, but when a single species develops into large populations, my skin crawls. Once bugs reach infestation levels on your vegetables they not only defoliate your plants and spread diseases, they can kill the crop when numbers get high enough. This is the organic farmer’s worst-case scenario because it’s nearly impossible to knock down an infestation without pesticides.

Over the years I’ve learned that observation, prevention and prompt control are key to avoiding an infestation. This is the foundation of integrated pest management, which demands timely action using the least toxic means when the first signs of problem insects appear. Each new growing season presents opportunities for different bugs to flourish, so pest management is more than doing what you did last year.

▪ Practice detailed daily observation. I often advise people to inspect their garden with coffee or an after-work cocktail so the beverages remind us to do it. This helps you become familiar with each plant so you know the moment something is amiss. Often the cause is found on the underside of the leaf, which is rarely seen unless you get down there and study samples up close — with your reading glasses on if you’re over 50. This is where bugs hang out during the heat of the day and why sprays often don’t discourage them unless carefully applied to both sides.

▪ Recognition. When inspecting plants, know that the first signs are tiny. They may be a cluster of pinhead-sized eggs stuck to the backside of a leaf, or fine webbing dotted with small red or black spots. There may be small dark feces pellets accumulating on surfaces from caterpillars feeding invisibly on the foliage. While you don’t need to know the exact genus and species of a bug, just knowing its general appearance such as the tiny aphid or the enormous tomato hornworm is the precursor to selecting the right control.

▪ Prevention. Dirty plants tend to suffer more bug damage because the dust blocks light from photosynthetic cells, weakening their food-making potential. Dust also creates an ideal environment for spider mites. This is why it’s recommended you wash off your vegetable garden every couple of weeks with a strong jet of water. This scours the leaf surface to dislodge tiny sucking bugs, eggs, nymphs and newly-hatched larvae before they damage the plants. Use an articulating head water wand to shoot water from the ground upward to hit the back sides of leaves where bugs accumulate protected from hot sun and rain. If a weaker plant tends to draws abnormal numbers of bugs, remove it altogether.

▪ Control. The least toxic means of pest control is to begin with nontoxic methods, then raising the bar step by step as required. The first step is to wash the plant to knock down the population. If it’s localized and small, apply insecticidal soap. If you find caterpillars or signs of them, use BT (Bacillus thuringiensis) controls that are natural, quick-acting and very effective. Next step up might be releasing beneficial organisms and insects such as ladybugs and praying mantises that prey on the bugs you don’t want. Only if all these fail, raise the bar with botanically-based pesticides such as neem oil or pyrethrins.

Prevention is always easier than controlling an infestation, so follow these four steps throughout the garden season to keep your veggies thriving. Study your plants, recognize the early signs, keep a clean house and stick with the least toxic approach before reaching for chemical pesticides. A little bit of prevention goes a long way in avoiding infestations in the house, in the landscape, and above all, in the vegetable garden.

Maureen Gilmer is an author, horticulturist and landscape designer. Learn more at www.MoPlants.com.