The Perfect Insect Barrier!


20150507DOne of the most unusual yet effective “pesticides” is floating row cover, also simply called row cover. This is a transparent, lightweight fabric that lets rainwater, air and sunlight through to the plants it covers. It was originally designed to provide frost protection for early plantings and can still be used for that purpose. However, I’ll bet dollars to donuts that more gardeners use it to protect their crops against insect pests. And here’s how it works.


These very frustrated potato beetles can smell and see their host plant, but the row cover keeps them away.

Loosely cover the row or bed of the susceptible plant with floating row cover (install it on a windless day if possible) and use stakes, bricks or stones to pin it down, otherwise it will quickly blow away. When the plants emerge underneath the barrier, its pest will quickly find them by the smell they give off and will land on the row cover, ready to eat. But it can’t penetrate the barrier! You’ll see the poor bug pacing, turning in circles, examining every fold in the fabric, but there’s nothing to do. Hungry, it will either fly away to some other garden or simply die, unable to feed itself.


A cloche tunnel held up by hoops. You don’t need this kind of structure with floating row cover.

One precision: unlike a cloche tunnel that is installed over a structure to hold it above the plants it covers, floating row cover is so light it is simply lifted upwards by the plants as they grow, so there is no need for a support structure. That said, a lot of overly zealous gardeners do put in a support structure of some sort. That’s all right, but it is extra work for you!

20150507AThe down side of the floating cover is that it can keep plants too hot when heat waves hit, but that’s easily remedied. Simply remove it! Of course, your plants are then exposed again to their insect pest, but by the time heat forces you to remove the cover, the vital first generation of the pest has already waned. You’ll only be dealing with the second generation (if there is one) and it tends naturally to be much smaller than the first one. Better yet, since you deprived the pest of its main source of food at the beginning of the season, the second generation will be even further reduced locally, with usually only scattered bugs reaching your plants, enough so that the stragglers no longer cause damage worth mentioning. Plus, your vegetables are no longer weak seedlings, but well-developed plants better able to resist if a larger second generation of the insect were to arise.

For a floating row cover to be an effective insect barrier, though, you have to follow one rule: you must practice crop rotation, that is, plant the vegetable in a spot where it did not grow the previous year. If you plant your potatoes, cabbages, carrots, etc., exactly where you grew them the previous year, its insect pest will most likely be overwintering in the soil in just that spot. So when it does climb out of the ground as the weather warms, it will find itself inside your insect barrier and will therefore be able to eat away to its heart’s content. Not very effective!

A floating cover is very useful against a wide range of insects: cabbage butterflies and flea beetles on cabbages and other crucifers, potato bugs on potatoes, carrot flies on carrots, leek moths on onions, garlic and leeks, etc. You’ll end up with an excellent crop without having to spray insecticides over and over, which is less work for you and good for the environment.

Better results, less effort? The floating cover is the perfect tool for the laidback gardener!


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