Let Beneficial Insects Do Their Work

carob tree in the spring

same carob tree in midsummer

How eager we are to find culprits or villains, whether in life or in the garden. Often, that search is merely an indication of our own impatience, stress or lazy thinking.

Let’s say I get lots of headaches. Instead of examining my life to find the underlying issues that bring on the headaches, I may blame my boss, a whiny customer, or a fellow employee for my throbbing head. Then I will probably just take a pill or two and the pain will go away.

But, soon enough, the headaches will return, until I might think there is something organically wrong with me. Yet, if I truly wanted to get rid of the headaches for good, I would probably have to make a change or two in my life.

In the garden, a similar frame of mind, where you seek to assign blame to some pest that, on the surface, may be chemically controlled, can keep your plants from flourishing. Nearly all garden problems can be fixed by adjusting a watering schedule, by moving shade-loving plants out of the sun or sun-lovers out of the shade, or by improving the soil. Instead of reaching for the spray bottle or soaking the soil with a systemic drench, think about what could be the source of your plant problem and you will usually discover that a nonchemical solution is at hand.

And sometimes, both in life in general and in the garden in particular, if you just let nature take its course, everything works out fine. Your kids may be giving you lots of headaches at the moment, but chances are good they will eventually grow up and learn how to function in the world.

This just-wait-and-see approach is highly recommended in the garden. This past spring, for instance, on a nearby carob tree (Ceratonia siliqua), all newly emerged foliage was blanketed with aphids. While the idea of spraying a docile target like aphids is tempting, there was no need to do so. Each flush of new carob leaf growth had fewer aphids than the last so that by midsummer there were no aphids at all on new growth and older leaves were virtually aphid free as well.

The aphids’ disappearance may be attributed to the arrival of tiny parasitic wasps, green lacewings, ladybugs and other aphid predators.

You may have noticed that the appearance of aphids and other sucking insects is often accompanied by the presence of ants. Your first thought on seeing the ants might be: “Oh great. Now I not only have an aphid problem, but an ant problem, too.” However, from the plant’s perspective, attracting aphids, which can cause some damage to them, is a price they are ready to pay to attract ants, which do an excellent job of fighting off pests whose damage would be much worse than that inflicted by aphids.

The problem is that ants also fight off aphid devouring insects such as ladybugs and parasitic wasps.

Researchers have shown that the fall colors in the leaves of certain plants are meant to attract particular types of aphids, which lay their eggs near these leaves. (Interestingly, the same colors that attract certain aphid types are repellent to others.)

In the spring, as the aphids hatch and multiply, ants are attracted to the aphids, whose excretions of undigested plant sap are licked up by the ants. Some ant species even carry aphids back to their nests where, by stroking the aphids with their antennae, they milk the honeydew from them. In this context, aphids are often referred to as “ant cows.” Just before winter, ants have even been known to take aphid eggs to their nests for safekeeping.

Then, in spring, they move the eggs back to the aphids’ host plant where they will start feeding and producing honeydew to the ants’ benefit.

As gardeners, we do not have the plants’ long-range perspective in terms of what is beneficial to them.

In certain fruit orchards in tropical Australia, China and Southeast Asia, weaver ants have proven more effective in controlling insect pests than chemical sprays. Plant physiologists note that the mutually beneficial relationship between aphids and ants, or even scales and ants, is beneficial to plants as well — in keeping away more serious insect pests — although it may be difficult for us to appreciate this benefit since we are only interested in the fruits or vegetables that we harvest this year and don’t share the plants’ longer view.

One proven remedy for ant control, courtesy of diynatural.com, involves making a paste out of Borax powder and powdered sugar (1 part borax, 3 parts powdered sugar). Place bottle caps filled with the paste directly in your ant trails.

Another option is to mix 3 tablespoons of Borax and 1/2 cup of sugar in 1 cup of warm water and soak up the mixture with cotton balls that are then placed in small dishes around your ant trails. In both cases, the ants will take the sweetened Borax back to their colonies, whose populations will be significantly reduced, if not wiped out completely.

There is some controversy over whether Borax is pet safe. The government mandated material safety data sheet on Borax classifies it together with baking soda and salt in terms of toxicity, and Borax is sometimes used to control fleas on pets and as a treatment for scabies/mange.

Still, to be absolutely safe, I would advise keeping pets away from Borax powder ant control formulations or products.

Tip of the week

The key concept in managing aphids or any other pest is control, as opposed to eradication. You do not want to eradicate any pest completely because then the beneficial insects which, given time, would naturally control the pest also will disappear. For this reason, when pruning a hedge, for example, where an insect pest and its beneficial insect predators are present, it is advisable to deposit the clippings under the hedge so that the population of beneficials will stay in place. Even if there is no visible evidence of predators, they could still be present in the form of minute parasitic wasps that are difficult to discern with the naked eye.

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