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Natural Allies: Renewing ancient methods of controlling bugs--with bugs.

HAVING CULTIVATED citrus trees for thousands of years in a country that was the birthplace of entomology, it is no surprise that Chinese farmers had experience with pests and non-toxic pest controls. They were aware, for instance, that the citrus stinkbug, citrus leaf-miner, leaf-feeding caterpillars, and aphids could--and would--attack their lemon, orange, pomelo and tangerine trees. Not having access to malathion, acetamiprid, cyhexatin+tetradifon, methidathion, spinosad and other modern weapons of the war on insects, they tried working with nature, rather than running immediately into battle. Perhaps they had read the advice of Sun Tsu in The Art of War, written many centuries BCE (Before Common Era), "The supreme art of war is to subdue the enemy without fighting."

Chinese farmers are credited with instigating the first documented use of insects to control other insects. About 1700 years ago, they discovered that a strain of weaver ants--yellow citrus ants (Oecophylla smaragdina Fabr)--would eat a wide variety of plant-eating pests. In the early years, they tracked down and collected nests from the wild. Later (about 985 CE), using fat as bait, they trapped the ants in hog and sheep bladders. After about 1600, the farmers discovered that, if they constructed bamboo bridges between the trees, the ants would occupy the whole orchard even if only a few of the trees were seeded. Winter was a challenge, as the ants had trouble surviving the cold, so the farmers started collecting the ants in the fall and feeding them citrus fruits until the warm, spring days returned. Finally, some observant farmers noticed that the thicker foliage of pomelo trees provide better protection--a sanctuary if you will--for the ants. If the farmers have mixed groves of oranges and pomelos, and build bamboo bridges among them, the ant nests in the pomelo trees serve as an annual, renewable source of insect control.

In Six-legged Livestock, a 2013 Food and Agriculture Organization report on edible insect farming, collecting and marketing in Thailand, authors noted that weaver ants are also used for pest control in mango orchards. Some farmers maintain their own nests, but finding queens and good sanctuary trees is a challenge, so that often the ants are foraged. The farmers create ant highways between trees with rattan or cane ropes, which the ants--who are remarkable engineers--then use to move to new sites, where they build new nests from larval silk. Weaver ants are celebrated in songs and dances in the Northeastern Thailand, where their eggs, pupae and adults are incorporated into salads and omelettes. Eating other pest control products, such as insecticides, is not generally recommended.

European and North American agriculture expanded most rapidly during the period when industrial pesticides were widely available and only minimally controversial. Non-bug-insect-eating cultures have become addicted to these toxins, and have aggressively marketed their drug habits abroad. Now, after decades of pesticide addiction, many agriculturalists in China, Europe and worldwide are rediscovering "beneficial" insects.

Generally, the less toxic and more ecologically sustainable approaches to pest control--that is, those most compatible with entomophagy--require much more sophisticated agricultural practices and knowledge of ecology than using insecticides. In a 2016 report on the control of cochineal pests in prickly pear plantations in central Mexico, the researchers concluded that six different species of natural predators did keep the pest populations in check, as farmers had reported. They cautioned, however, that such "autonomous biological control" methods depended on agroecosystems with structural complexity and species diversity.

Often, just to hedge their bets in the face of scaremongering by pesticide manufacturing companies, 21st century farmers use a combination of natural predators and pesticides. So-called Integrated Pest Management considers and uses all forms of insect control, and then targets insecticides at specific times in the growth cycle of crops. The medical-war analogy for this would be surgical strikes. Many of the IPM methods use natural enemies of insects, such as bacteria or protozoa. If seeded into standing water, different strains of Bacillus thuringlensus for instance, kill mosquitoes and black flies. Bacillus popilliae kills Japanese beetles.

Eat up the details on this David Waltner-Toews adaptation from his book. They are found at the bottom right of page 45.
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Publication:Alternatives Journal
Geographic Code:9CHIN
Date:Sep 22, 2017
Words:691
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