Codling Moths: How to Safely Control This Fruit Tree Pest

How a California scientist and an apple farmer combine efforts to organically control codling moths.

| May/June 1984

Three years ago Pike Mountain Apple Orchard, nestled in the foothills of the Sierra Nevada mountain range in northern California, faced a ruinous infestation of codling moths. In fact, the 12-acre spread (containing 988 trees laden with Golden and Red Delicious and Rome Beauty apples), under the management of organic farmer Molly Breen, lost a whopping 60% of its 1981 crop to the voracious insects. However, today—thanks to entomologist Dr. Louis A. Falcon, of the University of California at Berkeley, and the codling moth virus he championed—Molly's orchard has been saved! Current moth damage is down to a mere 2%, and (according to the local agricultural commissioner) Pike Mountain apples are now among the finest grown in all of northern California.

The story behind this miraculous turn of events should prove valuable to anyone whose crops are prey to codling moths and who's looking for an environmentally safe means of getting rid of these despoilers of fruit and nut trees.

Codling Moth Virus

Molly Breen, a fervent proponent of organic farming techniques, came to Pike Mountain Orchard in 1974. Since the 30-year-old orchard had sat abandoned for half a decade prior to her arrival, she had her work cut out for her. Over the next few years Molly saw to it that—among other chores—tons of manure, rock phosphate, and fertilizer were added to the soil, and that clover was established as a ground cover. Finally, thanks to her conscientious use of primarily biodynamic farming practices, the orchard was restored to peak production. But as the trees became healthier and more productive, they also became increasingly infested with hungry codling moths.

Meanwhile (unbeknownst to Molly), Dr. Louis Falcon was hard at work trying to develop a new microbiological insecticide that would control the codling moth in its destructive larval stage. (As you may know, it's the larvae—not the moths—that bore into the fruit. Adult codlers lay their eggs on the fruit, and as the apples develop, the newly emerged larvae eat their way into the fruit to feed on the seed.)

Dr. Falcon began researching a treatment for codling moths in 1963, when a microorganism called Codling Moth Granulosis Virus (CMGV) was first discovered in Mexico. The disease, which was reported to be nearly 100% fatal to codling moths, caused the larvae to become puffy and lethargic . . . then to liquefy . . . and finally to literally drip off the host plant.

In the years following his introduction to the virus, Dr. Falcon began rearing codling moths in his lab and testing the effects of the disease on them in an effort to determine whether CMGV might provide an effective natural control for these orchard menaces. In the early stages of his research, he infected live larvae with the virus and then crushed them into a paste that could be mixed with water to form a sprayable solution.

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