Eco-efficient pest control—a lesson from the past?

8 April, 2011 by (comments)

New study finds ancient communities in the Andes controlled potato weevils through “sustainable monocropping”

It seems that ancient farmers in the Andes knew a thing or two about eco-efficient agriculture—particularly when it came to protecting their vitally important potato crops from insect attacks.

According to new research published in the latest edition of the journal Ecological Applications, farmers in the Central Andes of Peru and Bolivia used to control infestations of the Andean Potato Weevil by aggregating their fields into large common fields, reminiscent of modern-day industrial monocultures.

Widely reviled by environmentalists, monocultures—large-scale plantations of single crop varieties—have long been blamed for an increased likelihood of pest outbreaks, and the rise in the need for insecticides.

But the research, led by CIAT entomologist Soroush Parsa, found that when the flightless weevils—the region’s most significant potato pest—migrate to new potato fields, they concentrate along the field edges, causing little damage to crops in the interior. Accordingly, the larger the field, the greater the proportion of potatoes in the interior that are protected from attack.

“There is a widely held view that monocultures invariably lead to increased in pest pressure due to the large concentration of food,” said Parsa. “But in the case of the Andean potato weevil, we found completely the opposite.”

When Parsa studied the history of the weevil, he noticed that reports of significant damage in potato crops only began to appear in the early 1900s, coinciding with the progressive breakdown of traditional farming systems in the Central Andes, involving the fragmentation of common-field agriculture.

“It was like playing ecological detective,” he explained. “Initially I couldn’t understand why, after 5,000 years of indigenous agriculture, the potato weevils suddenly became key potato pests. Why hadn’t the locals found a way to control them? It turns out they already had.

“This is a really important missing link.”

The findings suggest that combining individual potato fields into large single areas may be a more effective solution to the weevil problem than the usual method of targeting overwintering sites with insecticides. While work is currently ongoing into the possible benefits of edge effects in controlling pest outbreaks in cotton monocultures, Parsa is quick to stress that his findings relate to one specific pest.

“Insects are very idiosyncratic,” he continued. “Some walk, some fly, some have multiple generations in one season— so it’s important to resist the temptation to extrapolate.

“But this is one clear example of why we have to work on a case-by-case basis, and why we shouldn’t make broad brush generalizations about pests, or what about sustainable, eco-efficient solutions necessarily entail.”

Rescource concentration dilutes a key pest in indigenous potato agriculture, was published today in the latest edition of the journal Ecological Applications, produced by the Ecological Society of America.

Filed Under: Agro-ecology and Economics @en, Latin America and the Caribbean, Regions