California Releases Wasps to Control Apple Moth Infestations


Light brown apple moth; photo by Donald Hobern via Flickr CC

California is taking a more natural approach to pest control -- instead of spraying for light brown apple moths which are considered a pest by the USDA, the state is testing out releasing a type of wasp that lay their eggs inside apple moth eggs. The tactic comes after protests in 2007 by Californians over plans to spray pesticides to deal with the moths. PhysOrg reports that the California Department of Food and Agriculture attempted to get rid of the moths by spraying a pheromone mixture on crops in Monterey and Santa Cruz without completing an environmental impact report. The response by citizen was swift. The LA Times reports that, "Within a month [of the 2007 spraying], dozens of residents complained to local health officials of illnesses they thought were connected to the spraying, but no definitive link has been made. And two courts ruled that the agency had no grounds for an emergency program."


Photo by Kevin Krejci via Flickr CC

Instead of spraying, this time California is looking to control the moths by releasing hundreds of wasps -- tiny, stinger-less wasps that lay their eggs inside the eggs of the light brown apple moth. They'll first release the pupae of the wasps in San Luis Obispo and Sacramento counties and if they find it is an effective strategy, they'll release them elsewhere. The wasps are not dangerous to humans or pets, though experts are hoping they will have a big impact on apple moth populations.

The LA Times reports that at least one pesticide watchdog group is happy that a more natural approach is being taken. "Asael Sala, a community organizer for Pesticide Watch, a Sacramento-based organization that promotes sustainable pest control, praised the state's approach. 'Stingerless wasps are an important part of ... green pesticide practices,' Sala said. 'We're definitely glad to see that continuing.'"

However, some environmentalists are a little more concerned about potential unintended consequences. Humans don't have the best track record in trying to control one species by using another. Often there are unintended consequences that aren't necessarily favorable. And whether or not the wasps are even needed is another question in debate.

"Using wasps may be a preferable solution in a situation where crops are going to be devastated," Nan Wishner of California Health Initiative told reporters, "but the insect hasn't been a threat."

According to PhysOrg:

A 2010 state environmental impact report confirms that there have been "no published studies of crop damages," but Steve Lyle, a spokesman for the Department of Food and Agriculture, said the apple moth has "caused a small amount of damage to California crops and plants and may have the potential to cause much more." The agency's preventive measures stem from apple moth infestations that damaged crops in Australia, where the moth originates, and New Zealand...

...Tom Kelly, a California Health Initiative member, says the apple moth has long been in California, where farmers have fought it the same way they fight the native leaf-rolling moth. "Farmers deal with them day in and day out, but we don't spend tens of millions of dollars on an eradication program," Kelly said.

The state, however, wants to move forward with eradication measures because the moth is listed as a pest, and therefore the state has to eradicate it to ensure that California produce isn't a host to moth eggs that could spread to other states or countries. In other words, it's an issue with trade, not necessarily immediate crop health. The concern is that releasing the wasps could be dangerous not just for the light brown apple moth but for many other insects -- including beneficial insects like butterflies -- since the wasps don't necessarily stick to moth eggs. While experts say that the wasp species being released has a short life span and limited mobility, the wasps could still potentially pose a problem.

Still, this natural solution is likely safer than the sprays that sparked protests a few years ago. No doubt, environmentalists will be following the impacts of the wasp releases closely to ensure there are not negative impacts on the ecosystems worse than damage moths might potentially cause to crops. Wasps have been considered for natural pest control in other areas before, and researchers believe they could hold significant potential for reducing crop loss from insects if managed correctly.

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Tags: Agriculture | Ecology | Farming | Insects

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