Seen any weird-looking bees lately? Super wasps released in Laredo to combat Carrizo cane

Arundo wasps recruited to fight Carrizo cane along Rio Grande

Laredoans are well acquainted with the question of the non-native, invasive carrizo that has just about taken over the banks of the Rio Grande. A few years ago, there was an attempt to use pesticides to help eradicate the encroaching carrizo. The Border patrol was adamant about spraying the river banks in order to get rid of the cane and allow them a better view of the river. Although the exact sequence of events escape me, they spraying was ultimately called off. Now, scientist are employing another strategy; super wasps that might actually be effective in combating the almost invincible carrizo.  From the Texas Observer :

This unnatural density is one hallmark of an invasive species. The Arundo cane has spread so fast in Texas because nothing is feeding on it. In Europe, where it originates, specialized insects keep it under control. When the Spanish brought the cane to colonies in South Texas in the 1500s for basket-weaving, they didn’t bring anything that would eat it. Now, 500 years later, we are paying the price.

“Every native plant species in the Rio Grande Valley has spent millions of years in constant competition with every other plant and animal species in the region,” Adamczyk said. “They have bred to keep each other in check. But there’s nothing doing that for the Arundo. Nothing is eating it or slowing its spread, and it’s able to out-compete everything.”

There are three primary ways to control invasive plant species: Kill them with herbicides, clear them with bulldozers and machetes, or attempt to introduce a new predator. The least controversial approach, clearing the cane, is not going to work. There are thousands of square miles of the stuff, and Arundo cane is nearly impossible to cut out. Each stalk has a thick taproot that sends shoots in every direction. You can bulldoze or chop the cane down, and it will grow right back. Worse, any stress on the plant—say a machete blow—causes it to send out more root stalks. Every chopped-up joint of cane that floats downstream can sprout another stand.

Killing the cane is not going to be easy, and until recently, the USDA was considering spraying the Rio Grande and its tributaries—an area known for its intensive agriculture, which drains into the Gulf—with Monsanto’s Roundup herbicide. The drawbacks are obvious. In 2009, scientist John Goolsby of the USDA’s Beneficial Insects Research Unit proposed using “biocontrol” on the cane. The approach involves fighting one invasive species with another invasive species. In this case, wasps. The Arundo wasps are what entomologists classify as “primitive wasps”—they don’t live in colonies, they don’t build nests, and they can’t sting. They can, USDA scientists hope, help control the cane.

The wasps are from the same part of the Mediterranean as the cane, and the female wasps have sharp, tapered abdomens that they use to inject their eggs deep into the green stalks. The eggs cause the cane to form galls and grow outward, seriously retarding growth. Later, the young wasps emerge from the galls, and the cycle continues. Since 2009, the USDA has begun releasing them in test sites in Laredo and McAllen.

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