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Plant-Eating Beetle: Cheapest Way To Kill Weeds

Skeletonization of a Gainesville air potato leaf shows why the air potato beetle is considered one of the most successful biocontrol approaches in recent decades compared to other projects — current or past.
Skeletonization of a Gainesville air potato leaf shows why the air potato beetle is considered one of the most successful biocontrol approaches in recent decades compared to other projects — current or past.

The air potato beetle, a native to Asia, has been hard at work controlling the air potato, Dioscorea bulbifera, but its future relies on how well it’s received with landowners and nature enthusiasts.

“We have now released approximately 340,000 beetles at nearly 1,000 different locations in the state,”  entomology professor William A. Overholt wrote in an email.

Comparable programs like the air potato beetle project, seen by Overholt,  show that the air potato beetle has had to follow some pretty successful biocontrol programs.

In comparison, Overholt and his colleagues released about 250,000 leaf-feeding beetles specificaly for the tropical soda apple, Solanum viarum Dunal, which has golf-ball-sized fruits that closely resemble watermelon along with thorny stems and leaves. 

reduction in annual control costs between $3.5 million and $8 million was estimated for the tropical soda apple.

During that time, the eight-year control of the tropical soda apple, which primarily invaded pastures and untouched areas in Florida, helped save landscapes, livestock and elevate future project endeavors.

According to a BioOne research review document in 2006, an economical calculation of the tropical soda apple in Florida revealed that the invasive Brazilian species cost Florida ranchers about $15 million a year, with the biggest losses in central Florida.

In a span of two years, the leaf-feeding beetle reduced tropical soda apple densities to an average of one plant in an area of 16 meters.

Comparatively, the air potato beetle saved about 50 percent of management costs statewide and had a total effectiveness-savings of about $108 million to $266 million for the program.

The cooperative efforts among federal, state and county-level agencies along with outreach to landowners successfully impacted landscapes and helped with the biocontrol program against the topical soda apple.

Alligatorweed, Alternanthera philoxeroides, was the first major successful biocontrol of weed biocontrol in Florida, Overholt said.

With the herbicides needed to treat the long-stemmed alligatorweed, the cost is high. To apply these weedkillers like glyphosate and fluoridone, the cost is approximately $170 to $370 per hectare – a metric unit of area defined by 10,000 square meters.

Scientists later discovered the flea beetle to be the best potential way to control the South American-native alligatorweed.

The flea beetle’s work greatly reduced the need for chemical control of the weed and saved 76 percent of the costs for the areas treated.

Eric Rohrig, a biological scientist for the Methods Development and Biological Control in the Division of Plant Industry, said the air potato beetle project is saving money that was previously spent by outlets like labor costs and supply costs.

“What we spend on the program is a drop in the bucket compared the total cost of treating air potato in the state,” Rohrig wrote in an email. “Biocontrol costs money in the front end but once the insects establish they carry on providing free, safe, environmentally friendly, persistent control.”

Less than $200,000 is spent per year on the total salaries for one scientist and three technicians working on the research along with supplies like pots, fertilizer, soil and gas for vehicles, Rohrig said.

“This is definitely one of my top 10 projects I’ve been involved with,” said William Lester, an Urban and Commercial Horticulture Agent. “So far it’s been really successful. So far we haven’t had any problems or issues and the beetles have performed better, honestly better than I expected them to.”

Populations for the air potato beetle will increase and some will continue to eat the air potato. However, some air potato plants will always be present in natural locations.  

The vine will not completely die off, but the amount of vines will be reduced to a controllable amount. This will allow funds to be moved that use to go toward chemical or mechanical control of the plant and  those savings someplace else — possibly future biocontrol endeavors.

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