JORDAN RIVER COMMISSION

What is Biocontrol and is it safe?

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What is Biocontrol?

Biological control is a method of controlling pests (including insects, mites, weeds, and plant diseases) using other living organisms.  It relies on predation, parasitism, and herbivory, or other natural mechanisms, but typically also involves an active human management role. It can be an important component of integrated pest management (IPM) programs.  Importation (or “classical biological control”) involves the introduction of a pest’s natural enemies to a new locale where they do not occur naturally.

 

Biocontrol on the Jordan River Parkway:

The Jordan River Commission and it’s partners (Salt Lake County Weed Control and Salt Lake City) are experimenting with the use of two weevils (Microlarinus Lareynii and Microlarinus lypriformis) to reduce the infestation of puncturevine (a.k.a. goatheads) along the Jordan River Parkway Trail.   Goathead weed thorns are notorious for puncturing bicycle tires and are a major barrier to regular use of the Jordan River Parkway Trail.

We started with a small release of approximately 5,000 insects in 2012 along the Jordan River Parkway Trail in two areas:  between 2100 South and 3300 South in South Salt Lake, and near the Northwest Recreation Center in Salt Lake City.  The effectiveness of the biocontrol in reducing puncturevine infestations in these areas was monitored and tracked through mapping, photo reference points, and observation.  The strategy appears to be effective in at least helping reduce the extent of the problem, and the Jordan River Commission and its partners have expanded the use of biocontrol each  subsequent year.  In 2015, roughly 25,000 individual insects were released at 120 points along nearly the entire length of the trail corridor.

The use of biocontrol to reduce puncturevine along the trail has a number of benefits. While our volunteer crews are making a great dent in the puncturevine problem, the weevils are working even when we’re not.  In addition, biocontrol reduces the need to apply chemical herbicides, which protects water quality, and the health of trail users and the animals living in the corridor.

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Is introducing a new species safe?

Both Microlarinus Lareynii and Microlarinus lypriformis have been cleared for importation and release throughout the US for the control of puncturevine by the USDA Agriculture Research and Animal/Plant Health Inspection Service.   All approved biocontrol species have been extensively tested in quarantine facilities on native plants, endangered plants, and any other plants related to or found in similar environments as the target weed. If a biocontrol lives on other plants, it is not approved for release.  Puncturevine weevils have been used effectively since the 1960s in parts of Texas and California, and no issues have been reported.

 

Puncturevine Weevil Biology:

stemweevilFemale weevils chew into the side of a young (green) puncturevine bur, deposit eggs into the seed and seal it with fecal material. Females may deposit between 250 – 450 eggs. Weevil grubs develop inside the seed and pupate therein. Each seed may produce 1-3 weevils. The life cycle from egg to adult requires about 25 days. Adult weevils may also feed on the plant but do not cause appreciable damage to the plant. The number of weevil generations produced per year depends on the climate.

In an ideal situation, biocontrol agents will naturalize and reproduce, year after year until the weed population they depend upon is reduced to the point that the biocontrol no longer has a sufficient food supply to survive. Puncturevine weevils have been used in Utah for the past few years, but the weevils do not seem to be able to survive our cold winters.  This winter kill prevents the weevils from becoming established populations.  Because they are quite expensive to purchase (approximately $0.30 per insect) and they cannot establish a permanent population, puncturevine weevils have not been used extensively within the state of Utah.  However, that they can still be effective as a seasonal weed control strategy.  The weevils have been very successful in controlling the spread of the weed in parts of the country with warmer climates.

To learn more about biocontrol in Utah contact:

Amber Mendenhall
USDA-APHIS-PPQ
biological control
435-830-4146
utahsbuggirl@gmail.com