Salvinia Biological Control Project at Caddo Lake.

Dr. Allen Knutson Professor and Extension Entomologist Texas A&M AgriLife Research and Extension Center, Dallas Dr. Abhishek Mukherjee, Post-doctoral Researcher Entomology Dept., Texas A&M, College Station Lee Eisenberg Extension Associate Texas Water Resources Institute Texas A&M AgriLife Lucas Gregory Project Manager Texas Water Resources Institute, Texas A&M

2011. Establishment of Salvinia Weevils at Caddo Lake in Texas.

Total of 110,00 adults reared at Texas A&M Rearing Facility and released at four sites on Caddo Lake.

Lost all sites due to low water following record breaking drought.

Bird Roost Release Site 2012

2012. Bird Roost site.

65,000 adults released in May and July, 2012. No further releases.

Density increased to 20 adults/kg by September, but no reduction in salvinia mat.

Last sampled in October, density of 11 adults/kg

2012-2013. Success at Bird Roost Site.

Following a mild winter, weevils were recovered in the February 2013 (4 / kg), documenting the first over wintering of weevils at Caddo Lake,

Water carried salvinia and weevils from the release site, and only 0.5 to 0.1 adults/kg present in April and May.

No samples taken during summer.

2012-2013. Bird Roost Site.

Boaters reported salvinia mat heavily damaged in early October.

Sampling found large numbers of adults; 55 adults/kg and extensive weevil damage to salvinia mat.

December 16, 2013, weevil damage across ca. 10-12 acres. 21 adults/kg

Bird Roost Site. 2014.

Following a very cold 2013-2014 winter, only 0.1-0.3 weevils were recovered in February and March.

No weevils recovered in June, 2014.

Will this population recover ? Are additional releases needed ?

Summary, Bird Roost, 2012-14.

A release of 65,000 adults in May and July across a 2 acre area required two summers before destroying a dense and extensive salvinia mat across about 12 acres.

However, following a very cold winter, only a few weevils were found the following spring.

Lone Pine Strecth Release Site: 2013

Field Release, Lone Pine Strech. 2013-2014.

42,000 adults released in May and

July, 2013 in 0.25 acre plot at Lone Pine Stretch.

Weevils increased to 40/kg in October and destroyed the salvinia mat within an area of ca. 2 acres.

Lone Pine Strecth, Release Area. Aug, 2013.

Field Release, Lone Pine Strech. 2013-2014.

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Dec 13, 2013, weevil density 26/kg.

Jan 12, 2014, weevil density 1.6/kg.

No weevils recovered in Feb-March.

Weevil density in June - 0.5/kg

Caddo Lake 2011-2014.

Releasing large numbers of weevils,

(30,000 +) resulted in destruction of the salvinia mat 2 years after release.

Cold increases winter mortality and delays population increase in the spring.

Salvinia weevils can effectively reduce salvinia infestations at Caddo, but annual releases will be needed achieve early season reduction in salvinia.

Targeted herbicide sprays early season could supplement weevil impact.

Salvinia weevils from Australia Survive Freezing Longer than Weevils in the US

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24 30 36

Hours Frozen

Weevil Survival Following Freezing for 24, 30 and 36 hours

Florida

Texas

Louisiana

Australia

Chill Coma Recovery. Salvinia weevils from Australia are more cold-tolerant than weevils in the US

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B B

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Are There More Cold Tolerant Weevils in Argentina ? The Search Continues…

Questions ? The Caddo Lake Giant Salvinia Project. Center for Invasive Species Eradication Texas Water Resources Institute, Texas A&M AgriLife Extension

Questions ? The Caddo Lake Giant Salvinia Project. Center for Invasive Species Eradication Texas Water Resources Institute, Texas A&M AgriLife Extension