Tamarisk beetles eating the invasive tamarisk trees in Kansas
Good news! Tamarisk beetles have survived their first winter in Kansas! They are now hard at work eating the tiny new foliage as it emerges on the tamarisk trees. In Kansas in 2013, the Larger tamarisk beetle, Diorhabda carinata,was located in Clark, Meade and Comanche counties, a first for Kansas! To see a current map of tamarisk beetle distribution within US, click here (http://www.tamariskcoalition.org/announcements/2013-final-updated-tamarisk-leaf-beetle-distribution-map-available).
These beetles are biocontrol agents that have been released into the US to control the highly invasive tamarisk trees. Invasive tamarisk trees are thought to occur in almost every Kansas County. Thousands to millions have been spent on control measures yet the tamarisk trees keep coming back. These beetles are excellent biological control agents because they are extremely specific to tamarisk species of trees and don’t cost landowners anything. There are a number of reasons tamarisk trees are not welcome in the US. Just to name a few, they crowd out our native trees and shrubs, they uptake more than 200 gallons of water per day and can grow in very dense thickets, they accumulate salt around the tree base, are a fire hazard and provide little nutrients to wildlife and livestock. The amount of water they steal is estimated to be enough for 20,000,000 people or enough to irrigate 1,000,000 acres for one year! (http://www.discovermoab.com/tamarisk.htm)
Above is a photo of a tamarisk tree infested area in Clark county where the beetles were first located late last summer (2013) and it demonstrates the damage they can do to the trees in just one month. These trees were defoliated by the beetles, but aren’t dead yet. After repetitive defoliation events, the trees aren’t able to get enough nutrients and die within 3-5 years depending on the size of the tree.
The exact emergence date of the beetles in these SW counties is not known for sure, but as of April 10, 2014 they were out and feeding. The orange arrows in the picture above show a few of the clumps of beetles that give the tree a unnaturally bumpy, dark appearance on the branches that can be seen from several feet away. On leafed out trees, they appear to be dripping with adults and and their dark colored young (see below).
No mating was observed on April 10th, but we will be revisiting these areas next week to look for mating and egg laying. This species of tamarisk beetle is the only species that lays its eggs on the bark of the branches, the other species lay eggs on the leaves of the tree. We may see up to five generations of this beetle in Kansas if they continue to do well.
This isn’t the first time tamarisk beetles have been to Kansas however. In 2005-2008, several attempts were made to establish the Northern tamarisk beetle (D. carinulata) in parts of north-central Kansas (Phillips and Rooks counties). These beetles were taken from established populations in Utah then held in Colorado at a rearing facility until release dates occurred. The Kansas releases were made by the USDA in conjunction with the Kansas Dept of Ag, but failed for various reasons. Problems with permits or other paperwork issues delayed the release in 2005 until early fall, which probably didn’t give the beetles enough time to establish. In another year, dry lake beds filled up again when the rains returned and drowned both the tamarisk trees and the overwintering population of beetles. In another year, a tornado came through the night after the beetle release! Despite these problems, this tamarisk beetle species may not have been well suited for our harsh Kansas climate. Although I refer to our beetle as the Larger tamarisk beetle, work conducted by Texas A&M recently showed our population had a past hybridization with the Mediterranean tamarisk beetle, D. elongata. This hybridization seems to be key to its survival in Kansas. Our population moved into into SW Kansas from Oklahoma last summer. Since their move into SW Kansas, the beetles have endured temperatures as low as -10°F in early March and since they emerged from the soil, as low as 20°F. If these beetles continue to do well in Kansas, they could potentially move into other counties and start to devour those tamarisk trees as well.
It is illegal to move tamarisk beetles between states, however established beetles may be moved with in the state. Beetle releases by individuals into other counties in Kansas is not recommended at this time, since we are trying to understand the biology of this hybrid and its’ movement. Releases are planned for certain Kansas counties this summer by KSU and KDA and those populations will be monitored closely. This will be critical since Larger tamarisk beetles and Northern tamarisk beetles can mate, but produce little to no viable offspring. The Northern tamarisk beetle is currently established in Colorado approx 80 miles from Hamilton county, KS border. If these two beetle populations come into contact, it could potentially wipe out both populations. A coordinated effort of many individuals will be needed to map out and research this beneficial biocontrol agent and its effect on invasive tamarisk trees in our area.
Please contact me at email@example.com if you spot a population of these beetles in Kansas or if beetles are moved so we can keep track of populations. More info to come soon…