Learn About Whitehall Bio Control: 8/2/2023

The Whitehall Bio Control team managed to collect all 120+ releases of leafy spurge flea beetles. Thank you to the local landowner who allowed us to collect on their fine property. This week we have a bit of a lull in insect collections as the toadflax and spurge insects are finished and the spotted knapweed insects have not emerged in great enough numbers to be collectable. We will clean up the insectary at the high school and monitor past and future release sites. We are hearing from many landowners that have received releases of insects from us in the past that they are really starting to work! It is encouraging.

A noxious weed that we do not have much of in our part of Montana is the woody shrub called salt cedar or tamarix (Tamarix ramosissima). It is a problem in eastern Montana. This deciduous shrub/small tree has scale-like leaves that look like cedar leaves and pink or white flowers in spike-like drooping clusters. It has been purposefully planted in North America as a flowering shrub in landscaping and along water courses as erosion control. There have been several planted in yards in the Whitehall area that have been removed as they are identified. If you see this "decorative shrub" for sale in a store, please report it to your County Weed Coordinator.

It comes from the middle east, and I have personally seen salt cedar in its native habitat along the Nile River in Egypt. It can survive both flood and drought conditions because of its deep roots. It gives off a salty exudate that makes the surface of the soil beneath the tree so salty that it kills most other plants. It is a water-wasting plant that often dries up watering ponds, ditches, and small streams that are thickly infested.

Hand pulling, mowing, chaining, cutting, burning, tilling as well as grazing do not work to control this weedy tree. Some herbicides can control salt cedar via either basal bark, cut stump, or foliar treatment. If managed properly, our native cottonwoods and willows can out-compete it. There is one biological control insect that has been released in Montana. It is the northern tamarisk beetle (Diorhabda carinulata). The adults and larvae feed on the foliage. However, so far these insects are not working well in Montana, so the Whitehall Project does not work with them. This northern tamarisk beetle is working well in some states further south of Montana. Researchers are trying to solve this problem.

Keep hacking away on those weeds and be heartened that some of our Montana noxious weeds are being really knocked back by some of the insect biocontrol agents.