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Trial Release of a Knotweed Psyllid to Control Invasive Knotweeds in Southeast Alaska

Invasive knotweeds in Southeast Alaska are known to replace desirable vegetation such as salmonberry in forest, beach and stream edge habitats. These knotweeds are difficult to manage with herbicides and do not decrease in cover with other forms of management. Our team worked with U.S. Department of Agriculture and Oregon State University to do host specificity testing, which ensures that a potential biological control agent will primarily target the intended pest and not harm non-target species, including beneficial organisms or other plants. We are now conducting a trial release of the knotweed psyllid to determine if it is a viable option for control in Alaska.  

Managing Cabbage Root Maggots by Creating a Cover Crop Habitat for Beneficial Insects

Cabbage root maggot is a problem for brassica vegetable production throughout Alaska, ruining crops of cabbage, rutabaga, radish and other species. Cover crops are increasing in popularity because of the benefits to soil health. Radish and clover are two popular cover crops. Radish, though, brings the possibility of drawing in root maggot flies to lay eggs, while the clover may provide other habitat for beneficial insects. The study aims to determine what ratio of radish to clover cover crop seeding might benefit cabbage production, and if that benefit is from increases in populations of natural predators.  

Biochar Amendments to Tie Up Herbicides in Soils.

Persistent herbicides can do a great job of controlling invasive plants and weeds for multiple seasons with a single application, which can reduce the amount of pesticide used overall. The downside is that those herbicides remain active in the soil and can kill sensitive, desirable species when weed control is no longer necessary. Biochar additions have shown some promise to tie up those herbicides in the soil, making them unavailable to plants, but not all types of biochar work. Our research seeks to determine what properties of biochar work to tie up aminopyralid, a highly persistent herbicide, in Alaska soils.

Managing Herbicide Impacts to Revegetation After Bird Vetch Removal

Bird vetch is a common weed in many parts of the connected road system in Alaska, and is a nuisance in yards, farms and on roadsides. Managing bird vetch with herbicides is fairly straightforward. However, little is known about which native pollinator-friendly plants will thrive after herbicidal removal. This project treated bird vetch with three herbicides of high efficacy on bird vetch with varying soil persistence times. We are planting bioassays —  a method of measuring the effect of a substance, like herbicide, on living plants — of native pollinator-friendly plants in these soils to determine how the herbicide residuals affect germination and growth.

Managing Weeds with Persistent Herbicides in Alaska and Investigating Why Some Herbicides Persist

Invasive weeds are a problem for producing certified weed-free straw, and some persistent herbicides can help reduce the total amount of herbicide necessary for weed control. This project showed that one herbicide, aminopyralid, with the most soil persistence, outperformed other products in controlling weeds to allow for certification of weed-free straw for up to two years after treatment. However, herbicide-sensitive field peas were unable to grow in aminopyralid-treated plots three years after treatment, indicating the presence of biologically significant concentrations of herbicide. Lab experiments then determined how the chemical structure of aminopyralid is more persistent in acidic soil environments.

Control of Chokecherry and Managing Non-Target Impacts

Invasive chokecherry trees are a growing problem in Alaska due to their toxicity to ungulates such as moose, and they form monocultures in some infestations. Invasive trees can be treated directly with herbicides intended to kill the target tree while minimizing the spread of the chemical to nearby vegetation.  This project sought to compare three herbicides using a specific direct treatment — basal bark applications — at varying rates to determine if any non-target impacts occur and how effective the treatments were. The study found that after treatment, trees can release the herbicide from their roots or from decomposing root parts. The released herbicide can impact nearby vegetation and is more problematic with aminopyralid than triclopyr, although for both, the non-target impact is minimal. The amount of non-target impacts decreased with lower application rates and was consistently higher with aminopyralid than with triclopyr. The results indicate that lower rates and use of less persistent products (triclopyr) can have effective control with less non-target impacts.

Pollinator Visitation to a Selection of Native and Non-Native Roadside Flowering Plants in Southcentral Alaska

White sweetclover and bird vetch are aggressive roadside invaders that have been the target of removal efforts in Southcentral Alaska to help restore habitat for native plant communities. These showy flowers are also attractive to some native pollinators, which has led to public hesitancy toward removing these invasive plants. This project explored pollinator visitation to common roadside native and invasive plants with the goal of developing recommendations for mixes of native plants that support diverse pollinator communities and would be suitable for revegetation of habitats where invasive bird vetch and white sweetclover have been removed. The combination of any two native plants from this study attracts more species of pollinating bees and wasps than the combination of the two invasive species, supporting the removal of these invasive species and the inclusion of native flowering plant species in revegetation to support diverse pollinator communities in Southcentral Alaska. Three native species, dwarf fireweed, prairie cinquefoil and northern goldenrod, attracted a high abundance and diversity of native pollinating bees and wasps.