Mulch & bugs

Asked April 26, 2013, 8:00 AM EDT

What is the risk of importing pests to my yard, when bringing in untreated wood or bark mulch? Thanks!

Oceana County Michigan mulch

1 Response

Hello, Thank you for using eXtension ask and expert. Almost all wood mulch is "untreated" wood and is an organic way to protect your plants and soil while helping to control weeds, plus people find it attractive in the landscape. If the mulch is chipped or shredded in to approximately 1 inch pieces the chances of surviving damaging insect pests, (such as the emerald ash borer), are pretty slim and those pests would probably be specific to the tree they were in originally not your flower or vegetable garden. The concern that woody mulches will attract termites, carpenter ants, and other pests is unfounded, especially in Michigan. Many wood-based mulches are not attractive to pest insects but are actually insect repellent. Here is a great piece that has more details about wood based mulch and it use: http://www.puyallup.wsu.edu/~linda%20chalker-scott/horticultural%20myths_files/Myths/magazine%20pdfs/Woodchips.pdf . Wood mulch that is chipped is pretty safe to use in your landscaping. It is best if it is aged a bit before you use it, but if you are going to use if fresh, make sure you put some nitrogen down first as the beginning decomposition process will uptake that nutrient before re-releasing it more slowly later. Make sure you do not mound it up around your plants or trees leaving a gap between the plant base and the mulch. Here is a nice article about insect concerns and mulches from Illinois Extension: http://web.extension.illinois.edu/state/newsdetail.cfm?NewsID=15506. For more information about gardening in Michigan visit Michigan State University Extension’s MIGarden at http://migarden.msu.edu . Happy Gardening!