Beverly Shaw
Master Gardener
Purdue University







Question and Answer

Q.  I have four large trees in my backyard, causing quite a bit of shade. There is a pine, an oak, ask an and a  maple. The lawn is too dark for grass, and the quantity of leaves is overwhelming in the fall. I'd like to take down one tree but can't decide which one. I don't feel particularly attached to any, although the pine screens the neighbor's yard somewhat. All seem to be roughly equal in size and health. Any thoughts? -- Janice Laskey, West Lafayette, Ind.

A.  Any other year, this question would be difficult to answer definitively. However, a new threat to ash trees is bearing down on our borders. The emerald ash borer has killed over 6 million ash trees in the Detroit-area alone. Although quarantines are in place to slow its progress, this pest has already reached our border with Ohio. Our ash trees are threatened, and no good chemical treatment has proven effective yet. Many municipalities and entomologists are recommending no ash trees be planted in the near future, but instead, any new plantings should work to increase the diversity of our forests and landscapes. Given that the ash may be attacked and killed by the emerald ash borer, and the other trees are healthy and desirable species, I would remove the ash. For more information, go to http://www.ppdl.purdue.edu/PPDL/.

If you decide to keep the ash for some reason, you can lessen the likelihood of attack slightly by keeping the tree free of stress. This means providing water during dry periods and fertilizing to maintain health and vigor. Borers tend to attack trees already under stress. Unfortunately, the emerald ash borer seems to be less particular about a tree's well-being than other ash borers, and will eventually work its way to non-stressed trees, too.

This is bad news for all Indiana gardeners. It is a good time to add other species to your landscape!

Q.  My Siberian irises are filled with ants in the ground around the stems. Are ants pests of Siberian iris? Or are they not a problem? Thanks. -- Cheryl Kolb, Lafayette, Ind.

A. Siberian iris and ants are not a common pairing, It's probably coincidental that the ants are making their home in your irises. If there is some distance between the ants and the plants, they don't need to be treated, but it sounds as if they're interacting more directly than that. If the ants are actually in the rootzone, treatment may be necessary. Ant tunnels provide a means for cold, winter air to get down to the iris roots and this could damage or kill the plants. If this is the case, treat with an appropriate insecticide following label directions carefully.


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