Here at DMGCC we have just over 60 Linden Trees on both golf courses. Last year we saw some significant damage to these trees from the new pest in our area the Japanese Beetle.
Here is what a good Linden tree looks like in the Iowa landscape.
Here is what a Linden tree looks like after a visit from Japanese Beetles.
The Japanese beetle (JB) is a serious pest of turf and ornamental plants. Here is what it looks like in the Adult stage.
Grubs feed on the roots of grass and adults feed on the foliage of more than 300 plant species. Japanese beetles were first found in United States in 1916, after being accidentally introduced into New Jersey. Until that time, this insect was known to occur only in Japan where it is not a major pest. It is controlled in the eastern United States by soil-inhabiting protozoans that are not present in Iowa. So here in Iowa we have a couple of ways to combat this pest. I also believe that JB is going to be a much bigger threat to us because of the mild winter that we had.
The most common way to fight this pest is with a contact insecticide like "Sevin". This is a contact insecticide that is sprayed directly on JB and it kills it in the adult stage. This is an ok way to protect plants but you have to be very vigilant with your monitoring of the situation and continue to spray if JB is present.
This year we are going to try a different approach to protecting our Linden Trees. We have applied an insecticide that is a systemic type with a very long term residual. The active ingredient is imidacloprid. This product is applied to the tree as a root drench and the roots of the tree will take it up and the insecticide should be present when the JB chews on the leaves of the tree. Now there will be a little damage because the insect has to ingest some insecticide to kill it. But our defoliation should not be as bad as we saw in the past.
We are also going to have to be watching other species of trees to make sure they are not getting ate by this pest. The second stage of this pest is the home yard. All predictions by entomologists, is one item. We are going to see more grubs and insects because of the mild winter. So late June is the time of year to put down a good long term grub control to combat these pests.