Join the crowd! Bunkey noticed a patch of browning grass in June but didn’t think much about it. That is until the patch started to get bigger and seemed headed toward his garden. By that time the crows were busy digging for lunch during the day and the skunks at night. Now what?
The life cycle of the Japanese beetle is: egg, grub and june bug. In June, the grub turns into a pupa. It pops out of the soil as a june bug in late June or early July to mate, lay eggs and bug the heck out of us. The females only live for a few weeks, feeding on trees, shrubs and roses in the morning and returning to the turf in late afternoon to lay more eggs. The eggs hatch in July and grubs are almost fully grown by late August. They burrow deep into the soil for the winter then start to move back up in the spring as the soil warms up. Their favorite turf is slightly moist with plenty of organic matter and tender grasses. That being said they can survive in almost any soil.
Almost any insecticide you put on the soil is highly toxic to bees, birds and fish. They shouldn’t be used nearer than 100 yards from a lake. Two exceptions are GrubEX and Mach2. They both have low toxicity to birds and fish but don’t use this after Aug. 15. A problem arises if we have a lot of rain as it can reduce the toxicity below effective concentration. Some of the insecticides have short residual effects so you will have to reapply them. You will need to treat your lawn every year for the next three years to get rid of all the grubs.
Several years ago, nematodes were suggested as a nonchemical control of grubs. At that time the entomologist at the University of Minnesota told us that they didn’t work in Minnesota. That seems to have changed as local gardeners have used them with good results. This is worth a try if, like Bunkey, you don’t want to kill your bees, birds and fish. The package suggests they may be effective against the iris borer. Worth trying. Iris borer shows up about this time of year as brown streaks in the iris leaves. The borer spends the winter in the soil, hatching to a moth in the spring. She lays eggs, then the larvae start at the top of a leaf and eat their way down to the rhizome. This can lead to a rotting rhizome that stinks just like rotting potatoes, really yucky.
If you have had this problem, cutting down the leaves in the late fall and removing them from the garden will help at least reduce the problem.
Next month is the time to thin your iris and lilies. Discard any part of the rhizome that doesn’t have a fan of leaves on it. Hill up the soil and replant with the toes facing out of the soil as they grow.
With lilies, only replant if they are really crowded. The small bulbs can be planted in a row where they won’t be disturbed for several years. Don’t forget to mark what color each row is. When they get big enough you can either share them or replant in your own garden. This trick keeps you from having the babies popping up in places you don’t especially want lilies.
Let’s hope the downpours at least slow down so we can murder some grubs effectively.
Bev Johnson is a Master Gardener with the University of Minnesota Extension. Her column appears in the Weekend Edition.