Home > Great Big Greenhouse Blog > July 2015 > GARDEN TALK with DOUG - JAPANESE BEETLES


                I hope everyone had a wonderful and safe Fourth of July!  With my blog last week I mentioned that customers are reporting Japanese Beetles.  So, let’s talk about Japanese Beetles and what you can do to protect your plants.
                My first recommendation is to understand the life cycle of the Japanese Beetle so that you can apply timely control measures.  The adult beetle will mate and lay eggs during the summer.  The eggs hatch into larvae that will move deep into the soil later this fall.  Here is where they will winter over as white grub worms.  Next year, usually in early March depending on our winter temperatures, the white grubs come to the surface and begin feeding on plant roots.  Pupation occurs in early summer, resulting in hungry, leaf-chomping adult Japanese Beetles – THE LIFE CYCLE STAGE THAT IS OCCURING NOW.
                Knowing the timing of the life cycle is important in how and when to control beetle damage to your plants.  Here, in order of use, are the control measures that I suggest:
  1.  MID-THROUGH LATE SUMMER:  I suggest setting out beetle traps in remote areas of your yard.  You want to lure the Japanese beetle away from the plants that you are wanting to protect from damage.  Capturing as many beetles in these traps as possible is the goal in order to decrease the adult population before they mate and the female lays her eggs.  In addition to the beetle traps you can apply some topical insecticides to kill adult beetles.  Liquid Sevin, Sevin Dust, Captain Jack’s Dead Bug Brew are just a few examples of good and effective topical products that can kill Japanese Beetles.
  2. SEPTEMBER:  This is the month when the white grub worm begins to burrow down below the frost line to avoid being frozen over winter.  Naturally, there is nothing for them to eat down that deep in the soil so they survive on all that body fat that they put on by eating the roots of your turf grass.  September is a good month to apply a grub control pesticide while they are near the surface and while the grubs are young.  There are many good soil insecticide products BUT with some side effects.  Some of these lawn pesticides are not discriminatory and therefore can also kill some beneficial soil insects, such as earthworms.  My strong recommendation is to use MILKY SPORE in September for control.  Milky Spore is a disease that only affects white grubs.  It won’t hurt earthworms or even a bird that eats a grub that has the disease.  As each grub eats some milky spore, the disease multiples and spreads and becomes more effective naturally.  Yes, Milky Spore may be more expensive product to use but the cost is justified because it last longer and is more of an environmentally discrete product to the white grub worm only.
  3. MARCH:  Is the month to apply another application of Milky Spore.  In March the remaining white grub worms are beginning to surface as the soil warms.  These grubs are very hungry after hibernating in the soil for months.
Unfortunately, total eradication of Japanese Beetles will be impossible.  The beetles are here to stay.  But these timely control measures can greatly reduce the population and the damage inflicted on your turf and host garden plants.
Posted: 7/9/2015 by Doug Hensel | with 1 comment(s)
Doug, all great advice. I will go out and get the Milky Spore. Any thoughts on who is more likely to have it and at a lower cost?
7/17/2015 9:50:05 AM

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