Horticulture Hotline 05/20/24
By Bill Lamson-Scribner
Walking through the Lowcountry and smelling the Magnolias and Gardenias must be right up there with smelling the Tea Olives in the fall. The Tea Olives indicating cooler weather still is number one with me, but the Magnolias and Gardenias are a close second.
Japanese Beetles have emerged from the ground and are munching down on our ornamental plants like there is no tomorrow, leaving behind lacelike foliage everywhere they dine. I answered the phone three times in Possum’s on Saturday and two questions were about Japanese beetles and one was about fleas.
Japanese Beetles come out of the ground earlier this year as beetles. In parts of the country, they are the number one damaging insect to ornamentals, and they seem to be gaining a stronghold in the Lowcountry. In the 1990’s, I can remember talking to friends in Charlotte, whose plants were getting devastated by this ferocious eater, and they would say how lucky we were not to have them down here in the Lowcountry. At the time we were using products for mole crickets that are off the market now that might have kept them in check. In the 1990’s Charlotte did not have mole crickets. Roses and Crepe Myrtles are some of their favorite plants.
Once the Japanese Beetles come out of the ground, they eat and mate. A female returns to the ground to deposit between 40 and 60 eggs (you can see how the populations can grow rapidly). The female beetle must burrow in the ground to lay eggs and the eggs need moisture to survive. A well-irrigated landscape is a lot easier for the beetle to dig in than a dry, hard, area. The adult beetle dies off and the eggs turn into grubs over the summer. By mid to late August, the grub is full-grown and overwinters in the soil. In late May to early June, the adult (beetle) emerges again and the life cycle starts over.
The grubs from this beetle damage grass and other plants by eating the roots. Using a product like Grubz Out in late August or early September (if your grub populations warrant treating) or in April will help your turf; however, do not fool yourself into thinking all your beetle problems will be solved. The adult beetle can fly for miles to chow on your precious ornamentals! Milky Spore is an organic option that seems to do a good job now that our grub population is high enough for the spores to have a steady food source.
Using a ground drench systemic insecticide in the early spring like Dominion will help protect your plants, and you might get lucky and kill a few grubs while you are drenching! Once the beetles are eating your plants, use a good contact insecticide to kill them. Cyonara and EcoVia EC (National Organics Program Compliant) are two of the many products that will help control these beetles. Since contact insecticides have limited residual activity, plan to reapply the product according to the label.
Traps for Japanese Beetles are a little controversial. The attractants they use (one is a virgin female beetle scent) can lure more beetles to an area than the trap can trap! Many ornamentals on the way to the trap and near the trap can suffer extensive damage. For this reason, place the traps away from the plants you are trying to protect.
Now that we are getting some rain, which is a great thing – free water, large patch fungus is popping up as well as grey leaf spot on St. Augustine. Mosquitoes and fire ants are biting.
Bill Lamson-Scribner can be reached during the week at Possum’s Landscape and Pest Control Supply. Possum’s has three locations 481 Long Point Rd in Mt. Pleasant (971-9601), 3325 Business Circle in North Charleston (760-2600), or 606 Dupont Rd, in Charleston (766-1511). Bring your questions to a Possum’s location, or visit us at possumsupply.com. You can also call in your questions to “The Garden Clinic”, Saturdays from 10:00 AM to 11:00 AM, or listen to the replay of Saturday’s show, Sundays from 11:00 to noon on 1250 WTMA (The Big Talker). The Horticulture Hotline is available 24 / 7 at possumsupply.com.
