Beetles In the City
Mario Villarino
County Extension Agent for agricultural and natural resources in Hopkins County.
I wish you are enjoying your thanksgiving celebration. By the time I wrote this my family was getting ready cooking traditional thanksgiving dishes. Grandma fixed the turkey and tried to get the stuffing done. My children were running around pestering each other like healthy siblings do. The temperature Thanksgiving Day dropped significantly compared to days before, which hopefully will take care of those beetles covering the lawns all over the county.
Black june bugs (Diplotaxis ) are ½ to 5/8 inches long, and black. There are more than 100 species of scarab beetles from several genera (e.g.,Diplotaxis, Cyclocephala, Phyllophaga and others) in Texas that are considered to be white grubs, May beetles and June bugs. Their biologies are similar, but species differ in distribution, habitat preference, length of life cycle and seasonal occurrence. Adults begin to emerge in spring.
During adult flights large numbers of beetles can be attracted to lights. For some reason, and I am presuming the higher than normal temperature that have occurred during the last few days made white grubs mature and became adults. Females, less attracted to lights, tunnel 2 to 5 inches into the soil and deposit eggs. In 3 to 4 weeks, small grubs (larvae) hatch from eggs and develop through three stages (instars), with the first two stages lasting about 3 weeks. The last larval stage remains in the soil from the fall through spring. In spring and early summer, white grubs pupate 3 to 6 inches deep in the soil. Adults emerge from pupae in about 3 weeks. There is one generation per year, but in north Texas, development may take two years. Feeding of large numbers of grubs causes lawns to turn yellow and die. Severely damaged grass can be "rolled up" like a carpet. Grubs also feed on the roots of weeds, vegetable transplants and ornamental plants.
In agriculture, they are important pests of forage, corn, sorghum and sugarcane. Most severe injury to plants is caused by large (third stage or instar) grubs feeding on roots in the fall and spring. White grubs are frequently encountered tilling garden soil or by sifting through soil underneath damaged turfgrass. White grub damage can be detected by the presence of irregular- shaped areas of weakened or dying grass in the lawn. Less severely damaged turf lacks vigor and is more vulnerable to invasion by weeds. Depending on location within the state, damage may appear any time between the months of June and October.
Turfgrass damaged by white grubs has a reduced root system and is easily pulled from the soil. Grubs should be readily found in the top few inches of soil, in the turfgrass root zone. Turfgrass usually recovers from white grub damage by fall or the following spring. Turfgrass-infesting white grub larvae feeding on grass roots. Grubs are most damaging when they reach a length of 1⁄2- to 1-inch. Proper timing and chemical application are critical to suppressing white grubs. New white grub insecticides are more persistent and less toxic to beneficial arthropods and earthworms. However, these treatments must be applied early enough to kill the smaller (less than 1⁄2-inchlong) larvae. Once white grubs reach the third-instar life stage and adults they are more difficult to control with the new products.
The insecticides imidacloprid and halofenozide are used most today for white grub control. Imidacloprid is most effective against small and medium-sized grubs but may kill some grubs larger than 1⁄2 inch long. Imidacloprid trade names include Merit®, Bayer Advanced Lawn™ Season Long Grub Control and Scott's® Grub-Ex®. The lethal effects of the insect growth regulator halofenozide are limited to early white grub life stages. Halofenozide is ineffective if applied too late, after grubs have reached the third-instar life stage. Halofenozide trade names include Mach 2, Spectracide® Grub Stop™ and Hi-Yield® Kill-a-Grub™. Fortunately, both halofenozide and imidacloprid can be applied early and persist in the soil. Ideally, both products should be applied within six weeks of egg-laying. Where grub damage is already evident in lawns and larger grubs are present, use products containing trichlorfon or carbaryl. Because they bind to soil particles and remain close to the surface even after irrigation, pyrethroid insecticides (such as permethrin, esfenvalerate, cyfluthrin and bifenthrin) are less effective against white grubs, especially in clay soils. Adult june bugs can damage shrubs and foliage.
Controlling adult june bugs is not very effective since those can move and avoid the insecticides. It is much better to turn off outdoor lights so those do not get close to you house and apply white grub control to your lawn next spring.
The Hopkins County Master Gardeners are organizing a master gardener training class for early next year. If you are interested in learning advance lawn, shrub and plant care. Please contact the Hopkins County Extension Office for more training details at 903-885-3443.
_____
