MAY and JUNE BEETLES Contents:
Introduction
May and June beetles are in the
genus Phyllophaga and in the white grub family known as Scarabs.
There are over 200 species of these beetles in North America with
about 25 species reported to feed on turfgrasses. The group name
May or June beetles refer to the time period of adult emergence.
The larval stage, white grubs, are root feeders.
Identification
There is considerable variation
in size and color of adult Phyllophaga
beetles due to the number of species. Their size will
vary from .3 to 1 inch in length, have reddish brown to black
bodies, and have an oval body shape. Species determination is
difficult and often requires an expert analysis of adult
males.
The larvae are white grubs; C-shaped, reddish brown head, and six legs. Length will range from 3/4"-1 1/4" with a distinctive Y-shaped anal slit. Also two parallel rows of spines are present on the raster.
Distribution
Mixed species populations found
throughout the U. S.
Hosts
Species prefer open woods, meadows, lawns, grasslands, cultivated fields and ornamental plant beds. Grubs feed on organic matter and plant roots. The adults of several species do cause defoliation of ornamental and shade trees.
Life Cycle
May or June beetles may take 1-4 years to complete their life cycle which is due to species and location differences. Adult reproductive flights will occur throughout the season (May-August) based on light trap results conducted in Maryland. Eggs are laid and individually rolled into earthen balls of soil.Larval development, passing from a first to third instar, may take less than 1 year to several years. Overwintering stages will be either second or third instar grubs.
Damage
Larval damage to turf is similar to that caused by Japanese beetle grubs. No thresholds are available in the literature. Limited studies in Maryland show that 5-7 grubs per square feet may damage turf under drought stress conditions.
Biological-Biorational Control
Several reports of infectivity by Bacillus popilliae have documented the efficacy of the Japanese beetle milky disease but it is considered a rare occurrence and of minor influence. Since these species are native to the American soils, many species of nematode, bacteria and fungal pathogens have been recovered throughout their range.The entomophathogenic nematode, Heterorhabditis bacteriophora , has shown good activity against white grubs and is commercially available as Cruiser.
A new product which mimics the insect molting hormone, ecdysone, and causes premature molting is Mach 2 (halofenozide). This product has shown consistent and excellent control for a number of white grub species.
Similar to the diverse microbial pathogen fauna, numerous species of parasitic wasps and flies attack the adult, grub and pupa stage. These natural control agents appear to maintain populations in most areas below aesthetic damage levels.
Chemical Controls
Insecticidal control may be warranted if threshold levels of 5-7 grubs per square foot exist. Improved control will occur if the following conditions are met; proper timing of insecticide application, sufficient irrigation after application (1/2") and removing excessive thatch layers (more than 1/2"). The preferred timing for a majority of the recommended insecticides is in late summer to early fall when damage is first noticed. The other time period is in the Spring from April to mid-May.The following insecticides have labeling for white grub control however a number of these products have restrictive labeling and may require a certified applicator to apply them.
Organophosphates: Dylox, Proxol, Mocap*, Mainstay, Crusade*, Oftanol*, Triumph*, and Diazinon*
Carbamates: Sevin and Turcam*
*Restrictive Labeling
A new product for white grub control which was released in 1996 is Merit. This product can be applied earlier in the season (May-early August) due to its longer residual activity. However, it does not perform well in later instar or on older grubs and is not recommended for application after mid to late August in this area.
by Dr. Lee Hellman, Department of Entomology and Dr. J. Kevin Mathias, Institute of Applied Agriculture