Green June Beetle

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Green June beetle adult feeding on ripe raspberries.
Turf thinned out by green June beetle grubs and their mounds.
Third instar green June beetle grub "creeping" on soil surface.
Green June beetle grub raster pattern.
  • Scientific Name: Cotinus nitida (Linneaus) [Phylum Arthropoda: Class Insecta: Order Coleoptera: Family Scarabaeidae]


  • Common Names: green June beetle, fig eater


  • Climatic Zone: subtropical to temporate


  • Geographic Distribution: This pest and its subspecies (one in Texas and another in southern Florida) is a native of North America where soil does not regularly freeze below 3 to 4 inches. It is most common from southern Pennsylvania across to Oklahoma and south. It most commonly a turf pest in the transitions zones of Tennessee and Kentucky to the Carolinas. California populations cause damage around the San Diego area.


  • Damaging Stage: adults damage fruit and larvae damage turf


  • Hosts: The adult beetles have been given the common name of "fig eater" since they often congregate around seeping wounds of trees, and are very common on ripe grapes, figs, peaches, plums, melons, and some vegetables and ears of corn. Some have claimed that they skeletonize leaves of trees like Japanese beetle, but this has not been confirmed. Adult green June beetles often land in trees that have been skeletonized by Japanese beetles. The larvae can infest any turfgrass species - cool season, transition or warm season. They apparently feed on the thatch, grass clippings and leafy tissues of turf.


  • Damage Symptoms: Adults feed on ripe fruit and larvae thin out turf and throw up mounds of soil.


  • Description of Stages:

Eggs: The white oval eggs are packed into a ball of soil about the size of a walnut. These egg clusters are formed in a small cavity in the soil 2 to 5 inches deep and they may contain 10 to 30 eggs each.

Larvae: The larvae resemble regular white grubs except that they have the habit of moving by rolling over on their backs to creep along with an undulating motion. Because of this mode of movement, the legs are considerably smaller than other white grubs. This movement is a specific characteristic of this species. First instars are 1/4 inch (6 to 6.5 mm) long, second instars are 5/8 inch (15 to 17 mm) long and mature third instars are 1 3/4 inch (45 to 48 mm) long. The raster pattern on the underside tip of the abdomen consists of two irregular rows of large and small bristles and the entire abdomen is covered with fine hair.

Pupae: The pupae are cream colored first and become light reddish-brown with age. The average pupa is about 1/2 inch (14mm) long and 1/4 inch (7mm) wide.

Adults: The adults are about 13/16 to 1.0 inch (20 to 25 mm) long, and generally are velvety green in color with tan-yellow margins. The lower surface is a shiny metallic green. The head has a distinctive flat horn.


  • Life Cycle and Habits:

Adults begin to emerge in late June, flying during the daytime, and are very common in July and August. The adults are attracted to ripe fruit and vegetables as well as oozing tree wounds. Once a feeding site is established, several adults may be actively flying about or attempting mating. Newly emerging females call males to the ground for mating by producing a milky fluid that acts as an attractive odor. On many golf courses, for some unexplained reason, the adults die and accumulate in the sand traps.

Mated females dig a burrow into the ground, pushing up a small mound of soil. Females prefer soils with high organic matter content, soils covered with compost or soils fertilized with manure-based fertilizers. Once a suitable site is found, the females pack 10 to 30 eggs into a compact ball of soil about the size of a walnut. Females may emerge and dig a new burrow elsewhere but more commonly continue in the first burrow to form 1 to 2 additional egg chambers. The eggs swell as they absorb moisture and the grubs hatch in 2 to 3 weeks.

Young grubs are very active and can move a considerable distance on the surface in a short period of time. Since the eggs are clustered, infestations appear to be in groups or colonies. The grubs feed on organic material, but their habit of constant burrowing and tunneling loosens the soil causing plant desiccation, the primary cause of damage to turf. By the time the grubs are second instars, they construct individual burrows which average 6 to 12 inches in depth. At night, the grubs deposit soil around the burrow entrance, making small mounds 2 to 3 inches in diameter which resemble ant or mole cricket mounds or large deposits of earthworm castings. The grubs may also emerge and crawl about on their backs during warm, wet evenings. This is especially common after a warm afternoon thunderstorm. They may end up in garages or swimming pools!

As winter weather reduces soil temperature, the grubs dig deeper and remain inactive at the bottom of the burrow. These grubs may become active at any time when the soil temperature rises. Larval digging may occur any time during late summer through winter and into spring, especially in more southernly states. By late May and early June, the grubs have matured and they construct an earthen cell glued together with a secretion. Pupation takes about three weeks at which time the adults break out of the pupal cell and dig to the surface.


  • Control Approaches:

Cultural Control - Habitat Modification - Green June beetle adults are attracted to decaying organic material such as composts and manures, under which the females construct egg chambers. Reduction of thatch layers that have begun to form peat-like organic matter, as well as avoidance of compost top dressings or application of manure-based fertilizers will reduce the attractiveness of turf to ovipositing females.

Biological Controls - Insect Parasites - A parasitic wasp, Scolia dubia Say, has been very effective in reducing green June beetle larval populations. However, this large hairy, black wasp with orange markings may cause considerable concern by those afraid of being stung. Fortunately, the adult females do not sting unless severely provoked (i.e., picked up or trapped). Avoid applying general contact/stomach insecticides when these wasps are flying and laying eggs on green June beetle grubs since they can often bring damaging grub populations under control.

Biological Control - Metarrhizium Fungus - The insect parasitic fungus, Metarrhizium anosophilae, which is often called the “green” fungus of insects, commonly attacks larvae and pupae when soil conditions are suitable. Warm, moist soil is essential for this fungus to invade the grub cuticle. Unfortunately, exact conditions for green fungus infection are difficult to control so the predictability of this biological control is low.

Chemical Control - Insecticides -

Targeted Treatments. Insecticides are most effective when small stage grubs are the target. First instar green June beetle grubs are present from late July through August. Applying an insecticides at this time, followed by sufficient irrigation to move the insecticide into the thatch zone usually yields satisfactory results. Target areas that have a previous history of green June beetle or where adults were concentrating their landing and hovering behavior. First instar grubs molt into second instars which feed from mid-August through September. These middle stage larvae are also very susceptible to control, but if not controlled, turf damage may begin to appear in September. At this time the grubs have formed burrows and they only emerge on nights following irrigation or a warm rain. Since the larvae feed in the thatch and on grass clippings or leaf blades, insecticides should be targeted for these areas. Therefore, DO NOT irrigate after application. Irrigation before application may help coax the larvae to the surface.

Curative Treatments. From mid-September through October, most grubs reach the third instar stage and are very large. While still easy to kill by using a pretreatment irrigation and no irrigation after the application, intoxicated grubs remain on the turf surface. Hundreds to thousands of these large grubs may litter the surface after an insecticide application. In the sun, the bodies of these grubs quickly decay producing a considerable stench. Great care should be exercised when attempting to control third instar grubs because of this stench potential. From March through April, green June beetle grubs clean out their overwintering burrows and resume feeding in the thatch and on the surface on warm nights. If the soil mounds are the major problem (i.e., actual grub damage is not evident), avoid attempting to control the grubs to avoid having the dead grubs littering the turf surface.

Preventive Treatments. The use of long residual (>120 days) chloronicotinyl and diacylhydrazine insecticides has not been very successful in controlling this grub when application is made in May, June, or July. Apparently, the active residues move from the feeding zone of the green June beetle grubs and they survive the early applications. Almost any insecticide registered for control of white grubs will work when the first and second instar grubs are feeding on the surface.

Monitoring

Grub infestations should be evaluated as early as possible by monitoring, accurate identification and mapping of infested areas. Though the standard golf course cup cutter is a convenient tool to survey for infestations in golf courses, sports turf and home lawns, green June beetle second and third instar grubs dig too deep to use this method. If a cup cutter is used, it should be used from mid- to late August. Areas that have had a previous history of green June beetle infestation, areas where considerable adult landing and hovering was observed in July, or areas that have been treated with compost or manure-based fertilizers should be sampled.

If second or third instar grubs are encountered or suspected, thoroughly irrigate a section of the area (a few hundred square feet is sufficient) and apply a curative insecticide (carbaryl and trichlorfon have been very effective for this purpose) in a band across the area. DO NOT water in this application (unless required on the label). Spray applications are much more effective than granular insecticides. Check the treated area at daybreak (birds may pick up the exposed grubs). Foraging green June beetle grubs will remain on the surface since they will not be able to find their burrows.

Thresholds

Many books and extension publications on grub management often mention “population thresholds.” Thresholds are the numbers of pest insects present in a given area (usually per square foot) that warrant control. The principle behind using thresholds is to reinforce the IPM principle that application of a pesticide is not always warranted simply if pests are present. Pests must be present at populations high enough to eventually cause damage.

There have been no generally accepted levels for green June beetle grubs. However, grub populations of 10 to 15 grubs per square yard have caused severe thinning and soil disturbance.

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