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Extension Entomology

Author: Sharon Schroll

Green June Beetle Larvae

–by Dr. Raymond Cloyd

We have received numerous inquiries regarding large grubs (larvae) crawling on their backs across pavements or other hard surfaces. Well, these are the larval stage of the green June beetle, Cotinis nitida. Larvae are 3/8 (early instars) to 1-1/2 (later instars) inches long, and exhibit a strange behavioral trait—they crawl on their back (Figures 1 and 2)—likely due to having a constant itch J. This behavior of crawling on their back is unique among turfgrass-infesting larvae.

 

 

Fig 1. Green June Beetle Larva (Grub) Crawling On Pavement Surface (Auth–Raymond Cloyd, KSU)

Photo for Fig. 2 not available

 

The larvae are abundant now due to the excessive moisture (rain) we have received. Young larvae are generally located at the interface between the soil and thatch layer feeding primarily on organic matter including thatch and grass-clippings; preferring material with a high moisture content. The larvae can be found in swimming pools, garages, and basements. Green June beetle larvae can tunnel 18 inches into the soil; and even deeper in sandy soils.

 

 

 

 

 

 

Wheat

–by Dr. Jeff Whitworth

 

Some reports are being received mainly from south eastern/south central Kansas relative to “worms” feeding on early-planted wheat. First, it is usually better to plant wheat as late as possible to help avoid all wheat pests, whether pathogens or insects. The “worms” reported so far, have been either armyworms or fall armyworms, both of which will do about the same type of damage. They feed on leaf tissue and consume more, as they get larger, thus it is best to monitor wheat fields early to detect any larvae while they are still small. They usually do not reduce wheat stands, just remove the leaf tissue, but under stressful growing conditions plant stands may be impacted. Under good growing conditions, plants should be only temporarily affected. However, if there are 8-10 worms per sq. ft. and the worms are small, i.e., less than ½”, treatment may be justified. Remember also, if the leaf feeding continues into the winter it might be caused by army cutworms, which will feed all winter anytime temperatures are over 45 F, and into the spring. However, armyworms and fall armyworms will only feed until the 1st hard freeze, but not through the winter.

 

Sorghum

–by Dr. Jeff Whitworth

Most sorghum throughout north central Kansas is past the soft dough stage, thus not susceptible to “headworms.” However, a few late-planted fields, just coming into the “boot” stage, have sporadic small colonies of sugarcane aphids (SCA) (see pic of SCA’s from Saline and Dickenson counties (pic3)). However, there seems to be significant numbers of beneficials, but these late developing fields should still be monitored as these populations can “explode” quite quickly.

(Pic 3) SCA Colony

 

 

Soybeans

–by Dr. Jeff Whitworth

Most soybeans in north central Kansas, even double cropped fields, are getting to the stage where the pods are hardened enough to protect the beans inside (see picture of pod feeding scar by bean leaf beetles and an adult bean leaf beetle (pic1). Woollybear caterpillars (pic 2) are becoming more noticeable as the soybean leaves start to senesce, the caterpillars are getting larger and thus more visible, and as they move to the ground, looking for overwintering sites.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Scolia dubia: Parasitoid of the Green June Beetle

–by Dr. Raymond Cloyd

 

We continue to see large “wasps” (not cicada killer wasps) feeding on flowering plants such as goldenrod (Solidago spp.) and wild onion (Allium spp.). This is Scolia dubia, which is a parasitoid of green June beetle (Cotinis nitida) larvae or grubs located in the soil. Since there were so many green June beetle adults flying around this year, there is likely to be high populations of grubs/larvae for the parasitoids to attack.

The parasitoids are approximately 3/4-inches long with purple to black wings. The abdomen has red-brown markings with two conspicuous yellow spots on both sides of the third abdominal segment (Figure 1).

Fig 1. Scolia dubia adult feeding on flower (Auth–Raymond Cloyd, KSU)

The parasitoids can be observed flying in a figure-eight pattern several inches above turfgrass infested with green June beetle larvae. A female enters the burrow of a green June beetle larva, uses her ovipositor (egg-laying device) to paralyze the larva, and then she attaches an egg to the underside of the larva. The larva hatches from an egg and consumes the paralyzed green June beetle larva. The larva overwinters in a cocoon at the bottom of the burrow and then pupates in the spring. Adult parasitoids typically emerge from August through September, and feed on flower nectar. They are likely emerging and present later than usual due to the weather conditions we have experienced this year (lots of rain and cool temperatures). Scolia dubia adults, unlike cicada killer males, are not aggressive and females will only sting when handled.

 

 

Sorghum Update—headworms, corn earworms, fall armyworms

–by Dr. Jeff Whitworth

Much sorghum has been treated throughout north central Kansas for headworms (corn earworms and/or fall army worms) and most treatments seem to have been very effective. Again, Sorghum is most vulnerable to headworms from flowering to soft dough, so past the soft dough stage headworm treatment will not be necessary.   The headworm shown (see pic1) has approximately 7-10 more days of feeding before pupating. Still no reports of sugarcane aphid problems – but monitoring should continue because in 2016 insecticide applications were still justified into late September.

 

Pic2: These two larvae were collected from a Heligen treated field. The dead (smaller) larva is obviously pathogen-affected. If Heligen is responsible for the death of this larva, then it looks like the application was well timed to kill the larva before it caused much damage.

Photo by Cooper Wyckoff)

 

 

 

 

 

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