Penn State Entomology - Pennsylvania Christmas Trees

August 10 , 2007
Volume 15, No. 3

Christmas Tree and Landscape Pest Management Newsletter

Editor:
Paul Heller, Professor of Entomology, PSU

ISSUE HIGHLIGHTS

*TURFGRASS INSECT UPDATE – Early August Scouting Report
*EVERGREEN INSECT UPDATE – Early August Scouting Report

TURFGRASS INSECT UPDATE – Early August Scouting Report

SCARAB GRUB UPDATE: First instar Japanese beetle and northern masked chafer grubs were observed actively feeding on August 8 at a Central PA research site. Damage from scarab grub feeding may be earlier than expected this year. The only way you can distinguish the various larval instars of white grub species is to measure their individual head capsules. I would suggest that sampling for scarab grubs should be completed on a regular basis to determine grub populations, map their distribution, and keep a close eye on possible damage symptoms. In the future a registered ‘curative’ control measure may be needed. Some individuals may be interested in the use of insect parasitic nematodes. I would direct interested individuals to Ohio State’s excellent web site on IPNs which is located at http://www.oardc.ohio-state.edu/nematodes/ . Our 2007 Curative Scarab Grub Applied Research Program intends to evaluate insect parasitic nematodes as part of our program. Research results will be shared at 2007-08 turfgrass conferences and workshops.

GREEN JUNE BEETLE: Green June beetle surface grub damage was observed in Lancaster County on August 3. The typical mini-volcanoes were present on insect infested turfgrass areas. Early instar grubs frequently can be found tunneling in the top 4 inches of soil. They will loosen the soil and eat or thin out the thatch. Grubs seldom consume enough turf roots to cause significant damage. However, their disruptive burrowing and mound-building activities can disfigure turf. The latter mounds frequently are 2 to 3 inches in diameter; plus, grubs leave distinct open, vertical soil burrows averaging 6 to 12 inches in depth. The diameter of the burrow is about the size of your thumb. It is important to recognize that this grub species is not the only animal that makes mounds on grass. Earthworms also make mounds, the particles of which are distinct pellets. Green June beetle grubs are 3/8 (first instar) to 1½ inches long with a white stubby body and short legs. The grubs have an unusual habit of crawling on their backs rather than relying on their small legs, which are extended upward as they move across surfaces. Ridges located on the upper surface of the grub’s body are covered with short, stiff hairs that assist them in moving on the surface of the grass.

Green June beetle
larva

Holes in grassy area which were created by the green June beetle.

Green June beetle
surface damage
(hole on surface of grass)

CICADA KILLER WASP (CKW): Extensive damage from CKW nest building was observed on well drained dry areas of a golf course rough on August 3 in Mifflin County. Our program has received quite a few calls on this ‘beneficial’ insect whose mound building activities create headaches for home owners and golf course managers. Adult cicada killer wasps are very large, up to 1-1/2 inches in length. Adult CKWs are solitary insects and have a rusty red head and thorax, amber-yellow wings, and a black abdomen with pale yellow stripes. CKW prefers to build their nests in areas receiving full sun, scant amounts of vegetation and light textures, and sandy well drained soil. Each female adult CKW digs its own burrow into the ground. The burrow is ca. ½ to ¾ inch in diameter and about one foot in depth. The burrow may be a single tube or have several branches. A mound of soil excavated from the burrow marks its entrance. Adult females search for cicadas, then immobilize the insect by stinging it, and carries the large cicada back to her burrow, places it inside, and lays an egg on it. The egg hatches into a larva that feeds on the body of one or two paralyzed cicadas. The CKW larva feeds and molts as it grows throughout the summer. The fully grown larva remains in the burrow throughout the winter and pupates in the spring, emerging in the summer as an adult. Although these insects do construct mounds they are considered ‘beneficial’ insects. You can access Dr. Holliday’s (Lafayette College) web site at http://ww2.lafayette.edu/~hollidac/cicadakillerhome.html which provides information on CKW.

Lawn showing bare spots from Cicada killer wasps.

Cicada killer wasp
surface damage

Cicada killer wasp mound of dirt in grassy area.

Cicada killer wasp
and mound

EVERGREEN INSECT UPDATE – Early August Scouting Report

SPRUCE BUD SCALE: Alberta spruce samples were received in early August which had spruce bud scales present. Mature scales were located at the base of buds (recent growth still green) (for an image refer to the url at http://www.forestryimages.org/browse/detail.cfm?imgnum=1199023). There were quite a few dead mature scales at the base of buds on severely damaged twigs (i.e., both current and previous year’s growth). Likewise active crawlers were observed on twigs and needles, as well as settled crawlers on the needles. Mature scales are globular, reddish brown, 3 mm in diameter, and are typically found in clusters of three to eight at the base of new twig growth. One generation occurs annually. The publication titled Insects That Feed On Trees and Shrubs (Comstock Press; authors W. Johnson and H. Lyon), states that crawlers begin to appear about June 1. You should also observe honeydew from these soft scales but I did not observe large quantities of honeydew on the samples we received. You can access information on the above insect via the USDA Christmas Tree Pest Manual second edition, url at http://www.na.fs.fed.us/spfo/pubs/misc/xmastree/, which includes an excellent description with an image (see pg. 99 of the manual). The latter publication states crawlers are active through July.