Nursery & Forest
Volume 62 Number 11 Date 07/13/2017
JAPANESE BEETLE - Emergence continued to escalate over the past week. Inspectors observed beetles on field and container stock from Kenosha to Eau Claire County. Populations are already very high, and increased moisture in lawns and turf throughout the state is expected to bring more beetles this month. Removing beetles by hand or shaking them into jars filled with soapy water may be adequate where numbers are low. Foliar sprays of contact insecticides containing carbaryl, acephate, and pyrethroids offer immediate knockdown, while formulations of pyrethrins with PBO (piponeryl butoxide) are also effective. Neem oil products provide only about 3-4 days of feeding deterrence. Long-term cultural control by planning landscapes with less favored plants such as arborvitae common lilac, holly, rhododendron, yew, and many oak, pine, and fir species should also be considered.
SCALE INSECTS - An assortment of scale insect species were found this week, including Euonymus scale on American, Fletcher scale on 'Techny' Arborvitae, and Lecanium scale on American hornbeam. Adult scales develop a waxy covering impenetrable by insecticides, therefore any insecticide treatment must target the immature mobile crawlers. For the Euonymus scale, the period of mobile crawler activity is forecast to begin next week (July 16-22). Severe infestations can be controlled with horticultural oils, insect growth regulators, or conventional insecticides as soon as the presence of crawlers is confirmed using a 10X hand lens. Natural enemies are also helpful in reducing scale populations.
CEDAR-HAWTHORN RUST - The bright-orange spots characteristic of this rust were apparent on the leaves of "Winter King" and "Washington" hawthorn trees in southern Wisconsin retailers this week. As with the similar cedar-apple and cedar-quince rusts, this fungal disease requires a rosaceous host and a juniper host in close proximity to complete its lifecycle. Cedar-hawthorn rusts can infect the leaves, fruits, and stems of trees, causing disfiguration and premature defoliation. Selecting resistant hawthorn cultivars, removing diseased parts of the tree, or completely pruning out severely infected branches are the recommended controls. Trees can be protected from infection by fungicide treatments in spring and early summer. Junipers may be treated with a Bordeaux mixture every two weeks beginning in mid-summer.
PINE BARK BEETLE - Evidence of bark beetle infestation was found on balled-and-burlapped (B&B) eastern white pines at a southern Wisconsin nursery stock dealer. Trees stressed by drought and heat exposure from prolonged B&B storage are especially attractive to bark beetles, which create galleries that structurally weaken trees and holes in the bark that allow pathogenic fungi and bacteria to invade and cause disease. Bark beetle-infested pines should be removed from sale and destroyed to prevent further spread. Prevention of bark beetle infestations in pine includes keeping B&B trees well-watered and optional insecticide treatment prior to digging.
-- Tim Boyle, Shanon Hankin, Michael Falk and Konnie Jerabek, DATCP Nursery Inspectors
GYPSY MOTH - The annual moth flight began on July 5 in Dane County, and moths have since been reported from Adams, Grant, Juneau, Richland and Winnebago counties. Trap setting by the DATCP Gypsy Moth Trapping Program was completed on July 7. A total of 10,901 traps have been placed in 48 counties this season. Trappers have started trap check procedures south of Highway 21. Monitoring of traps located north of Highway 21 will begin once moth emergence is confirmed in that region.
-- Chris Whitney, DATCP Gypsy Moth Trapping Coordinator