Diseases and Weeds

Disease of the Month: White Pine Decline Pest of the Month: Pine Engraver Beetle

by Heather Prince

Disease of the Month: White Pine Decline

White pine decline becomes noticeable once deciduous trees drop leaves and evergreen become more prominent in the landscape. It is a reaction to environmental stress as opposed to a pathogen or pest. The pine needles thin in quantity, with yellowing and browning symptoms. Bark on branches and small limbs appears shriveled or wrinkled and will sometimes exude sap. Root systems when examined have few fine, white healthy roots. Treatment:

White pine decline is believed to be a stress disease, especially if trees are planted in heavy clay soils where rainfall does not drain readily. Decline is difficult to reverse. Alleviate stress of the affected tree by mulching, watering in dry periods, and fertilizing with products designed for acid-loving plants. Locate white pines where they receive good drainage; their preferred soil is moist, sandy loam.

Pest of the Month: Pine Engraver Beetle

Pine engraver beetle (Ips pini) is a bark beetle still active on warmer days in October into November seeking out trees that are newly planted, drought stressed, or damaged by surrounding construction. Adults overwinter under the bark or in surrounding litter at the tree base and begin to attack weakened trees in the spring. The male constructs a cavity under the bark and signals females via pheromones. After mating, females excavate three egg galleries off the central chamber, creating Y or H-shaped patterns and pushing reddish sawdust out the entrance holes. Eggs are laid along the gallery and young larvae soon hatch and begin tunneling smaller lateral galleries that lightly etch the sapwood. The small grubs, about quarter inch long when mature, are white to dirty gray, legless, with dark heads. In Illinois, three generations of these beetles usually develop per year. Trees may experience top dieback or dead limbs from girdling under the bark.

Treatment:

No chemical treatment exists for trees or wood already infested by ips beetles. If known infestations occur in the area of valuable trees, preventative treatment may make sense. Use insecticides with the active ingredients permethrin, bifenthrin, or carbaryl as drenching preventive sprays on the trunks and larger branches before infestation. Because of multiple generations, two treatments in early spring and late summer may be needed to protect high value trees. Avoid stacking firewood under pines as beetle populations may be in fresh cut logs and readily migrate to nearby trees.

Additional resources:

University of Illinois Extension Service https://web.extension.illinois.edu/state/ horticulture/index.php 217-333-0519 The Morton Arboretum http://www.mortonarb.org/Plant Clinic: http://www.mortonarb.org/trees-plants/ tree-and-plant-advice/ 630-719-2424 Chicago Botanic Garden Plant Information Service: https://www.chicagobotanic.org/ plantinfoservice 847-835-0972