Got Nature? Blog

Question: I have a blue spruce that is 40-years old and very tall. It is dying up the middle. I have read about the Needle Cast problem. Also read about Spectro 90 copper based fungus control. I can only spray so high. Is there a chemical that can be placed on the ground to be absorbed by the tree?

Answer: Thank you for contacting us regarding your tree issues. Rhizosphaera needle cast (Rhizosphaera kalkhoffii) is a foliar disease of spruce trees. It is most common in trees growing outside of their native range. It starts on the inner and lower growth and progresses upward through the tree. It can take up to 15 months for the needles to show visible symptoms after the initial infection. Young trees may be killed by this disease, but usually branches die off after 3-4 consecutive years of defoliation, causing trees to look disfigured.

Early identification of Rhizosphaera can prevent major damage to individual trees and prevent the spread to nearby trees. Protecting new growth as it emerges is very important. For best effectiveness, fungicides should be applied when the emerging needles are half elongated (1/2 to 2 inches in length). Needle cast diseases can be effectively controlled with fungicides containing chlorothalonil. For Rhizosphaera needle cast, two properly-timed applications per year for at least two consecutive years, and sometimes three years, is required for control. Heavily infected trees may require several years of fungicide applications but should be sprayed, soil drenches are not effective. Also, clean-up of any infected needles and branches will help reduce the spread of the disease.

Resources
Needle cast in Colorado Blue Spruce, Purdue Landscape Report
Blue Spruce Update, Purdue Landscape Report
Why Spruce Trees Lose Their Needles, Purdue Extension
Blue Spruce Decline, Purdue Extension
Diseases Common in Blue Spruce, Purdue Extension
Tree Installation: Process and Practices, The Education Store, Purdue Extension resource center
Tree Planting and Urban Forestry Videos, Subscribe to our Purdue Extension-FNR YouTube Channel
Find an Arborist, International Society of Arboriculture

Lindsey Purcell, Urban Forestry Specialist
Purdue University, Department of Forestry and Natural Resources