| General Recommendations: Fungal pathogens that infect the needles of conifer trees and cause the needles to fall are called needlecast diseases. Needlecasts are important problems in windbreaks and Christmas tree nurseries where large blocks of the same species is being grown in close proximity to each other. Needlecast diseases can also be important in residential landscapes where plantings are dense and humidity remains high because of the lack of air flow. Tip blights are caused by certain fungal pathogens that infect the growing ends of branches and cause the tips to die, resulting in needle drop and terminal bud death. Needlecasts and evergreen tip blights characteristically occur on the lower branches and work upward in successive years. When severe, limbs over the entire tree can be affected. Premature loss of needles disfigures the tree and eventually lowers its vigor. Needlecasts and tip blights can become so severe that after repeated annual infection, even large trees may die. Needlecasts in the Midwest can be quite damaging on Scots pine located in windbreaks, in ornamental plantings or in nurseries. Poor vigor due to other factors will increase the severity of needlecast and tip blight diseases. Symptoms of these diseases are similar. Needlecast diseases appear as spot infections on the needles that can turn into yellow or brown bands. Depending upon the fungal pathogen, infection can be either on current or old needles, or both. Control involves enhancing air flow, removing infected debris and therefore lowering the amount of inoculum, and the application of fungicides to prevent infection.
Control of Needlecast and Evergreen tip blights:
1. Purchase disease-free, healthy nursery stock. Avoid planting pine species and varieties that are highly susceptible to any needlecast or tip blight disease.
2. Promote good tree vigor by watering during drought periods and fertilizing according to a soil test report. Space plants to avoid crowding. This increases air flow and reduces free moisture.
3. Avoid planting new seedlings next to established, older evergreen trees when possible. Check plants several times each season to monitor needlecast and tip blight diseases.
4. Shear healthy trees before shearing infected trees to minimize any transfer of inoculum. Dip tools in rubbing alcohol or 1 part bleach mixed with 4 parts water between cuts. Avoid overhead watering or pruning when the trees are wet. Use a drip system if possible.
5. Spray a fungicide. Susceptible trees and those that are planted in dense stands can be sprayed with a fungicide at 7- to 10- intervals between applications. If trees are infected, identify the needlecast or tip blight disease first to determine the approximate timing of application. For example, some diseases infect only juvenile needles, and not mature growth. In these cases, apply fungicides when juvenile needles are present. |
