| HOST PLANT |
DISEASE |
SYMPTOMS |
MANAGEMENT |
| Cottonwood
Populus spp. |
Cankers, Valsa sordida (Cytospora chrysosperma),
Phompsis sp., Hypoxylon sp., Mycosphaerella populorum, Cryptodiaporthe
populea |
Fungi infect young twigs or wounds creating cankers on
branches and trunks. Fruiting bodies commonly form on the face of cankers.
Widespread and common on poplar, cottonwood, aspen and willow. Especially
serious on Lombardy and silver leaf poplars. |
Maintain plant vigor. Remove cankered branches during dry
weather. Avoid wounds. Avoid planting in areas with poor air circulation.
Trees prone to many cankers should be replaced with another tree
species.
CHEMICAL: None. |
| Leaf rust, Melampsora medusae and other species |
Yellow to orange pustules break through the surface on both
leaf surfaces in mid to late summer. Angular yellow lesions may occur on
the opposite leaf surface. Lesions turn black in autumn. Some defoliation
may occur. Alternate hosts include hemlock, Douglas-fir, larch, and pine
depending on rust species. |
Choose a poplar clone with resistance. Keep susceptible
conifers 500 yards away from poplar stock.
CHEMICAL: Seldom necessary
in landscape settings. Triadimefon or triforine. |
| Marssonina leaf spot, Marssonina populi |
Small brown leaf spots with yellow margins. Infection may
advance into stem tissue. May be severe during wet seasons resulting in
defoliation. |
Collect and destroy leaves. Plant in areas with good air
circulation.
CHEMICAL: Fungicides seldom warranted in landscape
plantings.
NURSERY: Chlorothalonil at bud break and every 7-10 days if
necessary. |
| Shoot blight, Venturia tremulae on Populus
sp. and hybrids; V. populina on black cottonwood and balsam
poplar |
Brown to black leaf spots rapidly expand on succulent
tissue to cause shoot blight. Affected tissues dry out and become
brittle. |
Remove and destroy infected shoots. Increase air
circulation. Rake and remove leaves in the fall.
CHEMICAL: Seldom
necessary in landscape settings. |
