DISEASE SYMPTOMS

 

The downy mildew fungus infects both above ground and below ground portions of the hop plant.

Downy Mildew(pseudoperonspora humuli)
(#1)
The root and crown tissue will have reddish-brown flecks and streaks. This should not be confused with normal reddish tissue found in the center of hop roots and crowns.
In the spring infected shoots will appear with normal shoots, growing from a crown.
Infected tissue will often develop a black rot.
The leaves appear yellowish green, stunted and are cupped downward.
Under favorable weather conditions the mildew spreads from these shoots and infects leaves and other shoots. In the summer the leaves of infected vines often turn yellow and the vine may die. Other vines may be dark green and leaves cupped and arms stunted. Cone blight often occurs if favorable moisture conditions are present.


Control options for the mildews. The use of Cocide, a copper based fungicide, and sulfer are two possible solutions to controlling both downy and powdery mildews.

VIRUS

Symptoms become particularly common during cool periods following a period that has been favorable for hop growth.
Yellow ringspots and line patterns develop on the leaves. As the disease progresses the yellow areas die and may evolve the whole leaf.
On some varieties the leaves roll upward with considerable interveinal necrosis.
The side arms are shunted and vine growth is poor. Quite often the growing tip of the vines curves downward and becomes brittle and dies. As the new shoots grow this also happens to them. The leaves are dark green and curled downward. The cones may also turn brown and fail to develop.


Text and Photos courtesy of:
J.R. Simplot Company
Pocatello, Idaho 83201


Counter installed 07/20/97