INJURIOUS INSECTS OF I9OQ AND IQIO. 159 
All plant remains and rubbish should be destroyed in the fall. There 
is some question as to varietal resistance; wax varieties are said 
by some to be least resistant while the limas are more resistant. 
Downy MiLpEw: The fungus attacks mostly the pods, but 
may also be found on the leaves and, in some cases, on the stems. 
It produces white patches which may become so numerous as to 
cause the pods to die. In some cases, when the disease is especially 
severe, it also gets into the seeds. It is pretty well establishd that 
insects aid very greatly in its spread. 
Clean seed should be selected, all old vines should be destroyed 
in the fall and, if the disease has been particularly bad, a rotation 
of crops may be necessary. Careful spraying with bordeaux has 
been found to effectually prevent the occurrence of the disease. 
Buicut: All above ground parts may be affected by the dis- 
ease. It is most noticeable on the leaves and pods, producing on 
the leaves large, irregular brownish patches which later become dry 
and brittle. On the pods watery brown spots with no very definite 
boundaries are produced. 
The disease is of bacterial origin. The first infection is gener- 
ally supposed to come from the seed in which the bacteria have 
lived over, and is then quite largely spread by insects. Seed should 
be selected from fields in which there was no infection, all affected 
parts should be burned, and a crop rotation should be practiced. 
Rust: Small pustules, about one-sixteenth of an inch in 
diameter, are formed usually on the lower surface of the leaf. Just 
opposite these pustules, on the upper surface, pale yellowish spots 
appear. Later these pustules break open, liberating a mass of dull 
reddish brown spores. The disease has not been reported as being 
very troublesome. Burning of dead parts in the fall and clean cul- 
ture methods should help keep it in check. 
Powpvery MiLtpew: Grayish patches, appearing as though 
dusted with a grayish powder, appear. Usually the disease is not 
very destructive. It can be controlled by means of dusting with 
sulfur or spraying with potassium sulfide. 
Beet. 
The principal insects of the beet are the leaf-eating forms, which 
can be controlled with any of the arsenical insecticides. 
Lear Spot: Brown spots, with a purplish tinge around the 
edge and with a grayish center, appear. They may become dry and 
