The Kennewick courier-reporter. [volume] (Kennewick, Wash.) 1914-1938, 1929-08-08
RED SPIDER INJURY
By R L. Webster, head of dept. of
Zoology, State College of
Washington.

| v
Red spider or orchard mites have
attacked foliage of various kinds
of fruit trees this season in Wash
ington, according to numerous let
tiers received by the department. of
entomology at Washington State
College. The mites thrive in sea-
sons of little rain and in 1929 con-
ditions have been favorable to
their increase and development.
Injury by these orchard mites
is characterized by a yellowing of
foliage in midsummer. Affected
fruit trees appear as If suffering
from drought. By an examination
with hand lens hundreds Of the
tiny reddish mites may be easily
detected. Three different species
of these mites are really concerned
in attacks Of this kind in the Pa
cific Northwest although control
measures recommended are sim
liar.
First there is the ssbrown mite"
which winters over in the egg
stage on fruit trees. Often we re-
ceive twigs sent in here at the col
lege on which the spherical, scar
let eggs are so abundant as to give
the bark rusty appearance.
Second there is the European
red mite" which also winters over
in the egg stage but the eggs are
somewhat different in appearance,
being vertical with short, verti-
cal stalk. Like the eggs of the
brown mite those Of the Euro
pean are reddish in color. New
conner and Yothers, in their recent
bulletin on the Biology of the
European Red Mite" say that the
eggs of these two specie often are
indistinguishable.
| Third is the red spider, which
spends the winter on the trees as
a mature or nearly mature mite,
protected under web. These mites
deposit eggs on leaves during the
summer, but the eggs are white,
almost colorless in appearance.
Infestation by fred spiders" is
likely to involve all three of these
mites although the European red
mite has been most common in the
Yakima Valley Of Washington, &C
cording to observations by federal
entomologists working there.
The highly refined summer oil
sprays are recommended for treat
meht during the warm months
when damage by orchard mites
occurs. Several commercial oils are
available and are being used used
by orchardists where trees are Sc
|verely attacked. These may be used
at the rate Of one gallon of the
prepared emulsion to 100 gallons
of water. This allows for an actual
oil content varying from IS to 81
per cent.
Apple thees affected with red
ispiders at this time can be sprayed
with combination of oil nicotine
sulphate and this APPLICATION will
serve to replace a cover spray OF
lead arsenate for codling moth. In
his bulletin on codling moth con-
troll published by the Washington
Experiment station in March, 1929
Spuler reports that results on cod.
/ ling moth control with oil-nice
tine combinations were as good as
if not better than, the standard
lead arsenate treatment. The com
bination, while a more expensive
spray, does not take care OF thu
spider mites, which are not affect
ed by the lead arsenate.
To replace late cover spray
combination Of 3-4 per cent OF
and nicotine sulphate at the rat
of 1-16OO0 (1-2 pint to 100 gal
lons) may be used. This combin
alton has a double use on appl
trees. It will replace a lead arse
nate treatment in late codlin'
moth spray and will dispose Q
orchard mite, woolly aphis, lea
hopers apnd other sucking insect
on the foliage at that time OF tn
year.
Under no circumstances shoul'
an oil intended for dormant use b.
applied during the summer. Oil
used in emulsions intended fol
dormant use are less refined ant
more likely to cause injury to thu
| leaves. The summer oils spra,
made from refined oils, have prov
en- more efficient than dilute lime