822 
ground is more or less constantly moist. 
It seems to be more serious also where 
there is a heavy stand of alfalfa. 
The disease is known to attack clover 
almost as seriously as alfalfa. It is prob- 
able that this disease is one of the causes 
for the difficulty frequently experienced 
in obtaining and holding a stand of alfalfa 
or clover in Western Oregon. 
Symptoms 
The disease is characterized by a wilt 
brought about by rot developed on the 
stems at the surface of the ground or 
some distance above. The disease fre- 
quently kills the plants and on this ac- 
count large areas may be found in the 
field where the plants have been entirely 
killed out. The roots, however, may not 
always be destroyed, and may later throw 
out new sprouts. The rotting is invari- 
ably accompanied by a white cottony 
growth of mold over the surface of the 
stems and leaves and on the ground 
around the bases of the diseased plants. 
In this cottony mold are developed, quite 
abundantly, black irregular shaped bodies 
of fungus tissue known as sclerotia. In 
exceptional cases these are as large as a 
pea. They may also be found inside the 
stems of plants which have been killed by 
the disease. 
Cause 
This fungus is similar to the one which 
causes lettuce drop and by some author- 
ities is considered identical, though this 
has not been proved by careful investiga- 
tion. It seems best for the present to 
consider it distinct and to use the name 
Sclerotinia trifoliorum. This fungus de- 
velops no summer spores. The cottony 
growth is the mycelium which is also de- 
veloped inside the tissues. The sclerotia 
are resting bodies from which there devel- 
ops stalked fruiting bodies known as apo- 
thecia. These are usually described as de- 
veloping only after a period of rest, com- 
monly in the spring of the year in nature. 
In Oregon, however, they are found devel- 
oping in fall, almost immediately after 
being formed, without any period of rest. 
Under our conditions the disease seems to 
Spread most abundantly during the fall 
and winter, though this has not been as 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
thoroughly investigated as would be 
desirable. 
Remedy 
No remedy for diseased plants is known. 
On account of the nature of the host 
plants, it is probable that no practical 
remedy will be developed. Where the 
disease has become serious, rotation 
should be practiced. The disease seems 
to be more abundant on heavy soils, es- 
pecially where the drainage is not rapid, 
and such soils, if possible, should be 
avoided. 
YELLOWING. 
CLOVER AND ALFALFA PESTS 
Alfalfa Crane Fly 
Tipula simplex Doane (Family Tipulidae) 
General Appearance 
The adults are long-legged, slender- 
bodied insects of a light brown color. The 
females are wingless while the males are 
winged and somewhat smaller, lighter in 
color and with longer, frailer legs. The 
average length of the adult female is about 
one-half of an inch. 
Life History 
The small, oval, dark gray eggs are de- 
posited as deeply into the soil as the 
length of the female’s abdomen will al- 
low. They are laid throughout the early 
spring and summer. These soon hatch 
into light colored maggots, which begin 
to feed upon the roots of plants. When 
full grown they are from three-fourths 
to nearly an inch in length—the color 
being a very dark brown. The maggots 
remain in moist or wet places, breathing 
water through spiracles at the posterior 
end. The pupae greatly resemble the lar- 
vae in shape and color until nearly time 
to develop into the adults, when the 
wings and legs begin to appear. The 
body segments are provided with sharp 
spines which project backwards and by 
which they are able to wriggle to the sur- 
face when ready to emerge. The broods 
overlap so that all stages may be found. 
The insect probably hibernates in the lar- 
val forms and pupate early in the spring, 
giving rise to the adults. These bring 
forth young larvae, which become de- 
structive early in the summer. 
See Bacterial Blight. 
