154 
WISCONSIN HORTICULTURE 
July, 1919 
THE INSECT PAGE 
Conducted by the Department of Economic Entomology College of 
Agriculture 
THE POTATO LEAFHOPPER 
Ev:,poasca Mali 
Life History and Habits: The po- 
tato leafhopper (see cut), former- 
ly known as an apple leafhopper 
is a very small, greenish insect 
found on the under side of the 
leaves of potato and bean as well 
as some other plants. The adult 
insects both fly and hop and when 
disturbed dart from one plant to 
another so quickly that one is apt 
to overlook them unless they are 
present in large numbers. 
The minute eggs are laid in the 
midribs and petioles of the leaves 
or in the stems of the plant. They 
are so small and so well hidden 
by the female that it is practical- 
ly useless to hunt for them. In 
about ten days the eggs hatch in- 
to very small young or nymphs 
looking much like the adults but 
without wings. These nymphs 
moult and grow, feeding upon 
the leaves, until ready to change 
into the adult stage. There are 
probably three generations of the 
insect in southern Wisconsin, the 
last adults feeding upon potato 
until frost. 
These insects like plant lice 
have sucking mouth parts and 
with their beaks suck the juices 
of their host plants. This feed- 
ing injury alone would be in pro- 
protion to the abundance of the 
insects but should seldom if ever 
be sufficient to kill whole fields of 
potatoes. A serious complication 
has arisen, however, in the estab- 
lishment, beyond a reasonable 
doubt, that the leafhopper trans- 
mits a disease. This disease, usu- 
ally spoken of as “tip burn” (see 
cut) spreads through a plant very 
rapidly during the hot summer 
months. Whole fields of potatoes 
may turn brown and die in a few 
weeks. It is the disease then that 
makes vital the control of the in- 
sect. 
Control: About every ten years 
the potato leafhopper appears in 
vast numbers and for a year or 
two causes serious losses to potato 
growers. Indications point to a 
heavy infestation of the insect this 
summer, heavier even than last 
year. If the potato crop is to be 
saved, control measures should be 
started at once and kept up. 
Bordeaux mixture 4-4-50 com- 
bined with an arsenical is probab- 
ly the best early treatment for po- 
tatoes and should be applied at 
least every two weeks. The Colo- 
rado potato beetle can thus be 
controlled and the potato flea 
beetle and leafhopper largely re- 
pelled. In applying the spray the 
under side of the leaves must be 
covered to assure protection. This 
is not a contact spray and does 
not kill the leafhoppers but tends 
to repel them and delays the ap- 
pearance of disease. It is not fea- 
sible to attempt killing the adults 
by spraying, for with their quick 
movements it is impossible to hit 
many of them. 
Early in July when the nymphs 
are nearly fullgrown and before 
any have become adults a thor- 
ough spraying with nicotine sul- 
fate (40%) at 1 to 1200 should be 
given. The nicotine may well be 
combined with Bordeaux mixture. 
It is essential to hit the under side 
Potato vines showing curled, di- 
seased leaves attributed to the potato 
leafhopper. (Orig.) 
of the leaves. If the nymphs are 
not all killed another like appli- 
cation should be given ten days or 
two weeks later. 
By keeping potato plants well 
covered with Bordeaux mixture 
and applying nicotine sulfate 
when nymphs are present in abun- 
dance the best protection from in- 
sect attack and disease may be ex- 
pected. 
John E. Dudley, Jr. 
ELM AND MAPLE LEAF 
GALLS 
Numerous inquiries nave recent- 
ly come to this office regarding 
some “disease” attacking elm or 
maple foliage. The injury to elms 
