20 BULLETIN 784, U. S. DEPARTMENT OF AGRICULTURE. 
Class exercise. — The following topics are suggested as the basis of 
the class-room discussion: 
A. Fundamentals of control: 
Thorough spraying, clean cultivation, destruction of rubbish, and rotation of 
crops. Since there is a similarity in general methods, control of insects and 
diseases may be considered together. 
B. Insect pests: 
Insects damaging the potato crop may be classified as follows: (1) Insects 
chewing the leaves; (2) insects sucking the leaves and tips; (3) stalk 
borers; (4) insects affecting the tubers. 
The following may be considered the chief insect pests of the potato plant : 
Colorado potato beetle — Eats the leaves; controlled by spraying with 
arsenate of lead or Paris green. 
Blister beetles — Leaf eaters; controlled same as Colorado beetles. 
Potato flea-beetles — Leaf eaters; harder to control; spray with Bordeaux 
and arsenate of lead as probably the best means of control. 
Leafhopper and plant-lice — Suck the leaves and tips; control by spray 
of nicotine sulphate or kerosene emulsion. 
Potato-stalk weevil — Bores into the stalk ; burn all infested vines ; clear 
ground and burn all old stalks ; destroy all related weeds ; rotate crops. 
White grubs (the larvae of May beetles or June bugs) — Commonly known 
as " grubworms ; " control by fall plowing and turn soil again in spring ; 
rotation of crops. 
C. Potato diseases: 
1. Common diseases affecting the skin of the tuber : 
(a) Common scat* — Control; treat seed, rotation of crops. 
(6) Russet scab — Control; treat seed, change of soil, deep prepara- 
tion and cultivation. 
(c) Powdery scab — Control; treat seed. 
(d) Late blight dry-rot — Control; Bordeaux for blight, careful sort- 
ing and storing of the tubers. 
(e) Powdery dry-rot — Control; care in handling; sorting out of in- 
jured potatoes. 
(/) Eelworm — Control; careful selection. 
2. Diseases of stem and leaves: 
(a) Blackleg — Control; selected seed, formaldehyde treatment. 
( & ) Fusarium wilt — Control ; rotation and sanitation. 
(c) Bacterial wilt — Control; clean seed, sanitation. 
(cZ) Early blight — Control; Bordeaux spray. 
(e) Late blight — Control; Bordeaux spray. 
(/) Rhizoctoniose — Control; clean seed, formaldehyde treatments, ro- 
tation. 
{g) Tipburn — Control; in a measure, by Bordeaux, thorough cultiva- 
tion. 
D. Summary of control measures: 
1. Results of seed selection ; results in eliminating wilts, blackleg, eelworm, 
and other diseases which show on vines. 
2. Results of seed treatment and rotation; reduce injury from Rhizocto- 
niose, scab, and blackleg, give clean seed. 
3. Results of spraying ; prevents early and late blight, prevents the blight 
rot, reduces injury from tipburn, repels flea beetles, kills most of the 
other insect pests, stimulates the vines to longer growth, gives in- 
creased yields. 
