42 The Colorado Experiment Station. 
Tubers treated with formalin solution so'as to preclude any chance 
of planting the fungus with the tubers, have been grown in pots of 
soil that were sterilized with steam, and the plants watered with 
boiled water. When the tubers formed in these pots part of them 
were inoculated with the fungus Rhizoctonia and typical scab was 
produced, while the checks were perfectly free from scab. As we 
know that scab may be produced from a fungus, Rhizoctonia, 
present in all our soils, we cannot hope to eradicate scab by any 
treatment of the seed. Rotation of crops with good drainage and 
cultural methods are the only preventive measure that can be rec¬ 
ommended. See under Seed and Its Treatment, a report of field 
trials. 
POTATO INSECTS 
By S. ARTHUR JOHNSON 
the Colorado potato beetle, (Leptinotarsa decemlineata.) 
Native Home and Food .—This insect is a native of a strip of 
country which lies just east of the Rocky mountain range and 
includes eastern Colorado. In its native state the beetle lives upon 
the wild weeds of the potato family. The chief of these is the 
buffalo bur, but the beetle is quite a general feeder on plants of this 
group including not only potatoes, but tomatoes, egg plant, tobacco 
and pepper. 
The Insect .—The adult beetle is oval in shape, about three- 
eights of an inch in length and a trifle narrower than long. The 
ground color is yellow and the wings are marked by ten black lines 
running lengthwise. There are also black markings on the thorax. 
The eggs are bright yellow when fresh and are generally laid on the 
under surface of the leaves in patches containing from ten to fifty 
each. The young are dark red or brown grubs with black heads. 
The color becomes lighter as the grubs mature. 
Life History .—The adult beetles live over winter usually in the 
ground at a depth of from four to six inches. Where the ground is 
loose they frequently go much deeper. When the ground becomes 
warmed by the spring sun, the beetles emerge and seek food plants 
on which they may feed and lay eggs. They are more or less 
abundant every year and do considerable damage to early potatoes. 
The late crops in Colorado generally escape because most of the 
adult beetles die off before the potatoes appear above ground. 
The eggs hatch in from four to eight days depending on the 
temperature. The larvae feed at first on the surface of the leaf 
where they hatched, but soon migrate to the top of the plant and 
eat the tender young leaves which are just unfolding. The young 
