The European Corn Borer. 41 
destroyed, unless it is possible to work these portions deeply into 
manure that is in a heating condition. 
DESTRUCTION OF WEEDS. 
Weeds serve as refuges for the corn borer and may be killed by 
spraying with certain chemicals in solution. Many chemicals have 
been used for this purpose but the two in most common use are iron 
sulphate and sodium arsenite. Young corn borer larve feeding in 
the tips of weeds may often be killed by such chemicals, but the num- 
ber destroyed is not sufficient to render this method of value against 
the corn borer. However, such methods are valuable in destroying 
weeds on uncultivated land, as in meadows, lawns, borders of road- 
sides, on public dumping grounds, and on vacant city lots, thus pre- 
venting the weeds from becoming a possible source of infestation. 
Any reliable type of sprayer may be used in applying these solu- 
tions. For large operations on rough land a power sprayer equipped 
with long lines of hose is most useful. In the experiments carried 
on by the Bureau of Entomology, a large power sprayer carrying a 
400-gallon wooden tank, mounted on an auto truck, was used: A 
single line of 4-inch hose was run from each tank and fitted with 
a solid-stream nozzle carrying a 34-inch tip. The method of opera- 
tion was to run out the entire length of hose, and working back to- 
ward the pump, spray a strip about 50 feet wide, repeating this 
operation until the entire field was covered. 
Care should be taken to protect the skin of the operator from the 
solutions containing sodium arsenite, as this produces severe burn- 
ing. The remedy for such burns is to apply vinegar to the parts 
affected. 
Weeds should be sprayed before they go to seed, but should not be 
sprayed when too young as their places may be taken by new plants 
that sprout from old seed, or new stems may arise from the roots. 
The best time to spray weeds is when they are in flower, or just 
before the flowers are formed. 
Iron sulphate is often used for killing mustard in grain fields and 
dandelions in lawns. It will kill almost all broad-leaved weeds, but 
does not kill grass. There is no danger of poisoning animals which 
may graze on such sprayed plants. Iron sulphate is also useful. for 
destroying meadow and roadside weeds. 
Sodium arsenite is one of the best of the chemical weed killers and 
is the basis of many of the commercial weed-killing solutions on the 
market. It is very poisonous to animals and precautions should be 
taken to prevent live stock from grazing where plants have been 
sprayed. It may be used effectively on public dumping grounds, on 
vacant city lots, along railroad right-of-ways, or any place where 
there is no danger of animals grazing. This solution is used at the 
rate of 3 pounds of sodium arsenite to 100 gallons of water. 
Kither of the foregoing solutions may be used for destroying 
weeds on farms, but care should be taken to prevent animals from 
grazing on plants that have been sprayed with sodium arsenite. It 
should also be remembered that these solutions kill cultivated plants, 
and it is difficult to use them along fences and ditches, because the 
wind is likely to carry some of the solution to the crops. They are 
useful for destroying weed patches where the land is uneven or 
