CULTURAL DIRECTIONS 
405 
Because of its hardiness the Egyptian tree onion (top 
onion) is a favorite throughout the North. For the ear- 
liest bunching onions, the sets should be planted in the 
fall at least six weeks before freezing' weather, and 
mulched if possible with manure, after the ground is 
frozen. 
Considerable quantities of bunching onions are also 
grown from seed sown in the open ground, for market- 
ing during the summer. This method requires the free 
use of seed, 20 to 30 pounds an acre. It is an economical 
method of production, and good profits are possible when 
prices are materially lower than for bunching onions 
grown from sets. 
Bunching onions are sometimes prepared for market 
in the field (Figure 51), but it is better to take them to 
the packing shed, where the dead leaves can be removed 
and the onions properly washed and bunched. From 4 
to 10 onions are tied in a bunch, the number depending 
upon size and market requirements. 
548. Insects. — The imported onion maggot (Pegomya 
cepetormn) may be controlled on extensive areas by a 
poison bait consisting of sodium arsenite, molasses, 
water, and chopped onion. This material is placed in 
cans about the field immediately after seed sowing and 
refilled at intervals. For small plots, carbolic acid emul- 
sion applied as a spray is effective (Pa. Sta. Bui. 171). 
Rotation and clean culture are also important. 
The onion thrip (Thrips tabaci) is often a destructive 
enemy, especially in the South and in the Southwest, 
where Bermuda onions are grown. It is very minute in 
size, not exceeding 1-20 inch in length, and provided 
with sucking mouth parts and bristle-like mandibles. 
When present in large numbers thrips cause the plants 
to turn brown and die. Spraying with kerosene emulsion 
or nicotine sulphate, or dusting with a material impreg- 
nated with nicotine sulphate, are successful treatments. 
