242 VEGETABLE GROWING PROJECTS 



Close planting of rows prevents the use of horse-drawn implements 

 so that growers are apt to bear with insect depredations rather 

 than resort to the use of hand outfits. Some extensive truckers 

 are now planting onions with skip rows, so that when spraying 

 operations are necessary traction machines can be used without 

 injury to the plants. 



It is not uncommon for the leaves of onions to turn white in 

 midseason and wilt. This is due to a small, white, soft-bodied, 

 insect (onion thrips), the larva of a minute fly, which punctures 

 the leaf with its needle-like mouth parts and destroys the cells 

 while sucking the plant juices. The adult thrips pass the winter 

 in old onion tops or in rubbish. In the spring the " flies " go to 

 new onion plantings where they deposit eggs in the leaf. Adults, 

 eggs, and larvae may be found on the plants during the summer 

 or until reproduction is stopped in the autumn. Contact sprays 

 applied before the leaves are badly affected will control the insect. 

 Black Leaf 40, one pint in 100 gallons of water to which is ap- 

 plied 4 or 5 pounds of dissolved soap, is effective when applied 

 with force and in large quantities. 



Onion bulbs are sometimes dwarfed or the plants destroyed 

 soon after growth has commenced by a whitish maggot which 

 bores into the underground stem. Entire fields are often destroyed 

 by this pest. The insects pass the winter usually as puparia 

 from which adults emerge in the spring. Eggs are laid in the 

 leaf sheath or on the ground, and upon hatching the maggots 

 work into the young bulbs. In two or three weeks the maggots 

 mature, change into pupse in hardened, brownish puparia. 

 Several broods of the insect occur each year. Until recently 

 no satisfactory control was known. Sweetened poison bait has 

 proved the most satisfactory remedy. 



Smut is a disease of onions which sometimes causes serious 

 losses. The fungus causing the disease lives through the winter 

 in the soil and attacks young seedlings. Onions grown from sets 



