BULB CROP PROJECTS 243 



are never diseased. Smut may be recognized by dark spots on 

 the leaves. Later these spots break open exposing black sooty 

 masses of spores. In truck gardening regions it is often necessary 

 to disinfect the soil at planting time by applying a formaldehyde 

 solution. This is done by a drip attachment on the seed drill. 



Downy mildew, a disease which has many of the characteristics 

 of the late blight of potatoes, is sometimes a destructive disease. 

 Its first effects are noticeable by the peculiar withering of the 

 tips of leaves. The affected plants soon wilt and the trouble 

 spreads to other plants. Spraying with Bordeaux is the best 

 method of control. 



Black spot may develop on the outer scales and become con- 

 spicuous especially during storage. The chief injury is to ap- 

 pearance. Neck rot often causes severe losses in storage. Thorough 

 drying before storage is important in controlling these troubles. 



1. Describe the injury done by thrips to onions. CL : 245, 248. 



2. Is soil a factor in the attacks of thrips? CL: 245, 247. 



3. What is the life history of the onion thrips? CL : 245, 247. 



4. What are some contact sprays, and which is the most efficient 



against onion thrips? CL : 248-249. 



5. What is the life history and appearance of the onion maggot? 



CL : 243-244. 



6. What are the puparia? CL : 244. 



7. What is the form,ula for poison bait? CL : 245. 



8. How may onion smut be recognized ? SH : 201-203. 



9. In severe cases what measures are necessary to control onion smut ? 



