22 



MASS. EXPERIMENT STATION BULLETIN 352 



Table 21. Response of carrots to mulch paper stimulation 

 Waltham, Mass. 1930-1931. 



Repellent Effect of Onions 



Early in these studies it was suggested that the odor of onion might have a 

 repellent action against the carrot rust fly, and from 1929 to 1933 onions and 

 carrots were planted in alternate rows. The rows were 14 inches apart and there 

 were at least four rows of onions and three rows of carrots in each planting. 



As shown in Table 22, damage by the carrot rust fly of the first or second gen- 

 eration, or both, was slightly less where the carrots were interplanted with onions 

 than where the carrots were grown in solid blocks. However, the practice did not 

 seem to give sufficiently positive protection for reliable results and is recommended 

 only where the two crops can be grown together without inconvenience to the 

 other farm practices. 



Table 22. Repellent effect of onions on the carrot rust fly when 

 interplanted with carrots 



Waltham, Muss. 1929-1933. 



Year Seed 

 Sown 



Carrot 



Onion 



First Generation 



1929 May 1 Danvers Half Long Danvers Yellow Globe 



1930 May 1 Hutchinson Danvers Yellow Globe 



1930 May 1* Danvers Half Long Danvers Yellow Globe 



1931 Chantenay White Southport 



1930 June 10 Hutchinson 



1931 June 10 Hutchinson 



1932 June 10 Hutchinson 



1933 June 10 Hutchinson 



Second Generation 



Danvers Yellow Globe 

 Danvers Yellow Globe 

 Prizetaker 

 Prizetaker 



*.A.t Danvers. 



Rotation 



Since the known host plants of the carrot rust fly are few in number and the 

 only important vegetables in this list are carrots, celery, parsnips, and parsley, 

 the cropping plan of the vegetables can be adjusted to avoid heavy infestations 

 of this pest. The operation of a market garden with none of these crops might 

 be difficult, but this should not be necessary except in emergencies following a 



