THE CARROT RUST FLY 9 



In these experiments the damage to carrots and other host plants has been 

 classified as follows: 



None. — No evidence of feeding by the maggot. 



Slight. — Some feeding on the surface of the fleshy root or on the hair rootlets, 

 not enough to make the vegetable unmarketable. 



Moderate. — Tip injury which stunts the root, one or two small tunnels in the 

 fleshy root, or badly misshapen roots due to attack when small, although 

 the vegetable may haye a small market value when mature. 



Severe. — Extensive surface feeding and scars, three or more tunnels in fleshy 

 root, rotted or badly discolored areas due to infestation when small, and other- 

 wise unmarketable because of damage by the carrot rust fly. 



Commercially Damaged. — Those vegetables showing either moderate or severe 

 injury. 



LOCATION OF LARVAE AND TUNNELS IN CARROTS 



In October 1928, carrots which were heavily infested with rust fly larvae were 

 examined and the location of the larvae recorded. In the larger carrots, which 

 averaged 8 inches in length, the maggots were quite evenly distributed from the 



Table 4. Location of larvae and tunnels in carrots 

 Second Generation, Waltham, Mass. 1928. 



L.\RGE CARROTS 



Number Percent Average 

 of of Total Number of 



Larvae Larvae Larvae 



per Inch 



1st inch 9 4.74 0.36 



2nd inch 23 12.11 0.92 



3rd inch 20 10.53 0.80 



4th inch 32 16.84 1.28 



5th inch 26 13.68 1.04 



6th inch 27 14.21 1.08 



7th inch 26 13.68 1.08 



8th inch 21 11,05 1.17 



9th inch 6 3.16 0.55 



10th inch 0.00 0.00 



Large Carrots Small Carrots 



Variety Hutchinson 



Number examined 25 



Length — Maximum 10 inches 



Minimum 6 inches 



Average 8 inches 



Rust Fly Larvae 



Total number 190 



Number per carrot 



Maximum 17 



Minimum 3 



Average 7.6 



Chantenay 



25 

 5 inches 

 2 inches 



3 . 3 inches 



90 



13 

 

 3.6 



