6 MASS. EXPERIMENT STATION BULLETIN 352 



indicate that growers had observed damage in 1930. In 1932 it was considered 

 a serious pest of carrots in the northeastern part of the State. Injury was most 

 severe on carrots remaining in the ground late in the fall, and parsnips and celery 

 were slightly damaged. 



Idaho. — A museum specimen was collected at Moscow, October 5, 1931, but 

 no reports of damage to vegetables are known. 



Colorado. — Melander (20) lists museum specimens of P. rosae from Colorado 

 but no other report of its occurrence in this State has been secured. 



Indiana, Illinois, Wisconsin. — In 1931 and 1932 entomologists in these states 

 reported to the Insect Pest Survey, United States Department of Agriculture,, 

 that although they were on the lookout for this pest no injury by it was known to 

 occur nor were there specimens in the insect collections. 



HOST PLANTS 



Serious injury by the carrot rust fly, causing a definite loss to the grower, 

 has been observed on carrots, parsnips, and celery. In Massachusetts severe 

 damage to celery has occurred rarely, especially when one considers that about 

 500,000 boxes are produced annually; but in New York heavy infestations have 

 been reported. Considerable damage to parsley and celeriac occurred in the 

 experimental plantings, and a slight chewing on the surface of the roots and crown 

 of coriander, caraway, fennel, and dill was observed. Even though such injury 

 was found on 52 percent of the coriander plants in 1928, it could not be called 

 commercially destructive, and there is no definite record that the carrot rust fly 

 developed to maturity in these herbs. 



Pettit (23) states that it has been reported attacking wild carrot, but, although 

 this plant grows abundantly in eastern Massachusetts, Psila rosae has not been 

 found or reported breeding in it here (24). Chittenden (4) quotes a Scandinavian 



Table 2. Rel.\tive susceptibility of host plants of the carrot 



RUST FLY 



Waltham, Mass. 1928-1932. 



DEGREE OF INFESTATION 



1929 1930 



and and and and 



Severe Severe Severe Severe 



Carrot 0.00 90.00 13.09 61.78 1 00 14.00 



Parsnip 9.80 29.42 1.00 10 00 5 00 15 00 0.50 2.00 



Parsley 17.6.S 23.53 14.00 19 00 37.93 0.00 



Celeriac 9.00 28.00 0.00 0.00 



Celery (Early) . 13.21 13.21 * 0.00 



Celery (Late) . . 16.67 0.00 



Fennel 9.16 0.76 3.53 0.00 



Coriander 52.69 00 



Caraway 23.70 0.00 3.00 100 



Dill 8.47 0.00 



*33 plants showed slight injury to roots, which was suspected but not definitely determined 

 as caused by P. rosae. 



