﻿STRAWBERRY ROOTWORM on GREEHHOtJSE ROSES 



from 3 to 5 inclies long. During this period no marketable blooms 

 were obtained from these plants. 



The beetles seldom attack the flowers, but when present in large 

 numbers sometimes feed on the sepals, probably because they contain 

 chlorophyll. In severe infestations the blooms of Columbia and 

 Ophelia roses occasionally suifer injury, but the double white Kil- 

 larney is rarely attacked. 



Although the damage to the foliage occasioned by the beetles is 

 more conspicuous, the roots are severely injured by the feeding of 

 the larvae, which not only devour the young feeder roots but also 

 interfere with the normal functioning of the root system by girdling 

 and gnawing into the older roots. (Fig. 2.) After two or three 

 successive seasons of this feeding the plants become considerably 

 weakened and the foliage assumes a " sickly " appearance, due to the 

 cumulative effect of this injury. In some infested greenhouses the 

 resulting mortality of plants in some beds ranged as high as 75 per 

 cent, as indicated in Table 1, in which are recorded observations 

 taken in 1920 by Prinma and Chambers. 



Table 1. — Mortality due to larval injury ty the straw'berry rootworm in 11 



ground 'beds, each containing 800 rose plants 



Bed No. 



Number 

 of dead 

 plants 



Mor- 

 tality 



Bed No. 



I 



Number 

 of dead 

 plants 



Mor- 

 tality 



] 



333 

 279 

 333 



Per cent 

 41.6 

 34.9 

 41.6 

 18.1 

 53.1 

 34.5 

 26.1 

 35.0 

 5.3 

 2.3 



11 



25 



5 



22 



67 



27 



312 



600 



Per cent 

 3.1 



2 . . 



; 12 



0.6 



3 



13 



2.8 



4 



145 

 425 

 276 

 209 



14 ... .. . . 



8.4 





15 



3.4 



6 



16 



39.0 



7 



17 



75.0 



g 



280 

 42 

 18 



Total and average 





10'-. 



3,398 



25.0 







' Plants not cut back the previous season. 



In one badly infested bed containing 800 plants 6 larvae, on an 

 average, were found among the roots of each plant, and in one case a 

 maximum of 23 larvae and pupae were collected. When it is con- 

 sidered that these plants had been in the bed for five years and 

 there subjected to larval attack for at least three years, it is not 

 surprising that the foliage was yellow and that no flowers of any 

 value were being produced. 



Wounds in the roots are favorable points for the entrance of 

 pathological organisms, and the resulting weakened condition of 

 the plants renders them more susceptible to plant diseases. 



The enormous number of beetles actually present in a heavily 

 infested greenhouse may be readily appreciated from the following 

 data: Since other control measures appeared inadequate, one estab- 

 lishment hired schoolboys for several weeks to hand-pick the adults, 

 paying them at the rate of 25 cents per 100 beetles. The pay roll 

 Tor these boys showed that as many as 60,000 were collected in one 

 week at a co.st of $150 {3?^, p. '2H5'^. Although several hundred 

 thousand beetles were removed in this way, no diminution in their 

 numbers was apparent. At another place many beetles were shaken 



