STRAWBERRY ROOTWORM ON GREENHOUSE ROSES { 
_ from 3 to 5 inches 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 suffer 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 larve, 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 ‘Yable 1, in which are recorded observations 
_ taken in 1920 by Primm and Chambers. 
| TABLE 1.—Mortality due to larval injury by the strawberry rootworm in 17 
_ ground beds, each containing 800 rose plants 
Number Number 
Bed No. of dead He Bed No. of dead ee 
plants Y plants y 
Per cent || Per cent 
1h ip RT rea em Reto eae 333 Ce Cari a FY ing agtes aa che es earatee oes oui ge 25 3.1 
pie eh eS 279 SA OND SS AA 5 0.6 
Co x cate a a ue ek NS EN 333 AVG BS eo Be ai ais MRE ES AES 2h 22 2.8 
Axe os 2 [eee Sips bys eau li os halts 145 18.1 Ait Ns ae ep DON ah mE 67 8.4 
Deke ed acer oe an leet a et a 425 Dae eal eee en aes aay Cae e e 27 3.4 
(Gh eh A een pe De lies eae 276 3 te Ha 6) SN eh esol aS MAE 312 39.0 
"i255 LOLS A Ale ee eo Ne 209 Dat yaad TRON REE 600 75.0 
Sees (oso So ety radia Meee 280 35. 0 
(8) 4 aig eg ae Dae se Ng LE 42 5.3 Total and average--_-_-._- 3, 398 25.0 
Srl SERS Ak ON Pe Le 18 2.3 | 
1/Plants not cut back the previous season. 
In one badly infested bed containing 800 plants 6 larve, on an 
.verage, were found among the roots of each plant, and in one case a 
maximum of 23 larve and pupe 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 
nfested 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, 
| Pfaying them at the rate of 25 cents per 100 beetles. The pay roll 
| for these boys showed that as many as 60,000 were collected in one 
_ week at a cost of $150 (32, p. 285). Although several hundred 
_ tihousand beetles were removed in this way, no diminution in their 
niumbers was apparent. At another place many beetles were shaken 
