STRAWBERRY ROOTWORM ON GREENHOUSE ROSES 45 
Observations have shown that plants retained in beds for three 
_ years or longer are usually the more heavily infested. By removing 
the plants and soil at the end ‘of three years at the latest, the chances 
of severe infestation are very much reduced. A rotation should be 
planned and followed whereby the plants in no section will remain 
in the beds longer than three years. For example: If a range of sev- 
eral houses is divided into three separate sections—A, B, and C—all 
of the plants in section A should be completely torn out and re- 
planted the first season, all those in section B the next season, and 
those in section C the third season. In this way the 3-year-old plants 
in section A would be replaced the fourth season, and so on. Several 
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‘ florists are now of the opinion that forcing their plants as much as 
possible for three years, instead of retaining them for a longer 
_ period, increases their production and more than compensates for 
any extra expense due to the more frequent replanting. 
SUMMARY 
Within the last seven years two varieties of the strawberry root- 
worm, Paria canella—quadrinotata and gilvipes—have appeared in 
greenhouses in the commercial rose-growing districts east of the 
Rocky Mountains and have done great injury to the rose plants. 
Although normally an outdoor pest on strawberry, raspberry, and a 
number of miscellaneous plants, this insect has become one of the ~ 
serious enemies of roses grown under glass. | 
The plants are injured by the larve and adults. The larve feed 
' on the roots and the adults eat foliage, stems, buds, and flowers. 
The overwintering adults appear in February and lay eggs during 
a period of two or three months. The larve from these eggs feed on 
the roots for a period of from 33 to 74 days, after which they trans- 
form to pup. The adult beetles emerge from 8 to 17 days later. 
| Because of the long period of egg-laying, the emergence of the adults 
. during June and July is almost continuous. From the eggs which 
are laid by these beetles a second brood of adults develops and 
emerges during September and October. The two generations over- 
lap to such an extent that oftentimes no distinctions can be noted. _ 
Natural enemies of the strawberry leaf beetle are apparently few 
| in the greenhouse, as no parasites have been observed attacking any 
of the stages. Among the predators may be mentioned carabid 
| beetles, spiders, and toads. Uropod mites frequently attach them- 
selves to adults. 
Early experiments established the fact that the usual measures 
recommended for leaf-eating insects were practially useless in con- 
' trolling the strawberry rootworm. Spraying with the arsenicals 
did not prove practical under ordinary conditions, but was found to 
be successful in protecting the swelling and breaking buds at 
the time the plants were cut back. Under similar conditions a 
Bordeaux-arsenate of lead mixture served as a repellent. In exten- 
sive trials the use of a 10 or 15 per cent dry mixture of arsenate of 
lead or calcium arsenate and superfine sulphur showed that dusting 
with these materials was a satisfactory and effective method of keep- 
ing the foliage coated with an arsenical to repel the beetles. Experi- 
ments with Paris green gave unsatisfactory results. In 21 commer- 
cial houses fumigation with hydrocyanic-acid gas during the resting 
