﻿STRAWBERRY ROOTWORM ON GREENHOUSE ROSES 



43 



As shown in Table 18, the mortality in the preliminary pot ex- 

 periments was promising, hence nine plots of five or six plants each 

 were treated with sodium cyanide in solution. Sodium cyanide was 

 also pulverized and then spread around the base of every plant in 

 three plots of five plants each. The mortalities resulting from these 

 plot treatments are listed in Table 19. 



Table 19. — Results oMained in plot experiments with sodium cyanide, in solu- 

 tion and pulverised, against larvm and pupw of the strawT)erry rootioorm 



Dosage 



Period 

 after 

 treat- 

 ment 



Num- 

 ber of 

 plants 



Number of lar- 

 vse and pupse 



Control 



Dosage 



Period 

 after 

 treat- 

 ment 



Num- 

 ber of 

 plants 



Number of lar- 

 vae and pupas 



Control 



Exam- 

 ined 



Dead 



Exam- 

 ined 



Dead 



Grams 



0.5 



0.5 



0.75 



0. 75 



0.75 



1 



1 



2 



Days 

 4 

 7 

 4 



7 

 8 

 4 

 8 

 2 



7 

 4 

 4 

 4 

 3 

 4 

 7 

 2 



67 

 11 

 28 

 15 

 17 

 35 

 57 

 19 



4 

 1 

 4 

 3 

 1 

 4 

 7 

 3 



Per cent 

 ^.7.0 

 i9.1 

 14.3 

 20.0 

 5.9 

 11.4 

 12.3 

 15.8 



Grams 



2 



3 



3 



5 



5 



21 



3 1 



5 » 



Days 

 6 

 2 

 6 

 2 

 6 



1 



8 



3 

 2 

 3 

 2 

 3 

 5 

 5 

 5 



18 

 24 

 20 

 25 

 21 

 16 

 37 

 21 



9 

 21 

 13 

 24 

 11 



4 

 26 

 20 



Per cent 

 50.0 

 87.5 

 65.0 

 96.0 

 52.4 

 25.0 

 70.3 

 95.2 



' Applied in pulverized form. 



In these experiments the mortality of larvae and pupse in soil 

 which had been drenched with sodium cyanide was insufficient to 

 justify its use as a means of destroying the soil stages. Moreover, 

 the practical use of the pulverized crystals would be precluded 

 because the collars of the plants were severely injured by this treat- 



ment. 



WOOD ASHES AND TOBACCO DUST 



Because of their fertilizing value, wood ashes and tobacco dust, 

 but especially the wood ashes, are used extensively by florists. It 

 was thought that the free lye present in wood ashes, and the nico- 

 tine, which is an ingredient of the tobacco dust, might leach into the 

 soil and be effective in killing the larvae and pupse. To determine 

 its effectiveness in three plots containing 10 plants each, a handful 

 of this mixture was applied around the base of each plant and then 

 watered. Examinations of the larvse and pupse in soil around the 

 plants were made seven or eight days later, and the results are given 

 in Table 20. 



Table 20. — Effects on strawberry rootworm larvcB and pupw in soil treated with 

 tobacco dust and wood ashes 



Material 



Period 

 after 

 treat- 

 ment 



Number of 

 larrse 



Control 



Number of 

 pupae 



Control 



Larvae 

 and 



Exam- 

 ined 



Dead 



Exam- 

 ined 



Dead 



pupae 

 control 



Tobacco dust ..-. 



Days 

 7 

 8 



7 



44 



17 



4 

 2 



2 



Per cent 

 9.1 

 5. 5 



11.8 



41 

 33 



18 



9 



7 



2 



Per cent 

 22.0 

 21.2 



11.1 



Per cent 

 15.3 



Wood ashes. 



13.0 



Tobacco dust and wood ashes 

 mixed. . 



11.4 







