320 INSECTICIDES, FUNGICIDES, AND WEED KILLERS. 



(potato pox and rot of the stem of the potato) ; riiytophthora infestans, 

 De By. (potato disease). — The spores of these fungi adhere to the seed 

 potatoes and most often propagate the disease. To prevent this, the 

 soil and the seed potatoes are disinfected hy formol, and the results, 

 obtained were satisfactory. According to the experiments of Jones, 

 Orton, Selby, and Arthur, disinfection by formol is as effective as by 

 corrosive sublimate. The formol solutions recommended vary from 

 0-33-0-4 per cent of formol, say 0-16-0-13 per cent of formic aldehyde. 

 Steeping should last two hours. The following is a convenient method 

 of working according to Rolfs and Woods : Immerse the uncut tubers 

 for two hours in a bath consisting of 4 lb. of 40 per cent formol in 100 

 gallons of water, dry them, convey them to the field in disinfected 

 sacks and plant them. Tubeuf, Jones, and Morse recommend the dis- 

 infection of tubers by formol vapour generated by heating formaline 

 pastilles in a closed space. Delacroix advises against Bacillus solana- 

 cearuni the disinfection of the soil by a 0-13 per cent solution of formol 

 in the proportion of 10-12 litres (2-2-2-64 gallons) per square metre and 

 steeping the tubers for two hours in a solution of the same strength. 

 Against Rhizoctinia of the asparagus disinfection of the soil with 60 

 grammes (about 2 oz.) per square metre. Potatoes so treated only 

 gave 3 per cent of diseased stems, the untreated gave, on the contrary, 

 40 per cent. 



Botrytis cinerea (grey rot of the vine). — Tubeuf recommends formol 

 vapour in a closed space against this fungus. It is possible that on the 

 large scale formol solutions would act energetically against this mould. 

 If applied on grapes the moment the disease appears, the effect would, 

 without doubt, be salutary, for Trillat has shown the energetic action 

 of formol on the Penicilium mould, a closely allied species. 



3£icrosph(era c)rossularice, Wallr. (gooseberry blight). — Close records 

 that a formol solution of 0-08-0 12 per cent gives as good results as 

 potassium sulphide. It is necessary to begin the treatment as soon 

 as the disease appears. 



Fusarium DiantJii, Pr. et Del. — Delacroix having found that formol 

 vapours killed the cJilamydosjyores of this fungus advised the disinfec- 

 tion of the soil by formol to prevent this disease. 



Fusarium nov. sj)., Bolley (flax disease). — Bolley obtained very good 

 results by disinfecting the seed for sowing by immersion in a formol 

 solution of 0-5 per cent (0*2 per cent formic aldehyde). 



Tilletia and Ustilayo (bunt and smut of gi-ain crops). — The disinfec- 

 tion of seed-corn by formol was invented by Geuther. It is now 

 recognized as far superior to the other methods. It results from 

 numerous trials in this direction that 0-25 per cent formol solutions 

 (0-1 per cent formic aldehyde) are strong enough and that fifteen 

 minutes' immersion suffice to disinfect the corn-seed completely. By 

 this treatment crops can be obtained without any diseased ears. It 

 is essential not to wash the grain after treatment, for as Hecke has 

 shown washing reimparts all their vitality to the sjoores and thus totally 

 annuls the effect of the treatment. The seed is dried after immersion 

 or planted immediately after simple draining and whilst still moist. 

 Tubeuf and Neger have examined the disinfection of corn-seed in a 



