119 



A more concentrated dose of the gas applied tor a shorter period is most 

 satisfactory in its results. In a Wardian Case, containing about sixteen 

 cubic feet, I find a dose of half ounce cyanide, half ounce acid, and one 

 ounce water with an exposure of half an hour will kill every inaividual 

 of a colonv of Orthezia (the most resistent of all Coccids^ without in 

 the least affecting the plants. The treatment should be carried out only 

 after sunset. According to Mr. Lounsbury's tables, these proportions 

 of chemicals should be sufficient for a space of 140 cubic feet with a 

 longer exposure. 



The other materials tested were (1) a preparation of concentrated 

 nicotine, sold by the XL-all company ; (2) Mchougall's fumigation 

 paper ; (3) Jeyes' fluid ; (4) naphthaline ; and (5) common tobacco 

 leaves. Nos. 1, 3, and 4 were evaporated by means of a small spirit 

 lamp inside the case ; Nos. 2 and 5 were lighted and allowed to smoul- 

 der. All these materials applied in different strength and for different 

 lengths of time, resulted similarly in more cr less complete injury to 

 the plants, and very incomplete destruction of the insects. 



If there be no Government quarantine establishment in the general 

 planting interests, importers should safeguard themselves individually 

 by properly disinfecting all foreign plants before distributing them or 

 putting them out in their gardens. 



Further directions for the application of the s gas treatment 5 will 

 be found in the [next Bulletin]. 



Perhaps of equal importance as a preventive measure is the main- 

 tenance of plants in a vigorous free-growing condition. This i« a fact 

 that has been recognised by gardeners for many generations. Any- 

 thing that interferes with the free flow of sap immediately lays a plant 

 open to attack from its insect enemies. A weakly, hide-bound plant 

 falls an easy prey to every pest. Scale insects in particular, with a few 

 exceptions (and such exceptions chiefly imported scales), seem to avoid 

 a free-growing plant, possibly finding the healthy rush of sap too strong 

 for them. Unremitting attention to cultivation will go far towards the 

 prevention of insect pests. Amongst causes predisposing to disease 

 may be mentioned : (1) Careless selection of plants and the retention 

 of weakly seedlings : (2j Insufficient or injudicious drainage ; (3) Un- 

 suitable condition of soil, want of tillage, and — perhaps — of fertilisers. 



Under the category of remedial measures may be mentioned the 

 use of resistant stock. In the history of nearly every extensive plant 

 disease it has been observed that individual plants — or established 

 varieties of the plant — may show a marked freedom from the disease 

 prevalent upon the less favoured type. By breeding from such indivi- 

 duals, or accidental varieties, a more or less completely resistant stock 

 may be established. This fortunate fact has been frequently used with 

 great success in dealing with fungal diseases. Thus a special variety 

 of the potato plant — proof against the well known potato disease — has 

 been extensively cultivated. Some varieties of wheat are found to 

 suffer but little from 4 wheat rust ' (Puccinia). We have also examples 

 of certain established strains of cultivated plants that repel particular 

 nsect pests. In Europe the vine growers have found an American stock 

 that to a larger extent resists the attack of the dreaded Phylloxera ; and 



