146 Journal of A<jiiculture, Victoria. [10 Makoh, 1919. 



solution. Gas generation quickly follows, and after a period of about 

 45 minutes the tent may be removed to the next tree to be treated. ^ 



The results of the action of the gas on the insects may be determined 

 in about seven days after its application. If the scales be violently 

 disarranged, numerous mummified recumbent forms will be revealed; 

 if eggs be present, they will have become discoloured and shrivelled. 



Mr. A. A. Hammond, Orchard Supervisor, in charge of the Don- 

 caster district, in his article on " Fumigation for the Destruction of 

 Scale Insects,"* gives interesting details, including fumigation tables, 

 &c. 



Mr. S. A. Cock, Orchard Supervisor, in charge of the Bendigo and 

 Northern district, in his " Citrus Culture in Victoria,"! deals with 

 hydrocyanic gas fumigation, and also gives dosage, tables, &c. 



The articles mentioned ai'e written mostly in connexion with citrus 

 fumigation, but the main principles governing this are similar to those 

 involved in the like treatment of deciduous trees. 



Apple Bark Scale (Mytilaspis -pomorum). 



These small mussel-shaped scales so much resemble the bark to 

 which they attach themselves that, except when present in great num- 

 bers, they are difficult to detect. This pest, which is confined mostly 

 to the cooler districts of the State, like the San Jose scale, was probably 

 introduced into this country on nursery trees. If spraying treatment 

 be neglected, the insects quickly increase in numbers, and become a 

 menace. This is evinced by the annual rapid multiplications of scales, 

 which in winter contain great numbers of eggs. The young hatch 

 out in spring and crawl over the bark until they find suitable parts on 

 which to settle. Then they commence sucking the juice of the tree, and 

 construct their protecting scales. The fruit is frequently made the 

 host of many, resulting from later incubation. 



While in the egg stage is also the best time to begin operations 

 against this pest, and by the use of crude petroleum emulsion 1 in 8. 

 or red oil 1 in 15, it may be quickly subdued. The eggs are produced 

 under the female scales during autumn, therefore the infested trees 

 should be sprayed as soon as the leaves drop, and again during winter 

 if necessary. When dealing with scale insects, the need for a second 

 or subsequent spray may be determined by ascertaining the condition 

 of the treated insects or eggs, as the case may be. An ordinary pocket 

 lens is employed in the examination, and, generally speaking, when the 

 eggs present a dry, shrivelled appearance, and the scales are easily 

 detached from the bark, the spray has been effective. The contents, 

 whether insects or eggs, of the scales on which the spray is effective 

 will, normal weather conditions prevailing, have dried up in about 

 fourteen days. Then the effectiveness of the spraying ordeal may be 

 calculated on the amount of moisture appearing on the surface of a given 

 area of scale-infested bark after the blade of a pocket knife has been 

 carefully pressed over it. 



Thrips (Thrips tohaci). 

 These comparatively long, tiny insects, although only large enough 

 to be visible to the naked eye, do, when the weather conditions favour 



• Journal of Agriculture, Victoria, Jnne, 1912. 



t Bulletin No 32 (new series). Department of Agriculture, Victoria. 



