Aug. 2, 1920.] Agricultural Gazette of N.S.W. 579 



The blisters on the infested leaves are due to the presence of numbers of 

 tiny microscopic elongate cylindrical mites, which, wintering in the bark or 

 bracts of the leaf buds, crawl out on the expanding leaves and puncture 

 them as the leaf reaches maturity. The colonies of mites congregated in the 

 blisters cause the aborted tissue to turn yellow or brown. These mites are 

 white, and very similar in general form to those that blister pear leaves. 

 They have only two pair> of legs, and these are situated close behind the 

 head. The mites are so small that only with the aid of a good lens can one 

 observe their movements. In the earlier stages of the gall development 

 they are very difficult to make out ; but, as the leaves and galls mature in 

 March and April, the mites emerge from the mass of deformed hairs filling 

 the blister, and can be easily noted under the microscope. 



Essig says : " Sulphuring the vines early in the spring, soon after the buds 

 open, as is ordinarily applied for mildew, is usually sufficient to hold the 

 mite in complete subjection." Spraying with kerosene emulsion as recom- 

 mended by Slingerland and the burning of all vine cuttings from infested 

 vines would also be effective. 



The Silver or Orange Rust Mite. {Pkyllocoptes oleivorus, Ashmead). 



This mite is a native of Florida, where it lived originally upon the wild 

 citrus trees of the forests ; it was described by Ashmead and included in 

 Hubbard's " Insects affecting the Orange." It was accidentally introduced 

 into California with nursery stock, and though it has not spread much from 

 the original area in which it was first discovered, it is found, according to 

 Higgins, in the Hawaiian Islands. The writer saw oranges and grape-fruit 

 deeply discoloured by its presence in the citrus orchards of Cuba and 

 Jamaica, 



This mite takes the first of its popular names from the curious silvery sheen 

 on the skin of the infested lemons before they ripen ; this, later on, gives 

 place to a network of cracks all over the rind as it hardens. When the rind 

 of the orange is attacked it assumes a russet tint ; this discolouration of the 

 skin (due to the presence of the tiny mites embedded in the surface) is 

 identical with that known in Australia as " Maori disease " of oranges, 



Olliff discovered the mite upon oranges from an orchard at Emu Plains in 

 1891. He identified it with the orange pest described by Hubbard, and 

 noted in the pages of this journal its presence in Australia. Under the 

 heading of " Orange Rust Mite or ' Maori ' " he reported in the following 

 season (Gazette, vol. ii, page 671), the successful application of sulphur and 

 soap wash at the infested orchard. This is one of the smallest mites, 

 and is very difficult to separate from the tissue of the skin of the fruit. 

 Though 01liff"s identi6cation is doubtless correct, the writer finds it difficult 

 to believe he found the mites in the discoloured orange skin. Hubbard, 

 however, states that he collected them in large numbers when they were away 

 from the fruits resting on the leaves. 



Though infestation by this mite is still often noticed in our orchards, it 

 does not seem to be a very serious citrus pest in Australia. 



