42 



seemed to be especially favorable for the multiplication of this mite; 

 it increased suddenly in enormous numbers during- the dry weather of 

 the early summer and was responsible for very considerable damage 

 to the foliage of the orange. 



The original food plant of this mite is unknown. It was first noted 

 on wild orange, from which it spread to other citrus trees. It is prob- 

 ably a native of Florida. 



Like its allies, this insect is greatly influenced by climatic conditions, 

 and needs for its excessive multiplication dry hot weather. Therefore, 

 in rainy seasons it is not especiall}^ troublesome, and it usually disap- 

 pears as soon as rainy weather sets in. In Florida its period of greatest 



destructiveness falls between February 

 and the middle of May. This mite 

 was carried to California a decade or 

 more ago with Florida stock, doubtless 

 at the same time that several other Flor- 

 ida citrus insects were transported to 

 the Pacific coast. In California, how- 

 ever, the principal mite injury seems to 

 be due to an allied species, also brought 

 from Florida, T. mytilaspidis.^'- 



The attacks of the six-spotted mite 

 are confined largely to the under sides 

 of the leaves, which are covered with a 

 fine web, beneath which the mite feeds. 

 The first indication of its presence is 

 usually a yellowing in streaks and spots 

 of the upper surface of the leaves. The 

 under surface becomes soiled by the 

 accumulated excrements in the form of 

 minute black spots and by the web of 

 the mite. On badly attacked trees the 

 foliage curls and shrivels and the trees 

 may lose half or more of their leaves, and similarl}'^ also a large per- 

 centage of the half-formed fruit. Being an accompaniment of drought 

 in Florida, part of the damage may undoubtedly be ascribed to the 

 eflfect of the dry weather. 



The remedies are the same as for the rust of silver mite. The bisul- 

 phide of lime is also an effective wash. It can be made very cheaply 

 by boiling together in a small quantity of water equal parts of lime 

 and sulphur. Five pounds of lime and 5 pounds of sulphur, dissolved 

 by boiling, should be diluted to make 100 gallons of spray. Gassing 

 !s ineffective. 



5^10.34. — Six-spotted mite of the orange 

 {Tetranychus sexmaculatus): a, dorsal 

 view of adult mite— vastly enlarged; 6, 

 greater enlargement of foot; c, d, mouth 

 parts (from " Insect Life"). 



«See Bui. 145, Cal. Agr. Expt. Sta., for detailed account of this species. 



172 ^ 



