Citrus Red Mite 



Finding a virus disease that kills the citrus red mite has been called 

 a break for pest control research, because it is the first evidence that 

 viruses can attack a member of the spidermite group. 



ARS scientists stationed at the USD A laboratory in Whittier, Calif., 

 discovered this disease in 1958, when they were studying the biology of 

 the citrus red mite and found that a strange infection was killing off labora- 

 tory specimens. They collected and observed citrus red mites from 

 southern California areas of the coast and interior, and some of these 

 lots were virtually wiped out by the same disease in the first brood and 

 several succeeding broods. 



Suspecting a virus, the pathologists ground up diseased mites, passed 

 the material through filter paper, and diluted the filtered substance to 

 make a spray. This spray on healthy mite colonies caused infection and 

 death in 7 to 18 days, and appeared lethal to all stages of the mites' life 

 cycle except the egg. A scientist at Cambridge, England, confirmed the 

 virus nature of the disease by studying diseased mites with an electron 

 microscope. Since discovery, the virus has been found in nature in scat- 

 tered citrus groves of southern California. 



In recent field tests in California, the method of applying the virus in 

 a spray has been compared with introducing infected live mites into tree 

 plots already mite -infested. This work is in preliminary stages. 



Much remains to be learned about the mite -killing virus and its agri- 

 cultural value. ARS scientists have developed improved methods of pro- 

 ducing the virus in materials suited to field experiments and have supplied 

 some to other researchers. 



Scientists are interested in testing this virus on additional species of 

 mites, because many of these pests have been developing resistance to 

 chemical miticides. If the virus does not prove versatile for mite control 

 uses, it has, in any case, alerted pest control workers to look out for other 

 viruses that may be doing protective work in mite-infested crops. 



LOOKING AHEAD 



Insect pathologists regard their scientific specialty as a young one, 

 but rapidly coming of age. In pest control work, they look forward to ad- 

 vances along lines indicated in this report. Finding ways to culture patho- 

 gens such as viruses, protozoa, and bacteria-carrying nematodes would be 

 particularly useful. 



There is prospect that the research will extend to new fields. For 

 example: 



Chemists and toxicologists can contribute notable assistance by deter- 

 mining the chemical properties of a toxic crystal, such as that produced 

 by Bacillus thuringiensis . More exact knowledge of such crystals would 

 go to the root of understanding the diseases, and could lead to short-cut 

 ways of applying crystals directly, and possibly to synthetic production. 



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