MORE RESEARCH NEEDED 



Experience in Texas and Mexico has established a broad knowledge of 

 the pest and its habits. Research also has provided a partial means of pre- 

 venting spread in the form of a treatment for fruits to be shipped from quar- 

 antine zones. But we do not have exact knowledge of what damage the pest 

 can wreak under the mild climate of the western coastal region. 



Department scientists, in whose effort California has joined, are seek- 

 ing to answer the question of climatic influence. Research work was initi- 

 ated in August at Brownsville, Texas, in which bio-climatic cabinets are be- 

 ing used. These cabinets enable the scientist to duplicate temperature, hu- 

 midity, and possibly other factors of climates in various areas of California 

 and other parts of the United States. 



With the aid of the University of California, U.S. Department scientists 

 recently have developed a satisfactory artificial medium for rearing lar- 

 vae, and also techniques for obtaining large populations of flies from the re- 

 sulting puparia so that flies will be available for the studies conducted in the 

 cabinets, as well as for other research purposes. 



The effort to develop baits and lures more attractive to the fly has been 

 resumed. Improvements in this field would make it possible to detect exist- 

 ing infestations at earlier stages and thus aid in eradication. More attractive 

 baits also could make toxic sprays more effective. The baited spray used at 

 present--made up of 4 pounds of tartar emetic (the toxic agent) and 20 pounds 

 of refined sugar (the bait) in 100 gallons of water--is safe to handle by those 

 applying it. It does a fairly effective job. Emerging flies are attracted to the 

 foliage of the host trees where they feed on the honeydew and wild yeasts on 

 the under surfaces of the leaves for about 2 weeks until they reach the egg- 

 laying stage. As long as residual quantities of spray remain on the leaves 

 there is little chance of the flies surviving. Nevertheless, migrating flies 

 could lay a few eggs in the fruit even in trees that are sprayed regularly. 



Some of the newer insecticide formulations, which are much more toxic 

 to flies, show considerable promise for improved bait sprays. Preliminary 

 studies show that one of the phosphates, malathion, together with one or an- 

 other of the protein hydrolysates, is an effective spray. It attracts flies and 

 kills those that feed on it. Malathion is less hazardous to use than the more 

 toxic parathion, but, like any highly toxic material, it must be handled with 

 extreme care. Studies also have been conducted with several chlorinated hy- 

 drocarbons, but these materials have shown no marked improvement over the 

 tartar emetic spray now in use. 



The vapor-heat treatment of fruits grown in quarantine areas guarantees 

 no survival of the pest, and is adequate to prevent its spread. However, the 

 treatment is not always satisfactory to citrus growers. Some types offruit 

 other than citrus will not stand up after the vapor-heat treatment. Further 

 studies, particularly on fumigants such as ethylene dibromide, are continuing. 



