October, '13] FORBES: GASOLINE TORCH FOR SCALES 415 



THE GASOLINE TORCH TREATMENT OF DATE PALM 



SCALES 



By R. H. Forbes, Director, Arizona Experiment Station 



Date palms imported from the Old World into Arizona during the 

 past 23 years have been found generally infested with two scale insects, 

 Parlatoria hldnchardi and Phoenicococcus marlatti, commonly known as 

 the Parlatoria and the Marlatt scales. These two scales are very 

 highly specialized in their food habits, subsisting so far as j'et known 

 only upon the date palm. 



Parlatoria hlanchardi infests the outer parts of the tree, including 

 leaf stalks, foliage and fruit. Phoenicococcus marlatti, however, shuns 

 exposed situations and is found deeply buried between the over- 

 lapping bases of the leaf stalks, only rarely appearing where the in- 

 sects may be seen without digging into the tree. Occasionally, also, 

 the Marlatt scale may be found upon partially exposed date palm 

 roots. 



In devising a method for the extermination of Parlatoria hlanchardi 

 several years ago the writer, guided by his observation of the Mexican 

 practice of burning date palms to clear them of dead foliage, drenched 

 the trunks of a number of palms with gasoline and set fire to them. 

 The gasoline blast torch was afterwards found to be much more 

 effective, penetrating inward and downward into the spaces between 

 the leaf bases and thus reaching and exterminating the Parlatoria 

 scale. This method has been in use in the Salt River Valley for the 

 last eight years and this treatment, combined with judicious pruning 

 of the older foliage of infested palms, has been found to accomplish 

 the control of Parlatoria thoroughly and economically. 



The Marlatt scale, however, by reason of its deep seated location 

 in the date palm is not reached and exterminated by a treatment which 

 suffices for Parlatoria. However, by cutting the old leaf stubs of the 

 palm clear down to the bole of the tree, thus largely removing infesta- 

 tions of the Marlatt scale, and by then thoroughly burning the ex- 

 posed bole of the tree with the gasoline torch, this scale may be 

 entirely removed. 



The old Egyptian palms on the Experiment Station Farm near 

 Phoenix, Arizona, thus thoroughly pruned down to the boles and 

 burned in 1906, are found at this time (1913) to be entirely free from 

 Parlatoria and Marlatt scales. On the basis of these observations 

 the following treatment of infested date palms is recommended, and 

 has been adopted by the Arizona Commission of Agriculture and Horti- 

 culture: Destroy Parlatoria hlanchardi on infested date palms and 



