246 ANNUAL EEPOETS^OF DEPARTMENT OF AGRICULTURE. 



being general!}^ recognized as practicable and efficient methods of 

 handling infested orchards. This is particularly true in reference 

 to the so-called citrophilus mealybug. The study of this insect was 

 begun during the year in response to a petition from citrus associa- 

 tions and fruit exchanges in western San Bernardino County, where 

 considerable alarm had been aroused b}'^ the rapid spread and great 

 damage done by this scale insect. The citrophilus mealybug is a 

 comparatively new pest, which started with an invasion of a few trees 

 in 1015, but now covers an area of about 1,000 acres. A 20-acre 

 demonstration plot has been freed from this mealybug by the com- 

 bined procedure of control of the Argentine ant, spraying the trunks 

 of the trees, and utilization of predatory natural enemies. 



The important relationship of the Argentine ant to infestation by 

 mealybugs in southern California has necessitated as a first step 

 the control of this ant. This is accomplished by the use of poisoned 

 ant sirup. This method of control has already been extended to 

 upwards of 200 acres in this district, and a great expansion of this 

 work is now in progress. 



The hydrocj^anic-acid gas investigations in southern California 

 have been continued more particularly with relation to the use of 

 liquid hydrocyanic acid — a method which on account of its conven- 

 ience and efficiency bids fair to supplant the okler methods of gener- 

 ating gas by a combination of the necessary chemicals at the moment 

 of use. The most economical method of production of this liquefied 

 gas is being worked out, together with field experiments to determine 

 the best methods of use and to eliminate the risk of accidental poison- 

 ing of workmen. A Farmers' Bulletin (No. 923) has been issued, 

 bringing down to date the standard method of fumigation hitherto 

 used and giving full instructions for such fumigation. 



Citrus-fruit insects in Florida. — The work of this department in 

 the control of citrus insects has taken the form in Florida of regional 

 orchard demon'^tration and is coordinated with the extension work 

 in this State. During the year two bulletins in relation to this work 

 have been published. One (Department Bulletin 645) is entitled 

 " Some Reasons for Spraying to Control Insect and Mite Enemies of 

 Citrus Trees in Florida," and the other is a Farmers' Bulletin (No. 

 933) giving specific directions for spraying for the control of such 

 insects. 



Control of the fluted scale in new Orleans.- — This project was 

 completed during the year and was discontinued June 30. It was an 

 enterprise conducted by the city of New Orleans, the State of 

 Louisiana, and this department in cooperation. The control of the 

 fluted scale has been accomplished in New Orleans and neighboring 

 places by the propagation and liberation of thousands of the natural 

 enemy of this scale insect, the Australian ladybird, Novius cardinalis. 

 Over 300 colonies of these ladybirds were liberated over an area' of 

 40 square miles. The distribution of this beneficial ladybird has 

 been extended to the known outlying infestations of the fluted scale 

 in Louisiana, Mississippi, and Texas. In connection with this work 

 some very interesting studies have been made of the fluted scale, its 

 ladybird enemy, and particularly the symbiotic relationship between 

 the fluted scale and the Argentine ant. The results of this work 

 demonstrated that this ant by protecting the fluted scale from its 



