I 



THE COMMON MEALYBUG IN CALIFORNIA. H 



the mealybug by these natural enemies is often noted. For example, 

 one severely infested orchard was observed to be cleaned in less than 

 two months to an extent satisfactory in commercial control by two 

 species of predatory brown lacewing flies.^ Other groves have enjoyed 

 similar respite from mealybug injury through the activity of these 

 brown lacewings, aided by one or the other of two species of ladj^bird 

 beetles.^ Undeserved credit is often given to insecticides, in the case 

 of orchards that have contained these natural enemies in large num- 

 bers at the time of spraying or fumigation, while in fact the mealy- 

 bugs have been destroyed by these predatory enemies unobserved 

 by the orchardist or operator. The natural enemies are most effica- 

 cious during the autumn and early spring. 



RELATION OF ANTS TO NATURAL CONTROL. 



Since the meal^'bug is beset with so many efficient natural enemies, 

 it has been the cause of considerable wonder that the pest is not more 

 generally kept in check. The infestation may be reduced during 

 the autumn or spring to a point bordering on control or even eradi- 

 cation, yet it is a matter of common observation in some localities 

 that in spite of these conditions one severe infestation follows an- 

 other year after year. This failure of the natural enemies to hold 

 the mealybug in check throughout the year has been found to be due 

 mainly to the presence on the trees of large colonies of ants, the 

 Argentine ant ^ being the greatest offender. The experimental work 

 reported in this bulletin has been confined to the Argentine ant, 

 which has been observed to carry living mealybugs, to destroy and 

 carry off the larvae and eggs of natural enemies, to interfere with 

 the free movement about the tree of certain beneficial insects, and by 

 their constant attendance upon the mealybugs to prevent normal 

 egg laying and feeding of the adult parasites and predatory enemies. 



Remarkable results have been secured by keeping the Argentine 

 ant off of trees infested with mealybugs by banding with a sticky 

 mixture. In Los Angeles County during 1915 and 1916 trees that 

 when first freed from ants were infested severely with the mealybug 

 became commercially clean, without exception, within a period of six 

 weeks to three months. The mealybug remained under control 

 throughout the year or during the period of the experiments, while 

 trees in adjacent check rows only a few feet away continued to be 

 severely infested. The natural enemies responsible for this control 

 were the two brown lacewings and a ladybird beetle.* 



1 SympheroMus harherl Banks and Sympherobius californicus Banks. 



2 Either Hyperaspis lateralis Muls. or Cryptolacmus montronzieri Mills. 

 •'' Iridomyrmew humilis Mayr. 

 * Hyperaspis lateralis MhIs. 



