422 



Smith (H. S.)- The Argentine Ant as an Orchard Pest. — Mthly. Bull. 

 Col. State Commiss. Hortic, Sacramento, vi, no. 6, June 1917, 

 pp. 254-258, 3 figs. 



While the Argentine ant, Iridomyrmex humilis, has long been 

 recognised as an unrivalled household pest, it is only recently that 

 fruit-growers have realised the damage this insect indirectly causes 

 to the fruit industry owing to its influence on infestations of mealy- 

 bugs, black and soft brown scales. By protecting the mealy-bugs 

 from their natural enemies, such injurious pests as Pseudococcus citri, 

 which infests citrus and fig trees, and P. calceolariae, a pest of the 

 sugar-cane, are allowed to increase unchecked. Experiments carried 

 on for two years have demonstrated that if ants can be kept from 

 citrus trees the citrus mealy-bug is kept in complete subjection by its 

 natural enemies. The most successful methods of control as yet 

 devised against I. humilis consist of barriers which the ants cannot 

 cross, and poisoning. Tanglefoot, to which finely powdered sulphur 

 has been added in the proportion of one part sulphur to six parts 

 tanglefoot, is placed in a band about 5 inches w^de around the trunk 

 of the tree and is effective if properly mixed and kept in good condition. 

 The preparation of this barrier, and also of a corrosive sublimate band, 

 has already been described [see this Review, Ser. A, v, p. 105]. A more 

 promising method, although it is at present rather in the experimental 

 stage, is that of poisoning, using a poison which is so dilute that the 

 ants will carry it to their nests in large quantities as food for the queens 

 and larvae, which succumb to its effects in two or three weeks. A 

 strong poison is far less effective, as it would kill the workers before 

 they are able to reach the nest. The formula given for this poison is : 

 granulated sugar, 15 lb. ; water, 7 U.S. pints ; crystallised tartaric 

 acid, I oz. This, when boiled for 30 mins. and allowed to cool, forms 

 a syrup. A poison solution of sodium arsenite (C.P.) | oz., in 1 U.S. 

 pint hot water, is allowed to cool and then added to the syrup and well 

 stirred ; Ih lb. of honey is then stirred in. A good container for the 

 poison consists of pound or half-pound paper bags with flat bottoms 

 into the sides of which a few holes are punched. They are then dipped, 

 closed, in hot paraffin and opened before cooling. About 2 oz. of 

 syrup are placed in each bag, the top being then folded over and the 

 bag tacked to the trunk of the tree. In experimental plots where the 

 poison has been out for a month the ants are difficult to find on the 

 trees, while in untreated plots in the same orchards they occur in 

 enormous numbers. If at the end of the season the poisoning method 

 has proved an effective control of the ant, a general campaign should 

 be organised on these lines. 



Severin (H. H. p.). Dark Currant Fruit Fly in California {Rhagoletis 

 ribicola, Doane). — Mthly. Bull. Cal. State Conmiss. Hortic., Sacra- 

 mento, vi, no. 6, June 1917, pp. 258-260, 1 fig. 



A single specimen of this fly was captured in California in 1915 at 

 an altitude of 7,500 feet. It is of considerable economic importance 

 in Washington, where it is found about currant and gooseberry bushes 

 in June and July. Eggs are deposited beneath the peel of the berry 

 and the larvae upon hatching eat to the centre of the berry, '\^^len 

 mature, after three or four weeks, they bore their way out of the fruit 



