37 



owners of adjacent olive groves should work together, the careful 

 spraying of one grove in the midst of a number of unsprayed ones being 

 held to be labour more or less thrown away ; it has, however, been 

 shown that this is not altogether the case, but that treatment, even 

 of a non-isolated, small olive grove, would reduce the infestation by 

 40-50 per cent. Experiments were made in 1912 with the poisoned 

 bait spray on 10,000 trees in isolated plantations, the formula used 

 being 2| lb. sodium arsenite and 33 lb. of molasses in 22 gallons of 

 water, at a cost of about a halfpenny per tree. The results were most 

 satisfactory, a reduction of from 60-80 per cent, or more in the in- 

 festation being effected, though there is no doubt that the complete 

 isolation of the groves was an important contributory factor ; but the 

 commercial value of spraying is undoubted, as the weight of sprayed 

 olives required to yield a given quantity of oil is three as against five 

 of unsprayed ones. Careful analysis has shown that there is no fear 

 of the oil containing appreciable quantities of arsenic, the only dis- 

 advantage being, that if the spray contains less than 30 per cent, of 

 sugar it is apt to promote the growth of certain fungi. The dry method 

 has the advantage of abohshing spraying and thus warding off danger 

 from fungi ; the cost is reduced, the unfavourable action of rain is 

 overcome and the difficulty of procuring water in certain regions, 

 such as Southern Italy, is met. Various devices have been adopted, 

 such as bottles containing the mixture and provided with cotton 

 wicks along which it drips, or small canvas bags filled with bran 

 and sawdust soaked in poisoned molasses, 8 parts bran, 21 sawdust, 

 and 71 molasses by weight. The results from the use of these poison 

 bags in an isolated plantation of 620 trees, though showing a great 

 diminution of infestation, were not so good as those obtained by spray- 

 ing in the two preceding years, and in a non-isolated grove of 675 trees 

 the results were little or nothing. Pans of poisoned molasses with 

 pieces of rag floating in them, to afford a resting place for the insects, 

 were tried by Chapelle and Ruby at the rate of 1 pan to 40 trees, but 

 the method was found to have no practical value. 



The mixed treatment consists of a combination of spraying and 

 the bag method (1 bag to 5 trees) the object being to reduce the number 

 of sprayings and keep down the labour bill. The results were only 

 fairly good and not satisfactory in all cases. Poisoned bait is not so 

 effective in olive groves containing cultivated shrubs or situated near 

 woods, as the fly can obtain shelter and food from other plants. The 

 maximum effect is obtained when the grove is isolated and free from 

 all other vegetation. The omission of the treatment in the plantation 

 experimented upon for one year caused an increase of infestation 

 from 22 to 81 per cent. The treatment was therefore clearly of value. 



While working on the control of the Mexican or Morelos orange 

 worm, Betan25os discovered the usefulness of a common poisonous 

 Mexican herb {Haplophyton cimicidum). Two pounds of the herb, 

 cut fine, were thoroughly boiled in three gallons of water, 2 pounds of 

 sugar added, and the whole decoction was then strained and used as a 

 spray. Rangel obtained very satisfactory results from the use of this 

 preparation in combating the Mexican fruit-fly {Anastrepha ludens, 

 Loew). 



O'Kane used a mixture of arsenic, molasses and water to control 

 the apple maggot, Rhagoletis pomonella, Walsh, in New Hampshire, 



