December, '19] ROBINSON: LIME IN LIME SULFUR 429 



The number of parasitized individuals averaged 50 per cent. There 

 were two species of parasites which were from the larvae and pupae. These 

 were determined for me by Mr. H. S. Smith as a (Chalcidoidea) Tet- 

 rastichus sp. and a (Braconid) Calyptus sp. The primary parasite was 

 not determined and it is possible one is a hyperparasite. The writer also 

 found quite a number of larvae of some Coleopterous insect which re- 

 sembled a Dermestid. 



Explanation of Plate 18 



Fig. 1, the adult weevil. 



Fig. 2, the pupa. 



Fig. 3, the larva or grub. 



Fig. 4, section of apple limb with bark removed showing channels of larva; and 

 pupal cells. 



Fig. 5, section of bark removed from limb showing channels of larvie and pupal 

 cells. 



Fig. 6, section of bark showing egg punctures or cavities where eggs are laid and 

 the emergence holes of the adults. 



THE BENEFICIAL ACTION OF LIME IN LIME SULFUR AND 

 LEAD ARSENATE COMBINATION SPRAY 



By R. H. Robinson, Associate Chemist, Oregon Experiment Station, Corvallis, Ore. 



It is a prevalent custom among horticulturists throughout the country 

 to use combination sprays, that is, mix two spray materials and make the 

 application as a unit whereby the extra expense of making two separate 

 spra}dngs is saved. If, however, two sprays are so combined that a 

 chemical reaction occurs in which their peculiar insecticidal or fungicidal 

 properties are destroyed or some product of the reaction is formed, that 

 would cause burning of foliage or other injury, the practice in that case 

 should be discouraged. It is probable that where combination sprays 

 have given unfavorable or even harmful results and the cause attributed 

 to poor quality of original materials used, that the actual reason may be 

 due to products formed following chemical reaction between the two 

 sprays combined, when the insecticidal properties are thus destroyed. 

 In many such instances the deleterious action might be partially or en- 

 tirely prevented by the addition of some inert substance that would 

 retard chemical changes. 



We have, ])y mixing hme sulfur and lead arsenate, one of the most im- 

 portant combination sprays now generally employed. It is plainly evi- 

 dent that both of these sprays immediately begin to ciiange in apjicarance 

 and a dark prccijntatc settles out after they are mixed. Owing to the 

 chemical action that occure in which the insecticiilal properties of this 

 combination spray is dostroyod to a certain extent, means of overcoming 



