-5- 



mant application of a lubricating oil spr^^ dili^ted to contain Z% or more 

 actual oil. In the past, dormant or delayed/applications of oil sprays 

 were made quite regularly, especially in orchards where the European red 

 mite was troublesome. In recent years, oil sprays have been omitted more 

 and more frequently, and the remarkable effectiveness of the summer type 

 of DN sprays and dusts in controlling red mite during the growing season 

 has encouraged this practice. 



Liquid lime sulfur, even at the summer dilution 1-50, killed many 

 young scales especially when applied at the time the young were hatching, 

 as frequently happened when it was used in a complete scab schedule, letta- 

 ble sulfur and sulfur dust are much less effective and kill many of the 

 predators smd parasites. 



Outbreaks of San Jose scale in Massachusetts have been sporadic and 

 we may expect that the present infestation v/ill be temporary, but it behooves 

 every fruit grower to nip the current outbreak in the bud by applying a dor- 

 mant or delayed dormant spray containing 2 or 3^o actual oil in 1945. 



— W. D. Vrtiitcomb 



YCIY "FRESHLY" HYDRATED LIME FOR SPRAYING P URPOSES? 



During our meetings with fruit growers, the question is frequently 

 asked, "T/hat is freshly hydrated lime?" or "How long can I keep spray lime 

 and still use it with safety?" To answer these questions, let us first 

 understand how spray limes are made and what changes they undergo when al- 

 lowed to stand for some time afterward. 



Manufacturers take from the quarry limestone . If agricultural lime 

 or limestone is desired for applying to the soil, they merely grind it up 

 finely. Chemically, limestone is Calcium Carbonate . If, instead, hydrated 

 lime is sought for spraying purposes, they take .the unground limestone and 

 burn it. This process drives off carbon dioxide and leaves just Calcium 

 Oxide, also known as "burnt lime," "hot lime," or "stone lime." This form 

 of lime has a great affinity for water. 



The manufacturers add water slowly to stone lime, thus slaking it. 

 It takes up the vmter cheraically and is then known as slaked lime or hydrated 

 lime. Chemically, it is Calcium Hydroxide or Calcium Hydrate. It is this 

 form of lime, and this one only, that functions in the spray tank to counter- 

 act arsenical injury and to slow up the undesirable chemical reaction be't\'.'een 

 lime-sulfur and lead arsenate. It has the property of remaining well in (Sus- 

 pension, and it is partially soluble, both of which contribute to its 

 "safening" value. 



Just as stone lime (Calcium Oxide) has a strong attraction for water, 

 so has hydrated lime a great affinity for carbon dioxide. Just as soon as 

 hydrated lime is exposed to the air, it begins to absorb carbon dioxide from 

 the atmosphere. In doing so, it is changed from Calcium Hj'droxide to Calcium 

 Carbonate. In other words, the spray lime undergoes carbonation and thus 

 eventually changes back to the original carbonate-rock or limestone which 

 was taken from the quarry at the outset. 



