Vngc Eight 



BETTER FRUIT 



March, 1 922 



after Ic.irning of this evident failure. 

 After ftudying the composition of Spra- 

 Mulsion it seemed that it was not the right 

 type of miscible oil for leaf-roller control 

 and that possibly there might be other mis- 

 cible oils that would give better results. It 

 uas decided to find out by correspondence 

 with entomologists in states where the le.if- 

 roller had occurred just what brands had 

 given best results and then to try these out 

 under Montana conditions. The result of 

 correspondence led us to select Scalecide, 

 manufactured by the B. G. Pratt Company; 

 Dormoil, manufactured by the Hood River 

 Spray Company; and Universal Brand Dor- 

 mant Soluble Oil, manufactured by the 

 General Chemical Company. Of these 

 three, Scalecide seemed to be the most 

 highly recommended, but was also by far 

 the most expensive, largely because of the 

 high freight charges from the point of 

 manufacture in the east. 



Preliminary tests of these oils were con- 

 ducted during the \yinter months in order 

 that we might be able to advise the fruit 

 growers which to buy the following spring. 

 It was realized that this was not an ideal 

 time to conduct leaf-roller contact experi- 

 ments, but it was believed that that the oil 

 which would give the best results under 

 winter condition? would also give the best 

 results when used in the spring and this 

 later proved true. 



The tests were conducted at the Univer- 

 sity Heights orchard on December 1. Five 

 g.illons of each oil were used, "Dormoil" 

 and "Dormant Soluble Oil" being diluted 

 1 to 12^, and "Scalecide" 1 to 15. A 

 power outfit equipped with spray guns was 

 used. The trees were very carefully 

 sprayed and were completely drenched. 

 The weather at the time of spraying was 

 quite mild with a temperature of about 

 5n degrees at mid-day. Three weeks after 

 the trees were sprayed a quantity of 

 branches heavily infested with egg-masses 

 was cut from each tree and held in a warm 

 greenhouse until egg-hatching on unsprayed 

 check branches was complete. 



For comparison with the outdoor spray- 

 ing, infested branches from the same trees 

 were sprayed with a hand sprayer in a 

 warm greenhouse, where they were h^ld 

 until egg-hatching on unsprayed checks was 

 completed. The same oils and the same 

 dilutions were used as in the outdoor tests. 



In both tests hatching began in 28 days 

 after the branches were taken into the 

 greenhouse and continued over a period of 

 nearly three weeks. After hatching was 

 completed on the unsprayed branches each 

 egg-mass was examined and classed as 

 hatched if five or more individual eggs 

 were hatched. All counts were restricted 

 to egg-masses deposited during the season 

 of 1920, all old egg-masses having been 

 previously removed. The results are shown 

 in Table I. 



It will be seen from Table I that Dor- 

 moil was the most effective in both the 

 indoor and outdoor tests and it was, there- 

 fore, recommended to the fruit growers 

 for the season of 1921. 



Spring Spraying Experiments in 1921 

 — It was realized that the winter spraying 

 tests were conducted on a very small scale 

 and at a time when the best results perhaps 

 cculd not be expected. It was, therefore, 

 decided to conduct comparative tests of the 

 same materials on a larger scale in the 

 spring just before the eggs hatched. In 

 this experiment 50 gallon lots of Dormoil, 

 Scalecide and Universal Brand Dormant 

 Soluble Oil and Spra-Mulsion were used. 

 Dormoil and Universal Brand Dormant 

 Soluble Oil were used at the rate of 16 

 gallons of oil to 184 gallons of water, or 

 1 to 11.5. Scalecide was used at the 

 strength recommended by the manufac- 

 turer, 1 to 1 5, and also at 1 to 1 1.5 in order 

 to compare it directly with the others. Spra- 

 Mulsion was used at the rate of 22 gallons 

 to 178 gallons of water, or 1 to 8. 



Adjacent blocks of uniformly heavily 

 infested 1 5 -year-old trees were used for 

 the experiment. The first spraying was 



TABLE III— SHOWING AMOUNT OF DAMAGE TO FOLIAGE BY LEAF ROLLER LARVAE 

 ON PLOT SPRAYED W.ITH VARIOUS MISCIBLE OILS 



done on April 25, the weather on this date 

 being cool and cloudy, with a temperature 

 of 40 to 45 degrees during the greater part 

 of the day. About an inch of snow fell 

 duing the night, but this was blown off 

 the trees the next morning without wetting 

 the bark to any extent. 



13ECAUSE of the somewhat unfavor- 

 -'-' able weather conditions which fol- 

 lowed the first spraying, the tests were 

 repeated on additional unsprayed trees on 

 April 30. The weather on this date was 

 warm and bright as was also the day fol- 

 lowing. The second day after spraying 

 was cooler and there were light showers. 

 Spraying day on both dates was done with 

 power outfits, using spray guns and a pres- 

 sure of 250 to 300 pounds. 



The leaf-roller eggs at the time of the 

 spraying were well incubated and by care- 

 ful searching a larva could now and then 

 be found. The leaf buds were almost 

 breaking. The effectiveness of the various 

 sprays was judged by a careful examination 

 of 20 to 25 trees in each plot during the 

 last week in May. The percentage of 

 unhatched eggs and the number of leaf- 

 roller larvae present on the trees were the 

 factors upon which effectiveness was judged 

 at this examination. Any evidence of 

 spray injury was also noted. The results 

 of the two sprayings are given in Table II. 



During the second week in July, at 

 which time larval feeding was practically 

 over, the- various plots were .again carefully 

 examined with the object of determining 

 the amount of injury to the foliage which 

 the trees had suffered as a result of the feed- 

 ing of the leaf-roller larva:. All of the 

 sprayed trees had been almost completely 

 defoliated the previous year, thus prevent- 

 ing the formation of fruit buds and in 

 judging the amount of injury we were 

 confined entirely to the foliage. The 

 amount of injury in the various plots is 

 shown in Table III. 



The amount of foliage injury on all the 

 plots was less than would be expected on the 

 basis of the percentage of the eggs that 

 hatched and it is believed that the per- 

 centage of unhatched eggs cannot be taken 

 as the true percentage of control. There 

 seems to be a very high mortality among 

 newly hatched larva; from sprayed egg- 

 masses and It m.ay be that many larva; with- 

 in the egg-masses are almost killed by the 

 oil, but still have life enough to eat through 

 the egg shell and then perish shortly after 

 they emerge. 



Summary of Resui-ts — Dormoil, at th<~ 

 strength of 1 to 11.5, gave the best results 

 In both winter and spring spraying tests. 

 Practically no spray injury resulted from 

 the use of this oil at the above strength and 

 leaf-roller injury to the foliage was so 

 reduced that it was scarcely noticeable. A 



(Continited on page 21) 



