February, 1916. 



THE CANADIAN HORTICULTURIST 



K 



The Control of Fruit Insects, With Special Reference 



to Nova Scotia 



G. E. Sanders, Field Officer in Charge Dominion Entomological Laboratory, Annapolis Royal, N. S. 



THE day when entomologists and 

 plant pathologists laid down 

 rules for spraying, and the con- 

 trol of insects which they considered 

 applicable for a continent, is long past. 

 The more the life histories and habits 

 of insects and diseases are studied, the 

 less are experts inclined to recommend 

 treatments for districts outside those 

 in which they have conducted experi- 

 mental work or made careful observa- 

 tions. The making of blanket recom- 

 mendations, supposed to be applicable 

 to all conditions, has in the past been 

 a frequent source of embarrassment, 

 loss of confidence in experts and finan- 

 cial injury to the farmer or fruit 

 grower following such recommenda- 

 tions. 



To-day the expert knows that cli- 

 matic conditions may cause unequal 

 variations in the various periods of 

 plant growth, which in turn may react 

 in a different manner on each insect 

 feeding on that plant. The life his- 

 tories and habits of insects may vary 

 with, or as sometimes happens, with- 

 out any apparent change in weather 

 conditions. Again the varieties grown 

 in different localities are usually not 

 the same, and varietal susceptibility 

 is one of the things to be considered in 

 recommending treatments. The tend- 

 ency is now to have each insect or dis- 

 ease investigated locally, and local 

 recommendations made therefrom, by 

 this means effecting a saving to the 

 farmer or fruit grower, either in ma- 

 terial for treatment or in efficiencv of 



treatment, as well as gain in prestige 

 of the expert both as an individual 

 and as a class. 



The investigation of apple insects in 

 Nova Scotia during the past four years 

 has demonstrated the value of the 

 ptudy of local insects under local con- 

 ditions in a striking manner. 



First, in regard to the growth of the 

 apple tree, in relation to the budmoths, 

 which ai'e the most destructive Insect.s 

 attacking the apple in Nova Scotia: 

 in 1915, a period of twenty-four days 

 elapsed between the time the first 

 Gravenstein buds began to show green 

 until they were out in full bloom, or 

 from May 11 to June 4. The bloom in 

 Gravensteins lasted six days, or from 

 June 4 to June 9 inclusive. The period 

 of emergence of budmoth larvae from 

 their winter quarters covered a period 

 of fifteen days, or from May 9 to May 

 23 inclusive. 



Tt is not an unusual occurrence in 

 Nova Scotia for the buds to start and 

 the leaves to become, say, one-half inch 

 across, and then a period of cold or 

 rainy weather set in and hold the 

 trees in practically the same condition 

 for a week or ten days, insect life dur- 

 ing such a period not being retarded to 

 the same extent as the trees. A study 

 of these dates easily accounts for the 

 budmoth reducing the set in blossom 

 clusters infested, by seventy-five to 

 eighty per cent, in Nova Scotian or- 

 chards. They also show the futility 

 of depending on a spray applied just 

 when the buds are beginning to show 



Jt* 



A dust sprayer at work 



;i X'jw York aiatu t rchard. This form of sjjray lias been elvlng 

 unusually Kood results across the border. 



green at the tips to control budmoth. 



In order to control budmoth we must 

 find a means of getting poison to it 

 after the bud has opened, and when 

 some of the budmoths have drawn a 

 cluster of partly eaten leaves about 

 themselves. In this regard the Friend 

 Drive Nozzle has proved our salva- 

 tion. It has, in every case where it has 

 been used, given greater control of 

 budmoth than the mistry, whirlpool 

 and calyx nozzles, against which it was 

 tested ; and where used twice before 

 the blossoms in 1915, the first time on 

 May 15 and the next on May 31, with 

 of course two applications after the 

 blossoms, gave us the greatest control 

 of budmoth we have ever obtained, 

 namely ninety-two per cent, of the 

 larvae, which would normally become 

 adults, killed. The poison used in this 

 case was paste lead arsenate. The 

 value of this nozzle in budmoth con- 

 trol lies in the high nozzle velocity of 

 the spray, which when it strikes the 

 clusters of leaves gathered together by 

 the budmoth, does not settle on the 

 .outside without wetting the inside as 

 the fog and mist sprays do, but drives 

 in through the chinks and crevices of 

 the cluster of leaves, thoroughly coat- 

 ing t/he inside of the cluster -with 

 poison. 



The biting insects ranking next in 

 importance in Nova Scotian orchards 

 are the fruit worms, of which there 

 are upwards of a dozen species, the 

 most common being Xylina bethunei. 

 We have found that the life histories 

 of the various species are very similar; 

 the eggs, which are mostly deposited 

 singly on the twigs of the apple, begin 

 to hatch just when the Gravenstein 

 buds begin to show pink, but owing to 

 the cool springs of Nova Scotia the 

 period of emergence is long drawn out, 

 the la.st of them hatching one month 

 later. During the first two weeks of 

 their existence as larvae, they feed on 

 leaves and blossoms, later feeding 

 mostly on the young fruit. When feed- 

 ing on fruit they are very hard to 

 poison as they eat so little surface for 

 a meal. The control of fruit worms 

 lies in having the leaves coated with 

 poison during its period of emergence, 

 or by applying poison in a spray when 

 the buds are showing pink, and in an- 

 other immediately after the blossoms. 

 These two sprays will give on an aver- 

 age sixty-five per cent, reduction in in- 

 jury to the picked fruit. 



In 1915 it was thought that on ac- 

 count of the tendency in the larvae of 

 the fruit worm to drop to ground when 

 disturbed, that the mechanical effect 

 of the drive nozzle in disturbing the 

 leaves might increase control to a cer- 

 tain extent. To prove out this point, 

 two plots were sprayed with water, one 

 with the drive and one with a mist 

 nozzle and twt) left unsprayed. Where 



