December, 1916. 



THE CANADIAN HORTICULTURIST 



287 



The Fruit Tree Leaf Roller in New York State' 



Glen W. Herrick, Professor of Economic Entomology, Cornell University, Ithaca, N.Y. 



BECAUSE of the proximity of 'the 

 principal fruit distriets of this 

 State to those of Ontario, Canada, 

 whatever is of interest in the way of 

 insect pests here is also of interesit to 

 Ontario entomologists and fruit grow- 

 ers. It was with this thoug-ht in mind 

 that the writer chose to discuss briell;,- 

 the fruit-tree leaf-roilJer in New York. 

 The leaf-roller is not an insect new 

 to this country. Since 1896, at least,, 

 it has been put among the enemies of 

 the apple in New York. It wias not, 

 however, until 1911 that the leaf-roller 

 began to attract particular attention 

 in this State. It furnishes a fine ex- 

 ample of an insect previously unimport- 

 ant which has suddenly and inexplic- 

 ably multiplied to an enormous degree 

 and reached the rank of a serious pest 

 at a single bound. During the sea.sons 

 of 1912, 1913, 1914, and 1915, it causeil 

 serious and widespread i'njury in West- 

 ern New York. During the i>ast sea- 

 son it was less in evidence, but no pre- 

 diction can be made regaixiing it, for 

 it nmy break out again at any favor- 

 able time. 



Habits and Injuries. 



The larvae appear as the buds are 

 bursting, and begin to attack the un- 

 folding leaves. They bend over and 

 tie them together with silk. Within 

 this nesit the larvae live and eat the 

 leaves. As soon as the blooms appear 

 the larvae begin to eat off the blossom 

 sitems and tie them together with silken 

 threads, ajtong with the leaves sur- 

 rounding the blossom cluster. This 

 webbing and tying together of the 

 'blossoan clusters is a most pernicious 

 haibit, beoause it interferes seriously 

 with spraying for the codling moth. 

 In one Baldwin orchai-d in w'hich the 

 larvae were very albundant, the blos- 

 som eluiiters were so webbed together 

 and covered over with silk, dried 

 pettals, and leaves that it was almost 

 impossible to get the spray mixture 

 into tihe callyx cup. 



As .socn as the youii'g apples begin to 

 set they are tied together with silk. 



• Extract from a paper read before the On- 



tnriii Kntomolotrical Society. 



while the larvae live inside and gnaw 

 cavities inlto the sides of the young 

 fruit. To give some idea of the num- 

 ber of larvae present, the writer count- 

 ed 17 worms in nine blossom clusters ; 

 Braucher counted 21 larvae on one 

 twig 21 inches long, and 19 larvae on 

 another twig 22 inches long. 



The larvae also work on the leaves, 

 mlling them Jiiul livint!' within the roll. 



The leaf-roller, natural size. 



Motli of tlie leaf-roller, much enlarged. 



Here, effectually hidden, they feed on 

 the tender tissues of the leaves. When 

 distui'tbed, they drop down out of their 

 hiding places and remain suspended by 

 silken threads like cankerworms. 

 When all is quiet, they climb back to 

 their hiding places and begin their 

 work again. Their injuries to the 

 leaves are often very serioiis, especi- 

 ally wlhen tlhe larvae are abundant. 

 Gillette says, "I have seen small ot- 

 chaixls entirely defoliated by this spe- 

 cies so that not a green leaf could be 

 seen." 



Life History. 



The eggs are deposited in greatest 

 numbers during the last of June and 

 the first part of July. They are laid 

 in small, oval, convex patches about as 

 large as the end of a lead pencil on the 

 bark of Hhe smaller twigs. Here they 

 remain until the following May or for 

 a period of about ten months. 



TIhe hatching period extends over 

 a.n interval of two to three weeks, al- 

 though the majority of the iairvae ap- 

 pear about the time the buds are burst- 

 ing. 



The full-grown larva is about one 

 inch in lengtJh, ligfht green in color, 

 with a black liead, and black thoracic 

 shield. lit takes from three to four 

 weeks for the larva to become full- 

 grown. It pupates in a flimsy web in 

 a rolled leaf and in about twelve days 

 the adult motths appear. These begin 

 to deposit their eggs, thus completiiig 

 the life cycle. 



Natural Enemies. 



The fraitJtree leaf-roller seems to 

 have a naim'ber of natural enemies. We 

 bred at least four species of hymenop- 



terous parasites from the larvae and 

 pupae in our cages. Gill has recoitled 

 several species of birds feeding on the 

 larvae and has also found a few insect.S' 

 wihich are predaceous on the leaf-roller. 

 Noitwithsitanding this rather large list 

 of enemies the leaf-roller has not been 

 held in check, but in spite of them has 

 increased enormously at certain 

 perio'ds. 



Methods of Control. 



The leaf-roller has been one of the 

 most difficult of lepidopterous apple 

 pests to control. Its habit of rolling 

 leaves, tying them together, and living 

 within these protectiv"e coverings 

 makes it difficult to get at. Attempts 

 were made to control the insect by 

 thoroughly spraying the infested trees 

 with arsenate of leatl and lime-sulphur 

 about the time the buds were bursting, 

 and aigain jiisit before the blossoms 

 opened, but t)he results were not satis- 

 factory. In this connection the work 

 of one of the better and more intelli- 

 gent fruit-growers in New York is of 

 interest. 



The large orchards of this fruit 

 grower were sprayed five times and 

 sprayed thoroughly and intelligently. 

 The orelhards were sprayed first, in the 

 dormant condition, just before the 

 buds burst, with lime-sulphur, 1 gallon 

 to 61/2 gallons of water with 1 pint of 

 iblackdeaf-40 to every 100 gallons for 

 the aphis. The second spraying was 

 made jusit before the blossoms opened 

 with lime-sulphur 1 to 50 and 3 pounds 

 of arsenate of lead. The third applica- 

 tion was made just as the petals had 

 fallen and ^consisted of lime-sulphur 1 

 to 50, arsenate oif lead 3 pounds and 

 bkack-leaf-40, % pint to 100 gallons. A 

 fourth spraying was made about 10 

 days to two weeks after the third with 

 lime^sullphur 1 to 50 and 3 pounds of 

 araenate of lead. At aibout this time 

 the owners became much worried over 

 the roller and sprajed a fifth time with 

 arsenaite of lead alone, 4 pounds to 50 

 gallons. In sipite of this extraordinary 

 amount of careful and thorough spray- 

 ing the trees and over crop under the 



Leaf rolled by the larvae. 



