February io, 1897.] 



Garden and Forest. 



59 



horticulturists and economic entomologists could mutually 

 aid each other in studying the habits of injurious insects. 

 After a brief sketch of economical entomology in this country, 

 which began practically with Dr. Harris' famous treatise, pub- 

 lished in 1 S41, science has made great advances. But there 

 are many things to learn. Even when we have discovered the 

 proper remedies, there is sometimes uncertainty as to when 

 and how they should be applied. Besides this, there is more 

 than one fraudulent remedy on the market, as, for example, 

 the inoculation humbug, which claims to render a tree safe 

 from the attacks of many insects by a compound to be in- 

 serted in a hole bored into its trunk. Last year thousands 

 of pounds of the American Soil Renewer and Insecticide were 

 sold in Minnesota under a guarantee that it would kill every 

 chinch bug on a field where it was sown, and so impregnate 

 the soil that the insect would never again invade it. Chemists 

 showed that the compound consisted of salt, land plaster and 

 a little hellebore. The experiment stations have shown, too, 

 that a patent Potato Bug Exterminator is entirely worthless, 

 and that some really good insecticides are badly adulterated, 

 so that the practical fruit grower must be alert to keep 

 up with the latest investigations. We are learning some- 

 thing about it every day. For example, the arsenate of 

 lead brought out by the Gypsy Moth Commission in Massa- 

 chusetts as Gypsine is a promising remedy, so is an arsenite 

 of copper known as Shields' Green and the arsenite of 

 lead. Whale-oil soap seems to be destined to come into 

 general use as an effective remedy for the dreaded San Jose' 

 scale, and with the improved machinery worked by horse 

 power or steam engines there is every promise that it will be 

 possible to wage more successful war against the insect 

 enemies of crops in the future than has ever been waged in 

 the past. Those who know most about insects and their 

 methods of life will be most successful in destroying, and we 

 have much to learn of the habits of our most common ones. 

 We do not know, for example, how long the June bug lives as 

 a white grub, nor the click beetle as a wireworm. We do not 

 know where or when the click beetle lays her eggs, and no 

 one has yet reared a June bug or a click beetle from the egg 

 to the adult insect. Mr. Slingerland has been making a 

 special study of the apple worm, or codling moth, and he 

 seems to have thrown light upon some portion of the life and 

 habits of this insect which have hitherto been obscure. It has 

 been known that a spraying of Paris green, if applied to Apple- 

 trees just after the blossoms fall, will kill the caterpillars ; but 

 the explanation as to how this poison killed the worm has 

 been obscure, since no one seems to have made any definite 

 observation of the eggs and the newly hatched caterpillars. 

 The text-books say that "the moth lays its eggs singly in the 

 maturing blossoms of the apple just as the petals fall. As soon 

 as the caterpillar hatches it burrows into the apple." All 

 writers tell glibly where this egg is laid, but only one, so far as 

 Mr. Slingerland knows, has ever seen the egg, and this is 

 remarkable, since the literature of the codling moth began 170 

 years ago and is as voluminous as that of any other injurious 

 insect. Nevertheless, a bulletin of the Oregon Experiment 

 Station published in 1893 contains the first and only pic- 

 ture of the egg yet published. The author of this bulletin, 

 Mr. Washburn, thought that these eggs were laid any- 

 where it happened on the skin of the fruit, and they were 

 laid somewhat later than was supposed. Later writers have 

 overlooked these important observations, and Mr. Wash- 

 burn himself did not watch the young caterpillar after 

 emerging from the egg, and thus left it uncertain as to how he 

 gets his deadly dose of Paris green. Mr. Slingerland has found 

 that the greater part of the eggs are not laid until about a week 

 after the blossoms have fallen and when the apples are as big 

 as hickory nuts. The calyx lobes on the young fruit are by 

 this time drawn tightly together, so that it would be a hard 

 matter for the moth to insert her egg in the cup. In fact, the 

 ovipositor is only adapted to laying eggs on the surface of the 

 fruit. These round, thin, scale-like, translucent eggs, not quite 

 as big as a pin-head, are glued to the apple skin, with little 

 choice as to their location on the fruit. It is a week before 

 they hatch, and therefore it is ten days or two weeks after the 

 blossoms fall before the caterpillar begins operations. Now, 

 if the usual advice for spraying has been followed, the first 

 spraying is made a week before the eggs are laid, and the 

 second some days before the worms appear. How then does 

 the poison kill the worm ? A study of the growing fruit shows 

 that when the petals fall the remaining calyx lobes are broadly 

 spread out like a saucer and manv minute particles of Paris 

 green are caught in it, but as two weeks must intervene 

 before the little caterpillar begins to eat, much of the poison 

 would be washed out by rain and the first spraying would be 



useless. Nature prevents this, however, by tightening up the 

 calyx lobes at their tips as the apple grows, so that within a 

 week after the blossoms fall the cup has its deadly dose pro- 

 tected by a cover formed of these converging lobes. How 

 then does the worm, when he begins to eat a week or more 

 later, get hold of the poison ? Professor Slingerland watched 

 one of the little creatures as he came out of his egg and wan- 

 dered over the surface of the apple for two or three hours, 

 eating nothing, but simply exploring until it had worked its 

 little body through between two of these calyx lobes and 

 disappeared within the cup. Future field work confirmed this 

 observation and showed that the worms fed about the cup for 

 a day or more before they go deeper into the fruit. Apples 

 were picked from a tree which had been sprayed just after the 

 petals fell, and an analysis showed that there was arsenic in the 

 covered cup of the calyx. As eight-tenths of the first brood 

 of worms begin feeding in the manner described it is believed 

 that this first spraying just after the blossoms have fallen is of 

 the utmost importance and will kill more caterpillars than 

 several later applications. 



After detailing this bit of investigation and discovery, Pro- 

 fessor Slingerland had something to say about the Peach- 

 borer, showing that washes were comparative failures, and 

 that dendrolene, though it gave some promise as a preventive, 

 should be carefully used. He hopes that there will be some 

 easier method found of combating the borer than by digging 

 it out, but as yet this is the surest and most practicable remedy 

 to be commended. A thorough digging in the latter part of 

 June, when the worms are three-fourths grown, would be 

 more effective than a spring and fall examination together. 



Recent Publications. 



Vegetable Gardening. By Samuel B. Green, Professor of 

 Agriculture in the University of Minnesota. Webb Pub- 

 lishing Co., St. Paul. 



This is a compact little manual of 225 pages which was 

 prepared originally for use in the School of Agriculture 

 connected with the University of Minnesota, and it treats 

 of the growing of vegetables both for home use and for 

 market. It was written for the latitude of southern Min- 

 nesota, but a little judgment will enable any one to adapt 

 its directions to locations farther south and north. About 

 half the book is taken up with the usual description of the 

 various plants cultivated in kitchen gardens, together with 

 good instructions for raising them. Like most other man- 

 uals, it could be improved by the statement of some general 

 principles as the basis of special treatment, so that the cul- 

 tural directions would have rather less of the wooden "rule 

 of thumb " quality. A handbook would have more vitality 

 and its teachings would impress themselves more strongly 

 upon students if it contained such data, with the deductions 

 from them as were presented, for example, in an article on 

 Tomatoes, by Professor Tracy, in the last volume of this 

 journal (vol. ix., p. 37). When an intelligent reader once appre- 

 hends that the constitution and habit of the Tomato clearly 

 make it necessary to surround the plant constantly with 

 certain conditions, he will never forget the details essential 

 to its most profitable cultivation. Similar considerations 

 drawn from a study of the development and character of 

 other garden plants could be stated with great advantage, 

 so as to offer readers for their contemplation and study 

 some of the fundamental reasons for the different methods 

 of treating different crops. Directions given to be mem- 

 orized are easily forgotten ; principles once learned are a 

 possession forever. 



The rules for cultural practice, however, are all trust- 

 worthy, and embody results of the latest studies at the 

 Agricultural Experiment Stations and elsewhere. Besides 

 these the book offers a good practical chapter on injurious 

 insects and the methods of righting them, some excellent 

 notes on glass structures, a compact treatise on tillage and 

 fertilizing, with tables of composition giving the amount of 

 food elements required by different crops, the amount of 

 these elements contained in various farm manures and 

 commercial fertilizers, and much other useful matter written 

 in a straightforward, sensible way. It is helpfully illustrated 

 and has a fairly good index, but no table of contents. 



