1897 
THE RURAL NEW-YORKER 
389 
At this writing (May 24) it is a sight to behold ; looks 
as though every seed, both clover and oats, had grown. 
I shall cut the oats, in the milk, for hay, and expect 
to cut a fine late crop of clover this year. In the fall, 
1898, I shall set the land to apple and peach trees. 
Uallipolis, Ohio. f. m b. 
Life and Work of the Pear Slug. 
II. T. L., Brighton, Canada .—Last year, my pear orchard was 
attacked by a little green worm about five eighths of an inch in 
length. It ate all of the leaves on some of the branches, leaving 
only the skeleton, or frame, remaining. It worked most on the 
Lawrence, but some on the Clapp. It commenced to work, I think, 
in June, and continued to work until we had a very heavy rain 
for two or tnree days, after which it did not work so badly. 
ANSWERED BY M. Y. SLINGERLAND. 
The insect described by H. T. L., is the one com¬ 
monly known as the pear slug. It was especially 
numerous and did great damage in western New York 
and Canada last year. The adult insect is a small, 
four-winged fly about the size of a house fly, with 
black body and yellow legs. It closely resembles the 
adult of the well-known currant worms. As the 
females have a saw-like appendage at the end of the 
body with which they cut slits in the leaves in which 
they lay their eggs, they are known as saw-flies. 
These flies may be seen early in June sawing little 
semicircular slits through the skin of either the upper 
or under sides of the leaves of pear, cherry, quince or 
plum. A single egg is placed in each slit. In about a 
fortnight, these eggs hatch out small, white larv®. 
Soon a slimy matter oozes out of the skin and covers 
the upper part of the body with an olive-colored, 
sticky coating. This slimy appearance of their bodies 
reminds one of a snail or slug, hence arose the popu¬ 
lar name of pear slug for the larval stage of this pest. 
After shedding its skin four times, the slug attains 
a length of about one-half inch, and is then full 
grown. Several slugs of various sizes are shown at 
work in Fig. 170. They are disgusting looking crea¬ 
tures, with the slimy, greenish-black skins, with the 
head end of the body so swollen as to resemble some¬ 
what a tad-pole in form, and having a disagreeable 
sickening odor. The small, reddish head is almost 
entirely concealed under the front segments of the 
body. Each slug has 20 pairs of very short legs on 
the underside of its body. The last time it sheds its 
skin, it loses its slimy appearance and dark color, and 
appears in a clean, yellow skin free from slime ; it is 
also somewhat longer. After this change, it does no 
more feeding, but soon crawls or drops to the ground, 
where it buries itself to a depth of from one to four 
inches. By wriggling its body, it there forms an 
oval earthen cell, which it afterwards lines with a 
sticky, glossy substance, which makes it retain its 
shape. Within this little cell, the slug soon changes 
to a tender pupa, and in about two weeks after it left 
the tree as a yellow slug, the four-winged fly is devel¬ 
oped, breaks open the cell, crawls to the surface of 
the soil, and is soon ready to lay eggs for a second 
brood. 
About the latter part of July, the flies are actively 
engaged in depositing eggs for a second brood, the 
young slugs appearing early in August. They reach 
maturity in about four weeks, then retire under 
ground, change to pup®, and remain in that condition 
until the following spring. The flies which may be 
seen at work in early June, come from these hiber¬ 
nating pup®. 
Fig. 170 illustrates the way in which these curious 
slugs eat one skin and inner soft tissues of the leaves, 
leaving all the little veinlets and one skin uneaten, 
thus skeletonizing the foliage. The leaves, deprived 
of their substance, wither as if scorched by fire, and 
soon afterwards drop from the trees. In traveling 
through western New York last year, I saw thousands 
of trees in orchards, and even in dooryards, with 
scarcely an unskeletonized leaf on them. There is 
no occasion for such destruction being wrought by 
this slug on fruit trees, if the growers will only be 
on the lookout for the pest in June, or even as late as 
August, when the second brood is at work. Prompt 
work, however, in June, will kill so many of the first 
brood of slugs that the August brood will be insignifi¬ 
cant in numbers. Evidently, many people do not 
understand the simplest principles of insect warfaie, 
else how can any wideawake fruit grower see these 
slugs eating the foliage of his trees and not make an 
effort effectually to check their work by simply 
spraying a coating of Paris-green on the leaves, and 
thus including a poisonous dose in their menu ? One 
or two thorough sprayings with Paris-green, in .Tune, 
will so diminish their numbers that the second brood 
will not be numerous enough to cause any anxiety ; 
or the trouble of again poisoning their food. I have 
met some people who seem to want to fight this slug 
with the most trouble possible. Hence, the old 
remedies of dusting the trees with lime, road dust, 
etc., are often resorted to. Sometimes these measures, 
which are much more disagreeable to apply than a 
Paris-green spray, are quite effective. The dust-like 
particles stick to the slimy skins of the slugs and 
either smother them or kill by their alkaline action. 
Often, however, the slugs simply shed off their skins 
and thus rid themselves of their dusty coat, and con¬ 
tinue their feeding. With the dusts, one has to shoot 
at the insects, while the poison spray has only to be 
aimed at their somewhat spacious feeding grounds. 
In short, this pear slug is one of the easiest pests we 
have to combat, and it is a disgrace to any fruit 
grower to allow the slugs to skeletonize his pear, 
cherry, plum or quince leaves, and thus greatly 
weaken the trees for their vital effort to produce 
fruit buds for the next season. 
A Patent “ Tree Wash.” 
A. Q., Weedville, Pa.—Agents are offering a so-called patent 
recipe fora mixture for washing trees to “protect them from 
black-knot, blight, yellows, and the ravages of rabbits, mice, 
borers, etc.” The following extracts are made from the circular: 
“ To make 100 gallons, take four gallons gas tar, two bushels 
unslaked lime, slake in water, add one bushel of mud, free from 
grit, then strain through a fine sieve, then add four pounds 
copperas, two pounds gum shellac, four pounds saltpeter, two 
pounds potash; dissolve the shellac, saltpeter and potash in one 
gallon of water, then add it to the lime and clay, then add water 
enough to make 100 gallons. Directions for use: Dig the turf 
away from the base or trunk of the tree, then apply the prepared 
preparation to your trees once each year. The above prepara¬ 
tion will make your trees produce more and better fruit, as it is a 
fertilizer and a preventive of insects. To make a preparation to 
spray-your trees, take one gallon of the above invlgorator and 
insecticide in 20 gallons of water, and add two ounces of Paris- 
green and spray your trees with the above preparation just as 
the blossoms begin to fall, and then again in about two weeks 
afterward, which will complete the work.” I would like to know 
if it is safe to apply to trees, and is it likely of any benefit when 
applied ? 
Ans. —Probably the mixture, made according to the 
patented recipe, would not injure trees, but it would 
be more expensive and require more trouble to make 
than it would be worth as an insecticide or a fertil¬ 
izer. There is scarcely anything in it of an insecti¬ 
cidal nature, and the only effect it would have upon 
MAKING SKELETONS OF THE LEAVES. Fig. 170. 
insects might be to prevent them from boring into 
the trunk, and I very much doubt if it would prove 
very satisfactory for this purpose. The clay and 
lime alone would be equally as effectual as the whole 
mixture, so far as preventing the work of insects is 
concerned. As to its use for spraying upon the foli¬ 
age in combination with Paris-green, it would cost 
more and not be nearly so effectual as the standard 
Bordeaux Mixture, which has been thoroughly tested, 
and is reliable as a fungicide. 
Our knowledge of washes to prevent the work of 
insects on trees, is, unfortunately, very indefinite, 
since no careful experiments have been carried on 
and their results recorded. We have now been ex¬ 
perimenting for three years at the insectary with all 
sorts of washes, to prevent the attacks of the peach 
borer, and our experiments have shown that three- 
fourths, at least, of the washes are of little or no 
avail for this purpose. Some of the washes recom¬ 
mended have killed our trees in a short time. There¬ 
fore, on young trees, one should be very careful about 
the application of such mixtures as the recipe calls for. 
I would advise A. G. to try the wash upon one or two 
young trees if he cares to go to the expense and 
trouble of making it. 
One should always look with suspicion upon these 
patented insecticides until they have been thoroughly 
tested by one or more of the experiment stations 
throughout the country. There are altogether too 
many humbugs in the way of insecticides upon the 
market. Most of them have for their active prin¬ 
ciple some of the standard insecticides, like Paris- 
green, white arsenic or pyrethrum. It might be well 
to say here that our three years of experimentation 
with washes for the peach borer seem to indicate that 
it will be cheaper and more effective for the fruit 
grower to dig out the borers once a year. One or two 
washes are giving good indications of being fairly 
successful preventives, but the trouble of making and 
applying is usually greater than the work of digging 
out the borers. So far as the fertilizing constituents 
of the recipe are concerned, the fruit grower will get 
far better effects from the application of potash 
directly to the soil under the tree, rather than to put 
it into a wash and paint it upon the trunk. M. v. s. 
How to Figure a Fertilizer. 
C. II. O., Black Hall, Conn .—I have just used 1,400 pounds ot 
fertilizer on corn, and the following formula is on the bag : 
Per cent. 
Nitrogen. 254 to 3 
Equal to ammonia. 214 to 3 y t 
Soluble phosphoric acid. 414 to 5 
Reverted phosphoric acid. 514 to 0 
Insoluble phosphoric acid from bone... 2 to 3 
Total phosphoric acid.12 to 14 
Actual potash. 214 to 314 
This on corn, at the rate of 300 pounds per acre, has given good 
results, at $28 per ton. If I buy 1,500 pounds of bone meal, 500 of 
muriate of potash, and 500 of nitrate of soda, how much filling 
can I put in to get a result similar to this analysis, the filling to 
be fine manure from the bottom of the barnyard. Would half a 
ton of cotton-seed meal take the place of the nitrate of soda ? 
Ans. —The average composition of the chemicals 
named is as follows : 
Pounds in One Hundred. 
Nitrogen. Potash. Phos. acid. 
Bone meal. 
. 3J4 
25 
Muriate of potash. 
50 
Nitrate ol soda. 
. 16 
Cotton-seed meal. 
. 6*4 
1% 
i'A 
Your present fertilizer contains in one ton 45 pounds 
of nitrogen, 200 pounds of available phosphoric acid, 
and 50 pounds of potash. Now, 800 pounds of a good 
quality of bone will furnish 200 pounds of phosphoric 
acid ; 100 pounds of muriate of potash will supply 
the 50 pounds of potash, and 250 pounds nitrate of 
soda will furnish with the nitrogen in the bone more 
than enough to make three per cent in the ton. This 
mixture of 1,150 pounds, with 850 pounds of your dry 
and fine manure, will, evidently, make a better corn 
fertilizer than the one you have been using. A mix¬ 
ture of 800 pounds bone, 100 pounds muriate of pot¬ 
ash, 200 pounds nitrate of soda, and 200 pounds cot¬ 
ton-seed meal, with 700 pounds of the dry manure, 
will make a better mixture, because it will furnish 
two forms of nitrogen—the mineral in the nitrate 
which is at once available, and organic in the cotton¬ 
seed meal, which will be more slowly available in hot 
weather. 
Is Silica Needed by Crops ? 
A. M. A., Morton, Pa. —Prof. Johnson, in How Crops Grow 
(page 183), quotes evidence to show that silica is not indis¬ 
pensable to crops. Have later investigations borne out this con¬ 
clusion and, if so, why and in what manner, and for what use, is 
such a large percentage of silica found in all plants ? Surely, it 
is not accidental, it must be for some purpose. 
ANSWERED BY PROF. S. W. JOHNSON. 
Later investigations, referred to in the revised edi¬ 
tion (1890) of How Crops Grow, have confirmed the 
conclusion. In 1882, Jodin published to the effect 
that he had bred maize by “ water culture ” with 
the utmost practicable exclusion of silica, for four 
generations—whereby the substance was reduced to 
the merest traces—without interference with the de¬ 
velopment of the plant. It must, accordingly, be 
concluded that, as regards plant nutrition, silica is 
accidental. Silica is present in plants because it is a 
large ingredient in most soils, and commonly exists 
in solution in the water of soils, springs and wells. 
Plants appear to have no power to prevent the en¬ 
trance into their roots of any kind of mineral matter 
that is dissolved in the soil water which they absorb 
so copiously. When How Crops Grow was written, 30 
years ago, nothing was certainly known as to any use 
of the silica which is found in plants. In 1884, Wolff 
and Kreuzhage published an account of extended in¬ 
vestigations which led to the result that a supply of 
silica is accompanied by diminished root formation 
and increased seed production, and, also, has the 
effect to bring about a timely and uniform ripening 
of grain crops. Seed formation is largely carried on 
and. finally completed by transfer of the substance 
of the vegetable organs—roots and leaves—to the re¬ 
productive organs—flowers and fruit. It is reason¬ 
ably supposed that accumulation of silica in the roots 
and leaves checks their vegetative functions, ripens 
them off, and thus favors and hastens seed production. 
Wolff and Kreuzhage found that phosphates and lime 
salts employed in quantities considerably greater 
than needed for nutrition, had the same effect as 
silica. They concluded, therefore, that unessential 
silica partially takes the place and diminishes the 
consumption of essenial plant food in the reproductive 
processes. 
Southern Corn Fertilizer; Cow Peas. 
A. G. McN., Brookhaven, Miss. —What is a good formula for a 
commercial fertilizer for corn on clay land, with cotton-seed meal 
as a basis? Will it do to sow Crimson clover in corn at the last 
plowing in June or July ? Will the seed germinate and stand the 
heat of the southern sun ? 
Ans.— A mixture of 100 pounds cotton-seed meal, 
250 pounds muriate of potash, 500 pounds dissolved 
rock, and 250 of dried muck or black soil, will make 
a good corn fertilizer. Our opinion is that, in Missis¬ 
sippi, cow peas sown in the corn at the time men¬ 
tioned, will be better than Crimson clover. Crimson 
clover is a cool-weather plant. It will not make its 
best growth in the summer. Cow peas make their 
best growth in hot weather, and if sown between the 
corn rows at Lhe last cultivation, will make a heavy 
crop to feed or plow under. 
