366 



ARBORICULTURE 



ARBORICULTURE 



337. Tu:>sock molh lacva. 



nioinbors of several ilitTorent groups of inserts, certain 

 small moths, a few saw-flies and a small iminber of Hies 

 and bet^tles. All of tlie leaf-miners are \ery small 

 uisects whose larva- fe(xl upon the parenchyma of the 

 leaf, leaving intact the upper and lower epidermis. 

 In this position they arc protected froin most sorts of 



insecticides, although 

 in some cases, si)ray- 

 ing with a contact 

 insecticide containing 

 some tol)a(^(^o com- 

 pound in combination 

 with soap may be 

 efficacious. One form- 

 ula recommended is: 

 water, 800 gallons ; 

 nicofuinc, or "blackleaf 

 40," one gallon; hum- 

 dry soap, thirty-two 

 p o u n d s. Ordinarily, 

 leaf-miners do not pre- 

 sent a serious menace 

 to trees, but the pres- 

 ence of their blotch-like or serpentine galleries, which 

 show as faded areas, often greatly disfigure the leaves. 



Some of the more important shade-tree pests. 

 A. Defoliators. 

 The tussock moth, Hemerocampa leucostigma (Fig. 

 337), is perhai)s the most abundant caterpillar on trees, 



f)articularly in thickly .settled districts. The eggs are 

 aid in the fall in white fluffy masses the size of a dime 

 on the trunks of infested trees and hatch in the early 

 summer. The larva" bear several pencils of long black 

 hairs placed at each end and have four brush-like tufts 

 of pale yellow hairs above, with a bright red head. 

 These pupate early in July in crevices in the bark and 

 the adults .soon emerge to lay the eggs for a second 

 generation of caterpillars which will mature before fall 

 into moths that deposit the over-wintering eggs. The 

 female moth is without wings and lays her mass of 

 eggs on the bark where she emerges from her pupa 

 case. These caterpillars feed on all sorts of trees 

 except evergreens, but seem to be most destructive to 

 maple, elm and .-Vmerican linden. Two related caterpil- 

 lars have been imported from Europe into Massachu- 

 setts, the gypsy moth and brown-tail moth, and 

 although these are at present confined to that neigh- 

 borhood, they will undoubtedly become widespread 

 before many years have elapsed. The gipsy caterpil- 

 lars feed on many kinds of trees, preferring oaks; they 

 may be recognized by a double 

 line of round spots down the mid- 

 dle of the back, blue, followed by 

 red ones. Their life-cycle is like 

 that of the tussock moth, except 

 that there is only one generation 

 passing the winter as a mass of 

 woolly, dull ochre-ycllow eggs at- 

 tached to the bark. The brown- 

 tail is a brownish cateq)illar with 

 white spots, passing the winter in 

 email woven silk nests containing 

 many caterpillars. The nests are 

 attached to the tips of the twigs 

 of infested tre<». Orchard trees suffer most severely 

 from this species, although all sorts of broad-leaved 

 trees are attacked. 



Another common caterpillar of very different habits 

 is the American tf-nt-caterpillar, Malacosomti ameri- 

 cana. This is an inconspicuous brownish moth which 

 over-wmters as a band-like mass of eggs placed around 

 twigs of cherry and a number of other trees. These 

 hatch in very early spring and the larva; spin silken 

 nests in small forks of the branches from which they 

 crawl out to feed upon the opening leaves. They mature 



338. Cocoon of bag- 

 worm. ( X H) 



339. Euvanessa antiopa. 



in early summer and the eggs are laid in midsummer for 

 the next season's brood. 



The bag-worm, Thyridoplerix ephemcraformis, is a 

 defoliator at times very flestructive, although each 

 larva in his dependent bag docs not have a wide range 

 of operations. Fig. 338. Hand-picking and arsenical 

 sprays are the remedies. 



The caterpillars of the mourning cloak, Euvanessa 

 antiopa (Fig. 339), are a very common pest of elm and 

 other shade trees. They are black, coarsely spiny cat- 

 erpillars with red spots along 

 the back, and feed more 

 or less in colonies, usually 

 defoliating single branches at 

 a time. The butterfly passes 

 the winter as an adult, ap- 

 pearing in very early spring, 

 and laying its eggs in May. 

 The caterpillars from these 

 eggs become full-grown be- 

 fore July, and the butterflies 

 of another generation appear 

 in July to lay eggs which will give rise to the hibernating 

 butterflies of the next winter. 



A common saw-fly which occurs on willows is the 

 American saw-fly, Cimbex americana. The larva are 

 much like the defoliating caterpillars of moths and 

 butterflies in appearance and feed in the same way, 

 destroying the entire leaf -tissue. The larva; are pale 

 green, with a blackish hne down the back. When 

 mature, they descend to the base of the tree, where they 

 spin parchment-like brown cocoons in which to pass the 

 winter on the ground among fallen leaves. In the spring, 

 they transform and the adult saw-flics deposit their eggs 

 singly in slit-like cuts made into the tissue of the leaf. 



Pine trees often suffer from the depredations of 

 saw-fly larva; of the genus LophjTus which devour the 

 needles, near the bases of which they later spin their 

 small cocoons. 



Many saw-fly larvae feed only on the leaf from one 

 side, leaving the epidermis of the other side intact. 

 Arsenical sprays for the destruction of such species 

 must be directed against the side of the leaves attacked, 

 usually the under surface. 



Among defoliating beetle larvae, the imported ehn- 

 leaf beetle, Galerucella luteola (Fig. 340), is probably 

 most important. This occurs only in the eastern 

 states but is gradually spreading into the middle \\'est. 

 The small, yellow, two-striped adults live through the 

 winter and deposit tlicir bright yellow eggs in small 

 masses on the under side of elm leaves in early spring. 

 These eggs hatch into black and reddish slugs which 

 feed on the under surface of the leaves, leaving only 

 the veins and upper epiilermis. The leaves then dry up 

 and may fall off. The larva", 

 now changed to a yeOow color, 

 descend to the surface of the 

 ground to pupate and .soon 

 emerge as a summer genera- 

 tion of beetles. There are 

 two or three annual broods, 

 according to the latitude. 



B. Plant-lice and scale insects. 



There are many kinds of 

 plant-Hce (P"ig. 341), but all 

 pass through very similar life- 

 cycles. In general, this is as 

 follows: the winter is passed 

 as a large, shining, elongate- _^ „„.„o„.„^„ 



oval egg attached to a twig s^ace '.^rk's'b7l"vffi."' 

 or branch. This gives rise 

 in th(; spiing to a soft-bodied wingless female aphid 

 that gives birth to living young aphids, which in turn 

 reproduce in the same way. These suck the juices from 

 leaves, petioles or tender twigs and thus sap the vital- 



340. Larvae of elm-leaf 

 beetle. Holes made by adults, 



