\/ Circular No 7. Second Serics. United Stales Department of Agriculture, DIVISION OK ENTOMOLOGY. THE PEAR TREK PSYLLA. ilia pyricola Foerett i « , V ii overwhelming invasion of the pea lyllaTtn-thi hi the largest pear orchards in Maryland, together with Virginia and New Jersey in the same year, gives promim had nol previously been reported Bouth ol New York, although known to extend 18Jj:SI Fn. 1. -Pear-tree PsylU A.lult female Natoral riie indlcafa oe, (Original.) ■ l a- far aa Michigan and to occur generally in the New England States. '" Vl,u northern range, its sodden appearance in enormous number* BO tar small was a matter ol considerable surprise, and careful iminations of the work of the insect and experiments with remedies were made. The pear-tree Peylla (fig. I) is supposed to have been imported into Connec- ticut about 1832 from Europe, where this and one or two other spedes are well- known pear enemies. It is one of the true bags of the order Ilomoptera, and ^^^ family, the Psyllid.-e, is intermedial- between or connects the scale insects | K"" 1 t,u> plant-lice on the one hand with thi and larger plain ^^^•be other. The I'syllidie are commonlv known as the jumping plant-lice on r ' ' NATURE OF THE INJURY. The pear-tree Psylla has hitherto been by no means a common insect, and few pear growers are familiar with it. The insect, even in the later stages, is small and easily overlooked, but the effects of its presence upon the trees are startling enough, as seen in the falling of the leaves and fruit, the latter before it is half grown, but chiefly in the enormous secretion of honeydew by the larva' and nymphs. One who has not witnessed this sight gives credence with diffi- culty to the reports of the amount of this liquid constantly being secreted. Dur- ing the height of the invasion in Maryland the waterlike fluid or honeydew was reported not only to have covered the leaves and twigs, but to have fairly rained from the leaves, and, running down the trunks, extended in a discolored circle for from 6 to 8 inches outward around the baee of the trees. During cultivation the horses used became so drenched with the sticky 6ubstance that it became necessary to wash it off with sponges, the currycomb being useless. The weak- ened trees lost much of their fruit, the leaves were blackened and fell in great numbers, and the bodies of the trees appeared as if they had been smoked. 1 On July 20, when first seen by the writer, the leaves, limbs, and trunks were blackened by the growth in the sweetish liquid of the smoky fungus, Fumago salicina; and in the falling of the foliage and the diseased and smoky-looking fruit a startling picture of disaster was presented. The leaves were scarcely at all yellowed, but were covered with dead and dry patches or spots, sometimes investing almost the entire leaf, giving an appearance which might easily be mistaken for some fungous attack. This seems to be due not directly to the extraction of the plant juices by the insects, but rather to the sun-scalding resulting from the collection of the honeydew on the leaves in large drops. The Psylla was distributed over the entire orchard of upwards of 100 acres, but was much more abundant in the plats of older trees. The young orchards, perhaps amounting to one-third of the entire tract, were in vigorous condition and had not been seriously affected. This was noticeably the case with the Kieffer, Buffon, Le Conte, and Standard Lawrence. The Dwarf Lawrence, on the con- trary, was badly injured, and, with the Old Duchess and Bartlett trees, seemed to have suffered the most. OTHER OCCURRENCES SOUTH OK NEW YORK. The presence of this pest, as recorded above, is not the first instance of its occurrence in Maryland. A pear orchard about 8 miles south of this one was also very badly infested in the summer of 1891. The insect appeared during that year on pear trees next to and in the vicinity of the house, where some nursery stock had been heeled-in the winter previous. Its spread was confined to an area of 3 or 4 acres, which, however, was so thickly infested that the leaves and fruit fell, and the trees were so stunted and injured that they ceased bearing until the season of 1894, when they bore a fairly good crop. Curiously enough, however, in this orchard the Psylla disappeared entirely after the first year and has not again put in an appearance, nor did it occur in other pear orchards between and in the neighborhood of the two referred to. Similar outbreaks are reported this year for the first time in New Jersey by Prof. John B. Smith, with evidences of the same source of infestation, and about the middle of October it was found in Charlottesville, Va., by Mr. D. W. Coquillett. These records evi- dence an unfortunate tendency of the insect to spread southward— a course which, from the history of the pest during the sixty years of its occurrence in this country, was hardly to be expected. 1 1 Chester-town (M.I.) Transcript. July 10. 1904. 1 Ml I IM.]. ()K IS I ROD! CI H'N. I The -- n . l . i « ■ 1 1 1 1 . — and severity of the appearance of the Psylla, particularly In the Maryland instances, makei the question ol Its introduction one ol consider- able interest. Upon Inquiry 11 wu developed that In u the pear had been obtained from a New York nursery in 1800, or Jus) at the time when tin' Psylla appeared in Booh extraordinary onmbers in Wen York Btate; and it is unquestionably from this lonree thai the Psylla was introduced. The young trees secured in the fall "t the year mentioned were nndonbtedly Infested with hibernating Psyllas, as il was in the immediate vicinity of the point where tin- were beeled in that tin. outbreaks occurred. In one case tin' insect seemed t<> have gradually increased in numbers, reaching a destructive abundance in thr summer of 1894. Tin- entire disappearance ol the insect after the first year in tlir other orchard is probably to be explained on the ground of Bome local climatic condition. Sued modifying Influences arc not unusual in the peach licit of Maryland, as illustrated by the fact that orchards separated by only a few miles, ami with the same c ditions as regards s.>il ami variety of fruit, will ingly l>e so differently affected by \.-ry local cold waves or storms that one will be barren While the other will he full of fruit. or -. Kill [ON ami LIFE HISTORY. a in the development of this insect arc the egg, the larva, the nymph or active pupa, and the adult or perfect, winded insect, rhe egg itig. 2, a) is orange-yellow in color and bo minub to he almost invisible to the naked eye. Its peculiar structure is indicated in the drawing— the short arm serving as its attachment to the leaf. The newly hatched h\r\ a is somewhat larger than the egg and yellow in color, with crimson eyes, and has the characteristics indicated at f i jlt - '-', '.. With each of the earlier molts the form approaches more and more nearly the nymphal Stage, which is represented in its final form at tig. •'?. In this stage the prominent features are the large wing-pads. The general color is dark reddish-brown, with the lighter areas indicated in the illustration— tlie eyes remaining a crimson color. In all the preparatory active stages the insect is : oval and very much Battened, little, if at all, resembling the adult, but rather some scale insect, and is very sluggish. The adult (fig. 1) comes from the last nymph, and is a little, clear-winged insect , closely resembling the Cicada or harvest By vastly reduced. Like the latter, its wings close roof wise in repose, lor is reddish-crimson, with the brown or black markings indicated in the illustration. The last or hibernating brood turns uniformly br-.w nish black, with bronzy eyes and dark wing- veins, and was described as a distinct species [Psylla simiiltins), but has been shown by Mr. Slingerland ' to be merely a winter form, which result is confirmed by breeding records at this Department. The life history of the insect may be briefly summarised as follows: The adults hibernate in crevices in the bark of pear trees- and emerge with the first -Pear-tree Psylla: a, Kgg; b. larva. Both greatly enlarged. (Original.) 1 Bui. 14. Cornell Agr. Exp. Station. (><•; ■'iMi potto. i trees in an animated greenhouse toe adults rested exposed on tin- twlga ail winter Without making any attempt at concealment, ami began ovipositing early in March, the tir-t maturing early In April. The plants on which they win te red were, however. In time of leafing, fully four weeks in advance of those on the ground , 4 warm spring days, copulate, and begin the deposition of eggs before the leaves have expanded, placing them singly or in rows or bunches in creases of the bark of the twigs, on old leaf scars about terminal buds, and later, after the leaves begin to unfold, on the leaves themselves, as already described. The egg-laying goes on during April, probably later in the North than as far south as Maryland. The larva; hatch in from ten to seventeen days (from ten to twelve days being the ordinary summer period), station themselves on the leaf petioles and in their axils on the fruit, but chiefly over the surface of the leaves. The moment they begin feeding the secretion of honeydew commences, and in a very short while the bulk of the liquid will be several times that of the insect, rapidly increasing until it forms a good-sized drop. This, when there are mil- lions to aid in the work, soon becomes abundant enough to fall as a 6hower from the tree whenever it is shaken by the wind. Mr. Slingerland shows that there are five molts, including the last change from the pupa to the adult insect, and the life from the laying of the egg to the adult covers a period of about thirty days, the periods between molts varying from three to 6even days. RECOKD OF BROODS FOR MARYLAND. The adults were very numerous July 20 in Maryland, frequently fifteen or twenty resting along the midrib of a single leaf. They were depositing their eggs along the midrib on the upper sur- face, and also thickly along the serrated margin, but on no other part of the leaf. From July 31 to August 3, when again examined, the eggs were much more numerous and had been fre- quently deposited in small clusters, five to eight together, along the midrib and at the margin of the leaves. Scarcely any of the eggs at this time had been hatched, at least not more than 2 to 3 per cent, and the adults were still al- most as numerous as ever and busily ovipositing. This brood, which was the maximum one of the season, was with little doubt the third one from the hibernating individuals— a month be- ing the normal period for a generation. A fourth brood of adults appeared about the last of August, and a fifth about September 1. In breeding cages over young potted pear trees no diffi- culty was experienced in getting the fourth and fifth broods in large num- bers, but in the orchard on the mature foliage— prematurely mature, from the sapping of the insects — the fourth brood was very scanty in number, show- ing not more than one where there were a thousand before, and this in the face of the fact that more eggs had been deposited than for any previous brood. The further decrease with the fifth brood was as marked, and the greatest diffi- culty was experienced in finding a single adult. THE FUTURE OUTLOOK. Judging from the history of the pear-tree Psylla in the North, we may expect that the injury will be very much less in the future, even if there is not an entire cessation of the trouble and a disappearance of the pest. The fact that this insect was imported into the United States with pear trees over sixty yeai and was long since widely distributed throughout the pear districts of the Pig. :i.— Pear-tree Psylla: Nymph— greatly enlarged. (Original.) Northern Btatea and westward to the Mississippi, end bu yet, during all thii time, rarelj been reported aa Injuriously abundant, argnei thai the eonditiona '■ vor »bl« <" '■ are seldom met with, it. complete disappearance in one orchard, after ■ Tear oi excessive abundance, la ■ oaae In point; and the multiplication In New York State In 1891 wu followed the nezl pear ling to Mr. Blingerlend, bj acaroelj any injury in oompariaon. T tor the audden multiplication and quite aa sadden diaappearance oi this pi ,ll,lu '" lt to P ve - A ■""■ I two or three wintera favorable to bibernation to the unusual inoreaee, and the resulting attack bring* the trees condition which la probably prejudicial to the insect. With the later summer brooda, aa pointed oul above, the condition oi the leavea which have been seriously attacked by the earlier brooda la .such thai the insect becomes nuirk.Mll> leea abundant later in the season. The green, aucculenl foliage ol the K ';; ', full u-rown larva:- aevourtw a ' S51 '■ ' ; '■ a,1 " lt 'Meet 9, hea.l of same; A. adult, natural size. All enla A. (Original.) young spring growth ia especially favorable, and when the leavea become hard- ened and mature, and especially dry and innutrition,, from havin ready sapped of their vitality, they are distasteful and unsmted to the development of the later broods. The parasitic and predaceoua insects also become very efficacious by mid- summer, and a very interesting experience in the case ,,f the Maryland invasion will be now noted. HA rURAL BNSMIS8 nemy for this insect among the parasitic and predaceoua species has, previous to this year, been recorded. On my tirst visit t,, the Maryland orchard Shown what was taken to be the egg oi the PsyUa, which proved, however, H the egg of a common lacewing Qy, Chryaopa oeulata Say. The mistake I very natural one, for the eggs occurred in extraodinary numbers throng] •> UNIVERSITY OF FLORIDA 3 1262 09216 5009 out the orchard. On some trees nearly every leaf would have one or two of the eggs of the Chrysopa attached to it. Later nearly full-grown larvae of Chrysopa were found on the pear trees, attacking and devouring the adult Psylla in a very vigorous manner (see fig. 4, d), and the young larva- were found to feed with great readiness on both the eggs and the young larval Psyllas. It is a safe estimate to say that one lacewing fly larva will destroy several hundred eggs and larvae of the Psylla, in addition to the adults which it will destroy in its later larval growth. The great abundance of the Chrysopa eggs on the pear trees makes it not at all improbable that the lacewing fly has much to do with the marked decrease in the later broods of the Psylla. The predaceous habits of the lacewing-rly larvae are of common record, and their beneficial character is well known; but in view of the important role played by this insect in the economy of the Psylla, its life habits may be briefly summarized. The eggs (fig. 4, a), instead of being deposited in rather numer- ously placed clusters or groups; as is the case with some other species, are distributed almost invariably singly on the leaves, rarely two together on the same stalk. The young larva (fig. 5) cuts off the upper end of the egg on emerging, and is surprisingly large in comparison with the egg from which it issues. It is light ash-gray in color, the head abnormally large, and the body armed with immense curved hairs or spines, which give it rather a fero- cious appearance and undoubtedly make it seem to the young Psylla a ver- itable dragon. It crawls down the egg stalk and begins immediately its active search for food. On approaching the egg or young larval Psylla, it immedi- ately grasps it between its long, curved, mandiblelike organs, which amount to two sucking tubes, between the tips of which the egg or the young larva is held and rolled one way and the other, as between thumb and finger, the juicy contents being in the meantime rapidly extracted. It is a most interesting sight to watch this little larva at work and to note with what celerity it grasps the young Psylla, quickly extracts the juices, and casts aside the dry shell, the whole operation frequently taking less than a minute. The larva is an extremely hungry one and is always feeding, and its rapidity of growth is limited only by the abundance of the food supply. It eats anything that comes in its way, is totally fearless, and is also, unfortunately, cannibalistic, eating its own kind with as great readiness as it does any other larva. After about ten days the larva becomes full grown, and spins up in the curl of a leaf or in any partial protection, constructing a delicate, slightly oval, but nearly spherical silken cocoon, which is attached to the leaf by silken threads (fig. 4, e). This cocoon is very small, in comparison with both the larva which spins it and the adult which emerges from it, and is less than one-eighth of an inch in long- ?st diameter. The adult emerges in from ten to fourteen days, cutting off the Fig. .—Chrysopa oculata: Newly-hatched larva, with under side of head and claw at side. Greatly enlarged. 4