Blight Of The Pear Tree

Tuj pear tree is suoject tomreo ninas of blight, upon tlio nat'.iro of whieh tliere are nomo dift'evences of opinión ainnng pontologists. The íirst or most serious is the fire-bligbt, cslled by gome tlio peor tree bliglit. Theo thcro are the inwcct-bligbt, and the l'rozon-sap blight. All these liave nearly a similar effect, cauBine the sudden dealh of the leavcs and branches. The lire-blight generilly apppara carly ia the seasou, and sometimos attacks only branches, at times, it destroys uoarly theentire treo. Fire-blíght is occnsioned by a fungue, whicb germiDates'on the bark, ind pushca its way gradually through the tissue, eousuming cverything it comes iu contact witb. Sooietimes it does not entiroly girdle a brancb, and thon tho leaves do not die suddenly ; nt otber times, the branch is conipletelv ghdled, and all t lie leaves dio at the same timo. 'This parasitic fungus is propagated by Bínate seeds called spores, and if the diseased branches are cut awny before the spores are matured, the propagatioD will be arrested. The escisión and burning of the diseased branches at an early ttage of the growtb of the fuiigus is the best ijjode of checking tho progresa of this tlisease. The insect büght is caused by the attacks of an insect nauned scolytus pvri, which, in Julj or August, deposits ita cggs in the bark of the tender shoots, either behind or below a bud. When the egg is hatched, the littlo grub eats its way into the center of the shoot or twig, and rraching the pith, eats a passage around it. and eometimes dovours the pith completely. When tho insect is tracsformed f rom n grub to a beetlo, ït escapes from the brand) through a small hole which it cuts through the wood and bark. Tlie scolytus does not eonfine its attacks to the pear tree. Frozen blight is generally confioed to young branches. In his essay on the diseases of tho pear, Mr. Thomas MeeLan says that the büght oceurs as fol lows : "Wbeu a plant s ander very low temperature, evaporation is going on at an enorruou8 rato. If nt this time any particular part of the plant should loee its moisture faster Ihau tha roots pan supply it, tbat part loses its vital heat, and either dies at once, or has the vital . ity eo mach weakeucd, that it dies udder the first severe trial. This prinoi' ple is beautifully illustrated iq nursery roirs of fruit tree9. Sometimes we find lows of apple trees split for n few inches from the grouud on the sunuy side. Near the ground when the sun in winter strikes it, thero is a protty gtroog heat; evaporaüon hnnicdialely enaues, and the root, perhapa encased in frosl, having to expend to a considerable portion ot its heat ia thawiug moisturefrom the frozen ground, cannot supply moisture and with it beat - for heat is of no use to a plant escept in conneotion with moisture - fast enough for tbe evaporation. Heuce, with loss of hoat comes contraction ; and you will find in frozen eap blight it takes placo only in very porous wood or bark, or in thoso plante exposed to the sun, whose heat was suddenly abstracted b)' evaporntiou." Frozen sap blight may be known by a thick, olammj sap, whieh issues from the wounds mado by tbe pruning knif'e and also by the appearauce of blaok, ehriveled spots on the trunks or branches of the trees in the Spring. In Ihn Surumer months tho presence of the disease is denoted by the topg of tho branches shriveling up and docaying, as if suddenly blasted. If the iliseased branches are removed in time, the tree generally recovers ; but if the disease is not arreeted, it is iikely'to spread over and destroy the whole treo. It will be Been by the foregoing remarks that it is necessary to pay close atteation to pear trees in Sumuier, in order to prevent the spread cdiseasj, by removing and deatroying all affcetod ghoots or branches. CíVpk}pnrgs