CHE REFERENCE LIBRARY - ZetaTalk

198 7’IlE NURSERY-MANTJA I,certain dcgrce, in cbcmtrolling apple mildew, but the additionof 3 pounds of iron sulfate makes a more ctfec,tive mixture.l)usting with a mixture of 90 parts sulfur and 10 parts powderedarsenat.c of lead also has proved satisfactory in checking themildew.In some seiW2ns tile mildew is more prevalent than in otheryears, aiid when the disease is sbundant an efl’ort should bcriide to keep its much as possible of the newgrowth covered with the fungicide. The firstapplication should be made soon after the seedlingshave developed the first new leaves.Three or four subsequent treatments should bemade at. intervals of two to three weeks.YEI,LO~WAL~ I~SEA~+E OF CI~RI~T mn I'Lm.- - The yellow-ieaf may be very destructive tonurser) trees when weather conditions areFIG. A ‘q,3. y(+ fa\-orable. Mazzard cherry seedlings arc exlow-leafdiscasu of ceetlingly susceptible and often badly defoliclwrry.ated. i\Iahaleh cherry seedlings are commonlyafleeted, while myrobalan plum seedlings show a considerabledegree of resistaiicc. The sweet and sour varieties of cherryand the European varieties of plum are more susceptible to thedisease than thtb .Japanese plum varieties.Ihsr riptiob. - The disease appears on the cherry foliage asdark red sp( )t. c; , th:rt, ma). he abundant on the leaves (Fig. XS> .Tn the ad\xiicecl stages of the disea,se, a yellowing of the affectedfoliage may occur and the leaves fall premat.urely. On theplum foliage the disez;e is conspicuous because of the shotholeappe:rran[*e of the leaves caused by the d.ropping out ofthe c*irc&r areas of affected tissue. The same yellowingsometimes appears on diseased plum leaves but never so abundantlyas on sweet cherry foliage.Cause. - The yellow-leaf disease on cherry is caused by the