428 Diseases of Economic Plants 



Numerous anthracnoses, leaf-spots, rusts, and other dis- 

 eases also occur on orchids. Their discussion would involve 

 many pages. See also, p. 412. 



PALM 



Anthracnose {Colletotrichum) . — Palms often die and turn 

 black at the tips of the leaf segments, or similar spots may 

 appear upon other parts of the leaf. These spots near their 

 edges have a watery appearance. When they become dry, 

 purplish acervuli appear. Upon seedlings the disease is par- 

 ticularly troublesome, resulting in failure of the leaves to 

 unfold. 



The blighted parts should ])e cut away and burned and the 

 remaining foliage sprayed at least once each week with 

 Bordeaux mixture or anmioniacal copper carbonate. 



Graphiola blight {Graphiola phmiicis (Mong.) Poit.). — 

 Small, gray, tul:)orcular growths, 1-2 mm. in diameter, appear 

 scattered over the leaves. In greenhouses the disease is 

 commonly present but not in destructive form as it is further 

 south in the open. Numerous other leaf-spots also occur on 

 the many varieties of palms. 



PANSY. See violet. 



PEONY 



Mold ^^^ (Botrytis). — This mold was first noted in 1897 in 

 Europe. It has since been reported in Canada, Massachu- 

 setts, Rhode Island, Pennsylvania, and Maryland as causing 

 serious loss. 



Young plants are attacked almost as soon as they appear 

 above ground, and ashen gray spots are produced upon the 

 bud-scales, and stems. Among older plants the rot develops 

 upon the leaves, unopened buds, and at the base of the stem. 

 Brown mold similar to that described for lettuce not in- 

 frequently develops upon the affected parts. Numerous 



