PECAN ROSETTE. 17 
often showed marked signs of rosette the first year after trans- 
planting. Trees in low situations where humus and fertility ac- 
cumulate from year to year were almost always found to be uni- 
formly vigorous and free from disease. Briefly stated, 90 per cent 
of the cases of rosette were found under conditions indicating lack 
of humus, plant food materials, and moisture. 
Fertilizer tests (50) showed in two years a marked improvement 
in rosette cases and also many cases of [apparent] recovery. Stable 
manure, particularly, gave excellent results. Rosetted trees in the 
plat that received ground limestone at the rate of 3 tons to the acre 
not only failed to improve but were more severely attacked at the 
end of the third season following its application than at the be- 
ginning. 
Examination of large numbers of trees (50) showed that the feed- 
ing roots are distributed through the surface soil, and in proportion 
as this is deep and fertile do pecan trees usually attain their normal 
development and vigor. Long hot, dry periods often kill many of the 
feeding roots in the shallow surface soils ; and deep sand, clays under- 
lain by sand, and eroded hillsides were found particularly to favor 
rosette. An acid soil, according to McMurran, is probably not the 
cause, since river flood plains nearly all exhibit an acid soil, and 
pecan rosette under these conditions is a rarity. 
EXTERNAL SIGNS OF ROSETTE. 
Every phase of the disease is observed on trees of all ages, from 
young seedling or budded and grafted stock in the nursery row to 
trees of long-established maturity. 
In every distinct case the constant sign of rosette consists in the 
final development of undersized, more or less crinkled and yellow- 
mottled leaves (Plate I, fig. 2 ; Pis. II to IV), particularly at the ends 
of one or more branches. This phase may be properly designated as 
the secondary stage of the disease. The chlorotic areas are situated 
between the principal veins, while portions adjoining these veins and 
along the margins of the leaflets are green. In severe cases these in- 
tervascular chlorotic areas are thinner than in healthy leaves, while 
along the midrib and principal veins the blade is often somewhat 
thicker than normal. This condition gives the leaf a peculiarly rough 
and furrowed appearance and causes the veins to stand out char- 
acteristically. Such leaves do not attain their normal size, are 
often linear (PL IV) and otherwise malformed, and present a 
crinkled or undulated appearance of the laminae. Parts of the 
laminae are often suppressed ; sometimes the leaflet consisting merely 
of the midrib bordered by an edging of ragged tissue. In laminae 
otherwise fairly normal in general form, portions of the mesophyll 
76289°— 22 3 
