4 BULLETIN 616, U. S. DEPARTMENT OF AGRICULTURE, 
"stem-end ring" is the most characteristic form of fruit injury, 
and is caused by the thrips feeding and ovipositing in a circle under 
the protection of the sepals when the fruit is small, the injury ex- 
panding as the fruit grows. Injury resulting from feeding punctures 
in mature fruits appears as brownish, glossy discolorations due to 
cell sap drying on the surface. A large proportion of the badly 
marked fruit is undersized owing to failure to mature normally, 
and much of it is at times distorted by failure of the injured tissues 
to grow. 
The more characteristic injury to the leaves is the grayish streaks 
and areas (PI. II, fig. 2) and curling. At times cuplike depressions 
or pockets resembling aphid galls are formed, but oftener the leaves 
are crinkled or even tightly curled (PI. II, figs. 1 and 3). 
The unfolding leaf buds and especially the terminal buds are 
often attacked with such severity as to cause them to wither and 
die, these turning brown or black and 
finally dropping off. 
DAMAGE TO FRUIT. 
DROPPING. 
In exceptionally severe infestations, 
much of the young fruit is punctured 
over its entire surface during the first 
three weeks following the blossoming 
Fro. 3.— a, Eggs of the citrus period and thus is prevented from ac- 
Sf^in^Ur^SSe q« irin g ™«nal growth, the little fruits 
egg of the citrus thrips. eventually dropping to the ground. An 
Highly magnified. (Original.) appreciable percentage of the crop is 
lost in this way in certain orchards of Tulare County, Cal., in cer- 
tain years. 
SPLITTING. 
While onty a small proportion of the usual fruit splitting is caused 
primarily by thrips, a certain amount of splitting of young oranges 
does occur every season as a result of the long-continued feeding of 
thrips over an area usually near the navel end of the fruit. The 
affected tissues die and dry out and the scabbed area, unable to ex- 
pand with the growing fruit, cracks (PL I). 
MALFORMATION. 
From less than 1 to as much as 6 per cent of the orange crop, 
depending upon the orchard and the season, is so badly deformed by 
the citrus thrips that it must be culled out and sold at the packing 
house for whatever it will bring. The better culls usually command 
