16 
Make a prawinc from photograph 1; Cornell Bul. 272, fig. 16, or 329, 
fig. 114. Label fully. 
Blossom-blight. Bees and flies visit these active cankers in the spring, 
to feed on the exuding sap and then visit the opening blossoms where they 
leave behind them some of the bacteria which adhered to their bodies. 
Herein the nectar and in the injuries made by the insects’ claws in the tender 
tissue of the flower, the bacteria multiply rapidly killing the blossoms. 
Study the specimens provided; Ontario Bul. 176, frontispiece; Cornell Bul. 
329, fig. 112; or photograph 2. OBSERVE :— 
7. The dead and blackened flowers. The leaves of the spur are 
also dead and brown. The bacteria have spread down the pedicles into 
the spur. These dead and blackened blossom-spurs are usually the first 
striking evidence of the disease in the spring. The oozing cankers are 
usually overlooked. Make an outline prawinc of a blighted blossom- 
spur. 
Fruit-blight. Frequently only one blossom 6n a spur is infected and 
by the time the bacteria have killed it and worked their way down the 
pedicle to the spur itself, the uninfected blossoms have developed fruit 
of a considerable size. From the spur the bacteria now work into the base 
of these fruit-pedicles and by way of them into the growing fruit. Study 
photograph 3; Ontario Bul. 176, fig. 15-19; or illustration specimen. 
OBSERVE :-— 
8. The blackened pedicle and discolored lower half of the fruit. 
A fruit affected in this way usually shrivels and drops from the tree. It 
may cling to the twig as a blackened and shriveled mummy. The loss 
from fruit-blight is sometimes heavy. The curculio and aphids fre- 
quently introduce the bacteria into the fruit through their punctures. 
The pathogene does not always enter the fruit by way of the pedicle. 
Note that the leaves of the spur are also dead and shriveling. In rainy, 
muggy weather the bacteria ooze from these blighted fruits and blossoms 
in sticky drops as they do from the hold-over cankers. Study photographs 
4a and 4b. OBSERVE:— 
9. The discolored and slightly sunken tissues about the base of 
the stem and extending toward the blossom end. The sticky, milky 
drops oozing from the diseased area. A large one on the pedicle. Make 
DRAWINGS (from specimens or photographs) showing these different phases 
of fruit-blight. 
Twig-blight. The bacteria from the diseased blossoms and fruits 
are carried by sucking insects to the tips of the growing shoots and water- 
sprouts and are there introduced through the wounds or punctures made 
by the insects, into the tender succulent tissues. Here they multiply 
rapidly killing the shoot, causing the form of the disease known as twig- 
blight. Blighted and healthy twigs (fresh and preserved) are provided. 
Examine and oBsERVE:— 
10. The contrast between the diseased and healthy portions 
of both the twigs and leaves. You may be able to find the dried ooze. 
(See illustration specimen.) sKETCH to show contrast between diseased 
and healthy twigs. 
, il. That in some of the specimens the dormant buds in 
the axils of the leaves just below the ‘blighted portion have been pre- 
maturely forced. Explainthis. (Seeillustration specimen or photograph 6.) 
