PSEUDOPEZIZA LEAF-SPOT OF ALFALFA 
AND CLOVER 
This is an enphytotic disease of alfalfa and clover in most regions 
where these crops are grown. It annually reduces the yield, especially 
of alfalfa but rarely, if ever, kills out the plants. 
SYMPTOMS 
The lesions of this disease are confined to the leaves and stems. They 
are much less common and of little importance on the latter. 
On the leaves. Study the specimens provided and OBSERVE :— 
1. The spots on the alfalfa leaf. Do they show on both surfaces? 
Note their size, shape, color and position on the leaf. Compare with 
those on the clover leaf. 
2. That these are usually surrounded by a yellowish zone. 
Note that this is more pronounced between several adjacent spots. 
3. The darker, raised center of the spot made up of the fruit- 
body of the pathogene. Is this visible on both sides of the lesion? 
Make prawincs to show the character of the lesions on both clover 
and alfalfa leaves. 
With the hand-lens or with the low-power of the microscope examine 
several spots which show the fruit-bodies of the pathogene. NOTE:— _ 
4, The radially split crater-like openings and the waxy-appearing 
surface within. These fruit-bodies at the center of the spots serve to 
definitely distinguish the Pseudopeziza spot from other leaf-spots common 
on alfalfa and clover. 
DRAW to show the appearance of the fruit-body under hand-lens or low- 
power. 
5. A badly diseased leaf in comparison with one which has but 
few spots. Is there any difference in the general color? Does a single 
spot ever involve the entire leaf; if not, how is the leaf killed? 
6. The passepartout provided and determine where on the plant 
the most seriously spotted leaves occur, and what are the ultimate results. 
Compare photographs 1 and 2. 
Make SKETCHES to show the general effects on the alfalfa and the clover. 
ETIOLOGY 
The cause of this leaf-spot is a discomycetous fungus, Pseudopeziza 
Medicaginis (Libert) Saccardo. The pathogene on the clover is regarded 
by some as a distinct species and goes under the name, Pseudopeziza 
Trifolii (Bivona-Bernardi) Fuckel. They are probably identical. 
Life-history. But one kind of spores, the ascospores, are certainly 
known to be produced by this fungus. As repeated crops of these are 
produced throughout the season, the only distinction between primary 
and secondary cycles is that the former are those first initiated in the spring. 
Primary Cycle. 
Pathogenesis. The sources of the primary inoculum are the 
apothecia produced in early spring on overwintered living leaves. These 
leaves become infected late in the autumn but complete development, 
including apothecial formation, is halted until spring when with the arrival 
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