40 Florida Agricultural Experiment Station

 BORDEAUX INJURY
 There has been considerable controversy among growers as
to whether home-made Bordeaux mixture does enough harm to
cucumber plants to offset the good derived from controlling
disease. It is true that this fungicide is very active and it is
necessary to use care and
precautions in handling it.
If it is used too strong it will
burn plants to such an ex-
tent as to almost kill them.
 Figure 32 shows Bordeaux
burning on cucumber leaves.
Even though the mixture
was too strong, it burned
the leaves only where the
sun struck them. This burn-
ing was evident very soon
after the leaves dried after
spraying. The burned por-
tions of the leaves at first
appeared scalded,later turn-
 Fig. 32. Bordeaux injury caused by spray
ing brown and drying hard. and bright sunshine.

 Less than 10 percent of the
 leaves showed this burning.
 The older leaves were most
 seriously affected. The
 younger leaves and the
 growing tips did not show
 any signs of the burning.
 Another type of burning
 was found on cucumber
 leaves caused by Bordeaux
 mixture, but differed mark-
 edly from the type of injury
 just described. This second
 type, as shown in Fig. 33.
 did not develop until two
 days after the spray was
 applied and there was usual-
 ly only one leaf on each run-
Fig. 33. Bordeaux injury resulting from ly only one leaf on each run-
 liquid spray. ner affected. This was the