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Pests And Diseases |
 Generally speaking, water plants are not difficult to grow
and provided care has been taken in selecting the right
subjects for the conditions available, there should not be a lot
of trouble from pests and diseases. At some time or other they
may arise and it is therefore advisable to know what to look
for and what steps to take to arrest the trouble.
Aphids appear in every part of the garden, whatever plants
are being grown and the water garden is no exception. One
of the great advantages of stocking a pond with fish is that they
do devour aphis whenever they have an opportunity. Black-
fly seem to settle on a wide variety of plants and they can often
be dislodged by using a high pressure hose on them. As the
insects are knocked into the water they are quickly eaten by
the fish.
On. occasions, water-lilies become badly infested with the
flies, as will various plants when the water in ponds or lakes
becomes low during the summer. Great care is needed before
spraying or dusting with any insecticide, since many of these
will prove harmful, if not fatal, to fish and other occupants
of the water.
Caddis flies are frequently seen and are easy to identify.
The female lays her eggs near or even in the water and, as the
larvae develop, they hide themselves in such a way as to make
it difficult for them to be seen. If they are present in any
quantity, they may do 'real damage to the roots of water-lilies
which they bite and weaken, while they often attack the leaves
and flower buds too. "Where there are fish in the water they
will clear out the eggs or larvae of the Caddis fly. If there are
no fish, some other means must be devised of getting rid of them.
It is often difficult to see them in the water since they disguise
their shape by remaining under or close to sand, sticks and
leaves. When seen in shallow water, they can be picked out -
as they should be whenever a pond is being emptied.
The water-lily beetle is liable to attack various aquatic and
subaquatic plants, the result being most displeasing. The
correct name of this pest is Galerucella nymphaeae and both the
light brownish beetles and the shiny blackish-brown larvae,
which are yellowish underneath, chew the leaves and flowers
which are caused to decay and become unsightly. The female
beetle lays her eggs in small clusters on the upper surface of
the leaves in the late spring.
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