Nymphaea caerulea or the "Blue Lotus" is actually a water lily rather
than a true lotus.
[Growing great lotus -- Hoerr Nursery]
"The 'blue lotus' of the Nile is the waterlily, Nymphaea caerulea, not a lotus..."
Moreover the "Nile" blue lotus (Nymphaea caerulea) and the Cape blue
water lily (Nymphaea capensis) are now considered simply as varieties
of one species (Nymphaea nouchali):
[Nymphaea nouchali var. caerulea]
"This lovely aquatic plant with sky-blue flowers is South Africa's
most commonly grown indigenous water lily."
* * * * * * * * * * * * *
The most common herbivore pest warned about in cultivating this plant is the aphid:
[Blue Water Lily Seeds from Alchemy Works]
"Watch out for aphids, which you can see if you turn the leaves over."
[Robyn's Aquatic Plant Care Page]
"(Dealing with Aphids) Aphids love to attack plants, whether they are
on the land or in the water. They will suck the life out of almost any
plant including water lilies, lotuses, most marginals (they liked my
arum which later died), watercress, water lettuce, and more. Aphids
like to go for damaged or yellow lily leaves the most. Remove these
leaves often to deter aphids."
This site lists three herbivore insect pests that attack water lilies,
including the Nymphaea species, and has pictures of representative
leaf damage done:
[Waterlily pests -- Royal Horticultural Society]
- Waterlily beetle (Galerucella nymphaeae)
"Circular or elongated slots are eaten in the leaves
where both adult beetles and larvae can be seen during
the summer. The flowers are also damaged by the adult
- Waterlily aphid (Rhopalosiphum nymphaeae)
"Dense colonies of greenish brown aphids form on the
upper surface of lily leaves and on the flower buds.
White cast aphid skins also litter the leaves. Heavy
infestations spoil the appearance of the flowers."
- Leaf-mining midges (Cricotopus spp.)
"The leaves gradually decay and are eaten away,
especially around the leaf margins. Slender white
maggots, up to 6mm long, feed within the leaves at
the edges of the damaged areas."
Finally, this site mentions again aphids leaf-mining midges, and adds
a warning about the China-mark moth:
[Nymphaea, Water lily -- BBC Gardening]
"Water lilies are fairly trouble-free. However they may suffer a few
pests and diseases but these are mostly superficial and will do little
permanent harm to the plants.
"Be wary about using chemical controls if you have fish in the pond.
If aphids attack the leaves and flowers, blast them off with a hose.
The fish like to eat them.
"The China-mark moth can be a nuisance during summer by laying its
eggs near the edge of leaves. They hatch into larvae that cut
oblong-shaped pieces of the lily pads that they use to surround their
body. They continue to nibble away while inside this protective coat,
and eventually consume large chunks of foliage. The leaf-mining midge
shreds the foliage but is a less common pest. Both the China-mark moth
and the leaf-mining midge can be picked off badly affected leaves and
fish will also help reduce their numbers."
More about the China-mark moth appears on Robyn's Aquatic Plant Care
Page (linked above), for which she supplies the species name
She also provides a link there to this site, describing another
species in the same family:
[China Mark Moth]
"The China Mark Moth (Hydrocampa propraolis) is a moth with an
orange-brown wing that is patterned with white markings. It lays its
eggs on the edge/margins of aquatic leaves and the resulting larvae
will cut out two semi-circular pieces of the plant leaf, sandwich
himself between them, and float off to another plant to engore
himself. These little whitish colored larval worms can really
devastate a collection of plants. They usually prey on floating
leaved plants like waterliles or snowflakes."
It appears that there are several related moth species with this
life-cycle, possibly all in Family Pyralidae.
Another site, which lists three kinds of pests:
[Waterlily (Nymphaea) -- Connecticut Agri. Exp. Station]
- The waterlily aphid, Rophalosiphum nymphaeae
- Waterlily leaf beetle, Galerucella nymphaeae
- Waterlily leafcutter, Synclita obliteralis
* * * * * * * * * * * * * *
It should be noted that damage done by one species is sometimes
mistakenly blamed on another:
"Pond snails often get the blame for the damage done by caterpillars
since they can be found in the damaged areas as they begin to decay.
Other pond inhabitants sometimes take the rap. Be sure to look for
larvae before you try to kill off other creatures that may be
beneficial to your pond!"
I did find sites that blame leaf damage of water lilies on snails, but
the consensus seems to be that water snails confine their dining to
decaying vegatation, so I would not include them in the list.
* * * * * * * * * * * * * *
Finally let me mention that there are omnivores which eat parts of the
blue water lily! According to legend it was the Egyptian goddess Isis
that pointed out to humanity that the rhizomes of the "blue lotus" are
The Louisiana red crawfish is also believed to munch on blue water
lilies and other water plants, contributing to their periodic
disappearance. But like humans, the crawfish must be considered an
omnivore as it eats insects as well as plants (apparently prefering
the latter, though).