British and garden predators - the bad guys

We can divide up the animal pest and predators as:

(a.) Antisocial pond residents (b.) Unwanted guests.

(a.) ANTISOCIAL POND RESIDENTS

The Great Diving Beetle, Dysticus marginalis. This kills small fish considerably larger than itself. Net it out. Not to be confused with the Great Silver Beetle, which eats plants and is the largest beetle in the pond. The Great Diving Beetle has a paler brown margin around the edge of his shell.

Waterboatmen (Notonecta, 4 species) sometimes referred to as Backswimmers to distinguish them from the Lesser Water Boatman (Corixa, 36 species), they attack very small fry and damage larger fish. Net them out if they are too numerous. The Backswimmers are also distinctive by swimming upside down. They have a longer more pointed back than the Water boatmen.

Waterlily Beetle, Galerucella nymphaea - Dull brown, slightly larger than a Ladybird. It is hump backed grub as a juvenile and both feed on lily leaves by cutting channels in the surface. Eventually the channels merge and the leaf blackens and decays. (see Plant Problems for Specific Plants - Lilies.)

THOSE RESIDENTS WITH IMAGE PROBLEMS

Water Scorpions (Nepa cinerea and Ranatra linearis)- These large insects frightening to look at with their legs adapted to look and serve as giant mandibles, but they are harmless to all but the smallest of pond creatures.

Dragonfly larvae. These can be fearsome characters that can give you nip mistaking you for something a la carte. They do it fish but they pose no overall problem. They are to my mind an essential ingredient.

Frogs have been known to grab largish fish or fat slow ornamentals whilst in the grip of spring fever. This is a perennial subject of debate but this is so rare that they pose no real risk. Fat, slow ornamentals ought to be indoors at frog spawning time as they may be most at risk.

Mosquitoes and their larvae. They thrive without competition and also in very stagnant ponds. You may have a water problem. Get some more plant life in there. Fish soon eat all mosquito larvae but they wont tolerate stagnant conditions.

Newts. They eat fish fry but are good guys really. The Great Crested Newt is a protected species.

Snails. All snails eat plants. Planorbis corneus- the large Ramshorn is preferable to Linnaea stagnalis. You will find snail eggs underneath lily leaves. Rub them off. (See Plant Problems: Eaten Foliage).

The large Ramshorn water snail is far preferable since it eats algae in preference to plants, so I am told.

These beasties are all part of the fabric of the environment and unless their numbers get ludicrously out of control they will find their niche in the exciting cycle of life in the pond. If they do seem to be thriving at the expense of the rest of the pond community then they must be thriving on something that is itself thriving.

(b.) UNWANTED GUESTS

Cats, Herons, Otters, Mink and others.

There are certain visitors to the edge of our pond environment that we can regard as unwelcome since their intentions are always what we would consider as destructive. In order to deter them and of course if money is no object then technology provides a never-ending array of possibilities. But what is relevant to us of modest means and simple water gardens? We also love our furry four-footed friends and feathered chums and we like to have them around - sometimes. But it would be nice to know that if we depart from the tranquil scene that mayhem and murder isn't next on the schedule.