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Pond Plant Pests

Last Updated: 9/29/16

These are some of the animals that may eat or harm your aquatic plants in your pond. Some of them also attack aquarium plants indoors. My floating aquarium plants have aphids for example.

Dealing with Aphids
Other Plant Pests Introduction
Leaf-Mining Midges
Aquatic Moths
Waterlily Leaf Beetles
Water Lettuce and Water Hyacinth Weevils and Moths
Snails and Turtles
Plant Pest Links

Dealing with Aphids

Aphids (yellow aphids, milkweed aphids, oleander aphids) on milkweed on 9/18/16. Note the ant at the bottom. Ants collect honeydew from the aphids, and, in turn, the ants protect the aphids. To see a close-up of the same photo, click here.

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.

If you need to reduce their numbers, you have a few choices. Using any chemical is not a choice in a pond with any animals in it because pesticides will kill or harm ANY animal including goldfish, koi, other fish, and beneficial aquatic insects. In my ponds, I wipe the lily leaves off once a week, thus dunking the aphids into the water. My orfe and minnows eat some. Goldfish and koi do not apparently have much of a taste for them. Most manage to make it back to the leaves but I live with them. You can also squirt aphids off with a hose but this may damage lily leaves and sensitive plants. If the infested pond plant can be removed, it may be sprayed with soapy water or pesticides. After a good rinsing, it may be (not guaranteed!) safe for the animals. One in-pond recipe to kill aphids is to combine a cup of vegetable oil with four cups of water and add a squirt of dishwashing detergent. When sprayed on aphids on leaves, this will smother them. If any oil gets in the pond, it can be soaked up with towels. It is not a good idea to get soap in a pond though. Diatomaceous earth may also be sprinkled on plants to dry up the aphids.

The best way to help insure that aphids do not do severe damage is to introduce natural predators to your ecosystem. That means buying ladybugs and green lacewing eggs. Ladybug larvae and adults eat aphids. Green lacewing larvae eat aphids. Many garden suppliers sell these bugs including Gardens Alive!. You will never have an aphid-free system so learn to live with some of them. Unless you have a real infestation, the plants will cope just fine. When I set up my indoor tub pond in the basement, the aphids often kill off some overwintering tropical pond plants. Sometimes a ladybug or two will show up (having come in as an egg or larvae) to help with the situation. I do not mind good bugs in the house.

There is a new (2002 or so) product out that is a botanical insecticide herbal aphid control. It is safe for fish. The active ingredients are thyme and mint. I got some in April of 2001. I used it on some tropical water hibiscus. It seemed to kill some of the aphids but it also caused the water hibiscus leaves to wilt and some died even after rinsing the solution off. In July of 2001, aphids annihilated my water lettuce. After it was 95% dead, I sprayed the aphids and the surrounding water lilies with this product. Even when drenched in it, it did not seem to kill them! The water lettuce was then 100% dead, and the aphids were having fun on the lily leaves. Aqua-Mart (1-800-245-5814), Paradise Water Gardens (1-800-955-0161), Drs. Foster and Smith (1-800-381-7179), and Springdale Water Gardens (1-800-420-5459) used to sell Herbal Aphid Control. It says not to use it on water lettuce (the aphids killed mine!). I have also tried Bladerunner (see the next paragraph) on aphids on some milkweed near my pond but the aphids seemed unaffected. I think they stopped making this product.

There is a new product (8/14/06) that I have only seen at one store so far called Aphid X. It contains garlic juice to repel aphids and also, it claims, most insects and mammals. I do not know how well it works. It is safe for fish and plants. Here is the link: Aphid X

Other Plant Pests Introduction

Most of these pests below are found in relation to waterlily leaves but they can attack other aquatic plants as well.

I recently read that mosquito dunks not only kill mosquito larvae but that they are good to kill off some of the following aquatic plant pests (as long as the insects are in the water on the plant). Mosquito dunks may kill many insects, good and bad. I discovered another product called Bladerunner which is a white powder that kills most insects by dessicating them (dried them out). Avoid getting this on butterfly caterpillars and ladybugs. I bought mine from Aqua-Mart but they no longer sell it.

I have so much to do and so many plants, I usually do not bother to try to control plant pests since I do not want to use pesticides. Needless to say, some of my outdoor and indoor terrestrial plants as well as pond plants do poorly or even die off thanks to bugs. If you have tips on controlling various plant pests, please contact me.

Leaf-Mining Midges

The leaf-mining midge, Cricotopus ornatus makes trails all over lily pads. The vegetation at the trails dies, turns brown, and rots. The larvae can be found at the end of the trails and be removed. Adults look similar to mosquitoes. Mosquito dunks may be used to kill larvae in the pond.

Aquatic Moths

Aquatic moth larvae use pieces of leaves to make a blanket or home over top of the leaf they are eating (often lily leaves). Removing dry vegetation in and around the pond will deter them.

The China Mark Moth can become a real pest in some ponds. I have encountered some sources giving the scientific name as Nymphuliella daeckealis and another giving Hydrocampa propraolis. In small numbers, it is hardly noticed. In large numbers, it can eat its way through an entire pond full of water lilies, water hyacinth, and other plants. They are also called the "sandwich man" because they make a home from two pieces of water lily leaves and "sandwich" themselves into it for protection. The moth larvae may travel from plant to plant by floating around in the pond in their little sandwich boats. Their sandwiches/boats should be removed from the pond when found. If you look inside, there should be a moth caterpillar. Mosquito dunks may kill them but usually hand removal is the best method to control them. At least one research group is looking into safe methods of controlling the China Mark Moth. The adult moth is brown and white. Avoiding lighting near the pond at night may reduce the quantity of adults coming in to lay eggs. See under links below for more on this moth.

Waterlily Leaf Beetles

The waterlily leaf or Donacia beetles are predators of aquatic plants. Mostly they eat water lilies but may attack skunk cabbage, pickerel weed, and other plants. There are at least 36 species. They have a glossy body of black with green or yellow shiny specks. In the summer, adult females put o's in lily leaves and deposit their eggs through the hole under the waterlily leaf. Larvae make silk nests under the leaves. It takes about 10 months for an egg to result in an adult. Eggs and larvae can be wiped off leaves. If the infestation is bad, plants can be treated with insecticides outside of the pond and returned after a good rinsing. Remove dead vegetation around the pond to reduce the population of overwintering adults. Adults are a quarter to half an inch long.

Water Lettuce and Water Hyacinth Weevils and Moths

Thanks to Ballard in March of 2006, I learned that there are water lettuce weevils. They have been introduced in tropical areas where water lettuce lives year round to kill it where it is an invasive species. The problem is that sometimes the weevils come up from the south to plants that are put into Northern ponds where they pose no invasive threat (because they die over the winter). The water lettuce weevil is tropical. Water lettuce is sensitive to most methods used to kill insects that eat it. I have not found a good way to rid it of aphids for example which really go for water lettuce. A few weevils can easily be picked off but for an infestion, more drastic measures are needed. I do not know if they would work but mosquito dunks help with many fly and moth pest species. Otherwise, toxic pesticides (applied away from the pond) may be an option for those willing to risk it. Ballard says the larvae are worm-like and live in a small hole. The adults look like small beetles. In learning about the water lettuce weevil which feeds on water lettuce as both larvae and adults, I found out about the water lettuce moth as well. The larvae of the water lettuce moth feed on water lettuce. They are also tropical and introduced to control water lettuce. I also found out there are various weevils and moths used against water hyacinth as well.

Water lettuce weevil: Neohydronomus affinis
Water lettuce moth: Spodoptera pectinicornis
Water hyacinth weevil: Neochetina species
Water hyacinth moth: Sameodes albiguttalis

Here are some web sites for information and photos of water lettuce and water hyacinth weevils and moths. These links were last checked on 4/18/06.:
Water lettuce
Invasive.org and Forestry Images which are the same information on water lettuce pestson two separate sites (I am giving both in case one gives out.)
Invasive.org page on water hyacinth weevils.
Florida Biological Controls - lists a whole bunch of pests of various plants considered invasive there
Water hyacinth - has information and photos of pests used to kill water hyacinth.

Snails and Turtles

I stuck these guys in here because at high levels of snail individuals, their damage is often misinterpreted as being due to insects. At the same time, often damage done to waterlily leaves is blamed on the snails just because they are more visible and happen to be there. Normally, snail damage is not major. In my 153 gallon pond, I literally have a few hundred pond, ramshorn (two kinds), and perhaps other snails. Since they are overpopulated, I do get some waterlily leaf damage that I know is from them. I can watch them actually eating! Snails will cut and eat various patterns into leaves with chunks off the edges being most common. Snails can also leave circular holes in leaves too like waterlily leaf beetles do. Certain species of apple snails will eat a lot of various kinds of aquatic vegetation. Some aquatic turtles will also bite off the edges of water lilies. For more on these guys, see my snail page and turtle page.

I took this photo on 6/21/08 of some water lily leaves damaged by snails in my 153 gallon pond.
Waterlily leaves damaged by snails

Plant Pest Links

These links were last checked on 4/18/06.

China Mark Moth - this is an archived version as the original no longer exists.

Royal Horticultural Society page on waterlily pests including aphids, waterlily beetles, and leaf mining midges:

Waterlily Pests. Somewhat contrary to my other sources, this page lists these three species: waterlily aphid (Rophalosiphum nymphaeae), waterlily leaf beetle (Galerucella nymphaeae), and the waterlily leafcutter (Synclita obliteralis, I guess they mean the leaf-mining midges).

Waterlily Pests - China mark moth

Also, visit my aquatic insect index.

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Go to the main plant page (full index).
Go to the aquarium algae index.
Go to the pond algae index.
Go to the aquarium plant index.
Go to the pond plant index.
See the master index for the plant pages (quick index).

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