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Dealing with Pond Plant Pests

Patty here.

It’s inevitable. Just when you think your pond is looking its best and all is right with the world, they invade. Aphids, weevils, moths, beetles and others descend onto those beautiful lilies, floaters, and marginals like a summertime scourge.

So what are some solutions to these nasty little pests? Being that your pond is most likely home to other inhabitants like koi, goldfish, frogs and other desirables, you’ll have to consider safe treatments, and the factor will rule out most chemical solutions.

Aphids are one of the most common invaders, sucking the life out of lilies, water lettuce and other soft-leaved aquatic plants. To avoid or minimize their foothold, prevention is the first step. Remove yellowing or damaged leaves from plants, they serve as beacons for the little suckers to home in on. Resist the urge to blast them off of leaves with a hose, as it usually serves more as high speed transport to other plants than as an eradication method. If only a few are present, you may be able to dunk the leaves or pull out putted plants and spray them away from the pond, at least as a temporary fix.
For more serious infestations there are some other methods to consider. You can try natural predator introduction. Ladybugs and green lacewings are natural aphid predators and though you may have a couple of these arrive on their own, you can purchase them online or at many garden centers and introduce them to feast on your pests. Orfes, minnows and guppies may also eat those that you can rinse into the pond. There are increasingly available herbal sprays for pond plants that will not harm fish, but be sure to read labels carefully. These sprays are usually formulated with herbal extracts, so they’re natural and mild, but sometimes too mild to really handle the situation. If you have the means you may even be able to formulate a similar spray by making a strong tea of rosemary, garlic, thyme, chrysanthemum or mint. Some suggest adding a cup of vegetable oil or a dash of dish soap to the mixture as well, but especially in the case of the soap, be sure to spray and rinse the plants well outside of the pond.

Other common pests include mosquitos, Leaf miners, and aquatic moth larvae. Prevention of infestation of these pests consists mainly of good maintenance of the pond and surrounding area, good water movement and the absence of dead leaves and debris in and around the pond. The natural predators mentioned above as well as others like predator wasps and dragonflies that are drawn to flowering plants and water may help, as may the small insect-eating fish mentioned above. Mosquito dunks are effective for the control of many waterborne insects, but they will also affect beneficial water insect larvae, so if you like those dragonflies, they may not be the best option. They are safe for use with fish.
Even though these pests can create a real headache for those of us with a love for aquatic plants, the overall aesthetic and health of a well- planted pond is worth the hassle. If you have any questions about a pest plaguing your water feature or you have a remedy that has worked for you to share, please let us know!

Image referenced from MorgueFile here.

2 comments

  1. avatar

    I have a 75 gallon pond with three goldfish each about 5 to 6 inches in length. I am have problems with ammonia and then nitrite levels being too high. I have tried changing the water up to 50% but still have the problems. I have a biological filter and an ultraviolet sterilizer and fountain head. I was told that the size of the fish was ok for that size pond. Now I see fin and tail rot and the fish are listless and gasping. What do you suggest? Should I remove them and treat them with Metronidazole? I believe there may be parasites and the continuing problem with the water quality is making things worse.

  2. avatar

    Roger,
    Those three fish should be fine in a pond of 75 gallons, it is hard to say what is causing your water quality problems. what sort of biological filter are you using, and what is your waterflow rate like? How much are you feeding the fish, they should only be fed once a day, as much as they can eat in a few minutes. If they are being fed more than that, or extra food is bieng left in the pond, that may be contributing to your water quality problems.
    As far as treating for parasites, it is hard to say what you may have, and what the proper treatment should be. If possible, take some pictures and email them to us at marinebio@thatpetplace.com and we can take a look at them and try to help you out.
    Thanks,
    Dave

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