Aquabotanist: How To Keep Emersed Growth Pest Free

The best way to deal with plant pests is to eliminate conditions that make them happy.

Scale has many stages of its lifecycle but is most noticeable as an oval shaped, brown lump. Scrape them off with a wet toothbrush. Mist the plant and repeat with the toothbrush until all scale is eliminated. Photo by Stephen G. Noble
Scale has many stages of its lifecycle but is most noticeable as an oval shaped, brown lump. Scrape them off with a wet toothbrush. Mist the plant and repeat with the toothbrush until all scale is eliminated. Photo by Stephen G. Noble

A common problem with emersed growing aquarium plants is the potential for an infestation by pests such as aphids, spider mites and scale. These terrestrial pests sometimes plague uncovered aquariums, paludariums and ripariums.  Evidence of their presence is the appearance of mini spider webs, brown lumps and sticky leaves.


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Low humidity, crowded vegetation and lack of air circulation is a guaranteed formula for these nasty pests to thrive. Take the following measures to eliminate desirable conditions for plant pests:

  1. Remove dead or dying leaves. Cut stems with sharp scissors, below the water’s surface if possible.
  2. Thin the vegetation regularly. Give your plants breathing space. Try to avoid having leaves touching each other.
  3. Ensure there is sufficient air flow.  Consider using a small fan to gently increase air circulation around the plants.  Pests love still air. Try to point the fan so that circulating air strikes the plant leaves and the water’s surface. The fan’s circulation will accelerate water evaporation from the tank. But evaporation is not always a disadvantage because the evaporation increases humidity which is desirable.
  4. Frequently mist. Use a spray bottle and mist the plants at least daily. Misting is always desirable and cannot be overdone as long as there is some air circulation.

Here are some do’s and don’ts if your emersed growing plants are currently infested:

  1. Never use any chemical means of eliminating plant pests. Chemical removal includes insecticides, oils, soap and waxy coverings. These substances can be deadly to your fish and other aquatic life.
  2. Isolate sick plants. If possible, remove and treat sick plants to prevent them from infecting the entire plant population. During the summer months, take the plant outside in the hot, humid air. Put the plant in a container of water taken from the aquarium and position it outdoors in a shady area with circulating air. Avoid direct sunlight because it could ‘sunburn’ and kill the plant. Oftentimes, you will see the high outdoor humidity eliminates most if not all of the pests within a couple of days.
  3. Mechanically remove the pests. This method is appropriate for in-tank or outdoor treatment. Use a wet toothbrush to gently scrape scale and other pests from the stems and leaves. Pay particular attention to the underside of the leaves where scale is frequently located. Remove every visible scale or spider web. Some leaves are so heavily infested that it makes sense to simply clip the leaf and concentrate on less infected leaves that are worth saving.  Heavily mist the plant following mechanical pest removal.

Naturally, the best way to deal with pests is to eliminate conditions that make them happy. High humidity, good air circulation and pruning greatly helps eliminate the pests’ desirable habitat. Enjoy your planted tank!

Article Categories:
Fish · Lifestyle

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