Northwest, USA |

Dave Brigante |

Aphid infestation on a taro leaf
Photo from taropest.sci.qut.edu.au |
Insects on
Aquatic Plants
by Dave Brigante
Oregon USA
Click images to enlarge |
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What is really bugging you? As far as aquatic plants are concerned
anyone who has grown them has had some insect contact on one
level or another. Nuisance pests are inherent in this plant group
just as they are in all of the others. Over the many years that
I have been growing aquatics I have certainly noticed some trends.
I hope that by making pond plant growers and enthusiasts more
aware of the potential for insect invasions on certain varieties,
we can all cope with and possibly avoid some of the more typical
insect damage issues that can come along. |
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In preparing to write this article I started by making a chart
(I love charts) of most of the plants that I grow or that are
somewhat common in the aquatic plant field. Then I determined
which insects just can't seem to stay away from each of them.
This information is geared for aquatic marginals, but floating
aquatics are also prone to visits by an occasional pest or two.
One example would be the special fondness that aphids have for
waterlilies. The chart's main headings are aphids, spider mites
and white flies, plus my personal favorite category, none.
Aphids are far and away the most prevalent problem of the
"Big Three". It made me question whether there are
any plants that they won't suck on. These versatile insects can
be found in at least seven different colors. They can come into
the world from unimpregnated females and they can transmit disease
from one plant to the next. The earlier you can detect these
guys (or girls) on your plants before the damage is done the
better. Some of the various types typically show up on an annual
basis on the same plants, green aphids on variegated cattails,
black aphids on waterlilies and yellow aphids on Canna
lilies. If any of these are allowed to go unchecked you can end
up with some very sick looking plants. One good thing is that
they are not too hard to get rid of if only a small population
is found initially. |

Aphids on a baby Victoria leaf
Kit Knotts Photo |

Aphids on a taro leaf
Photo from taropest.sci.qut.edu.au
More aphid information
More aphid photos |

Spider mites on Eichhornia crassipes
Kit Knotts Photo |
The other two, spider mites and white flies, are less common
but still have the potential to explode onto the scene when you
least expect it. Spider mites often go undetected until you notice
the tiny white webbing that is usually associated with their
colonies. The use of a magnifying hand lens comes in really handy
when scouting for mites. |
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Spider mites
Photo from bio.scarletts.co.uk |
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Adults can be seen crawling around slowly and more than likely
there will also be some spherical egg clusters close by getting
ready to hatch. These little critters are more apt to create
havoc during the warmer seasons, then down cycling to a less
active demeanor as temperatures decrease below 60 degrees. Amazingly,
as you'll see on "The Chart" they even cause grief
for waterlilies. I've seen vast damage take place very quickly
in high density growing conditions.
More spider mite information |

White flies
Photo by Dr. Martin Fregene
from africancrops.net |
The last main player, white flies, can be equally as annoying
as the other two previously mentioned. I know I have a problem
when I first see them merrily fluttering about in all of their
pure white glory. Once again prompt action is required to snuff
them out before they can take hold. As a beginner grower I learned
that these insects absolutely need repeated eradication treatments
to stop their reproductive cycles. As with most insects it is
best to eliminate the present day adults and also take some type
of measures to suppress ensuing juvenile stage hatches.
As a general rule good clean maintenance practices can go
along ways towards reducing the potential for insect population
explosions. Taking the extra time required to inspect your plants
on a regular basis will also help. As "they" say, it's
best to "nip it in the bud".
If any of these assassins do make their way into your personal
jungle, there may be a few things that you may want to consider
before taking your flame thrower out for a spin. How important
are the plants to you? How bad is the infestation and what method
of treatment are you going to pursue? Tossing the plants can
be relatively easy, but you wouldn't want to make a habit of
using that type of treatment too many times. If the colony of
insects is so large that the plants have already suffered so
much that a short term recovery is looking bleak, a grooming,
hosing off and possible spray application could be a consideration.
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White flies on a taro leaf
Photo from taropest.sci.qut.edu.au
More white fly information |
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The options for treatment are plentiful, always using pesticides
only as a last resort. There are some garden-ready sprays that
are much less toxic to the environment and the applier too. For
the backyard pond, using something on that level or just hosing
off your plants on a regular basis may be best. If the plant
(or plants) can be submerged below the waters surface for a few
days, that can also be a very effective alternative. Of course,
if using a pesticide is necessary read the label completely to
be aware of any safety precautions and to check to see if it
is fish safe or not. On a commercial level using lower toxicity
insecticides that are insect specific and have a longer residual
prevention period should be considered.
The incidence of insect discovery is more common in a greenhouse
versus outside where mother nature is lending a hand. The greenhouse
environment is so controlled and the plant diversity is such
that it makes the prevalence of insect problems that much greater.
Unfortunately the season for the right conditions is also extended
indoors. This is usually from March to October; outdoors you
can probably take a month off each end of that time period.
The chart below highlights the potential for what may come
around for an unwelcome visit. With good plant spacing, keeping
your plants clean and regular monitoring, a lot of this can be
kept as just potential and not become a reality. |
|
Plant Name |
Spider Mites |
Aphids |
White Flies |
None or Other |
|
Acorus |
X |
X |
|
|
|
Anemopsis |
|
|
|
X |
|
Arundo |
|
X |
|
|
|
Bacopa |
|
X |
|
|
|
Baumea |
|
|
|
X |
|
Caltha |
|
X |
|
|
|
Canna |
X |
X |
X |
|
|
Carex |
|
X |
|
|
|
Colocasia |
X |
X |
X |
|
|
Cyperus |
|
X |
|
|
|
Cyperus haspan |
|
X |
|
|
|
Dichromena |
|
X |
|
|
|
Dulichium |
|
X |
|
|
|
Echinodorus |
|
X |
X |
|
|
Elettaria |
|
|
|
X |
|
Equisetum |
|
|
|
X |
|
Eriophorum |
|
X |
|
|
|
Glyceria |
|
X |
|
|
|
Gunnera |
|
X |
|
|
|
Hibiscus |
X |
X |
X |
|
|
Hippurus |
|
X |
|
|
|
Houttynia |
|
|
|
X |
|
Hydrocleys |
|
X |
|
|
|
Hydrocotyle |
|
X |
|
|
|
Iris |
X |
X |
|
|
|
Juncus |
|
X |
|
|
|
Lobelia |
|
X |
X |
|
|
Lysimachia |
|
X |
X |
|
|
Marsilea |
|
X |
|
|
|
Menyanthes |
X |
X |
|
|
|
Mimulus |
|
X |
X |
|
|
Myosotis |
|
X |
|
|
|
Nymphaea |
X |
X |
|
China mark moth |
|
Oenanthe |
X |
X |
X |
|
|
Peltandra |
|
X |
|
|
|
Pontederia |
X |
X |
X |
|
|
Ranunculus |
|
X |
X |
|
|
Ruellia |
|
X |
X |
|
|
Sagittaria |
|
X |
X |
|
|
Saururus |
|
X |
X |
|
|
Scirpus |
|
|
|
X |
|
Scirpus cernuus |
|
|
|
Wooly aphid |
|
Thalia |
X |
X |
|
|
|
Tulbaghia |
|
|
|
X |
|
Typha |
X |
X |
|
|
|
Vallisneria |
|
X |
|
|
|
Victoria |
X |
X |
|
|
|
Wedelia |
|
X |
X |
|
|
Zephyranthes |
|
X |
|
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