Originally given as a presentation at the 2011 International Aquaponics Association conference. Learn the unique challenges of pest management in aquaponic systems, the basics of Integrated Pest Management, and learn more about the 5 "most wanted" pests in aquaponics.

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2. So what’s the difference between growing aquaponically and growing using more
traditional methods? There are many fewer products and practices that are friendly
to all three of the living organisms in your system, plants, fish and bacteria.
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3. However, I do think there are lessons that can be learned from the more traditional
growing methods, and one of them is the concept and practice of Integrated Pest
Management. This quote from the EPA website states incredibly clearly what IPM is
all about.
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5. The best offense is a good defense – growing plants in a properly balanced system is
key, as well as monitoring the plants for nutrient deficiencies.
In outdoor systems, there are fewer options available in terms of controlling the
growing environment, but there are more opportunities to work within a larger
ecosystem and use that to your advantage; for example, providing attractive habitats
for beneficial insects and wildlife.
In indoor systems IPM focuses much more on environmental control, because once
an insect pest finds its way into a greenhouse or a building, there often are few
natural enemies to keep the growing population in check.
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6. The action threshold is simply the number of insects that when observed indicate
that action needs to be taken. This number will vary from growing environment to
growing environment, and from season to season. Recommendations can be found
in IPM literature for a variety of conditions and insects.
For example, when I was monitoring aphid populations at Sweet Water Organics, we
decided that when we found more than 5-7 aphids per lettuce plant it was time to
take action.
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7. In order to implement that action threshold concept, you have to be surveying your
growing area on a regular basis. The survey tools and methods that you use will vary
greatly depending on the scale of your growing operation.
Yellow sticky traps can be very useful in monitoring insect species such as winged
aphids, fungus gnats, leafminers and others. Greenmethods.com (one of my favorite
resources for IPM topics) recommends 1 sticky trap for every 250-1000 square feet
depending on operation size. Blue colored sticky traps are also available which target
thrips.
It’s also possible to just hand inspect plants for infestations, carefully looking at both
the top leaf surfaces and underneath.
Once you have found the insects, it’s very helpful to have a lighted hand lens, such as
the one shown here, to identify what you’re looking at.
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8. And it’s very important to keep records of your observations. I created this system
map that was used to monitor insect populations during our weekly surveys. As
times passes these records will become incredibly valuable, as it is very possible that
patterns will be noted and preventative measures will be able to be implemented
before problems occur.
For example, if every spring aphids were noted in the top left part of the map, it
would suggest that there is either a way that aphids are coming into the growing
environment if it’s in an indoor situation, or perhaps the environment is just perfect
for aphids and that’s why they have more success. In either case, aphid predators
could be introduced before aphids even appear, to ‘nip the problem in the bud.’
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9. Now that we’ve gone over the basics of IPM, let’s get to the most wanted list. This
list is based primarily on my experiences, although I did read over the Bug Battle
thread on the Aquaponics Community site to gain some insight into what other
gardeners have been experiencing as well.
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10. Aphids are small six legged pear shaped soft bodied insects with distinctive ‘dual-
exhaust’ tailpipes, called cornicles. There are over 4,000 species of aphids, 250 of
which are known as pests in agriculture. They come in many colors, from green to
red to nearly transparent. They damage plants by inserting their stylet, or mouth
tube, into the plant tissue and sucking the juices out of the plant. In doing so, they
can also transmit plant diseases and viruses. They also secrete a sugary substance
called honeydew which can in turn cause sooty mold problems. Some aphid species
are actually farmed by ants for their honeydew, so if you see ants around your
aquaponics system make sure to look for aphids.
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11. I first became acquainted with aphids in aquaponics when my partner Jesse called me
in to take pictures of the aphid infestation that he had noted on his first couple of
visits to Sweet Water Organics, before our employment there. We sent this picture to
a university extension entomologist, and almost immediately heard back from them,
saying that this was one of the most extreme problems they had ever seen. If you
look closely you can see at least 5 generations of aphids on one leaf of lettuce!
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12. It’s hard to imagine anything causing plants in an aquaponics system to wilt, but
when aphids get out of control, they can cause damage such as this.
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13. Aphids have a huge advantage that most other species on the planet lack. Almost all
aphids are female, and they don’t need males to reproduce. In fact, the majority of
the time, aphids reproduce parthenogenetically – the females give birth to more
females in a live birth process. In fact, some species actually have telescoping
generations – a female aphid will have developing female offspring inside of her that
are already reproducing, meaning that the offspring are already born pregnant! Each
cycle takes 20-40 days, meaning that one aphid female can lead to thousands of
aphids in one growing season.
There can also be sexual reproduction when food becomes scarce or when light
periods change, leading to eggs that are able to withstand winter conditions to hatch
in the spring. Winged aphids can be either sexually or asexually produced when food
becomes scarce.
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14. This photo, one of the few that I did not personally take, shows the live birth process
that aphids undergo.
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16. The lovely ladybug. Ladybugs can be ordered from many IPM/biocontrol companies.
Most species are native to California, where they are gathered from the wild with bug
vacuums every fall when they gather for hibernation.
Adult ladybugs do eat aphids, but what you really want to happen when you release
ladybugs is something slightly different.
(In this picture you can also see a large number of white flakes, which are from the
aphids shedding skin as they grow. These flakes are an important thing to watch for
in surveys.)
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17. Ideally the ladybugs that you release will want to settle down and raise a family.
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18. When they do, you may notice ladybug eggs on your plants. Here are some, next to a
winged aphid for size comparison.
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19. The eggs are incredibly tiny, and it’s easy to miss them!
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20. 4-10 days later, tiny little ladybug larvae will hatch out of the eggs. At this stage they
look like tiny black ants, and it’s hard to believe that they can eat aphids that are
bigger than they are!
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21. During their one year lifespan ladybugs consume over 5,000 aphids, and the majority
of those are consumed during the larval stage.
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22. As they grow they shed their skin and get larger with more well defined orange spots.
In this picture you can see a larvae that has just crawled out of its old skin. The light
color of the body will darken slowly over several hours.
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23. This is a photo of a larvae in one of the final stages, or instars, before pupating and
becoming an adult ladybug. This larvae seems particularly proud of the winged aphid
it’s munching on, doesn’t it?
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24. After four instar stages, the larva pupate, attaching themselves to a secure surface.
3-10 days later, an adult ladybug emerges.
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25. All stages of the ladybug are valuable predators of aphids, and to a lesser degree,
mites and other small pests.
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26. It may seem to take while, but give ladybugs a chance to work their magic against an
aphid infestation and pretty soon you’ll see ladybug larvae in every stage all over the
place, and the tides will have turned in the bug battle.
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29. Spider Mites are small (.3-.5mm) eight legged tiny mites (not insects) that are
commonly found on ornamental and vegetable plants. The most common species is
the “two spotted” spider mite, which has two dark dots that can seem to form a
saddle.
Because of their small size, they are usually not detected until webbing occurs. This
webbing is actually silk that the mites produce to provide a sheltered area for their
eggs, as seen in this photo here.
Spider mites cause damage by sucking plant juices out and killing plant cells. This
damage appears as tiny yellow speckling or stippling on the leaf surface. Despite how
tiny they are, they can reproduce quickly and cause serious damage, even plant
death.
Spider mites are survivors, in the winter they take on a red form and can crawl into
cracks and crevices in a structure only to emerge in the spring. They prefer hot and
dry conditions.
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30. Luckily, there are some biocontrol options for those of us that have had to deal with
spider mite infestations. There are several notable options.
Phytoseiulus persimilis, pictured here, are fierce predators that actively seek out and
destroy spider mite populations. They reproduce at a faster rate the spider mites and
can really bring a population under control.
Other options include a mixture of three predatory mites as well as hypoaspis miles.
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31. Here is a photo of the Phytoseiulus persimilis mites facing off against a spider mite.
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33. Thrips are small oblong winged insect pests that are known for their tendency to
transmit over 20 plant viruses. The adults are attracted to brightly colored flowers in
yellow, pink and blue. This allows means that blue sticky traps attract thrips
effectively.
Like aphids, thrips are capable of reproducing parthenogentically, with no males
present. A female thrips slices plant tissue open and deposits her egg safely inside.
Some species pupate in the soil or media before emerging as adults.
Thrips are able to reproduce rapidly and can cause serious damage to crops.
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34. Thrips feed on plants with their rasping and sucking mouth parts. The thrips first
scrapes at the plant tissue, damaging cells, and then once the wound is weeping,
inserts its sucking stylet to draw up the juices. This causes a distinctive damage
pattern of silvery or bronze patches, shown in this photo here.
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36. Fungus gnats are tiny weak-flying fruit-fly like insects that are generally seen in adult
form in aquaponic systems. The adults are annoyance, but they don’t actually
damage plants. The damage is caused by the worm-like larvae, which live in the
growing media and are known to feed on root hairs, especially troublesome in young
seedlings.
Adult image courtesy Flickr user EBKauai, larvae image courtesy Colorado State
University Extension
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37. Control of fungus gnats can be accomplished using several techniques. If you have a
media filled bed, the first step is to lower the level that your water fills to at least 2”
below the surface of the media.
BT variety israelensis, commonly available as Mosquito Dunks, can be applied as a
powder (pound up the dunks in a paper bag with a hammer) and then watered into
the media surface. Sticky cards can be used to capture significant numbers of adults,
preventing them from reproducing. Parasitic nematodes are available which will
control larval stages, as are mites that seek out larvae within the media.
When surveying for larvae, placing small chunks of potatoes on the surface of your
media and checking them once per week is a recommended practice.
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38. Caterpillar damage can be devastating, happening seemingly overnight. There are
over 110,000 species of caterpillars, many are unique to a geographic area, although
everyone most likely has some in their neighborhood that will eat the plants that we
grow in our aquaponics systems.
Even in their youngest stages, they eat an astounding amount of plant material.
Because of this, if you notice any damage it’s best to shift your scouting to a daily
practice.
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39. And as they grow larger, their appetite grows with them. One of the tell-tale signs of
caterpillar infestation, other than the lack of leaves on any of your plants, are the
droppings that are left behind, called frass.
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40. Some varieties of caterpillars are very interesting looking, like the tomato horn worm.
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41. Hornworms can grow to four inches in length.
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42. Strategies for caterpillar infestations really vary depending on the situation. Spraying
with BT variety kurstaki, commercially available as Dipel is highly recommended. A
fungal mycoinsecticide, Beauveria bassiana, offers another potential solution.
Hand picking of caterpillars can be effective if the scale of the infestation is small
enough. Some growers feed the little buggers to their fish. Spined soldier bugs may
provide some measure of control as well.
Since some of the species of caterpillars commonly encountered hatch from eggs laid
directly onto the plants by flying moths or butterflies, the best prevention may be the
use of lightweight floating row covers over susceptible plants. These non-woven
translucent fabrics let in the majority of light and air, but prevent insects from
reaching plant surfaces. We have successfully used them in both indoor and outdoor
settings.
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43. This brief introduction to IPM and commonly encountered insect pests is only one
small step toward finding the best approach for dealing with unwanted insect pests in
your aquaponics system. Bugs are everywhere (as you can see if you look carefully at
this picture) and we might as well learn ways of co-existing with them as much as
possible, using the least toxic methods of control and preserving as much life as
possible.
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