Know Your Bugs: Aphidoletes aphidimyza – The Aphid Eliminator.

Aphidoletes aphidimyza (common name: Aphidoletes [a-fid-o-lee-tees]) is among the most used aphid controls in agriculture, horticulture, landscapes, greenhouses and especially ornamentals. Like all the best biological control agents, Aphidoletes works with a combination of eating lots, but also by multiplying quickly, overcoming the pest. 

Aphidoletes larva searching for aphids

Where it comes from:

Aphidoletes were discovered by researchers in Germany. They were rearing Aphidius, but lost their colony when Aphidoletes contaminated and eliminated their aphid colony. Seeing how well and quickly it wiped-out their aphids, they turned them over to Producers like Applied Bio-Nomics Ltd. to try and rear them commercially. They have since been found in the wild all across the Northern Hemisphere and are considered native and appropriate for outside release in North America, Europe and Asia. Likely some of the “clouds” of midges you are familiar with that buzz around together at dusk are aphidoletes in their natural setting.

How it works:

Aphidoletes are midges. The adults are just like small mosquitos, but the larva (which are called maggots when they belong to the fly family) live on plants and eat aphids. 

Adults fly around (especially) at dusk when temperatures fall, humidity increases and winds decrease. It is at this time that they seek a mate, or use their sense of smell to source-out honeydew (the secretion of aphids or other sucking plant pests). Then, they eat the honeydew and look for aphids to lay their eggs near (or sometimes on top). The eggs are tiny, orange, and hatch quickly. The emerging maggot immediately goes to work.

As is common in nature, when predator populations are high, they usually have a dominant competitive trait. This is true of Aphidoletes. Because each adult can lay hundreds of eggs, each larva is in a race to feed as quickly as possible to out-compete their siblings. Each Aphidoletes larva will eat, on average, 18 aphids by biting their legs and injecting a toxin that kills and liquifies the aphid’s insides and sucks the “aphid-goodness” out through the leg. But, being the competitive little buggers that they are, they may choose to crawl around biting up to two-hundred aphids, killing that many, while only stopping to feed when necessary. 

This trait helps make them such a successful bio-control: When there are few aphids, the larva crawl around and look for enough aphids for them to successfully pupate. When aphid numbers are high, the larva will kill indiscriminately before pupating. So Aphidoletes can be used both preventatively and as a hot-spot clean-up. 

When larva are ready to pupate they drop or crawl to the ground. They find a suitable place to pupate, usually in soil, but sometimes under pots or other debris. Within a few days, you can expect clouds of the new generation of Aphidoletes ready to continue the hunt. 

Where you can get it:

Most commercial beneficial insectaries, like Applied Bio-Nomics Ltd. produce aphidoletes which are available through them or their distributors. Simply check out their websites and order aphidoletes. 

Not all Aphidoletes are equal:

While there are many sources of Aphidoletes, careful attention should be paid to the producer/supplier’s track record on supplying fresh, non-refrigerated insects and mites. (Typically the closer they are to you, the better.) 

Applied Bio-Nomics Ltd. is well known for supplying the top-quality beneficial insects, and with Aphidoletes there is an interesting case-study associated with this quality advantage:

A few decades ago, Aphidoletes producers in Europe were suffering a crash in their colony and producing no Aphidoletes. As a result they bought from Applied Bio-Nomics Ltd (Canada) in order to meet their sales. One grower in the Netherlands was trialing Applied Bio-Nomics’s Aphidoletes against one of the European producers. Applied’s products were dramatically better, so the owner of Applied visited that grower on the next trip to Europe. Little did the grower know, that he was placing Applied’s Aphidoletes’ in both green houses, but the under-producing ones had been handled by the European producer. After some time it became understood that Applied was selling all they could produce, so the grower in the Netherlands was receiving Aphidoletes from Applied as fast as they could be produced and that were not being stored. The European company was storing several weeks worth of Aphidoletes, and shipping their oldest stock. But at that time it was well known, and standard practice, to refrigerate the Aphidoletes pupa for several weeks in order to build up inventory. When warmed, adult emergence was always the same. So Applied Bio-Nomics Ltd contacted researchers to determine what affect this cold storage has. It turns out that while the adults appear healthy when they emerge from the cold, several things have happened. First, they lay fewer eggs. Secondly they have lost all searching ability. It’s as if they go into a type of survival mode, where upon release they lay eggs wherever they can regardless of aphid quality and quantity or if other predators and Aphidoletes eggs are already present. Aphid control with cold-stored Aphidoletes only occurs within a few feet of their release point. Alternatively, the fresh Aphidoletes are capable of smelling honeydew and providing aphid control across a hectare from a single, central release point. Researchers found that they would seek out honeydew, but lay eggs according to aphid population. And if other predators or aphidoletes eggs or larva were already present, they’d fly off in order to find un-touched or new aphid colonies…even single aphids. 

Researchers went further and found that being kept below 8 degrees celsius for as little as half an hour triggered these changes. And they further found that the fresh Aphidoletes had better heat and cold tolerance, making them suitable for hot greenhouses and cold frames down to 18C.

So before you order any Aphidoletes, consider asking for the best. Demand, un-refrigerated, or non-cold-stored Aphidoletes. Ensure the distributor and retailers are providing them to you the day they arrive and that never were they packaged or shipped with ice or other refrigerants. 

When Aphidoletes are fit and fresh they are simply the best tool for aphid predation. 

How do you use it:

Preventatively, buy fresh Applied Bio-Nomics Aphidoletes at a rate of 250 per hectare every two weeks. If aphids are present, but in low numbers, or you have a very susceptible crop, increase this to 1000 at the same schedule or provide it weekly. If Aphid numbers are high, consider up to three times this amount and apply more as necessary. 

Using Aphidoletes preventatively will save you money over the course of the season. If you see few aphids, it is working. Start these preventative applications around April or a couple of weeks before you typically notice aphids arriving. 

You will receive a container containing Aphidoletes in pupa form. Keep them out of direct bright light and at a cool room temperature and wait for them to emerge as adults.

  NOTE: Never open the container prior to this. There is a carefully measured moisture content within to ensure optimal pupal survival.

In these conditions the adults can remain within the container for 24 hours. Doing so is beneficial as it allows the adults to mate before release and allows you to do a quick Quality Control by counting the adults. When ready, carefully carry the container to the release point and open the lid.

NOTE: Adults are fragile. Once they have emerged, avoid shaking or stirring the media as it will kill them.

If you have fresh Aphidoletes, release them centrally – not necessarily near an aphid colony as this can mask the smell of more distant colonies. If your Aphidoletes are cold-stored, you will need to buy at least 10 x more and release them, spaced out around your green house. Always use directions from the company you have bought them from. 

For outdoor applications, wait until aphids are present then release one container per acre, you can use 250 for small amounts of Aphids or up to 5,000 if you need them gone. But, ideally, you don’t want to eradicate the aphids, just simply control them. If some aphids survive then the Aphidoletes will continue to cycle and protect your yard. Too much Aphidoletes and they will leave or starve after eating all the aphids. Then when aphids show up again, you’ll have to buy more Aphidoletes. Save your money – do it right the first time. 

Bonus:

Pea aphid. One of many species Aphidoletes will control.

Of all aphid predators, Aphidoletes has the biggest host-range: it controls almost every aphid species. The obvious exceptions are the Oleander aphid (toxic) and Foxglove aphid because (while Aphidoletes can control them) Foxglove aphids are happy and reproduce quickly at temperatures well below 18C, at which temperature Aphidoletes slow down and can not out-compete the aphids. Fortunately you can get both the Brown Lacewing and the American Hoverfly from Applied Bio-Nomics, which are active aphid predators down to 4C. (4C for the lacewing, 12C for the hoverfly). 

Vermiform larva (wormlike) do not elicit aphid defences making them better predators. Anything that walks with feet, or is large or flies tend to cause aphids to make defensive manoeuvres such as dropping off the leaf, kicking or walking away. Larva like those of the hoverfly and aphidoletes can crawl up to aphids and feed on them undetected. When ants or other Aphidoletes predators are present you can often find the Aphidoletes larva hiding under aphids.

Furthermore, because the adult Aphidoletes search for honeydew, they are attracted to the locations of other plant-sucking insects. Aphidoletes are regularly used to control greenhouse and bemisia whitefly outbreaks. It’s easy to see them working in this way: the (otherwise orange) larva turn yellow when feeding exclusively on whitefly. 

Aphidoletes turn yellow when they feed on whitefly species.

Best of all: Aphidoletes is the aphid control of choice for ornamentals or leafy green vegetables. Parasitoids, like Aphidius, only feed on the aphids and use them as hosts. The puparium that the Aphidius wasps leave can make ornamentals or crops like salad green unsellable. Likewise, beetles like ladybugs will also only eat the aphids leaving the mess of aphid molts and honeydew behind. But Aphidoletes adults will lick up all the honeydew causing the other debris to fall from the plants, and they pupate off the plants and are small enough to be overlooked anyways. There really is no better aphid bio-control agent. 

While these Aphidius mummies are a sign of control, the sight often discourages buyers.

Quick Tips:

For Gardens: Outdoor releases (without supplemental light) between September and April will result in larva detecting low light and feeding more, but they will diapause (hibernate) for the winter as pupa. All is not lost: when soil temperatures increase in the spring they will reemerge as adults. You can control some aphids with aphidoletes in this way, but there are better products available. If you must, hang a string of Christmas lights to increase the light to dark ratio to at least 14 light to 10 dark. This will keep them cycling as long as temperatures are comfortable.

For Cannabis: Most cannabis growers struggle with using beneficial insects for aphid control. The reason is simple: low humidity and high air velocity. The artificial air movement inhibits all flying insects from finding suitable places to lay eggs or to find food. But even non-winged insects will “hunker down” during high winds. In nature they just hold on and wait for the wind to die-down. With cannabis being constantly blown, beneficials suffer. Furthermore the low humidity results in poor egg development, some larval mortality and failures in pupation. This is true of all beneficial insects. Only Stethorus punctillum (a beetle for spider mite control is comfortable at these low humidities. So, turn those fans down and slowly increase the humidity to get pest control. Only rapid changes in humidity cause mildews to go into reproductive stages. (Like when you grow dry and then water your plants, it causes such a rapid change.) 

Read more: “Bio-control Strategy for Cannabis.”

For hydroponics / no soil media. Aphidoletes have to pupate protected. Without a suitable place you need to apply more Aphidoletes and more regularly in order to get the same control other growers may get with the cycling of generations. 

Ants: Ants protect Aphid colonies which they preserve in order to feed on aphid honeydew. Ants will kill or remove many aphid predators including Aphidoletes larva. Sometimes aphid control starts with ant control.

If you’re curious about alternatives to aphid control, try these:

Holy Aphids

Never Buy Ladybugs

Alternatives to Ladybugs

And don’t forget that aphid control in a garden is sometimes as easy as attracting predatory insects. Read more:

How to promote beneficial insects.

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