Fruit Tree Pest Control

Fruit Tree Pest Control

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Pests in trees usually come and go. Seldom will a tree die from regular pest pressure. When they do, there is a reason: An introduced pest with no natural enemies, or a stressed tree suffering from something else. In fact, when someone has shown me a tree dying of a normal pest infestation I usually find and show them that the roots show serious die-back and rot. Thus, something below the ground has weakened the plant and the above-ground pest is merely a symptom. 

This doesn’t mean you don’t have to treat for pests. Your tree’s roots must always be protected; an infestation during fruit-set can produce poor yields; even a recoverable loss of foliage will stress a tree and make it unable to reach its potential. So, here’s what to do.

They say the best time to plant a fruit tree was twenty years ago. Well the best time to apply Stratiolaelaps scimitus or Gaeolaelaps gillespii is yesterday. These two in-soil predatory mites will feed on anything that is feeding on the roots of your tree (also pupating thrips, root weevils, root aphids and overwintering spider mites). Remember the roots you see are only part of the picture. The tiny filaments coming off of those roots do much of the work and they are most often the parts being bitten and nipped. Much of this is normal and natural, but the presence of these mites (applied at 25 mites per square foot) will protect those filaments resulting in substantially-increased growth. The best part: you only need one of the mite species (your choice) and the application is permanent. Without any chemical interference, they will stay in a protective density for at least 20 years. (It could be longer, but we stopped checking after 20 years…it’s a tedious task.)

Stratiolaelaps scimitus3
Stratiolaelaps scimitus

Whenever you can apply a “permanent” bio control agent, you should. Our next “permanent” one is a foliar-predatory mite, Neoseiulus fallacis. There are lots of tiny nasties feeding on your fruit trees. Some are obvious, like spider mites; others less so, like russet and broad mites or pear blister mite. Fallacis (as we commonly call it) is best applied when your fruit trees have leaves.

Neoseiulus fallacis 1
Neoseiulus fallacis

At that time there is plenty of food for them to multiply. But, they are native (first identified in an orchard in Ontario) and likely drop to the ground and overwinter in leaf litter just like their prey. The best thing about fallacis: the application rate of fallacis from Applied Bio-Nomics ltd (because it’s reared on it’s intended prey and thus more fit and healthy) is only 2 mites per square meter! Think about that! The reason for this is their range of food is such that they can survive when prey is scarce (also feeding on wind-blown pollen). However, this low rate also means it will only ever be a preventative. When an influx of pests arrive, or the infestation requires a reaction, the low density of fallacis will only overtake the pest populations after damage is done. Reaction to a pest is dependant on the pest and information in that regard can be found at this website www.appliedbio-nomics.com . So again, the best time to apply fallacis: yesterday.

Neoseiulus fallacis egg and adults
Neoseiulus fallacis with eggs

I know, if you’ve read this far, you’re wondering about the fruit tree pests you’re familiar with: caterpilars, aphids, other defoliators or fruit damaging pests. Let me transition there by reiterating what we just covered: while the bad mites are small, their damage is substation and weakens the trees. Weak trees attract other pests. Just doing the application of fallacis and a soil predator will result in an eventual reduction of other pests. Additionally, because you’ve applied beneficial mites, you’ll be less likely to apply a chemical, or a soap/home remedy which  (in the process of killing the bad bugs – and the good) will strip the leaves of their natural oils and protective coating, stress the plant and attract more pests. However, applying the beneficial mites and stopping the application of any chemical/home remedy does not get you out of the woods.

Cold season protection: Micromus variegatus, our brown lacewing is a fierce generalist predator all the way down to 4 degrees celsius.

Mv adult 2
Micromus variegatus adult

It feeds primarily on aphids, but will also feed on small caterpillars, soft scale, mealybugs and more. Having them established in your yard prior to the spring influx of caterpillars and aphids will allow them to wipe-out small, budding colonies. 

Mv larva eating
Micromus variegatus larva

At flower: release of Eupeodes americanus our American Hoverfly will result in both pollination of your flowers (adults are incredible pollinators) and on-going aphid control. Their larva – established as eggs laid in aphid colonies – will each eat between 70 and 100 aphids (or more) in one week. 

Eupeodes americanus adult 1
American Hoverfly: Eupeodes americanus

Prunus: Prunus trees are hugely susceptible to aphids. A once-per-season release of Aphidoletes aphidimyza (a predatory midge) once aphids are observed in your trees will wipe out a population and maintain a balance for the rest of the summer.

Aphidoletes aphidimyza predation view 1

Tips and Tricks: Fruit trees do best when nothing else is planted near the trunk. If you wish to plant something near, however – consider flowering bulbs that bloom the same time as the adjacent fruit.

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These flowers will attract pollinators, but also other pests (like bulb mites) which in turn attract other predators. Similarly, planting sweet alyssum or buckwheat are both beneficial from a soil-building perspective but also attract (disproportionately) wasps. Wasps are key to your orchard – and I don’t mean the human-stinging type, although they are one of the few insects that will take out full-sized caterpillars. I mean the other thousands of species of native wasps (some near microscopic) that are almost always parasitoids of pests. A bed of alyssum or buckwheat WILL result in massive predation of aphids, caterpillars, leaf-miners…etc. If you do nothing else….plant lots these two plants in your garden. 

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Love it or hate it, birds are essential to take out the bigger pests: caterpillars, full sized grubs, stinkbugs…etc. Yes, they’ll eat honeybees, bumblebees and your fruit but keep in mind there is a natural balance that an orchard is resisting. It takes many chemical -free years and lots of adjacent natural areas to regain the equilibrium. In the meantime you’ll have to monitor, protect and react. 

Finally, sucking insects like aphids love nitrogen. Do not over-fertilize your fruit trees (or any plants for that matter.) Nitrogen promotes growth, but the growth is soft and favoured by most pests. Alternatively, the potassium and phosphorus rich nutrients promote boom and fruit set but also slower, stiffer new growth that resists pests. 

Happy growing!

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