Controlling Spider Mites

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The Spider Mite

The spider mite is truly a relative of the spider and therefore not classified as an insect.  They are most prevalent in your garden during hot, dry weather.  In greenhouses, however, the spider mite can be a continuous pest.

It is important to recognize the early warning signs of spider mites before they get out of control.  On roses and other woody ornamentals, the first signs will be a lightening or purplish yellow color change to the upper side of the leaves.  This can even be misdiagnosed as downy mildew damage, but a quick look at the underside of the leaf will make all the difference.  Spider mites also attack many annuals and perennials.

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Crystalline structures note the presence of mites

These mites are so tiny that it may be hard for you to see them without magnification.  But if you have good eyesight or good bifocals you will see them on the underside of the leaves.   It’s here that they puncture the plant cells and suck the moisture from them.  It’s likely you may also see tiny crystalline structures as well as some webbing in extreme cases.  They are very active creatures and can quickly defoliate a plant.  At the least, these can setback outdoor plants by six weeks.  In greenhouse plants, whole crops can be lost.

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Spider mite webbing

Spider mite eggs can hatch in as little as 3 days, and new mites can begin reproducing in only 5 days. One female can lay up to 20 eggs per day and can live for up to 4 weeks.   Think about that.  She is laying hundreds of eggs meaning one female mite could start a population of a million mites in a month or less!   This incredible rate of reproduction is one reason mite populations quickly build resistance to pesticides, so chemical control methods can become somewhat ineffectual when the same miticide is used over a prolonged period.

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Visible mite damage on rose leaves.

Since insecticides will not kill mites, let’s discuss how to rid your plants of this pest.  If you only have a few outdoor bushes, you may want to remove the mites mechanically with a water blaster.  Most water wands have a removable nozzle that you can replace with a blasting nozzle.  Set the nozzle to a wide pattern but don’t be too conservative.  You will need a good deal of pressure.  Simply point the nozzle upward and blast those mites off the underside of the bush.  In most cases the mites will find an easier target.

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Mites on leaf underside.

If the mechanical method is not for you, or if you are growing in a greenhouse, you will need to use a miticide.  Miticides have come a long way over the past 15 years and thank goodness there are many to choose from currently.  We already discussed how rapid reproduction leads to pesticide resistance.   (This is very important to acknowledge.)  Almost every miticide label clearly states you should not use the product more than three times a year.  For that reason, greenhouse growers and gardeners with many plants will need to rotate two or more miticides in their spray program.

When choosing a miticide, be sure to read the label for products that are approved for your particular crop or cultivar.  Some miticides only kill adult mites and this means you would need to spray them twice (initial spray and then three days later) to kill both existing adults and newly hatched mites from eggs.   Most modern miticides have incorporated what is called an “ovicide” into their formulations.  This means they will kill all stages of mites, including the eggs.  These are preferable and most of these newer products continue to work for up to 21 days!  Examples are Floramite, Forbid and Shuttle but there are others that are as good or better.  There are even a few miticides that are “Translaminar”.  This means that the miticide, while sprayed on the top of the leaves, will penetrate through the leaf tissue and to the underside of the leaves.  This can be a big help where it is hard to reach the underside of leaves.  In almost every case I recommend the use of a good spreader-sticker (surfactant) with your miticide application.

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Mite life cycle

Let’s discuss how your plants get mites in the first place.  For outside gardens they are simply part of the environment and in hot dry climates you will almost always deal with mites.  It’s important to remember that there are many natural predators of spider mites and if you do your best to encourage these (ladybugs, praying mantis, green lacewings etc.) you may be able to eliminate the need for expensive miticides.   One way to encourage the good insects is to simply refrain from spraying insecticides.   Most insecticides are not selective and kill all insects, even the ones we want in our garden so use these sparingly.  If you are growing in a greenhouse environment, you will most likely deal with mites on a continuous basis and a good miticide rotation will be a must!

Finally, be sure to put newly purchased plants or cuttings in quarantine to be observed at least one week for disease, insect, and mite problems.  I get many calls each week from growers who discover their favorite miticide no longer works.  What I usually find is they have brought new plants or cuttings into their garden or greenhouse without quarantine.   The strain of spider mite on the newly purchased plants were already immune to some miticides due to the previous growers’ spray program.   Now the new grower has inherited a generation of mites that is resistant to their miticide of choice.

Planting bare root roses.

raised bed blog

I planted roses today in a new bed  just outside our fenced backyard.   I live on six acres in a farm and ranch area.   I actually built the bed last year too late to plant bare root roses,  so the bed was planted in mass with marigolds.   Wow, it was beautiful.  We used just over 120 plants to fill the bed.

This year I removed the ends of the bed and brought my granddad’s old tiller out of the barn and gave it a good tilling.  The soil was full of dark matter and earthworms.   That got me excited I can tell you.

I know most of you in suburban areas wouldn’t want to use cross ties for your raised beds.  However, these work great on a large property in beds planted out of the “proper yard area”.    For nicer areas, Home Depot and Lowes have all kinds of keystone and other landscaping materials for raised beds.

 

 

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While many of the bare roots you will receive will have canes up to 16 inches long, I almost always cut these back to no longer than 8 inches.   It’s true that you will have more growth immediately if you leave the canes longer.  However, I’m more interested in growing roots first, roses later.   Therefore, I prune mine back much shorter.  I also remove any small canes and anything that is damaged or dead.

 

 

 

 

 

 

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Prepare planting holes approximately 14″-20″ wide and 12″-18″ inches deep (or the depth of your improved soil if less than 18 inches). Once you have prepared the hole, place some of the soil mixture back into the planting hole forming a cone shaped mound which should approximate the conical shape of the rose roots.    At this point I like to add my mycorrhizae (another blog to come at a later date.).

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Gently move the soil you removed around the roots of the rose and give the soil a gentle (not hard) press.   Next you will want to water the rose with a gentle flow of water to not only hydrate the new bush but to also make sure there are no air pockets in the new soil around the roots of the plant.

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Finally, cover the canes for a week with damp mulch to keep the canes from drying out before new feeder roots develop.

 

 

 

 

 

 

 

 

 

 

Tip:   Sometimes bare root roses will start to push out new growth during shipment.  This is normal, especially in the months of March and April.   If you cover this new growth with mulch it will usually tend to burn and die

tender growth blog

once the mulch is removed.  When I have plants that are already pushing out, I use a brown paper bag from the grocery store.   Simply cut a circle the size of a silver dollar in the center of the bottom of the bag.   Cut slits up the side of the bag about six inches long to be used as anchors.   Turn the bag upside down over the rose and then anchor the bag with soil.   The bag will keep moisture in.  The hole in the top will allow air circulation and just enough light to harden off the tender growth.  You can normally remove the bag after one week.

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Final thought:   Even if the new premature growth dies, the rose will push out another cane where this one originally formed.  Just be sure to take a good pair of sharp pruners and “clip” the dead growth off at the cane.  Do not twist it off as that could damage other immature bud eyes just beneath the surface of the cane.