Summer tips!

July, August and the first couple weeks of September can be trying months for the rosarian in parts of the country where there can be high heat.   It is easy for plants to become stressed and extra care needs to be given now to ensure not only the viability of the rose bush but those awesome fall blooms to come.  Small blooms are common in the summer as the heat causes the bloom to develop very quickly limiting petal count and size.  This is normal.

Watering-the-roses1.  Water, water water.   If your roses are in raised beds, it is impossible to water them too much.   At a minimum, in hot summer days I would water every third day and give them a deep soaking.   If your plants are in pots, you will need to water daily and in some cases, more than once a day depending on pot and plant size.   Be sure to have a saucer under the pot during hot summer months.  This will act as a water reservoir for the pot to absorb as the plant takes up the moisture in the soil.  If you have plants that continually need watering, consider adding some water crystals to your mix.  These will greatly improve the amount of water that can be captured in the soil.

I used the photo above to make a point……… despite what you may have been told, overhead watering is okay if you have a good preventative spray program.   In fact, in very hot areas, this will give the roses a “cool down” they can really use.  The downside…… it’s a bit hard on blooms.  :)

2.  Don’t let up on your preventative spray program.  Contrary to some old “spray stories” going around, it is not unsafe to spray your roses at temperatures over 80 degrees.  This might have been true when many pesticides were oil based.  However, most modern pesticides are water based and they WILL NOT harm your roses when sprayed at higher temperatures AS LONG AS YOUR ROSES ARE WELL HYDRATED BEFORE YOU SPRAY.   So it goes back to “water”.   Be sure and give your roses a deep watering the day before you spray.   Now I’m not saying I think you should spray when it’s 105 degrees outside.  While it may not hurt the roses it can hurt the rosarian by overheating.   Use common sense.   A few other spray tips:  Don’t spray when there is dew on the roses.  This will only dilute the chemical concentration and therefore make the whole application worthless.  Don’t spray so late in the evening that the spray does not dry before dusk.   Long contact times of the liquid pesticide can cause burning.

3.  Continue to feed your roses.  I prefer liquid feeding so I use a water soluble fertilizer like Mills Easyfeed.  One tablespoon in one gallon of water per bush every three to four weeks will greatly reward you.  Again, make sure your roses are well hydrated BEFORE you feed.

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HB-2 ph meter from Kelway. Industry standard.

4.  Check the pH of your soil.  Now would be a good time to invest in a accurate and reliable pH meter.   In most cases this is a one-time investment that will pay big rewards.  The pH of your soil should be between 6.0 and 6.5 for your roses to thrive.  Lower or higher pH values won’t allow the rose to use the nutrients in the fertilizers you give them.  I will talk about how to lower and raise pH in another blog.

5.  Last but not least, consider removing the salt buildup in your rose beds.   Years of chemical fertilizers leave sodium and other salts in your soil.   Over time these have a negative effect and this may be the reason the rose bed that looked so good two or three years ago doesn’t look as good this year.  There is a product called “Clearex” that works miracles on the salt buildup issue.   I strongly recommend you do a search on the Rosemania product pages for Clearex and read more about this product.   It can be the difference in having to replace your soil or not.

Blackspot or Downy Mildew?

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Blackspot

I get emails from many rose growers in spring and fall who think they have blackspot.   Many of them have been treating for this disease and don’t understand why the fungicides they are using are not working.    In most cases I find they have misdiagnosed their problem and what they actually have is downy mildew.

I will talk about how to control both diseases in future blogs, but for today let’s focus on what they look like.

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Advanced stages of blackspot

Blackspot (Diplocarpon rosae) starts as a small black spot/spots on otherwise green healthy leaves.   As the disease progresses, the leaves get more spots and the green tissue begins to be replaced with yellow.  Usually within two weeks of infection the leaves will begin to fall and the entire plant may be defoliated.  Left untreated the plant will try to put forth new growth, only to also become infected and again defoliated.

 

I find downy mildew is misdiagnosed for two primary reasons:

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Downy mildew on young growth.

1.  People associate the term “mildew” with something that should look like either powdery mildew or the black mildew on some very wet item or place.

2.  Because the lesions look similar in some cases to blackspot, the grower assumes that’s what it is.

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Downy mildew

Downy mildew (Peronospora destructor) is most prevalent in cool wet weather (spring and fall).   The spores normally produce  at night.  The disease usually starts as purple lesions on new growth.  This can sometimes even look like early stages of powdery mildew before the “powder” has formed.   Once the disease progresses, the leaves will continue to mature with dark purple (not black) lesions and sometimes even dead brown tissue surrounding the lesions.   In advanced stages the canes themselves will take on these purple lesions and at this point the plant is highly infected.  Left untreated downy mildew can destroy your entire rose garden.

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Advanced downy mildew.

We will talk about prevention and eradication in my next blog.

For now, know what to look for!

Quick update on the new rose bed!

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As I looked outside today from the back porch, I noticed three rabbits eyeing my roses with much admiration, one from the middle of my rose bed!  Regardless, I thought you might want to see the progress from the planting in late April.   Now that we have had the first bloom I will be giving them their first chemical fertilizer (Mills Easy Feed, 1 tablespoon per bush in one gallon of water.)

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.

Some photos from the Pacific

SexyRexy-6sprays-sh-prs-4-13-500web-C-kbelendezMy good friend Suzanne Horn is one of the top rose exhibitors in the country.   She sent me some awesome photos taken by another friend, Kitty Belendez, of Suzanne’s winning entries in a recent rose show.  Hope you enjoy them as much as I did.    Be sure to send your photos and I’ll post them as time permits.FrancisDubreuil-Vic-sh-prs13-500web-C-kbelendez Renegade-minQ-sh-prs13-500web-C-kbelendez FairBianca-6-sh-prs13-500web-C-kbelendez DrJohnDickman12-sh-prs13a-500web-C-kbelendez

Back from a great vacation

 

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Honestly I didn’t know what I was going to do with myself………   When I agreed to go with dear friends to the Dominican Republic, I thought we were going for a weekend.   You should have seen my surprise when I woke up to discover it was for 10 days!     What does one do with one’s self for 10 days on an island with nothing to do but “do nothing”.    It took me 3 days to get acclimated.   After that, I was “one with the island”.    What a beautiful place.   Now it’s “Back to Work”.    More rose blogs in the near future.

Be sure to click on the photos to see one of the most beautiful beaches in the world.

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Aphids and Roses Don’t Mix!

aphids3There are many insects that will visit your garden.   Because some are actually beneficial, I don’t recommend spraying insecticide unless you have an insect problem.  The trouble with insecticides is that most of them don’t kill selectively, so keep that in mind and learn what to look for.

The first critter you are likely to stumble upon is the common aphid.  These typically appear in the early spring and late fall when temperatures are cool.  Aphids feed themselves through sucking mouthparts called stylets.  Don’t be fooled by their small size as they can do major damage to your young growth by literally sucking the moisture right out of your plant.  The good news is that normally, they are easily controlled with insecticidal soaps or neem oil.   If that doesn’t do the job, you may have to resort to chemical insecticides like Orthene or Merit.

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Again, the thing to remember is this:  Spray for insects that are damaging your roses, HOWEVER, keep in mind that most chemical insecticides will also kill the good/predator insects like ladybugs and praying mantis.   If you eliminate these from your garden by preventively spraying insecticides, you will end up with spider mites come summer.  (A future blog.)

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Ladybugs are a friend to the Rosarian!