Plant Diseases

July 18

There is some fungus among us.  The rainfall and sometimes excess moisture has brought on a plethora of diseases not often noticed in the landscape.  Common diseases on trees and ornamentals are apple scab on crabapple trees, Diplodia and Rhizosphaera needle cast on certain conifer trees, and powdery mildew on lilacs and many other species.  This year there has been somewhat severe outbreaks of anthracnose on maples, white oaks and especially sycamore trees.  Scientists have developed varieties of crab apples that are mostly immune to apple scab.  A few more trees die every year from Dutch elm disease.  If you live in an area where oak wilt is present, have your trees treated professionally with Alamo fungicide to protect those trees.  One treatment lasts up to three years.  Make sure you treat desired trees near infected trees.  The disease passes from tree to tree through underground root grafts.

Now that the vegetable garden is growing you will see either septoria leaf spot or early blight on tomatoes.  Septoria starts with small dark bordered white spots while early blight has circular brown spots with margins of yellow; both start on lower leaves where those leaves die and the disease progresses up the plant.  Early blight will also be a problem on potatoes.  If weather remains cool and damp for a period of time potatoes and tomatoes will be susceptible to late blight, the disease famous for the Irish potato famine where 1.5 million people died in the mid 1800’s.  Powdery mildew will affect onions causing the leaves to die early.  A cercospera leaf spot will affect carrots and beets.  Of all garden diseases, early and late blight on tomatoes is probably the most damaging.  Downy mildew and anthracnose occurs on vines crops and a few other crops.  Several other diseases are caused by virus, vectored by insects, and bacterial spot diseases caused by soil splashing up onto leaves.  My raspberries grow in a very wind protected area with barely enough sun.  The disease, Botrytis fruit rot is common on most soft fruits.

Several species of vegetables, especially tomatoes get blossom end rot.  This disease is a physiological disease caused by a lack of calcium in plants.  As the plants go through a very quick growth stage and start to fruit the roots cannot mine from the soil and transport enough calcium to keep up with the growing fruits needs.  When the plant gets more mature it generally overcomes this disease on its own.  This disease can be alleviated with the addition of a foliar calcium spray from a product like Green Light’s Blossom End Rot Spray.  It and other similar products contain soluble calcium. 

The most common ornamental disease that is treated is rose black spot on roses.  Roses also get powdery mildew.   

The three best things you can do to keep diseases away is to choose plant varieties that are resistant to common diseases, plant in areas with good air movement to keep plants dry, and water in the morning so plants will be wet for the shortest period of time.  In order for a disease to grow it needs a susceptible host, the proper environment to grow in, and the causal agent.  This is called the disease triangle.  The next best item you can do is spray a fungicide.  The most common all around fungicides and the fungicides that controls the most diseases contain chlorothalonil.  It was originally named Bravo but now comes in all types of professional and consumer formulations.  Chorothalonil is a protectant and will not stop existing diseases.  It must be applied every 7 days.  Other common organic fungicides are Neem oil and the elemental copper and sulfur fungicides.  The elemental fungicides work well but must be reapplied often and at heavy rates every 5 to 7 days.  There are some diseases they do not control.  Neem oil is a fair protectorant fungicide and can stop powdery mildew.  It should be applied every 14 days to protect vegetation and every 7 days when a disease exists until it is controlled.  Neem oil also leaves a pretty shine on the leaves and fruit.  There are some new fungicides on the market that can be used on some fruits and vegetables.  They not only protect but have the ability to burn out infections up to four days after the infection starts.  These fungicides have not made there way to many consumer products and are expensive. 

When treating edible fruits and vegetables, pay attention to the preharvest interval (PHI).  Neem oil can be used up to the day of harvest.  Others have various intervals between treating and harvesting of produce. 

My most favorite disease is a lawn disease called fairy ring. This scientist researched how to control it for several years.  It grows as an ever expanding circle of green or sometimes dead grass and under certain conditions produces a ring of mushrooms.  Fairy ring has several different causal fungi and is one of the least understood of all diseases.  Every year the disease just grows a little more and a little more until some circles become very large.  One scientist found one that he followed for several miles.

Best of luck with disease control.

The Garden Doc

Raspberries

July 7, 2011    

My wife and daughter just finished picking the first raspberries of the year.  I didn’t see if they came back from picking with red juice stains.  However, they are delicious.  (I snuck a few berries yesterday)  The berries are about three weeks later than last year due to a cool spring.  Five years ago when the raspberries were established five plants of five different varieties were chosen.  I chose based on four criteria; will they grow in a cold climate, berry size, berry flavor, and productivity.  All varieties were from Nourse Berry Farm.

My choice as the best variety is Jaclyn. It is outstanding and it spreads the easiest.  The canes are the tallest of my varieties.  It produces a very large sweet berry, moderate crop size and a spring and fall crop.  There are a few odd berries all through the summer.  It is a primocane beater, meaning it produces berries on the canes the fall the first year the canes emerge.  Most varieties produce primocanes the first year which do not bear, then the following year those canes produce berries.  That fall those canes die and during the year new primocanes grew.    

My second berry choice is a similar but with less yield, smaller berries, and shorter canes.  However, the berries are really good.  The variety may be heritage, but I forget.  Two other choices are just summer bearers and are not my favorites.  Those berries can be small and one spreads faster than it produces average size berries, but they taste good.  They are forgettable and will slowly get replaced with Jaclyn. 

Royalty is my only purple berry.  It was advertised as really sweet.  I didn’t find that to be true.  However it yields for the shortest period of time but is the heaviest bearer. Royalty also spreads less than other varieties which will cause it to be replaced by natural spread of the other varieties. The berries have fair flavor but when looking to make jam or jelly it is a great variety to bring up the berry volume fast to have good jam. 

The first berries were all planted in one single row.  The row is now two rows and I regularly remove primocanes that are growing outside the desired rows.  The berries are kept inside a crude wire structure to help the berries be upright.

Raspberries are a hardy plant but can have insect and disease problems.  My berries have not had significant insect problems or stem disease problems but have had diseases on the berries.  Spray as needed to control problems.  A good neem oil or neem with pyrethrins should work well.  Green Light Neem Oil Concentrate or Green Light Fruit Tree Spray are good choices.  The main problem my berries have had is fruit rot or gray mold, (Botrytis cinerea or soft rot (Ryhizopus and Mucor spp.).  Regular use of Fruit Tree Spray or Neem oil should stop or slow most disease.   Once it fruit rots get established it may be treated with a stronger non organic fungicide Daconil, which is generic or Fung-onil.  Both contain chlorothalonil which must be used weekly and has a pre-harvest interval which should be adhered to.  Neem oil and Fruit Tree Spray can be used the day before harvest. 

Here are some management practices.  They are published in Hort Mag.

1.      Remove dead canes. The presence of empty fruit stems identifies dead or dying canes, as does their yellowing foliage, and roughness of the bark. These canes should be cut low to the ground and removed. (Primocane-fruiting canes that have been left to bear a second year’s crop can be left and will produce a spring crop.) Raspberry canes are less thorny than blackberries, but a leather glove on at least one hand will make handling the canes easy and protect your fingers.

2.      Thin new canes. A vigorously growing raspberry patch will generate an excess of new canes. Some of these will appear at the edges of the patch, causing it to spread. But even within bounds, too many canes left one year will block the growth of canes the next. Good raspberry pruning anticipates not simply next year’s harvest but the harvest of the summer after. Thin the one-season-old canes, leaving the thickest and tallest ones spaced an average of six inches apart.

3.      Weed. With the pruning completed, use a hand hoe or other weeder to clean out grass and other weeds, being careful not to injure the raspberries’ shallow root system. 

4.      Mulch. The first ten feet of row have now been pruned and mulched. Several inches of free-draining wood chips will help the weeds from reappearing. Twin horizontal strings will support the fruit-heavy canes when they bear next summer.

Berries grow different in different environments.  Varieties that do well for me may not do well for you.  They will also grow different in different soil types.

We truly eat all the berries we want all year around.  We bottle them for use during the winter months. Eat lots of a true fruit of the Gods, raspberries.

The Garden Doc

How to live with or control mosquitoes

July 02

My wife hates to go outside because she attracts mosquitoes, when I don’t even know there are any around.  Several products are available to repel mosquitoes but how effective are they?  Whether or not they are effective is a good question.  A single test can cost millions.  Some of the tests have been made available to the CDC or EPA.  Test results sent to the EPA are to support registrations of products and may not be available for public  use.  The CDC, Center for Disease Control, has research results and does publish some data for the public.  Below is a summary of products and there relative effectiveness.

By far, DEET-containing products are the top performers and most will last from 2 to 6 hours with a single application. Picaridin is the second most effective product with performance in the 1-3 hour range. Oil of Lemon Eucalyptus are considered botanicals and are often labeled as being “green friendly” (whatever that means!). Cedar oil is employed as a scent to repel mosquitoes. The scant data available suggests that these products only last for 15 to 20 minutes after an application. This can be partially solved by finding a formulation that slowly releases the scent into the air.  There are bracelets or tags that hang on clothing that offer a slow release of one or a combination of the above scents. Citronella is listed on the EPA or CDC lists as a mosquito control product. And some of the new mint oils are also not on the list of effective actives.  A pretty good study, done two decades ago, used citronella candles surrounding test subjects.  The test people got bit as frequently as people some distance away, but with no candles nearby.  However, citronella candles seem to be so entrenched in our culture and used for ambiance with everyone thinking they control mosquitoes.  We will likely continue spending millions a year on the little lanterns and keep buying the oil. 

A unique item was found that supposedly gives off a magnetic or electrical field that keeps mosquitoes away from people.  You simply wear it around your neck and they leave you alone.  My suggestion is to make ankle bracelets incorporating the items so they don’t get my wife’s ankles and legs.  Do these items work?  I really can’t say, but I haven’t invested any money in this company.

Mosquito traps have improved and are recognized as being able to reduce mosquito bites when mosquito populations are medium to low.  The expensive ones that work use CO2, a tiny light and a suction fan to attract, pull in and then kill the mosquitoes.  A rather new method of controlling mosquito activity is modifying air movement! Mosquitoes are very weak flyers and don’t like to travel when air movement is in the 8 to 10 mph range or greater. Therefore, using outside ceiling or side fans in an area can greatly reduce mosquito flight and landing ability.  The fans must be turned to blow on the subjects.  

Our family had a wedding reception at our house last summer.  The weather had been very wet and we had a terrific mosquito problem.  My assignment was to make the yard mosquito free.  The methods I employed were four fold.  First, I used my Black Flag fogger which produces a fog that floats on the air.  Any mosquito will have a minute droplet impinge on their body and the small insecticide dose kills them. The fogger was positioned so the fog drifted across the yard and into the brush and trees around the yard.   Next I directly sprayed the vegetation for several feet around the yard and the lawn so mosquitoes that landed would pick up a lethal dose.  This works, because when resting, mosquitoes land on vegetation and get liquids from the surrounding vegetation.  Third, I made sure any mosquito breeding sites were eliminated or treated so my yard did not provide breeding sites.  Fourth, the day of the reception I treated the yard with a cedar oil product from Green Light, YardSafe Insect Repellant.  The aroma kept new mosquitoes from venturing in to attack our guests.  The cedar oil smell was faintly in the air and lasted throughout the afternoon and evening. No one would object to the pleasant smell.  The result was no mosquitoes at the party.

Do yourself a favor when you plan on going outside. Don’t eat bananas.  Eating bananas makes people attractive to mosquitoes.    They are also attracted to CO2 but we do have to breathe.

The Garden Doc

Growing apples

Apple trees may start bearing every other year.  This is called alternate year bearing and can be avoided.  When apple trees produce every other year they set a huge fruit load that produces small apples and the fruit load may be so heavy it ends up breaking branches.  The fruit load also drains the resources of the tree and it doesn’t develop flower buds for the following year.  A tree that is bearing fruit in alternate years can be brought back into yearly production by managing fruit load with thinning the fruit, proper pruning, and specific summer pruning.

Frosts may cause the blossoms to freeze in the spring about blossom time which will also cause fruit not to set.  You can try keeping some air moving or lightly misting the crop with water a few times during the below freezing temperatures.  Water may freeze and cause branches to break.  Another method to keep trees from freezing is warming the area with fire.  One of my uncles wrapped Christmas tree lights on the branches and the small amount of heat from the lights kept the blossoms from freezing (that’s a lot of work).  The best method is to select a variety that is tolerant of the cold and selected for your environment.

Commercial fruit growers yearly thin the fruit after it is set when the new fruits are about the size of a dime or nickel.  They use commercial products that must be applied at precise rates.  I wouldn’t recommend this be done by amateurs.  Homeowners may have difficulty spraying an even amount of chemical over the whole tree.  If your tree has excessive fruit numbers, hand thin when fruit is about the size of a nickel and before it is the size of a quarter.  Prune until there are one or two fruits per terminal.  The terminal is the group of leaves at the end of a branch.  An old fruit grower said you need 40 leaves to produce one apple.  The fruit will be much larger and you will get a good yield with proper thinning.   When thinning, leave the apple at the very end of an apple bunch.  This apple grew from the king bloom.  In a bunch of blossoms the king bloom is the center and larges blossom and will produce the largest and nicest apple.  By good pruning and controlling the fruit load, you can have fewer apples but each apple will be a lot larger and the over all yield will be a good yield.

If you are bold and want to chemically thin the insecticide, Sevin is used commercially for apple thinning.  Consumer packages don’t include apple thinning instructions.  You will have to figure that out yourselves.  If you over thin you will have no apples.  If you under thin you will have to reapply or thin by hand.  Apple trees often have what is called the June drop where the tree self thins.  Some varieties and trees do a pretty good thinning job by themselves.  Others may have so many apples it looks like the fruit was wrapped around the branches like a rope.

Prune the tree each year to remove excessive branches and any branch that will brush or interfere with other branches.  Fruit should be able to hang without banging other branches. The distance between branches when pruned should be 2 to 3 feet.  During the growing season this distance will close and then you prune again the following year.  Determine whether you want the tree to have a single leader with branches coming off the main trunk or do you want an umbrella shaped tree with several main branches arching over.  When pruning remove all water sprouts.  Those are the shoots that grow straight up but are not the central leader.  Pruning will stimulate more water sprouts to grow.  There are very sophisticated trellising or staking methods for growing apple trees planted at very high populations. 

Trees with alternate year bearing usually don’t produce flower buds because of the high fruit load stressing the tree when it does bear fruit.  Proper fruit load reduces the excess stress so the tree has the strength to produce flower buds for the following year.  Flower buds develop mid to late summer then bloom the following spring and turn into fruit.  Pruning stimulates the tree to grow new growth.  You can stimulate bud production by a light pruning mid July.  Prune 8 to 10 inches of the tips of some small branch that don’t have fruit. The remaining leaf bunches will be stimulated to produce flower buds that will bloom the following spring.

Deer Control

June 11

My yard is home to deer.  Last summer, a doe raised her two fawns in the 50 yards of woods between myself and my neighbor.  In the woods there are three main trails crossing from one area to another.  Every year, the hostas in my yard get grazed, some to the point of looking like they were run over by the lawn mower.  Two years ago, every day lily flower bud except one was eaten just before it opened.  One year a dear ate several tulip flowers and my rose buds.  My fenced vegetable garden had an unsecure gate and a deer got in and ate all the carrot tops.  Deer love carrots.

How do you control deer from grazing in your yard?  Anyone with deer in the area knows how destructive they can be.  They are yard vermin.  Temptation to shoot them runs high but it is illegal, even though I feel like it is similar to shooting rats.  Here are some remedies:

Dogs – Don’t laugh, a good dog and deer don’t mix.  The dog has to be outside and the ability to run helps.

Deer fence – This works for some items but not for ornamental beds.  (Remember to keep the gate closed.)  For deer it must be a 6 foot tall fence.  Electric fences work but they require some maintenance like weed control and the electricity supply has to be reliable.  This is costly and not very aesthetic.

Ultrasound and electronic controllers – Here are words from one rater: “In theory this keeps deer away from the area because they dislike the sound.  However, ultrasonic devices don’t work around obstructions.”  Motion detectors set to turn on a real noise maker like a radio may work.  I have not tried these.  Products are named Deer Gard and Yard Guard. The cost $50 to $100.

Chemical deer repellents – The several types of repellents are those made of putrescent eggs or blood with mint oils, garlic and so forth; hot pepper sprays or capsaicin; products containing Bitrex, a bittering agent deer dislike; and large predator animal urine.  These all have the ability to work rather well.  However, they all need to be reapplied on a regular basis.  Some are malodorous to humans as well as deer.  They also shouldn’t be used on plants used for food.  Product are named Plantskydd, Deer Scram, and Deer Repellent. Cost is $10 to $20 a package.

Motion activated water sprinklers – My neighbor deploys this method with great success.  It does require water use.  The motion detectors and water sprinklers are physical objects in the landscape and some maintenance may be required.  This is one of the more costly methods.

Milorganite – Last year at a large nursery in the Twin Cities at which I spent the day working, I saw Milorganite.  It is a granulated dried, residue from the Milwaukee sewer system sold as an organic fertilizer.  It worked for deer control. Every week after I mowed my lawn, I spread two to three pounds around my yard over plants deer eat.  Not one plant was eaten until a month after I quit spreading it in the fall.  Then the deer again grazed the hostas.  My lilies were beautiful, my summer flowers all had heads on them and there was no browsing anywhere I treated. There is a human smell when you open the bag but after it was spread, I couldn’t smell it in the yard.  Over the spring, summer and fall I used one and a half bags for a total cost of about $15.  It was very easy to spread with my hand held granular spreader and only took 3 to 4 minutes a week.  In addition to deer control it does supply needed fertilizer.

Brown Marmolated Stink Bugs

June 3, 2011

Many articles have been written and much research is being conducted on the Brown Marmolated Stink Bug.  If you live along the I-95 corridor around Wilmington Delaware to Richmond Virginia and over into the Appalachian chain you had stink bugs, especially if you were in a somewhat rural area.  Smaller infestations were found in just about all Midwestern states.  They ruined fruit and vegetables, in the fall they congregated on houses trying to get in for the winter.  They are expected to be a problem in many farm crops and around home ornamentals this summer.  

The term stink bug is not a scientific name, but a nickname because of the unpleasant odor they emit. Stink bugs emit their odor as a means of self-defense and protection against harm. A stink bug’s odor smells very distinct, it is difficult to describe, only to say that it is sour, pungent and unpleasant. What do stink bugs smell like? I’ve heard the smell being compared to rotten cilantro and skunk.  They also stink when you crush them.

They and are expected to be a large problem this summer and fall all over the Midwest..  What can you do?  Protect vegetation, both small plants to trees with an insecticide.  Systemic products like Bayer Advanced Tree & Shrub or Green Lights Tree & Shrub Insect Killer with Safari will kill the bugs if the plant is treated in time for the insecticide to get through out the plant.  When the stink bug chews on the vegetation it gets the insecticide and dies.  There will be some damage when they chew some foliage to get the insecticide.  Other wise you will have to spray insecticide and reapply it about every 2 weeks.  Don’t believe the claims that a spray will last for up to 12 months.  It will only last about 2 weeks on vegetation.  Sprayable insecticides are Sevin, malathion, and pyrethroids which are most of the rest of the products.  These products will only give about 40 to 80% control.  Even if you spray, new bugs will come into your yard regularly.  This fall spray around your windows and doors and possibly the sides of your house to kill the bugs that are trying to get into your house for the winter.  An insecticide spray on the outside of your house will last longer than on vegetation but most decompose in sunlight.  You will have to re-spray once or twice through the fall.

Weeds, Weeds, Weeds, Will I Win or Will They?

May 25, 2011

This morning I weeded a couple of rows of my vegetable garden.  The plants from seeds are emerging but just as fast are all the weeds.  Perennial weeds were about 6 inches tall and annuals were an inch or less.  This post is ways to consider fighting the weed war.  Plan ahead and your battle will be much easier to win.  Perennial weeds were about 6 inches tall and annuals were an inch or less.

For perennial beds plan before you plant.  Before you plant anything, prepare the soil then cover the whole area with a quality weed mat or landscape fabric.  These come in long strips and are available at Lowes, Home Depot, Menards and garden centers.  They come in various lengths usually 50 to 100 feet long and 3 or 4 feet wide and then cut to fit.  Commercial sizes are much wider. After the area is covered cut X’s where your plants will go and plant the perennials.  Secure the fabric with stakes and cover with mulch or rocks to make the garden aesthetically acceptable.  In the future you can move the mulch, cut new x’s and plant annuals or perennials.  The more cuts through the weed mats, the more places for weeds to grow.  The weed mats will last for many years.

If your garden is in a new area, spray with a glyphosate herbicide like RoundUp or Com-Pleet to kill all the existing weeds before tilling.  This will kill the hard to manage perennial weeds.

Using mulch to cover the soil is extensively used.  It also looks very professional.  Some weeds come through the mulch but they can be physically removed or sprayed.  Many people add about 3 inches of mulch.  Experts recommend using about 1 inch of mulch.  A thicker mulch layer will inhibit the emergence of more weeds.  If you plan on using thick mulch take this into consideration and plant plants to be at the depth of the top of the mulch.  The worst item you can do for the health of perennials, especially trees and woody ornamentals, is to heap mulch up around the trunk.  Heaping mulch around trees, kills trees.  Still many people like the look and it is still done.

Weeds that come through mulch can be sprayed with RoundUp or Com-Pleet, but don’t allow the spray to contact the ornamental spray.

You may add commercial bagged topsoil to eliminate weeds.  They may still have a small supply of weeds in even though it comes in a bag.  A local topsoil may be ideal for fixing problem soils but be prepared to deal with a new brand of weeds brought in with the topsoil.

Herbicides are used extensively in commercial real estate.  Homeowners don’t have access to all the product used commercially but still can easily control the weeds.  Preen is most commonly used for both ornamental and vegetable gardens.  If this writer were to rate products, the highest rating for weed control with a granule would be Amaze.  If it is not available in your area, ask for it specifically.  Amaze from Green Light has two herbicides, one stronger on grasses and one stronger on broadleaf weeds.  It will last longer than other products for weed control around ornamentals.  Amaze covers more area per pound of granules and will be cheaper than other products.  Amaze should not be used in vegetable gardens.  There is also a Preen for Southern Gardens that uses dithiopyr but cannot be used in vegetable gardens.  It will control weeds for twice as long as regular Preen.  Some of the commercial crabgrass control products can be used in ornamental gardens.  However, read and follow the label directions before making application.  These products often control many more weeds than crabgrass.

Several companies such as Scotts Miracle Gro sell a similar herbicide as Preen.  One such product is Miracle Gro Weed Preventer.  Most Scotts Miracle Gro products use fertilizer as a carrier which may be an overuse of fertilizer.  A commercial product used in ornamental plant beds is BroadStar or SureGuard, a granule and liquid product containing a new herbicide flumioxazin.  If it becomes available for residential use by consumers it will provide long lasting excellent control of weeds. 

Another way to provide good long lasting weed control is to use one of the commercial products with glyphosate and a residual herbicide.  The most common product is RoundUp Extended Control or SeasonLong Grass and Weed Control.  These products kill all the weeds and lay down a layer of herbicide weeds won’t germinate through.  They will provide about 3 to 4 months of weed control.  If these products are sprayed on existing plants or you get too much on the green bark of young trees and shrubs they will also be killed.  Use with EXTREME caution around existing plants.

The historic way is simply hoe out the unwanted plants with a hoe.  If you are growing a vegetable garden, grow a small size garden, small enough so the weed war is small enough to keep under control. 

Happy Gardening!