Friday, August 12, 2016

Disease Identification

Seeing spots before your eyes? I'm sure this looks familiar...Tar Spot (Rhytisma acerinum) on Maples!

     Heat and humidity have arrived, we all know what that means for our plants...yes you guessed it, high disease risks. Although this weather is great for us, especially while enjoying some free time or taking vacation, however our plants never take a break. They work very hard which can make them easily vulnerable to all kinds of pests and diseases. Even though these issues are present and could potentially put our plants at risk, please be encouraged to know that there are successful ways in prevention, treatment and controlling spreading risks.

     If this is a concern with your garden, or you have already noticed disease activity, and may not be sure what it is or where it came from, then I invite you to continue to read on...
It's very unfortunate when these issues happen with our plants but awareness is the key to success. The first defense in treatment is to identify the cause.
 I have listed as well as included some photos of some of the more common ones.

     You are probably aware with any size vegetable or flower garden, whether large or small, your plants can become susceptible to disease. There are as many plant diseases as there are pests, however these can be controlled through early prevention and treatment as well.

     Of course there are "repeat offenders" each year and you can be sure to be ready for it. As mentioned, identification is the first step in diagnosing diseases. Once you have your diagnosis then you can begin the treatment. As preventative measures, you will have to apply treatment before possible onset of disease. Once certain diseases have set in then all you can do is prevent from further spreading as some of these diseases are incurable at this stage. I have listed as well as included some photos of more commonly known types and I can be sure that most of you that grow tomatoes or potatoes have been faced with this disease pictured below:

Late Blight- Affects mostly potatoes and tomatoes

Early stages of late blight
Late blight that has spread to stems       
     The above pictures are of both beginning and later stages of late blight that has affected tomato plants. You can also read more about this nasty disease by clicking on this link. As mentioned both Tomatoes and Potatoes are notorious for being infected by the fungal spores of this disease. Late Blight will ultimately destroy the whole tomato crop if no prevention is practiced. The best time to start your prevention regime on both tomato and potato plants is before humidity, wet or hot weather set in. Daily scouting this time of the year will help alert you to any changes. You can use this practice to scout out other diseases as well. There are some products that are safe to use on these plants if you choose to practice prevention. Other planting practices that will benefit your plants in ensuring disease risk is at its minimum is to plant them in an area where they can receive good air circulation followed by proper spacing and pruning. If watering is needed, be sure to water your plants preferably at ground level in the morning to ensure leaves will dry during the day. Watering prior to night time won't allow leaves enough time to properly dry, and as a result this can contribute to perfect breeding grounds for any types of blights,molds or mildews to set in.

     The most reliable way of ensuring you will have control of late blight as well as a harvest is to choose late blight resistant varieties. These varieties have shown great results time and time again as they can stand up to resisting late blight even if they are planted next to other varieties that end up with the disease. You may have also heard of early blight (alternaria), not to be confused with late blight, although this disease is nasty as well,it is not as fatal as late blight (phytophthora)To help determine the differences between both blights, you will find them pictured below:
Tomato affected by early blight
Tomato affected by late blight
      Another type of blight that you may have heard of in the more recent years is fire blight Erwinia amylovora, classed as a bacterial blight (mostly found on fruit trees as well as some Ornamentals in the rose family).  Pictured below certainly displays how it may have been named as it affects stem tips first by showing a wilted look later to result in what looks as if it had been scorched.


      It is quite possible that your plants may not even be infected with disease.  Some physiological issues can mimic those symptoms of what a specific disease may look like for example; a deficiency in a micro-nutrient such as magnesium may display yellowing or odd brown patches on the leaves of your plants (as pictured directly below), insect damage or disease can present themselves this way as well (as pictured further below to the right). It may leave a person in doubt of treatment and that is why it is always recommended to ask your resources. 


    Inspect the area for insects, as they too, can sometimes make leaves look as if it's diseased requiring a completely different type of treatment.  Often times if your plant is compromised with disease it will make it more vulnerable to pests.


                                                                                                                                                                                                                    Another very common disease among both flowers or vegetables is Downy mildew (Plasmopara viticola). You may have heard in the more recent years of the big scare of the ever popular walleriana impatiens being hit hard by this disease.                                                                                                                      These plants are loved by many as the common impatiens are so versatile for any garden.  This was a huge upset a few years ago, however things have seemed to improve with the dry weather as they grow quite successful when humidity and moisture levels are low.

If you take notice of the leaf pictured above, it shows the beginning signs of Downy mildew on the underside of the leaf. It tends to take on a more furry gray appearance, whereas Powdery mildew will look as if your plants were covered with a dusting of icing sugar. If only that was the case, we would have sweet pumpkins for sure.

     A cousin of Downy mildew is Powdery mildew (Podosphaera leucotricha), as mentioned above. I'm sure many of you have experienced this disease at one time or another especially with growing vine crops, like pumpkins or perennials such as phlox. This disease is caused and spread by a fungus and presents itself with an infamous dusting of white to gray powder. It coats the whole leaf surface leaving it to eventually wilt, brown and resulting in death. 

Your best defense against this disease is to; buy plants or seeds from reputable companies, plant in an area where there will be good air circulation, regular feedings of fertilizer and maintenance, and water early in the day at ground level trying not to splash on leaves. All these cultural practices apply for both Downey,and Powdery mildew as well as all other fungal diseases and will certainly help with ensuring your plants remain disease free. 

Other types of diseases that are quite common are leaf spots/black spot (especially on roses), Anthracnose, Rusts,Wilts, Root and stem rots as well as cankers, just to name a few.  Don't let this list despair you from growing the plants that you enjoy whether it's veggies or flowers. With this list in mind, preventative measures or even simple maintenance such as leaf picking will help solve these issues.  Diseases come with a vengeance but once they serve their time and we gain control over each specific one, they eventually won't pose as much damage year after year and you will be sure to benefit from that success in many ways.


  1. Really very amazing and interesting information about the vegetables seeds.
    survival seeds

  2. Thank you for your feedback, this topic really intrigues me and I'm hoping that it can help gardeners with an introduction on knowing what to look for and that if there is disease on plants they have that it can be treated resulting with a successful harvest in the end.