Our Warm Wet Winter - Plant Fungus

Black Spot Fungus on Loropetalum

I have seen more weeds on many of our customers' properties this time of year like I have not seen in several years.

Well, we did have a record-breaking wettest winter ever here in the Midlands and the temperatures were mild, to say the least.

What do weeds love? How about moist and warm temperatures, particularly while other plants (most) are dormant, even though some of our ornamental plants and grasses got busy a little earlier this year.

What else loves most and warm temperatures? Fungi. The problem with this during winter is we did not have the higher temperatures and as many hours of daylight as during the growing season to help aid in reducing the moisture on foliage, blooms and fruits. And, although we have had some breezy (air circulation) times over the last several days, I don't remember much of this happening during winter. Not to mention, it's not (ahem) like we are known for much humidity around these parts.

I have seen and had several customers contact me about black spots on some of their shrubs. It appears to be black spot fungus. In most cases, don't panic. Unless it has affected a majority of the foliage, it will most likely not be the demise of the plant. I have black spot fungus, very slight, on some of the leaves of my most mature loropetalum. The critically affected leaves will usually yellow and most likely drop.

Not seeing every single plant for which I was told this or something apparently similar was occurring, I am not adamant about identifying this as black spot fungus, but the corrective and preventive measures would help most and not harm any plant unless the disease is another like entomosporium, which affects Indian Hawthorns and Red Tips.

• Remove, by hand, the affected leaves and/or prune to remove affected areas and discard of cuts and/or fallen affected debris. Wash your hands and/or clean pruners with a 10-to-1 water/bleach solution before working with another plant to avoid transfer of the fungus. Using the same gloves while addressing other unaffected plants many also transfer the fungus.
• Apply (spray) neem oil on affected foliage and perhaps other nearby leaves. It is usually available in a near-raw liquid form which can be mixed in proportions to address fungus, mites and other pests. It is a natural oil and can cause the foliage to burn in strong direct sunlight, so use after the plant(s) has received its sun for the day. Read the manufacturer's label in its entirety.
• Check other plants which receive very little light or airflow such as those in corners or against foundations on the north side, or are understory plants which are well shaded by other plants and trees. My experience tells me that herbaceous plants such as hosta, coleus, caladium, etc. have less issues with fungi.
• Properly prune shrubs which are trimmed/shaped often as the typically become dense on the periphery, particularly the upper periphery, and reduce sunlight and airflow. This density and improper pruning can also result in other health issues.
• Avoid watering the foliage of plants (particularly those infected) and water the base of the plant and its root field (at least the diameter of the spread of the plant) instead. Yes, I know it rains, but rain usually comes from directly above or an angle not far off from such. Don't add to the problem. Leaves don't absorb water.
• In general, maintain mulch around your plants, for a variety of reasons - which help your plants stay healthy and more resistance to external forces. 
• Do not begin your quest to relieve your plants by searching for the most marketed synthetic fungicides. Ensure the issues are identified properly and there is no other alternative. And then, ensure you can safely apply it. Read the manufacturer's label in its entirety.

Camellia with Black Sooty Mold

Don't mistake black spot fungus with black sooty mold (usually found on the tops of leaves - the cuticle) which has a sooty, fuzzy or even slimy texture and is the result of fungus which feeds on the honeydew (excrement) left behind by aphids, whiteflies or scale. This can even be the result of these insects' activity on another overhanging plant or tree. Too much on a plant and black sooty mold can severely retard photosynthesis and affect the health of the entire plant.

You can easily identify black sooty mold by being able to scrape it away from the foliage and it can be removed by using a mild soap (not a detergent or degreaser), letting the soap solution remain until it loosens/breaks up the mold and then rinsing with water. A little pressure behind the water (not your pressure washer) and perhaps a little hand-to-leaf combat may be needed.

Neem oil can be used to treat the pests - aphid, scale, whitefly. It is usually available in a near-raw liquid form which can be mixed in proportions to address fungus, mites and other pests. It is a natural oil and can cause the foliage to burn in strong direct sunlight, so use after the plant(s) has received its sun for the day. Read the manufacturer's label in its entirety.

Again, don't panic!