Blog posts categorized as: Plant Diseases
Jun 20, 2016
I think most of us are still surprised by the amount of rain we're getting this spring, especially considering last year's downpours and flooding. While rain is usually more than welcome around these parts, the excess spring rain has created some ral challenges this year. Rain yet to come will perpetuate them.
Be sure your rain barrels are covered to prevent mosquitoes from breeding.
Some of the issues you may be having in your garden as a result of all the extra moisture include increased insect and disease populations. Fungal diseases are especially happy right now. Black spot on roses, sooty mold on ligustrum, entomosporium leaf spot on photinias and Indian hawthorn to name a few. Brown patch, gray leaf spot and take all root-rot are in just about every St. Augustine lawn in town. Reduce the frequency with which you’re watering and limit any supplemental watering to the early morning. Night watering breeds lots of fungus. If it’s rained in the last week, do not run your sprinklers.
Insects that have been a problem this spring include slugs, pill bugs and tent caterpillars. Slugs can be treated with Sluggo, a natural product, pill bugs can be knocked out with Spinosad and caterpillars treated with Bt (Bacillus thuringiensis). Mosquito populations are also booming due to the consistent moisture. Mosquito larvae can also be killed using the granular form of Bt, available in both bits and dunks. This is the best method (besides eliminating standing water) to prevent mosquito infestations. Visit your favorite local garden center for great tips on how to handle these diseases, pests and treatments.
Remember that your established landscape (trees, shrubs, turf) only needs an average of 1” worth of rainfall per week; be it from actual rainfall or your irrigation system. Water-wise and drought tolerant plants need less. So as long as the rainfall continues, keep those irrigation systems turned off. Once the rain subsides, you can add back in a weekly watering if you feel your plants are beginning to show signs of stress; as well as watering your foundation. Twice-per-week lawn watering is typically only ever needed in late-July and August when temperatures soar to the 100s. Even then, healthy lawns with a deep root system won’t need watering that often. New plantings will require additional waterings until they root-in and become established. Remember that Dallas watering restrictions are permanent and are still in place despite the recent rains.
Even if you see our expansive clay soil cracking after heavy rains, realize that there is probably still a fair amount of moisture in the soil beneath those cracks. Those cracks are a result of the clay soil quickly shrinking at the surface as temperatures rise after heavy saturation. Over-watering your lawns and landscapes will only lead to more root rot diseases and overblown insect problems.
Jan 17, 2016
Rose Rosette Disease: If you love your roses, then what you see in the photo above should move you to action immediately. The effect might seem "neat" but those witch's broom clusters of growth mean your roses have only a short time to live.
Rose rosette disease is a terminal virus that affects all types of roses. While your plants may limp along for an average of about 22 months after infection, death is inevitable. There is lots of research going on now to combat this destructive virus, there is currently no cure. It is a virus.
The best thing you can do for your landscape, and that of your neighbor's, is to remove the plants immediately. Don't compost them. It is best to bag them and dispose of them. The virus is spread by a mite that moves from plant to plant. Leaving infected plants in the ground will only cause more plants to become infected.
I provided a link below to an article I wrote on Rose Rosette for an industry publication last year that you may find helpful whether you're in the green industry or a home gardener.
Apr 15, 2013
In case no one has told you, you shoult not be planting standard Impatiens this year...even if you find them at a garden center or, heaven forbid a big box store. Why? Because there's a devastating fungal disease that has been a problem globally for Impatiens (Impatiens walleriana) for the past several years and it's now got a strong foothold in The U.S. Downy mildew, or Impatiens downy mildew has decimated this shade garden favorite...and there's no cure. The more folks keep planting them right now, the faster the problem will progress.
What to look for? First, look for stunted growth, pale light green leaves, leaf and flower drop and then eventual stem collapse. The disease spreads quickly so infected plants must be removed and distroyed. Don't compost these plants as you'll most likely not be able to destroy the pathogen in home compost. Also, the organism produces spores that can persist in the soil...so if you have it this year, you should not be planting Impatiens in the same bed next year.
Last year, suppliers were still stating they felt they could produce a clean supply, but honestly the disease just has too strong a foothold on the species at this point. It's already been spotted in Texas.
Is this a bummer? Yep. BUT, there are a ton of other beautiful plants you can use in your shady garden. Currently, the disease does not effect New Guinea Impatiens or SunPatiens. Personally, I'll be happy to see Dallasites be forced to try something new!
If you have shade and needs some color, give some of these shade performers a try:
• Lemon Lollipop
• Angel and Rex Begonias
• New Guinea Impatiens
• Upright Fuchsia
• "indoor" Tropicals are great for shade containers