Although most people are understandably concerned about boxwood blight, boxwood does suffer from a number of diseases, including Volutella blight and Macrophoma leaf spot. Unfortunately, boxwood also suffers from a stem decline, caused by Colletotrichum theobromicola. The following was written by Dr. Raj Singh, LSU. Boxwood Stem Decline by Dr. Raj Singh Available on line at: https://www.lsu.edu/agriculture/plant/files/PPCPNewsletter_January2015.pdf and https://apsjournals.apsnet.org/doi/10.1094/PDIS-09-14-0948-PDN Boxwood (Buxus sp.) is an important landscape shrub in Louisiana, the south and the nation. Several cultivars are commercially available, and its vibrant green color and evergreen growth make it a popular ornamental. Boxwoods are used as stand-alone specimens at the entrances to homes and businesses. They are also grown as low, clipped hedges around homes and commercial landscapes and have become the top choice ornamental for new developments across Louisiana. In 2011, the Plant Diagnostic Center received diseased boxwoods from commercial and private landscapes that exhibited symptoms indicative of a[Read More…]
Tree pruning causes wounds to the tree and a fast recovery is critical to reduce the opportunity for diseases. Tree wound dressing has been used for decades and can cause serious challenges in the wound recovery process.
A question that I often receive goes something like…. ‘How do I control grassy weeds in liriope and iris?’ At first glance, it would appear that those ornamental plants are very similar to grasses, but looks may be deceiving as they are actually not grasses. We know that broadleaf weeds can be controlled in grasses via broadleaf specific herbicides (Fig. 1), as well as grassy weeds can be controlled in broadleaf plants fairly easy with grass specific herbicides (Fig. 1 and Fig. 2). What is often misunderstood is the control of grassy weeds in grass-like ornamental plants. Broadleaf and grass weeds metabolize some herbicides differently. These differences allow herbicides to be selective in nature. True grasses are in the Poaceae family. Grass-like ornamental plants, such as liriope and iris are not in the Poaceae family, so the selectivity of grass-specific herbicides will not damage these plants. Grass-specific herbicides (called graminicides)[Read More…]
Oak leaf blister is caused by the fungus Taphrina caerulescens. Infections occur as buds swell and open during wet, spring conditions. Leaf blister symptoms usually appear within several weeks following infection as 1/4-1/2 inch circular, light green bulges on the top surface of leaves.(Fig 1) From the underside, the affected areas are sunken or depressed. These distortions may cause leaf bending or curling of narrow-leaved oak species. Some insect galls may resemble symptoms of oak leaf blister at first glance. (Fig 2) Upon closer inspection, the insect gall is a solid mass of leaf tissue as opposed to the distorted leaf blister caused by Taphrina. As the blisters age, they become dry, brown spots; severely diseased leaves may drop prematurely. (Fig 3.) Although this disease is quite conspicuous, it does not seriously harm healthy trees and control with fungicides is not usually recommended.
Q: I’ve attached pictures of the only tree we have on our property. Because it is our only tree, I am deeply concerned with the possibilities of irreparable damage to it. As you can see, one of the branches broke off during a November windstorm. Unfortunately, that left a bare gap on the trunk. Please let me know how to treat this damaged area so no further damage is done to it and tell me what can be done to preserve its longevity. I do not know the name of this tree but it’s local. It is found almost everywhere in this area. It blooms white flowers in the spring that fall off shortly after and changes to beautiful colors in the fall. As you can see, it is a beautiful tree. Please help and thank you so much. – L. G., Valparaiso, Indiana A: To answer the second part of[Read More…]
We all know that plants take up nitrogen in significant quantities, compared to some of the other essential nutrients. What most don’t know is that elemental nitrogen (N) is not what is taken up by plants. In fact, nitrogen can be taken up in only two forms, ammonium (NH4) and nitrate (NO3). Fertilizer labels will list the elements contained within, including the various types of nitrogen (Fig.1). What you should know about pH….. The definition of pH is the negative logarithmic of the hydrogen-ion concentration. What does this even mean? More simply put, the more H+ (hydrogen) ions, the more acidic, while the more OH– (hydroxide) the more basic. Always remember that the pH scale is logarithmic, which means each number on the scale is 10 times more acidic or basic than the next number on the scale. A pH of 6 is 10 times more acidic than a pH[Read More…]
People with lawn equipment can accidentally damage a tree, especially young trees which can cause the tree to die.
The Invasive Terrestrial Plant Rule was signed by Governor Holcomb and published on March 18, 2019. The rule goes into effect 30 days after publishing, so it will be effective later in April. The rule states with respect to the 44 plant species included on the rule: “a person must not: (1) Sell, offer or grow for sale, gift, barter, exchange, or distribute a species; (2) Transport or transfer a species; or (3) Introduce a species. (4) Subdivisions (1) and (2) of this subsection are effective one year after the effective date of this rule.” Note that section (3) “Introduce a species” is effective immediately (around April 16, 2019). Selling, offering, distributing and transport doesn’t go into effect until April of 2020, so nurseries will have some time to sell down their stock. This is an important component of the rule to minimize economic loss to nurseries that grow and/or[Read More…]
It is easy to confuse Hemlock (Tsuga spp.) and Yew (Taxus spp.) unless you can see the overall plant habit or have them both side by side. Further confusing them is that both species may be pruned into hedges or other shapes that obscure the natural plant habits. Hemlock has short needles, 1/4 – 3/4″ long, green above and distinctly whitish silver below due to prominent white stomatal bands. Cones are 1/2 – 1″ long, ovoid, and pendulous. Yew has a slightly longer and wider needle -about 1/2 – 1 1/4″ long, dark green above and light green below, overall coarser texture compared to hemlock. Cones resemble berries, the brown seeds are covered by a fleshy red aril (seedcoat).
Avoid injury from falling ash limbs by promptly removing dead and dying ash trees. Don’t do it yourself! Hire a professional to safely remove your brittle trees.