In this article:
|Emerald Ash Borer Has New Hosts|
|Management of Phytophthora aka 'Plant Destroyer'|
|Featured Plant Variety|
|Impact of Preemergence Herbicides on Centipede Rooting|
|Renew Your Pesticide Applicator Proficiency Test|
The emerald ash borer is an invasive metallic wood boring or flat-headed wood boring beetle of the Buprestidae family that kills species of North American ash trees. It was discovered in 2015 infesting ash trees in Webster Parish. In 2016 it was found infesting ash trees in Bossier, Claiborne, Lincoln and Union parishes. Now it has been detected infesting ash trees in three more Louisiana parishes: Bienville, Jackson and Morehouse. These eight parishes are quarantined by the Louisiana Department of Agriculture and Forestry.
Olive trees (Olea europea) and White fringe trees (Chionanthus virginicus) have been reported as new hosts of emerald ash borer.
Olive trees have been reported as a new host of the emerald ash borer by Wright State University. This was an in-lab study that showed it was capable for EAB larvae to develop into adulthood in olive trees. Read more here.
White fringe trees have also been discovered as a non-ash host for EAB. Damage on white fringe trees was not as significant as what the beetle would do to white or green ashes. Read more here.
It is expected that this insect will continue to expand its range in Louisiana. In preparation for the arrival of the emerald ash borer, the location of ash trees may be determined and the trees protected aggressively by using systemic insecticides. Biocontrol efforts are ongoing, and parasites may be released in attempts to reduce the numbers of emerald ash borers. Additionally, ash trees in poor health may be removed. The quarantine procedures should be followed. In particular, potentially infested firewood should not be transported outside of quarantine areas. Recent Louisiana Nursery and Landscape Association newsletters have included information on the emerald ash borer.
Raj Singh, Photos by Dr. Raj Singh
Root and crown rot caused by Phytophthora is the No. 1 ornamental plant disease in home gardens and commercial landscapes. In addition to root and crown rot, Phytophthora is also known to cause aerial blight, fruit rot, stem canker and stem rot. Phytophthora is a soil-borne, fungus-like microorganism commonly known as water mold. There are several species of Phytophthora prevalent in landscapes and most of them have wide host range.
Symptoms caused by Phytophthora may vary with the plant species, but primary symptoms include root and crown rot, wilting and yellowing of foliage followed by death of the affected plants. After infection occurs, roots start to rot and lose their ability to absorb water and nutrients. Reddish brown lesions appear on the infected roots (Figure 1). Rotted roots turn light to dark brown and easily slough off (Figure 2). Aboveground symptoms become obvious after considerable root rot has occurred. In the beginning, random sections in the canopy wilt and turn yellow. As the disease progresses, the entire plant turns brown and dies (Figure 3).
Phytophthora is a soil-borne pathogen and produces motile zoospores (infection propagules), which can swim in irrigation water. The pathogen also spreads in splashing water caused by overhead irrigation or rainfall. Soil compaction and poor drainage highly favor disease development.
In landscapes the disease is favored by poor landscape practices that create conditions conducive for disease development, such as deep planting, overcrowding of plants, excessive mulching, over-fertilization, over-irrigation, planting in clay-rich soils, soil compaction and poor drainage.
Disease management in landscape starts with avoiding diseased plants because once Phytophthora is introduced, it can persist in soil for a long time. Well-drained soils with good organic matter content are recommended for new plantings. Good cultural practices including proper planting depth, spacing, fertilization and irrigation may help reduce infection. Roots injured during planting become highly susceptible to Phytophthora infection. In landscapes where disease is prevalent, prophylactic treatment with fungicides containing an active ingredient such as aluminum tris, fosetyl-Al, mefenoxam or phosphite may help avoid infection. These fungicides do not completely eliminate the disease, and repeated applications may be required to suppress the disease. Follow fungicide labels for rates and frequency of applications.
Photo by Allen Owings
Originally found in central Florida, the Ocala Anise (Illicium parviflorum) 'Florence' is a rapidly growing large evergreen shrub that was introduced by the Woodlanders Nursery. Its leaves smell of licorice when bruised or crushed, and in spring it produces lightly fragrant yellow flowers, according to the University of Florida Institute of Food and Agricultural Sciences. The Ocala Anise is often used for dense hedges or screens, and it grows well in the sun or shade, but it becomes thinner in the shade, according to the UF IFAS. 'Florence' is growing in the Sun Garden at the LSU AgCenter Hammond Research Station.
Centipedegrass is a slow-growing turfgrass species with a moderately wide blade and medium green color that is grown in many home lawns throughout Louisiana. During late winter or early spring homeowners can apply preemergence herbicides to reduce annual weed encroachment for species such as crabgrass or goosegrass. The use of preemergence herbicides allows for an extended period of weed control and often does not damage turfgrass leaves. However, there have been some reports of preemergence herbicides altering turfgrass rooting in many species.
To determine the impact of preemergence herbicides, centipedegrass growing on a fine-textured soil was treated with several commonly available preemergence herbicides at manufacturers’ labeled rates during early spring, including dithiopyr, pendimethalin, prodiamine, simazine, and indaziflam. Then over time roots were measured to determine how or if rooting was affected.
Over a period of 11 weeks, centipedegrass rooting was not different than untreated centipedegrass. This may be the result of several factors, such as binding and reduced movement of preemergence herbicides deeper within the soil that limited root contact to mature centipedegrass with a more developed root system. Therefore, a healthy centipedegrass with a developed root system growing on a fine-textured soil does not appear to be prone to alterations in rooting from preemergence herbicides.
All licensed pesticide applicators are required to take a proficiency test in 2017. Additional dates are still available for Pesticide Applicator Proficiency Test. Please check for available dates here and for more information click the link below.
LSU AgCenter Service Labs
Start with the soil. Don’t guess, soil test. The LSU AgCenter Soil Testing Lab can eliminate the guesswork and reveal exactly how much fertilizer, lime or sulfur is needed for specific plants to be grown in a particular type of soil.
If your plants get sick, accurate and rapid diagnosis of the problem is important for selecting the best management practices at the most effective time.
The LSU AgCenter Plant Diagnostic Center can help.