Utah Plant Pest UTAH PESTS Diagnostic Laboratory USU Extension Winter 2020 QUARTERLY Vol. XIV NEWSLETTER IN THIS ISSUE Blue Alfalfa Aphid Biology, Impact and Research in Utah Profile of a Commercial Nursery Using Biocontrol EPA Approves New Recognizing Wood Rodenticide Decay in Trees Tomato Brown Rugose Fruit Virus: A New Pest of Concern IPM in the News NEW FACT SHEETS Winter is the perfect time for arborists and conditions (cool and wet or warm and wet). Peach Twig Borer homeowners to prune trees. At that time, Their presence indicates that the actual body (update) defects are visible in the tree structure, of the fungus (called a “thallus”) has already especially those caused by wood decay colonized a considerable portion of the Peach Twig Borer fungi. Understanding how to identify whether wood. When no fruiting bodies are present, Mating Disruption decay is present, and the hazards associated decay may not apparent from the outside of (update) with it, will help avoid accidents. the tree, and only detected after a branch falls or after a pruning cut reveals it. Western Cherry Fruit “Decay” is a term that describes wood that is Fly (update) being broken down by the “feeding” action Most wood decay fungi colonize stems or of microorganisms, particularly fungi. Wood roots of trees when spores land on wounds decay can occur in any healthy tree, but is that expose sapwood or heartwood. most common in older, established trees, and Wounds come in many forms, including may affect wood in large roots, trunks, and small scrapes that remove bark, fire scars, branches. canker-causing pathogens, insect feeding, ice damage to branches, poor pruning cuts Decay may be obvious when conks or or arboricultural treatments such as drilling mushrooms are present on the bark surface. into stems when cabling, bracing, or injecting These structures are called fruiting bodies trees. and are only formed under optimal weather continued on next page Wood Decay, continued UTAH PESTS TEAM Diane Alston Examples of Wood Decay Fungi Entomologist Head, Dept. of Biology The fruiting body on the surface of the bark will [email protected] give an indication of the type and amount of 435-797-2516 wood decay. Ryan Davis Arthropod Diagnostician School IPM Associate [email protected] 435-797-2435 Marion Murray IPM Project Leader Utah Pests News Editor [email protected] 435-797-0776 The woody conk of Fomitopsis pinicola is also Phellinus is a genus of many Claudia Nischwitz known as red belt fungus. It causes a brown destructive species, causing a white rot Plant Pathologist cubical rot of aspen and conifers. of deciduous and coniferous trees. [email protected] 435-797-7569 Ricardo Ramirez Entomologist [email protected] 435-797-8088 Lori Spears Prof. Practice Asst. Professor USU CAPS Coordinator [email protected] 801-668-4056 Nick Volesky Vegetable IPM Associate The fruiting body of Ganoderma [email protected] 435-797-0319 applanatum is called artist’s Armillaria mellea is known to conk because etchings on the cause a tree-killing root rot, but it spore-side of the conk turn can also cause a white-rot of the Utah Plant Pest black. It is a common fungus, trunk and branches, depending causing a white rot of deciduous Diagnostic Lab on where infection occurs. Urban BNR Room 203 trees. On oaks, the presence of a Utah State University trees stressed by drought or other conk is associated with extensive 5305 Old Main Hill disturbances are most susceptible. internal decay. Logan, UT 84322 • The fruiting body of Fomes fomentarius is called tinder conk. This fungus causes a white, spongy, mottled heart rot, primarily of birch. To subscribe, click here. • Several species of Inonotus cause a white rot on branches, trunks, and roots of several deciduous trees, including oak, maple, and walnut. All images © UTAH PESTS and USU Extension unless • Laetiporus sulphureus (chicken of the woods) is an edible conk, and its presence indicates otherwise credited. extensive brown, cubical rot. • Phaeolus schweinitzii causes Schweinitzii root and butt, a serious brown cubical rot of conifers. continued on next page utahpests.usu.edu Utah Pests Quarterly Newsletter / Winter 2020 / page 2 Wood Decay, continued Types of Wood Decay Depending on the decay fungus, it weakens wood by degrading either cellulose or lignin in cell walls. In wood fiber, cellulose is responsible for strength due to its linear orientation, while lignin holds fibers together and holds cellulose molecules together within the fiber cell wall. Because different fungal species may degrade different components of the wood fiber, not all decay is the same, and can be grouped into a brown, white, or soft rot. Brown rots are most common in conifers (pine, spruce, fir). Brown rot fungi remove the cellulose components from cell walls and leave the lignin behind. This type of rot causes a rapid loss in wood-bending strength (the load that wood can withstand perpendicular to the grain), making the tree very unsafe. The residue from brown rot decay–often cubical and crumbly–is an important component of carbon sequestered in forest soil. Robert L. James, USDA Forest Service, Robert L. James, USDA Forest Bugwood.org White rots are most common in deciduous trees, where the fungus consumes primarily lignin, followed by Wood affected by brown rot fungi (top) is much weaker cellulose. Because lignin is dark-colored, its removal than wood affected by white rot fungi (bottom). leaves the wood pale white in appearance, and the pattern of rot can appear pocketed, stringy, or laminated. • activity or nesting of carpenter ants or birds (such as White rot decay reduces compressive strength of wood woodpeckers) (the load that wood can withstand parallel to the grain). • stem bulges, swellings, or stem flattening, which are growth patterns of wood walling off or growing Soft rot fungi also degrade cellulose, but leave behind around decay microscopic cavities in the secondary cell wall. Decayed wood appears straw-colored and looks very similar to Determining the location of decay is important for arborists white rot. The name is misleading because soft rot in living to understand which portion of the tree is affected. trees is not noticeably softer than other decay types. • Butt rot decay occurs in the lower portion of the main trunk of the tree and sometimes on larger buttress Identifying Wood Decay roots. Trees with butt rot should be considered for removal if they are in high-traffic areas, and should Wood decay primarily occurs within non-living, structural never be climbed in windy conditions. wood fibers and non-functional water-conducting tissues, • Sap rots primarily decay xylem, but can also decay and therefore does not directly affect the vigor of the tree. phloem and heartwood. Never tie a rope into a limb In addition, trees actively respond to injury and fight the with evidence of sap rot. colonization of decay fungi through a cascade of pro- • Heart rot decay may be restricted to the center of the cesses. However, the main issue with wood decay is the trunk. Trees with heart rot are more structurally sound loss of tree strength and ability to withstand forces, such as than trees with sap rot, but should never be climbed in wind. Therefore, trees should be carefully inspected before windy conditions. climbing, hanging ropes on branches, or installing furniture or games underneath. Marion Murray, IPM Project Leader Look for signs or symptoms of decay, including: For more information • conks or mushrooms (rarer to see in Utah) Schwarze, F.W.M.R. 2004. Fungal Strategies of Wood Decay in Trees. • external cavities or visual evidence of decay in Springer-Verlag, Berlin Heidelberg New York. exposed wood Luley, Christopher. 2009. Tools for Testing Decay in Trees. American • old wounds, poor pruning cuts, and topping or Nurseryman, May, pp 6 - 9. heading cuts, which may or may not indicate that the Luley, Christopher. 2015. Biology and Assessment of Callus and wood has been colonized by decay fungi Woundwood. ISA Arborists News, April, pp 12-21 www.utahpests.usu.edu Utah Pests Quarterly Newsletter / Winter 2020 / page 3 GUEST AUTHOR SPOTLIGHT Blue Alfalfa Aphid Biology, Impact and Research in Utah Steven Price is a USU Extension faculty member in the Carbon County office, specializing in Agriculture, Natural Resources, and 4-H. Jody Gale is a USU Extension faculty member in the Sevier County office, specializing in Agriculture, Horticulture, and Agricultural Economic Development. Aphids can be a major pest of alfalfa in Utah. They reproduce much faster than their predators, and can become a secondary pest after broad-spectrum insecticide applications reduce predator populations. The common aphid species observed in Utah alfalfa are pea aphid, cowpea aphid, spotted alfalfa aphid, alfalfa aphid, and blue alfalfa aphid. Healthy alfalfa stands can withstand high populations of most aphid species. For example, the current treatment threshold for pea aphid is an average of 100 or more per stem when the alfalfa is more than 20 inches high. Below this number, yields are not reduced so much that insecticide treatments are warranted. However, blue alfalfa aphid damage is significant at much lower populations. Alfalfa stem infested with blue alfalfa aphid (left), and a Their saliva contains toxins which reduces Sevier County alfalfa field showing extensive aphid damage in 2018 right( ). alfalfa growth beyond typical feeding damage. It also causes residual stunting Producers have reported to us that traditional insecticides even after populations decline. offer little control. Sivanto (flupyradifurone) is a systemic insecticide option that, while more expensive than other The treatment threshold for blue alfalfa aphid on alfalfa products ($36 per acre), has a different mode of action more than 20 inches high is an average of 50 per stem.