Tested by Auburn University, Mississippi State University and the University of Georgia. Trees affected with bunch disease show the bunching symptom caused by excessive growth of slender succulent twigs from lateral buds that normally remain dormant on the main limbs. Effectively treating large trees requires equipment that most homeowners don't have. 1st Stuart then Success, Western, Desirable, Wichita, Cheyenne and now is Pawnee. In east, south and central Texas effective pecan-labeled fungicide sprays must be applied during periods of rainfall to prevent Pecan Scab. Primary scab lesions commonly occur on or along the leaflet veins but may be found between the veins. The roots of the pecan tree are invaded and killed disrupting the transportation of water to the leaves. Q: Each year I have a problem with my pecan tree that is now about 11 years old. Defoliation, susceptible varieties, leaf curling – Fungal leaf scorch (Fungus – several) – Although all varieties are susceptible to this group of fungi [funlfsc1], Shoshoni, Chickasaw, Cheyenne, Shawnee, and Stuart appear to be some of the most susceptible. Domestication of pecan began in the late 1800’s and much genetic potential remains to be capitalized upon. When the disease is severe, infected leaflets are killed causing defoliation of the trees in late summer or early fall and resulting in reduced tree vigor and increased susceptibility to invasion by other pathogens. Pecan scab before rainfall with regard to pecan scab disease and several of the fungal foliar diseases). An effective control for cotton root rot disease has not been developed. (even susceptible cultivars like Wichita can be planted). Nuts infected with this disorder drop from 1 to 2 weeks early. Articularia leaf mold does not occur in trees or in orchards which have been sprayed for disease control. Pecans:Copper sulfate is considered an organic fungicide, and some formulations are approved for use on pecans to control pecan scab and other foliage diseases. It is difficult for homeowners to properly manage pest problems so that large pecans can fill out properly. Notes on Taxonomy and Nomenclature Top of page. Shallow disking or removal of the old plant debris will help to reduce the amount of fungal pathogens and insects present in a grove. Apply zinc foliar sprays frequently at the beginning of the season. As plants are grown closer together, the more likely serious disease epidemics are to occur. Adapted varieties: One of the most important decisions in growing pecans is choosing a pecan variety that is adapted to the climate of your region of the state. Brison in his book Pecan Culture writes that the pecan is the most important horticultural crop native to the United States. DOI: 10.1094/PHI-I-2016-0620-01. 'Jenkins' (Jenkins 1, Alabama Jenkins)(Nut Photo) 'Seedling selection of pecan grown from seed of unknown parentage planted about 1977 by Travis Jenkins, Rena Lara, MS. It is to control this primary infection that the bud break and pre-pollination sprays are applied. If the fungus invades the kernel, it becomes oily and produces a rancid odor. The Texas Pecan Orchard Management Shortcourse is held annually during the last week of January at Texas A&M University in College Station. Pecans (Carya illinoensis) are common as a shade and nut tree in the southeastern U.S., where they also grow wild in native bottomland forests. Table 1 shows the critical periods for scab development during the growing season. Lesions resulting from these infection sites become visible to the naked eye within 7 – 9 days depending on environmental conditions. Nut Scab Airplane Application Of Fungicides Leaf and Nut Scab Airplane application of fungicides for pecan disease control is not as effective as ground application and should be used only in instances when it is not possible to put ground equipment into an orchard. There is no known effective control for bunch disease. We have dozen new varieties that might be the variety of the future but who will it be. Pecan Scab Disease Brown Dead Tissue Around the Edge of the Leaflet Chloride, Salt Burn Sticky Sap or Honeydew Dripping From Shiney Leaves Yellow Aphid Feeding Black and Yellow Areas on Leaflets in August or September Black Pecan Aphid Feeding Leaves Dull Color With Many Small Brown Spots and Defoliation Spider Mites Black Spots on Kernel Stink Bug Damage White Fuzz on Green Shucks … Welcome to PecanKernel! For more information. The use of fungicides will help reduce losses from these fungi. The pecan scab fungus causes its first damage in the spring, when it … Lesions are black, sunken, and shiny. Texas Pecan Handbook. Scab disease is most damaging to pecan trees grown east of central Texas. Foliage infection is a problem only on the lower, immature leaves of a tree and on nursery trees. – Crop sanitation Because rain and high humidity increase scab infection, pecan scab is more severe in Central and East Texas. Scab is a fungus which invades the young rapidly growing shoots and leaves and later the developing nuts. – Pruning Mycoplasm, sucker growth – Bunch disease (Mycoplasm) – Evidence indicates it is a mycoplasm [bunchdis]. diseases, especially pecan scab Current weather conditions Predicted weather conditions for next 1 to 2 weeks Status of disease pressure in and near the or-chard Commercial Pecans Controlling Rosette, Diseases and Zinc De˚ ciency Joseph P. Krausz and Thomas A. Those orchards in western Texas will probably not begin their sprays within that area. Eventually, the lesions become frosty in appearance. The following 8-spray fungicide schedule is provided as an example of one option to use for pecan scab management in light of the emerging scab insensitivity issues surrounding some of our fungicides. Venturia effusa is a fungal plant pathogen that causes pecan scab. Adapted varieties: One of the most important decisions in growing pecans is choosing a pecan variety that is adapted to the climate of your region of the state. Also, look for adapted varieties that are less susceptible to pecan scab, a serious fungal disease that attacks leaves and nuts. Even as pecan harvest is under way across Alabama, soon it will be time to plant new pecan trees. Early detection of the first symptom of bunch and pruning out of the affected branch may prevent spread of the disease throughout the tree. Galls can be formed on any below-ground tissue. Make sure to remove as many roots as possible. Even when sound cultural practices are followed, producers may need to apply a protective fungicide in some locations and on scab-susceptible cultivars. Other common diseases are downy spot, powdery mildew, shuck dieback, stem-end blight, and bacterial leaf scorch. Pecan trees are also grown for commercial trade in Texas, with the state usually ranking second or third nationally in total pecan pro- duction of approximately 60 million pounds. Insect and vertebrate pests Major insect pests on native pecans are pecan nut casebear-ers, hickory shuckworms, stink bugs, and weevils. To determine when sprays should be applied within a specific year, the number of hours of 90% relative humidity occurring must be recorded and accumulated. Symptoms of infection are similar on all parts of an infected plant. How do I get rid of it? Desirable 2010, 2011, cv. Pecan scab is the most economically important disease of pecan in the southeastern U.S. and can significantly impact the amount of quality pecans produced in a season. Variety selection – Air circulation Frequently, adjacent lesions coalesce forming large, chocolate brown lesions. For diseases on pecan trees, begin spraying Benlate for control of scab. Mar 12, 2015 | Written by Lenny Wells. Another reason to concentrate on insect control is the fact that pecan fungicides are available only in commercial-size packages. The spores are spread by wind and rain to adjacent leaves and to neighboring trees. Pecan Scab Control. The Pecan Scab Risk Assessment Map tool will not be operational in 2014 due to a lack of funds to maintain the integrity of the real-time data input/output processing required to continue to provide this service. On the lower surface of the leaves, the fungus produces a conspicuous growth of white tufts which contain masses of spores. Thus, although it appears to be causing considerable damage, no significant yield losses can be attributed to the presence of the fungus. ARS researchers in College Station, Texas, evaluated Nacono's performance beginning in 1986. The pecan, Carya illinoensis, is a member of the plant family Juglandaceae. The fungus overwinters in fallen leaves. “During the tour, we will see some definite differences in pecan varieties and in the susceptibility of varieties to pecan scab disease, one of our worst wet-weather-related problems.” Tommy Thompson, pecan specialist at the field station, will be the program speaker. Based on work in Georgia, 70 degree F appears to be the lower temperature limit at which spores are formed. This will allow for better movement of wind through the grove. scab in the low-mid canopy (≤35 ft) • Above 40 ft, there was no significant effect of fungicide on scab severity 30 Treatment <15.0 ft Tree height Vertical distribution of scab in the pecan canopy 15-25 ft 25-35 ft 35-40 ft >40 ft August 15 Within each column of charts, bars with the different letters are significantly different (P=0.05). This practice covers leaves with soil and prevents the discharge of spores into the air, thereby controlling primary infections of new leaves. 2132 TAMU College Station, TX 77843-2132; AgriLife Bookstore. Regional disease pressure – The environment within an area will determine how effective the scab resistance will be within that area. The accumulation of hours begins at that time. The Plant Health Instructor. Primary lesions develop on the lower leaf surfaces as small dots which gradually enlarge and become reddish-brown with a grayish cast. The downy spots usually appear during the late summer months on the under surface of leaflets. Secondary diseases, behind scab lurks pink fungus – Pink mold (Fungus – Trichotecium roseum) usually occurs on nuts infected with scab fungus. Scab disease development is favored by rainy periods and cloudy days when the leaf surfaces are wet. Sanitation measures, such as plowing or disk harrowing under fallen leaves and shucks, help reduce primary infections. Pecan Scab occurs on leaves, twigs, and nut shucks. Scab risk • Region – east to west gradient LA to CA • Site, Management – fungus life cycle • Variety – minimize susceptible, maximize resistant, diversity • Weather – frequent rains, mild temperatures • AU-Pecan (www.awis.com) ≥0.1” rains and % rain chance for 5 days; by variety scab resistance level for pecan scab. Scab is a fungus which invades the young rapidly growing shoots and leaves and later the developing nuts. Resistant to scab, downy spot and vein spot. This can result in 1 to 4 feet of die back. When infection is severe, the entire nut surface is black, kernel development is stopped, and the nut drops prematurely. Slow decline, zinc deficiency, nematodes – Root knot on pecans (Nematodes – Meloidogyne incognita) – Small swellings found on rootlets. Smooth, dark brown to black spots form on the vascular structures of the leaf which include: veins, midribs, petioles, and rachises. When spraying, always check foliage to see if you are leaving a moist film on all of the foliage. The Problem A problem that researchers face in the field is categorizing the infection level of pecan Pecan scam disease is caused by the fungus Fusicladium effusum. Infected leaves turn a reddish-brown, and infection occurs along the leaf margin or at the tip. Leaf veins, brown lesions, defoliation – Vein spot (Fungus – Gnomonia nerviseda) – Similar to leaf lesion symptoms of scab fungus, but fungus which causes vein spot, unlike the scab fungus, affects only the leaves. – Downy spot (Foliage loss, Stuart) If scab is controlled, pink mold will not be a problem. – Bunch disease (Mycoplasm, sucker growth) Recommended for trial plantings on the basis of resistance to pecan scab and nut quality. By mid-summer, black pimple-like dots become especially noticeable in the leaf spots after the surface spore masses have been removed by wind and rain giving the diseased areas of the leaves a black, shiny appearance. A thin film of the fungicide prevents the scab fungus from developing by killing spores before they can invade susceptible tissues. In some regions of the state, pecans are also attack… Pecan scab Scab fungus (Cladosporium caryigenum) invades young, rapidly growing shoots and leaves [clad2] and later the developing nuts [clad1]. http://pecankernel.tamu.edu/diseases/#vein Pecan scab is by far the most serious challenge facing pecan production in Georgia. When the tree is severely affected, it should be destroyed to protect nearby healthy trees from infection. Once inside the root, the bacteria can move systemically within the root system. If you plant scab-disease-resistant varieties, you may need to treat only for insects. Plant tissues are most susceptible when young and actively growing. Several fungi, insects, drying – Kernel discoloration (Fungi – several) – There are several fungi which have been associated with discoloration of pecan kernels. – Powdery mildew (White powdery fungus, high temperatures, dry conditions) (continued) Pecan weevil Carbaryl Refer to Treat areas with a history of pecan (Sevin® liquid, label. Pecan scab is the name for the disease associated with Fusicladium effusum. The long cycle time for pecan trees plus financial considerations dictate that new varieties go through an extensive vetting process before being widely planted. Total coverage is important to achieving effective control. Sanitation within the orchard is extremely important because many of the diseases and insects overwinter in old shucks, leaves, leaf petioles, and twigs. The disease symptoms first appear on the under surface of mature leaves in early summer as small, olive-green, velvety spots. These pecan cultivars do not produce the largest pecans. With warmer temperatures and rainfall in the spring, fungal spores are produced on the stroma. Under these conditions, spores of the fungus in contact with the wet leaf surface of a pecan leaflet germinate rapidly, invade the tender tissues, and initiate infection within 6 hours. Once the fall rains begin, the fungus is washed off the shuck leaving only the dead epidermal cells of the shuck. Crop sanitation Experiments for the Control of Pecan Scab Disease.. Texas Agricultural Experiment Station. The fungus has been observed causing the most damage in the West Cross Timbers and on the ‘Burkett’ variety. The fungus develops on the outside of the shuck and only feeds on the outer layer of plant cells. If the rows are planted perpendicular to the prevailing wind, the outer rows will block movement to the inner orchard. Hoefnagels, M.H. – Pecan scab For registration information, contact Texas A&M AgriLife Conference Services at https://agriliferegister.tamu.edu/ or (979) 845-2604. and B.D. – Kernel discoloration (Several fungi, insects, drying) Diseases affecting pecans are caused by bacteria, fungi, nematodes, mycoplasm, and physiological problems. Late season, defoliation, weak trees – Brown leaf spot (Fungus – Cercospora fusca) affects only mature leaves [brwnlfsp] and usually does not appear until mid-June or July. – Variety of causal agents 12). The pecan is the state tree of Texas and has an important place in the state’s history. 1 Response . – Resistant varieties Texas east of the Pecos River generally experiences one population peak in late July. Pecan scab is a common fungal disease of pecans. If you are not achieving thorough coverage, check the tractor speed, pump pressure, nozzle size and nozzle arrangement.