Impact of Hurricane Michael on seven year old pecan trees at Quincy Research Station. In an era of climate change with a higher frequency of tropical storms and hurricanes, resistance to storm injury should be considered as a criterion when selecting pecan cultivars. Credit: Pete Andersen, UF/IFAS
Pete Andersen, Horticulture Specialist, UF/IFAS North Florida Research and Education Center, Quincy
The pecan (Carya illinoenensis, family Juglandaceae) is native to the Mississippi floodplain of North America. Pecan trees are not well adapted to withstand hurricane force winds. Ironically, the best maintained trees with thick foliage and a large nut crop approaching late summer are most susceptible to damage as a result of tropical storm or hurricane force winds. A low input pecan variety trial was initiated at the NFREC-Quincy in February 2011. This trial consists of Amling, Caddo, Cape Fear, Curtis, Desirable, Elliot, Excel, Forkert, Gloria Grande, Kanza, Melrose, Moreland, Oconee, Pawnee, Stuart, Sumner, Kiowa. No insecticides or fungicides were applied in 2018.
Hurricane Irma had a negative impact on the NFREC-Quincy pecan orchard. Several trees were blown over and many leaves were blown off the trees in response to tropical storm force winds (Table 1). Hurricane Irma produced sustained winds as high as 37 mph at the FAWN measurement center in Quincy, although I suspect that wind gusts were as high as 50 to 60 mph. After Hurricane Irma and the high scab pressure of 2017, the 2018 crop was virtually eliminated at the NFREC-Quincy. Between 0 and 40 % of the trees were blown over by Hurricane Irma. Melrose was the cultivar most impacted by hurricane force winds, whereas all trees of seven cultivars remained upright. One tree each of Caddo, Curtis, Elliott, Gloria Grande, Melrose and Oconee that were blown down to a 45o angle were staked and tied to a vertical position with two posts and wire several weeks after Irma. They remained upright until hurricane Michael blew all of these trees down in a direction not supported by the posts (generally from south to north).
Hurricane Michael was far more damaging than Irma, with sustained winds of 55 mph recorded at the Quincy FAWN weather station. I believe that wind gusts on October 10, 2018 were as high as 70 to 85 mph. All trees of Excel, Lakota, Stuart and Sumner remained vertical after hurricane Michael (Table 1). At least 44 % of Caddo, Cape Fear, Curtis, Desirable, Forkert, Gloria Grande, Melrose and Moreland were blown over by the storm. Some varieties such as Curtis and Melrose were blown completely over with a broken major root system, whereas Desirable, Elliott, Forkert and Kiowa were leaning at an angle of 45 to 90o. Trunk circumference was usually between 22 to 29 inches (two feet in height). Curtis, Desirable, Kiowa and Oconee were the smallest trees, which I attribute to partial defoliation due to high pecan scab pressure. The three largest diameter trees (Elliott, Excel, Lakota) are all scab resistant cultivars. Incidentally, only two trees of Stuart sustained any significant limb breakage (data not shown).
The high frequency of hurricane events that impact regions within 50 miles of the Gulf of Mexico must be taken into account when growing pecan trees. However, what made hurricane Michael particularly devastating to the pecan industry was that category 3 hurricane status was retained into Georgia. This hurricane was probably the most devastating storm to ever impact the center of the pecan industry in Albany, Georgia. The timing was especially bad in that most varieties had not yet been harvested.
I would like to share one observation concerning a pecan tree’s tendency to sustain hurricane injury. As mentioned earlier, trees with heavy foliage and a good nut crop will sustain the most wind damage. Another factor to consider is the in-row weed free strip (normally 8 to 12 feet wide). Weed control will increase the efficiency of water and fertilizer use by pecan trees, and is necessary for sweeping nuts at commercial harvest. An unintended consequence of this bare soil is that tree roots cannot be held in place by surrounding vegetation. For example, the roots of bahiagrass (often used in row middles) can extend down to a depth of 3 feet or more. I observed that roots of blown down pecan trees were usually pulled loose from this in-row strip because there was no support from surrounding vegetation.
In conclusion, there was a cultivar dependent degree of hurricane injury in the NFREC-Quincy pecan orchard. The most resistant cultivars to blowing over were Excel, Lakota, Stuart and Sumner. The most injury was recorded for Desirable and Melrose. If we are in an era of climate change with a higher frequency of tropical storms and hurricanes, resistance to storm injury should be considered as a criterion when selecting pecan cultivars.
Dr. Clive Bock, USDA-ARS talked to attendees about pecan scab management at the 2018 Pecan Field Day
This year’s UF/IFAS Florida Pecan Field Day took place on Thursday, September 13, 2018 at the Jefferson County Extension Office in Monticello, Florida. Extension specialists from Florida and Georgia provided growers from across the state with information about current pecan production practices and management tips. Pesticide continuing education units (CEUs) were provided for Florida and Georgia pesticide applicators, as well as for Certified Crop Advisors. Simpson Nurseries of Monticello sponsored a barbecue lunch for the attendees.
The focus of the Pecan Field Day was primarily on production practices. Speaker topics included Best Management Practices (BMPs) and cost-share opportunities for growers, weed management, fertility, pecan scab management, insect pest management and information regarding new pecan varieties. The following provides a short summary of topics discussed by each speaker, followed by links to download PDF (printable) versions of the presentations given at the Pecan Field Day.
BMAPs, BMPs and Cost-Share Opportunities
Dr. Andrea Albertin, UF/IFAS Water Resources Agent provided information on the implications of the 2016 Florida Water Bill. According to this bill, farmers in a Basin Management Action Plan (BMAP) can choose to either: (1) enroll in the Florida Department of Agriculture and Consumer Sciences (FDACS) (BMP) program and implement BMPs or (2) monitor water quality on their farm. Currently, in the Florida Panhandle there are several BMAP areas: Wakulla Springs, Wacissa Springs, Jackson Blue Springs and the Suwannee River Basin. There is financial assistance available from FDACS, NRCS, water management districts, and the Mobile Irrigation Lab for farmers enrolled in the BMP program.
Herbicides for Pecan Orchards
Dr. Peter Dittmar, UF/IFAS Weed Specialist shared information on the current herbicides labeled for use in Florida pecan production. It’s important to know which weed you are targeting and selecting the proper herbicide for its control. He also discussed the benefits of using a pre-emergent herbicide to reduce the use of post-emergent herbicides and to decrease the likelihood of building herbicide resistant weed populations.
Dr. Lenny Wells, UGA Pecan Specialist discussed the importance of proper fertilization for young and mature pecan trees. Leaf sampling between July 7th and August 7th are the most effective means of determining nutrient requirements, and soil sampling should be done in the fall/winter to determine pH and toxicities.
Pecan Scab Management
Dr. Clive Bock, USDA-ARS-SEFTNRL Plant Pathologist spoke on the proper fungicide spray distribution and coverage for effectively managing pecan scab. He stressed the importance of rotating fungicide modes of action as resistance is an issue. Phosphite fungicides are effective for controlling pecan scab on the fruit and the foliage. There are organic options available for managing pecan scab.
Management of Common and Occasional Pests of Pecan
Dr. Ted Cottrell, USDA-ARS-SEFTNRL Entomologist discussed managing the black peach aphid using gibberellic acid, a plant growth regulator. He also talked about mating disruption as a possible control for the pecan nut casebearer and the hickory shuckworm. Mating disruption prevents the male insect from finding the female, thus the mating process is disrupted. There are several types of scale insects that occur on pecan, and timing insecticide applications to the crawler stage are effective.
New Pecan Variety Releases
Dr. Patrick Conner, UGA Pecan breeder provided variety data from trials in Georgia demonstrating trends in pecan performance. The pest resistance, yield, nut quality and tree attributes for several varieties were discussed. He also discussed tree availability for different varieties.
Sponsors of the 2018 Florida Pecan Field Day included Farm Credit of Northwest Florida, Savage Equipment of Georgia and Simpson Nurseries.
Florida Pecan Growers Association
Following the Pecan Field Day, the Florida Pecan Growers Association met for their annual meeting. The Florida Pecan Growers Association is looking to grow their organization and connect with pecan producers across the state. If you are a current or prospective pecan grower in Florida and are interested in becoming a member of the Florida Pecan Growers Association, please contact me. The Florida Pecan Growers Association will hold their next meeting at 9:30 EDT on March 1, 2019 at the Jefferson County Extension Office (2729 W. Washington Hwy. Monticello, FL 32344).
For more information on pecan production or about upcoming educational events, contact your local extension office.
Fall Webworm beginning to get started on a branch tip. Image credit: Matthew Orwat
Bare limb tips and clusters of webbing in pecan trees are often the first sign that fall is right around the corner.
This webbing is caused by clusters of the larvae of the Fall Webworm (Hyphantria cunea (Drury)) which is often also called Pecan Webworm. “Fall Webworm” is a bit of a misnomer in our region since they are able to strike in spring and summer thanks to our long growing season. They are most noticeable in the fall thanks to cumulative effects of earlier feeding.
The adult form of the fall webworm is a solid white or white and brown spotted moth that emerges in late March through August in southern climates. After mating they lay orderly clusters of green eggs, usually May through August. Soon after emergence, the larvae begin creating silk webs to protect themselves as they voraciously feed on their various host plants, of which Pecan is of primary agricultural importance in this region.
Although they are capable of defoliating complete trees, especially smaller ones, most seasons they are kept in check by beneficial insects such as the paper wasp. It is beneficial for small orchards or home growers to scout their trees from June through August. If small webs are observed in young trees, it is best to prune them out with a pole saw or pole pruner and dispose of the branch. Pruning of small branches does not harm the tree, but it may be of no benefit to remove small webs in larger trees, if they are being controlled by natural enemies.
Active feeding by webworm on pecan branch tip. Image credit: Matthew Orwat
Most large pecan orchards have a routine insecticide program, so fall webworm rarely creates problems. For smaller orchards or homeowners it is difficult to spray for control, due to the cost of the equipment required to get the spray into the tree canopy. If spraying is an option, many insecticides containing spinosad or Bacillus thuringiensis (Bt) exist. Both of these products target caterpillars while not harming beneficial insect predators that feed on these worm populations. Several more toxic insecticide products exist that will control fall webworm, but they often exacerbate insect problems by killing off beneficial insects that might be controlling other insect pests.
Fall webworm is not usually a serious problem for pecan production. Fortunately, when control is warranted, there are plenty of options available.
Leaves stripped by Fall Webworm. Image Credit: Matthew Orwat
The pecan (Carya illinoenensis, family Juglandaceae) is native to the Mississippi floodplain of North America. The pecan tree requires deep soils with an abundant supply of soil moisture. A large mature pecan tree can transpire 500-1,000 gallons of water per day. The climate of the native range of pecan is characterized by long, hot humid summers with moderate to high rainfall.
Traditionally, the Southeastern United States produced the greatest quantity of pecans in the world. Over the last 40 years there has been a shift in production to states with an arid climate such as Texas, New Mexico and Arizona. The reason for the shift is two-fold. Pecan scab, a fungal disease that attacks leaves and developing nuts, has increasingly become a problem in region with high spring and summer rainfall. Weekly fungicide sprays are required for many pecan cultivars. Second, most pecan cultivars that were produced from the USDA-Brownsville breeding program 15 to 40 years ago were very scab-susceptible. Thus, regions with an arid climate have had a competitive advantage, as long as they had access to abundant irrigation water. Mexico has also recently emerged as a significant competitor to US pecan production. Limited quantities of pecans are also produced in Australia, South Africa, and Brazil.
Pecan breeding and cultivar testing is a long term investment. Pecan trees usually require 5 to 10 years after a cross is made until first harvest. Long-term productivity assessments require more than 30 years. Also, the resistance of a given cultivar to pecan scab and other diseases (downy spot, powdery mildew, zonate leaf spot, pecan vein spot and anthracnose) can decline over time as these fungal organisms develop virulence toward specific cultivars when they are grown on a widespread basis.
The USDA and the University of Georgia have embarked on a pecan breeding effort for the last 15 years that specifically targets the Southeastern United States with the following specific objectives: 1) resistance to scab and other diseases; 2) early harvest date, which normally brings higher prices; 3) consistent high yields with a large nut size, and; 4) a high percentage kernel, light in color with high oil content.
The performance of 26 cultivars has been evaluated at the North Florida Research and Education Center at Monticello for many years. Yield, nut size, percentage kernel, resistance to leaf and nut diseases, and limb breakage were assessed over an 11 year period. The recommended cultivars from this trial were Elliot, Moreland and Sumner. Conditionally-recommended cultivars were Cape Fear, Curtis, Desirable, Kiowa and Stuart. For more information read the following publications University of Florida EDIS website: The Pecan Tree, and Pecan Cultivars for North Florida.
New information has become available concerning cultivar recommendations. In Georgia, the recommended cultivars are Elliot (excellent scab resistance), Sumner (good scab resistance), Caddo, Forkert, and Oconee (average scab resistance) and Pawnee (poor scab resistance). Conditionally-recommended cultivars for Georgia include Amling, Avalon, Byrd, Cape Fear, Creek, Desirable, Excel, Kiowa, Lokata, Mandan, McMillan, Morrill, Stuart, Treadwell and Zinner. For Alabama, the recommended cultivars with excellent scab resistance are Excel, Gafford, and Headquarters. McMillan and Baby B have good resistance and Apalachee, Caddo, and Giftpack have average resistance. Conditionally recommended cultivars for Alabama include Adams 5, Amling, Byrd, Creek, Desirable, Elliot, Forkert, Mandan, Sumner, Surprise and Syrup Mill.
A new, low input pecan trial was initiated at the NFREC-Quincy in February 2011. This trial consists of Amling, Caddo, Cape Fear, Curtis, Desirable, Elliot, Excel, Forkert, Gloria Grande, Kanza, Melrose, Moreland, Oconee, Pawnee, Stuart, Sumner, Kiowa. No insecticides or fungicides were applied in 2017. We evaluated leaf and nut scab resistance and yield in 2017 (Table 1). The highest resistance to leaf scab was Excel, followed by Amling, Lakota, Sumner, Gloria Grande and Elliot. Desirable and Pawnee had the lowest resistance to scab and require a rigorous spray program. For those cultivars that had at least a partial crop, Excel and Lakota did not have a single scab lesion on nuts.
Hurricane Irma had a negative impact on our pecan orchard. Several trees were blown over, and many leaves were blown off the trees. In addition, pecan scab, other leaf diseases, and pecan scorch mite had a negative impact on all the cultivars. Most cultivars had lost most of their leaves by the end of September. The only cultivar that produced a commercial crop was Excel. Excel yielded an average of 20.4 pounds per tree (Table 1). In addition, visual estimates after harvest indicated that there was at least 5 pounds per tree that remained on the ground under dried leaves or hidden in the grass between rows. Thus a more accurate yield of Excel was in excess of 25 pounds per tree.
Excel Pecan Cultivar from the evaluation trial at NFREC-Quincy. Photo Pete Andersen
Amling, Forkert, Gloria Grande, Lakota, Melrose Moreland Oconee and Sumner did produce a few nuts with low quality. The remainder of the cultivars did not produce any crop. The lack of any yield on cultivars such as Curtis, Elliot, and Stuart and was also due to the fact that these cultivars are not precocious, and often require eight or more years to produce a commercial crop under ideal circumstances.
The nut weight and percentage kernel was as follows: Excel 9.3 g. 47% kernel; Lakota 6.5 g, 50.6 % kernel; Gloria Grande 9.2 g, 38 % kernel; Oconee 6.1 g, 33 % kernel; Sumner 7.9 g 42.5 g, 43% kernel. Excel kernels were of good quality, high in oil and had a taste resembling Elliot. Lakota produced only a few medium-sized nuts but they had a reasonable 50.6 % kernel. The other cultivars did not produce a nut of commercial acceptance.
After Hurricane Irma and the high scab pressure of 2017, it is likely that the NFREC-Quincy trees will produce a light crop in 2018. Although this planting was established as a low input sustainable pecan planting, it is clear that a pesticide spray program will be required for most of the pecan cultivars in this trial.
Pecan tree grove in North Florida. UF/IFAS Photo: Thomas Wright.
Pecans are grown throughout the Panhandle of Florida. The western side of the Panhandle tends to be acreage dedicated to home gardeners, while the eastern counties have more commercial acreage. Regardless, many in the agriculture community are interested in pecans, because they either grow them commercially, or have some planted on their farm for local consumption. UF/IFAS Extension agents receive a steady stream of pecan questions throughout the year. A lot of the questions tend to focus on reinvigorating older orchards, remedying alternate bearing, and disease management. Pecan Scab is the most devastating of pecan diseases in the Southeastern United States. Disease samples containing scab are frequently brought in to Extension Offices seeking assistance.
Pecan Scab symptoms on the nut shuck (Photo Credit: University of Georgia Plant Pathology , University of Georgia, Bugwood.org)
Pecan Scab is caused by a fungal pathogen called Cladosporium carygenum. Scab can reduce yields 50 to 100%, if not managed. Years in which pecan scab is worse tend to be years with excessive rainfall, much like 2017. Symptoms are small dark lesions (spots) on the leaves, twigs, and nut shucks. The lesions can grow together, and with extreme scab infections, the lesions started on either side of the leaf will eventually go through the leaf, and some even develop a shot hole appearance. Conditions of prolonged leaf wetness is the optimal environment for scab development.
The best way to manage pecan scab is to plant resistant cultivars. Specialists in Florida and Alabama have developed a list of recommended cultivars with some varying levels of scab resistance. The varieties include Gafford, McMillan, Excel, Kanza, Adams 5, Philip, Gloria Grande, Lakota, Sumner, as well as several others listed in the chart below. Some of the recommended pollinator cultivars are Amling and Syrup Mill. The data in the chart were derived from Dr. Pete Andersen’s research of scab resistance in cultivars grown in Quincy, Florida, at the UF/IFAS North Florida Research and Education Center.
Dr. Pete Andersen’s 3 year research data of scab resistance on several pecan cultivars in Quincy, FL.
Choosing appropriate cultivars is the best way for homeowner pecan growers to deal with scab, as spraying protectant fungicides is not an option for non-commercial growers. For commercial growers a detailed spray schedule can be followed from bud-break to shell hardening. A plethora of fungicides can be used, but should be rotated to prevent resistance development. Some of the fungicides used for scab control include tebuconazoles, azoxystrobin, kresoxim-methyl, flutriafol, triphenyltin hydroxide, and dodine. Fungicide recommendations do change over time, so check with local Extension Agents to receive the latest recommendations.
Sources for additional information on Pecan production:
Tree shaker used for automated pecan harvest at a Texas A&M Research farm. Credit: Matt Lollar
The Texas Pecan Short Course is an annual, four day training offered by Texas A&M University. The short course teaches pecan orchard managers and prospective pecan growers how to plant, grow, harvest, and market pecans. A harvest equipment demonstration is one of the hands-on activities offered during this training. The following video that provides a quick review of pecan harvest equipment demonstrated at the Texas Pecan Short Course.
For more information on pecan production, utilize the following publication links: