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.
The warm February prompted early bloom in 2018, but March freezes wiped out most of the fruit in the variety trial at NFREC Quincy.
Peter C. Andersen University of Florida North Florida Research and Education Center
A one and one quarter acre (0.5 hectare) peach orchard was established during March 2015, at the North Florida Research and Education Center, Quincy. The cultivars included in the trial were as follows: Gulfking, Suncoast, Flordacrest, Flordaking, Gulfcrimson, GulfPrince, Gulfsnow, GulfAtlas and Gulfcrest. Flordaking and Flordaking are melting flesh peaches, Suncoast is a melting flesh nectarine, and the remaining Gulf series are non-melting flesh peaches.
The chilling requirement of peach and nectarine cultivars is measured by the cumulative amount of hours below 45°F required to break bud and flower. Approximately 625 chill units were recorded for 2018, and most of that total occurred during the month of January. February 2018 was extremely warm with 20+ days above 75° F, which promoted early bloom. The chilling requirement, the bloom date, and the number of fruit per tree measured in 2018 were as follows:
There was a compressed bloom period in 2018, with all cultivars blooming from February 14 through 27. Freeze events occurred on March 9 and 15, which almost eliminated the entire peach crop. The temperature at the NFREC-Quincy dropped to 27°, and was 28° at a nearby weather station. All varieties were well passed full bloom and had small fruit when the freeze events occurred.
Peach trees at nearly full size in the fourth year should produce at least 300 fruit per tree. The only variety that could justify a commercial harvest was Gulfsnow, which set an average of 50 fruit per tree. Unfortunately, in 2017 we also lost the entire peach crop to a March 15 freeze. Thus, despite a general warming trend for winters during the last two decades, erratic winter temperatures remain a potential problem for the culture of peaches in North Florida.
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.
Source: Pete Andersen
The relatively mild winter temperatures during the last two decades has led to a resurgence of interest in cold hardy citrus in North Florida. Satsumas account for almost all of the new commercial citrus acreage in the Florida Panhandle. Satsumas are the most cold-hardy commercial citrus. In North Florida, Satsuma fruit are ripe for harvest in a four to six week window from late October through early December. They must be hand clipped harvested to prevent tearing the peel and handled with care, because they are more prone to bruising than most other types of citrus. More than 100 new acres of Satsumas have been plated in Gadsden county alone, so it is important to identify some other varieties of citrus that are adapted to the region to offer a wide range of harvest date options.
If the next two decades have mild winter temperatures like the last two decades, we can successfully grow other cold-hardy citrus for the fresh market. The coldest temperature recorded at the NFREC-Quincy for the winters of 2015/2016 and 2016/2017 was 26° F. We have had temperatures as low as 15 and 16° F, and our older mature trees (satsuma, Navel, Minneola Honey Belle, and Valencia) have not experienced severe damage. A disclaimer, of course, should be noted that devastating freezes may still occur, despite this era of climate change and recent record warm temperatures.
The citrus varieties that ripen before Christmas probably have the best chance for success in North Florida. At the Research Center in Quincy, we have many citrus species/varieties and numbered selections under evaluation.The following is a list of the named varieties being evaluated. Table 1 at the end provides some preliminary data regarding the difference in fruit quality of these different varieities.
- Valencia: Although we have had good crops the last two years, I cannot recommend it for north Florida because of a late (late Jan. thru March) ripening date. In addition, other fresh market citrus offer more potential. There is also a new early ripening Valencia that we have not yet tested. The data in Table 1 reflect fruit that were not quite ripe.
- Navel and Red Navel: Navels have performed very well. I would estimate that our 12 year old trees have produced 400+ lbs per tree this winter. Little or no problem with Alternaria or citrus scab diseases. Our young trees also seem to be moderately cold hardy as well. Navel should be under consideration for north Florida. Harvest time can be just before Christmas.
- Tango: Tango is a seedless Murcott, although many fruit have a few (< 5 seeds per fruit when grown in a mixed block. Tango produces a small but sweet fruit. It is easy to peel. Cold tolerance is moderate. The two disadvantages are a late ripening period (Jan.) and extreme susceptibility to citrus scab.
- Nova: Nova mandarin was derived from a Clementine x Orlando Tangelo cross. It produces a small-medium sized fruit. Maturation is late January. It appears to be moderately cold hardy. More information is needed.
- Early Pride: Early Pride is low seeded Fallglo. It is an early maturing Mandarin hybrid. It produces a high quality, small-to medium-sized fruit with good flavor. It is easy to peel. Unfortunately, it is the least cold hardy (severe damage below 25 to 26 °F) of all the citrus that we have in our collection, and it cannot be recommended for north Florida.
- Sugar Belle: Sugar Belle was derived from a Clementine x Minneola Honey Belle cross. This mandarin hybrid is perhaps the most cold hardy of all non-satsumas in our trial. It produces a very attractive, bell-shaped fruit that is very high in sugar. It also is slightly higher in acid than is optimal. Fruit can have quite a few seeds when grown in a mixed block with citrus that can serve as pollinizers. Ripening date is November thru December. Sugar Belle could be considered for north Florida.
- Minneola Honey Belle: Minneola is an older cultivar that produces an attractive, medium-large, bell shaped fruit. It is less cold hardy than Sugar Belle and has a later ripening time period (late December). Minneola is very susceptible to Alternaria fungus, and a spray program is required for commercial production.
- Xie Shan: Xie Shan is an early ripening satsuma variety that ripens during October. In previous years Xie Shan has produced large, bumpy fruit that were not suitable for marketing. This year they produced a heavy crop (300 pounds/tree) of sweet, moderate-sized fruit. More observations are needed before I can recommend this variety.
- Owari: Owari is the most popular satsuma variety. It produces a consistent crop of small to medium-sized fruit. Owari and all satsumas are cold hardy down to about 12 to 14°F if the trees are cold acclimated. Ripening date is mid-November. It has performed well on Swingle and trifoliate orange rootstocks.
- Brown Select: Brown Select is the satsuma variety that produces the largest tree and fruit size. It ripens between between Xie Shan and Owari (early November). It has performed well on Swingle and trifoliate orange rootstocks.
For information on our long-term satsuma block, please refer to the UF/IFAS publication The Satsuma Mandarin. The performance of the experimental numbered selections will be dealt with in the future.
(Soluble Solids is a standard measure of sugar content)
Olive variety trial at UF/IFAS NFREC-Quincy. Photo credit: Pete Anderson
There is substantial interest in growing olives (Olea europaea) in northern Florida and southern Georgia. Thus far, olives have been relatively pest free, and appear to be a sustainable crop for this region. Olives are native to the Mediterranean region, can live thousands of years, and are adapted to hot dry summers and cool winters. It is likely that pest pressure will increase over time as the acreage in olives increases. Olive trees perform best on upland well-drained soils. One liter of olive oil can be produced from about 20 pounds of olives. The best cultivars and the best culture and management practices need to be determined for the southeastern United States.
A small block of olives consisting of Arbeqina, Arbosana, Koroneiki, Manzanillo, and Mission was established at the NFREC-Quincy in Feb. 2011. Trees were spaced at 10 and 20 feet within and between rows, respectively. Soil type was a Dothan loamy sand. Drip irrigation was provided during the establishment year, but not thereafter. Fertilization was generally at least twice a year with 10-10-10 N-P-K, except during 2016 when it was applied only in March. A weed free in-row strip was maintained with glyphosate. Insecticides or fungicides were not applied at any time. A very small crop was noted for Arbequina and Koreneiki during 2015.
Six-year-old trees averaged between 2.6 and 3.0 meters in height and 2.3 to 2.6 meters in width (Table 1). Tree size and tree vigor management will be important issues concerning olives grown in the southeastern United States. The first substantial yield occurred for Arbequina during 2016 (38% of a full crop). Koroneiki and Arbosana had a very small crop, (12 % and 3 % of a full crop, respectively), and Manzanillo and Mission produced no crop. Tree survival was also highest for Koroneiki (100 %) and Arbequina (93 %). Arbosana performed the worst with only 40 % of the trees surviving to six years of age. Although data from this planting are very preliminary, it is clear that research concerning the best cultivars, optimum culture and management practices, and tree vigor management will be necessary for successful olive production in the Southeastern United States.
For more information on this topic, please see the following UF/IFAS Publications: