Dan Anco & Kendall Kirk, Clemson, Ian Small, & David Wright, UF/IFAS
Figure 1. 2018 Peanut digging underway. Photo credit: David Wright
When it comes time to dig peanuts at the end of the growing season, many things influence how many pods make it into the basket. Research by Dan Anco and collaborators has documented two things which can decrease yield, over maturity and disease. Though slightly different, both have the potential to weaken pegs and increase pod loss, and both can be influenced by late season rains and delayed field access. In the past, Virginia type peanuts have characteristically exhibited more of a tendency for pod loss due to over maturity than runner varieties. The same appears to be the case when looking at losses due to late or early leaf spot diseases. While late and early leaf spot have some differences, they both cause lesions and can defoliate canopies.
Figure 2. Leaf spot defoliation. Credit: Ian Small, UF/IFAS
To reevaluate the role of leaf spot diseases and yield loss, researchers at the University of Florida teamed up with scientists across the southeast and in the Virginia-Carolina regions to pool together data and conditions from many years to look at two common questions: How much loss occurs with different amounts of leaf spot infection?, and Is there a disease threshold where we might consider digging a field early?
Each situation can be somewhat unique, but based on their research, the team was able to develop some rough rules of thumb. Mature runner type losses became significant after approximately 30% of the canopy was defoliated due to disease, whereas mature Virginia type losses became significant when 25% or more of the canopy was shed. For the second question, if a field is not yet at optimal maturity, it appears that when Virginia types pass 40% defoliation, they generally tend to increase losses (due to defoliation) faster than maturity is improving or yield is increasing in an otherwise healthy field. While it doesn’t look pretty, runner types appear to be able to sustain up to 50% defoliation while waiting on optimal maturity before losses increase more than the yield gains from additional maturity. In other words, if the crop is not mature there is a critical threshold (40% for Virginia types and 50% for runner types) where yield losses due to defoliation will outweigh any further improvement in maturity.
As a reminder, if you are thinking about making a fungicide application to prevent end of season defoliation, and to help maintain the integrity of stems and pegs, be sure to check the preharvest interval (PHI) on the label of any fungicide you are considering to apply. Do not apply the fungicide if you are not able to wait until after the PHI has passed to harvest.
Digger operation and setup is important during every harvest, but is particularly important if field conditions include sizeable leaf spot defoliation or over maturity. In another set of studies, we have seen above ground digging losses to be significantly impacted by conveyor speed. To assist with digger conveyor speed setup, a calculator is available at the link below.
List of the key collaborators from the Southeast and Virginia-Carolina regions that were involved in this project:
Dan Anco1, James Thomas1, Barbara Shew2, David Jordan3, Albert Culbreath4, Walter Monfort5, Hillary Mehl6, Nicholas Dufault7, Barry Tillman8, David Wright9, Ian Small9, Austin Hagan10, Howard Campbell10
1Clemson University, Department of Plant and Environmental Sciences, Edisto Research and Education Center, 64 Research Road, Blackville, SC 29817, USA; 2North Carolina State University, Department of Plant Pathology, 112 Derieux Place, Raleigh, NC 27695, USA; 3North Carolina State University, 100 Derieux Place, Department of Crop Science, Raleigh, NC 27695, USA; 4University of Georgia, Department of Plant Pathology, 2360 Rainwater Road, Tifton, GA 31793, USA; 5University of Georgia, Department of Crop & Soil Sciences, 2360 Rainwater Road, Tifton, GA 31793, USA; 6Virginia Tech, Tidewater Agricultural Research and Extension Center, 6321 Holland Road, Suffolk, VA 23437, USA; 7University of Florida, Department of Plant Pathology, 2550 Hull Road, Gainesville, FL 32611, USA; 8University of Florida, North Florida Research and Education Center, 3925 Highway 71, Marianna, FL 32446, USA; 9University of Florida, North Florida Research and Education Center, 155 Research Road, Quincy, FL 32351, USA; 10Auburn University, Department of Entomology and Plant Pathology, 149 ALFA Building, Auburn Univ, AL 36849, USA
Fall is not generally the right time to control many pasture weeds. However, some perennial weeds are effectively controlled by fall herbicide applications. Fall is a good time to treat for weeds such as cogongrass, blackberries, dewberries, biennial thistles, and Chinese Tallow trees.
Cogongrass is an invasive warm season perennial grass. It spreads by rhizomes and seed in north Florida. It can quickly spread from roadsides or forest areas into pastures. Established areas of cogongrass can have massive root systems making them difficult to control. Eradication of cogongrass infestations often take 3 or more years of twice a year treatments. Currently, only products with the active ingredients glyphosate and imazapyr are effective against cogongrass. Spring and fall treatments of either glyphosate, imazapyr or a combination of the two should be applied until the infestation is eradicated. Both of these herbicides are non-selective and will likely result in bare ground in treated areas. These areas are not going to produce adequate forage for animals so owners should consider this in their grazing management plan. For more information on cogongrass and treatment plans, please read the following UF/IFAS publication: Cogongrass (Imperata cylindrica) Biology, Ecology, and Management in Florida Grazing Lands
Blackberries and Dewberries
Blackberries grow upright and have hard, tough thorns.
Blackberry and dewberry control in pastures is difficult to achieve. The first step is identification of the plant. Blackberries grow upright while dewberries have a low vine-like growth habit. Dewberries have slender thorns and red hairs on the stem while blackberries have hard, tough thorns and no hairs. Blackberries grow up to 3-6 feet tall, however, dewberries rarely reach over 2 feet in height. Also, the seeds of dewberries are harder and much larger than that of blackberries.
Dewberries have slender thorns and red hairs on the stem and are low growing and somewhat vine-like.
For blackberries, effective broad spectrum herbicides include: Pasturegard HL (triclopyr + fluroxypyr), or Remedy Ultra (triclopyr ester). You can either apply these herbicides in the spring when the plants are blooming, or in the fall. Fall applications are more effective.
For dewberries, use Pasturegard HL (2pt/acre) but only expect 60-70% control.
Remember to wait at least 6 weeks after applying the herbicide before mowing. For more information on blackberries and dewberries in pastures, please read the following UF/IFAS publication: Blackberry and Dewberry: Biology and Control
First year thistles, in the rosette stage, are easiest to control.
Most thistles in Florida are biennial, meaning they live for two years. Thistles begin as a rosette and remain in this stage for the first year. In year two, the thistle sends up a stalk and flowers, produces seeds and dies. Thistles bolt (send up the stalk) January through July and flower from April through August. Each plant can produce up to 4,000 seeds. The key to controlling thistles is to keep the plant from flowering and producing seeds.
Thistles in the rosette stage are the most susceptible to herbicides but are hardest to see in the field since they lay flat on the ground. Once the thistles bolt, they are harder to kill with herbicides. Effective herbicides for thistles during the rosette stage include 2,4-D, triclopyr, GrazonNext HL, PastureGard HL and Weedmaster. For more information on thistle control in pastures, please read the following UF/IFAS publication: Thistle Control in Pastures
Chinese Tallow Trees (Popcorn Trees)
Chinese Tallow seedlings can be treated by foliar applications of triclopyr ester.
Chinese Tallow, also known as the Popcorn Tree, was introduced in the US over 200 years ago. They are prolific invaders of natural areas, pastures, wetlands, and yards. Mature trees can be cut down with a chain saw and the stump promptly treated with an herbicide with the active ingredient, triclopyr amine. You should try to make the final cut as low to the ground as possible. You can use a paint brush to apply the herbicide to the stump. A basal bark application of triclopyr ester plus a penetrant oil can be used on smaller trees. Treat the trunk to a height of 12 to 15 inches from the ground, thoroughly wetting it on all sides with the herbicide mixture. Basal bark treatments are only effective on saplings and seedlings less than 6 inches in stem diameter. Sometimes suckers may sprout from remaining roots. A foliar application can be used on these sprouts from July to October, before onset of fall color. For more information on Chinese Tallow, please read the following UF/IFAS publication: Natural Area Weeds: Chinese Tallow
For more information on pasture weed control, use the following publication link: Weed Management in Pastures and Rangeland
Figure 1: Research plots in 2017 affected by peanut collapse. Photo by B. Tillman
Shannon McAmis, De Broughton, Nick Dufault, Ian Small, Zane Grabau, Barry Tillman, and Diane Rowland, UF/IFAS Extension
In 2017, peanut growers of the Panhandle and North Central regions in Florida, and many areas in Georgia faced a number of issues. In addition to high disease, insect pests, nematodes, and Hurricane Irma’s aftermath, growers were faced with a new problem: peanut collapse or decline. University scientists hypothesized that abnormal weather patterns, including low solar radiation and decreased night-time temperatures during an important part of plant development, may have contributed to the collapse. Late in the season, growers noticed yellowing or necrosis of leaf margins, premature defoliation, plant stunting and weak pegs, all adding up to digging losses and reduced yield. This phenomenon was named peanut collapse or peanut decline by many growers and researchers (Figure 1: Peanut collapse). An estimated 25,000 acres fell victim to peanut collapse and experienced yield reduction of more than 1,000 pounds per acre. (retrieved from: Peanut Season has Begun in North Florida). UF/IFAS Extension Agents and researchers teamed up with University of Georgia and regional producers and scrambled to find the cause, but no main culprit was found.
Figure 2: A region-wide tour of peanut collapse took place with researchers, extension agents, and producers present.
In 2018, a team of Extension Agents and scientists are hoping to uncover more of this mystery and begin to gather the data needed to predict problems for harvest this year and into future years. They are using the help of a mobile app combined with drone flights. Researchers are using FieldX, an iOS app that is available through FieldX, Inc. that allows users to map field borders and upload geolocated pictures and notes conveniently on one platform.
Figure 3: Screenshot of the desktop app FieldX Dashboard.
FieldX is able to map and display multiple farms and fields at one time while individually tracking the geolocation of pictures and notes taken in the field. The app can track the exact path taken while scouting the field as well as record the specific location where pictures or soil and plant samples are taken.
Figure 4: Screenshot of the mobile app FieldX GeoNotes.
The FieldX app will allow for any incident of peanut collapse to be mapped, photographed, and described all on one convenient platform that can be shared with other users. This will help the team visualize the effect of peanut collapse for the entire region, and allow researchers to collect data about what happened when and where.
Recording the occurrence and progression of peanut collapse (and other diseases) will allow researchers to begin tracking symptom progression and begin to formulate models to assess risk in the future. Researchers will also combine drone or Unmanned Aerial Systems (UAS) images from identified fields to help develop early warning signals for the possible onset of collapse. Although the main focus of this work is to better understand peanut collapse, this technology can also be used to record and document other issues that may come up in the field, to better identify and predict risks to peanut production in the future.
The Peanut Decline Research Team encourages growers to report appearance of possible decline. If you suspect peanut decline may be an issue in one or more of your fields, contact your local county agent or De Broughton, Suwannee County Extension, who is coordinating this effort in Florida.
A few weeks ago I was lucky enough to attend North Carolina State’s Tomato Field Day, at the Mountain Horticultural Crops Research and Extension Center in Mills River, NC. Every summer crowds flock from all over the Southeast to learn what’s new in the world of tomatoes. Since it’s not always convenient for you to drop what you’re doing to make a road trip to North Carolina, I’ll highlight something I learned from the field day.
Jonathan Kressin, a PhD candidate in Plant Pathology at NC State, is researching the effects of grafted tomatoes on bacterial wilt management. Jonathan is not only researching rootstock varieties, he is also looking at cultural practice impacts on bacterial wilt.
A recently transplanted grafted tomato plant. Photo Credit: Josh Freeman, University of Florida/IFAS
Materials and Methods
Jonathan selected 12 rootstock varieties for trials at the 3 tomato growing regions in North Carolina (Mountains, Piedmont, and Coastal Plains). The cultural practice he is studying is transplant depth. He wants to determine if burying the graft union has any effect on bacterial wilt tolerance in grafted plants.
A tomato field in Florida with severe incidence of bacterial wilt. Photo credit: Mathews Paret, University of Florida/IFAS
- Several of the tested rootstocks performed equally well across the 3 regions. To help with disease resistance, it is important to rotate rootstock varieties and suppliers.
- The rootstock variety ‘Shield’ displayed the least bacterial wilt resistance overall.
- The rootstock variety ‘CRA66’ is recommended for open-pollinated varieties.
- Transplant depth (burying plants below the graft union compared to above the union) did not have any effect on bacterial wilt occurrence.
- Grafted plants have the potential to increase yield and average fruit size.
- Studies will be conducted to validate and understand the effect of transplant depth on bacterial wilt occurrence.
- Genetic testing will be conducted to help develop rootstock rotation recommendations.
Grafted transplants significantly increase the cost of production, but as agricultural automation becomes more prevalent, transplant costs should come down. Grafted tomatoes have the potential to increase yields and reduce inputs. It’s exciting to see what the future holds for the ever adapting business of tomato farming. More details on NC State’s tomato research can be found at the Mountain Horticultural Crops Research and Extension Center’s Tomato Production website.
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.
Russ Mizell and Xavior Martini, UF/IFAS Entomologists, NFREC, Quincy
Citrus production in North Florida is expanding rapidly in response to the devastation of citrus in Central and South Florida due to citrus greening disease. Citrus acreage in southern Georgia is also increasing. Florida’s climate is situated in the temperate (North) and subtropical (Central and South Florida) regions. Thus, non-native pests from other similar habitats around the world can and frequently do become established in Florida. For example, some non-native pests of citrus that are well established in subtropical Florida include Diaprepes abbreviatus, better known as the “Apopka weevil,” the sugarcane rootstook borer, and the Sri Lanka weevil, Myllocerus undatus. Both of these weevils feed on citrus leaves as adults and their immature stages feed on the roots. Both species also feed on a wide range of other plant species damaging leaves and roots.
The annual low temperatures observed in North Florida the last few years have been higher, possibly due to climate change, and as a result have enabled some pests usually restricted to the subtropical areas of Florida to expand their ranges into the North Florida temperate zone. In addition, expansion of citrus culture with the corollary acceleration of plant movements across the state increase the risk of pest introduction from southern parts of Florida.
Via this article, we are alerting extension personnel, home gardeners, and more specifically citrus growers and nurserymen that the Apoka weevil, Diaprepes abbreviatus has been detected for the first time in an established population in Jefferson County, FL. The Apopka weevil was found in a nursery in Jefferson County, and has not been found in citrus in North Florida to date. The Apopka weevil has several hundred known host plants including citrus, sugarcane, vegetables, fruits and many woody landscape plants. Sicklepod, Senna obtusifolia, and pokeweed, Phytolacca americana, appear to be favorite adult hosts in North Florida in August-September. The large black and white-striped and often orange colored adults (Fig. 1 – C and 1D) feed on fresh leaves where they place their white egg masses in pouches (Fig. 1 – A) made from 2 leaves connected together. The larvae (Fig. 1- B) hatch and fall to the ground where they feed on plant roots often at depths of 1-2 feet or more. There are 2 generations per year in southern Florida, but the number and timing of those that will occur in north Florida remains unknown. Adult weevils are easily detected, and often occur as mating pairs. They are not known to be great fliers; however, the larvae can be found in, and be spread around while infesting plant roots in containers.
Fig. 1: Diaprepes abbreviatus (A) eggs (B) larva, (C) orange form adult, and (D) white form adult. Picture by Tai Huang (A) and Lyle Buss (B, C and D).
This weevil is a quarantined pest, so nurseries in infested counties are required to follow specific insecticide treatments prior to shipping outside of the quarantine area. Producers of any potentially infested crops should monitor visually for the adult weevils by looking for feeding damage and adult weevils on the crop and associated weeds.
Further information on this insect pest can be found in the following UF/IFAS publication: Diaprepes Root Weevil, Diaprepes abbreviatus.