To Dig or Not to Dig: Optimizing Peanut Digging Decisions in the Presence of Leaf Spot Defoliation

To Dig or Not to Dig: Optimizing Peanut Digging Decisions in the Presence of Leaf Spot Defoliation

Dan Anco & Kendall Kirk, Clemson, Ian Small, & David Wright, UF/IFAS

digging peanuts

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.

peanut defloation series

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.

Peanut Digger Conveyor Speed Calculator

 

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

Rapid Response Team Deployed to Investigate Peanut Collapse

Rapid Response Team Deployed to Investigate Peanut Collapse

Research plots in 2017 affected by peanut collapse

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.

 A region-wide tour of peanut collapse took place

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.

creenshot of the desktop app FieldX Dashboard

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.

Screenshot of the mobile app FieldX GeoNotes

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.

Grafting Tomatoes for Disease Resistance and Improved Yield

Grafting Tomatoes for Disease Resistance and Improved Yield

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.

Grafted Tomato Transplant

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.

Bacterial Wilt in a Tomato Field

A tomato field in Florida with severe incidence of bacterial wilt. Photo credit: Mathews Paret, University of Florida/IFAS

Results

  • 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.

Future Research

  • 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.

Highlights from the 2018 Florida Pecan Field Day

Highlights from the 2018 Florida Pecan Field Day

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.

Presentation link: Albertin – BMAPs BMPs and Cost-Share

 

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.

Presentation link: Dittmar – Herbicides for Pecan

 

Pecan Fertilization

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.

Presentation link: Wells – Pecan Fertilization

 

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.

Presentation link: Bock – Pecan Scab Management

 

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.

Presentation link: Cottrell – Insect Pest Management

 

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.

Presentation link: Conner – Pecan Cultivars

 

Sponsors

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.

Pest Identification is Essential and Sometimes Surprising

Pest Identification is Essential and Sometimes Surprising

Throughout my 22 year history as an Extension Agent, I have been the first responder for all sorts of strange things farmers, ranchers, and landowners encounter.  This is one of the critical roles county agents play all over the country.  If you see something odd or unusual, whether it is a new weed, insect or disease, your county agent should be one of the first people you contact to get information.  It is very possible that if you find something you have never seen before, others may not have not seen it either.  County agents are connected to a vast network of experts and identification labs that can help figure out what those strange new things are. Because of the ports, huge numbers of visitors, and tropical storms, new pests and diseases show up in Florida on a regular basis.  It is very important to have new pests identified, before they have the opportunity to spread.

Most of the time the plants, bugs, and diseases agents have identified by experts are harmful in some way to the crops we grow.  Whether it is toxic weeds in pastures, insects feeding on plants, or diseases in crops, the first thing you need to know is, “What is it?” Once the issue is identified, most of the time there are some type of control options available.  Sometimes, however, things are not at all what you expect.  Such was the case this summer as four types of plant pests were identified that turned out to be harmless, and in some cases were actually beneficial.

Specimen #1

Aschersonia aleyrodis on Satsuma is a fungus that feeds on whitefly nymphs. Photo credit: Doug Mayo, UF/IFAS

A citrus grower thought that his satsuma trees were under serious attack.  White flies were already an issue as noted by the sooty mold growing on the leaves, and then this terrible scale that he had never seen was all over the undersides of the leaves of the trees.  While from a distance this looks much like a harmful scale insect, it turned out to be a beneficial fungus that destroys whitefly nymphs!

Dr. Xavier Martini, UF/IFAS Entomologist in Quincy shared the following information:

What you have is not scale, it is citrus whitefly nymphs that have been attacked by an entomopathogenic fungi called Aschersonia aleyrodis. It is very good to have this fungus, because it helps control the whitefly population.

You can read about this in the Featured Creature article entitled: Citrus WhiteflyScroll down to the section called: Parasitic fungi for more details.

Aschersonia aleyrodis fungus on the underside of a satsuma leaf looks terrible, but it was actually making a bad situation better by reducing the whitefly population on young satsuma trees. Photo credit: Doug Mayo, UF/IFAS.

Specimen #2

The beneficial fungus Beauveria bassiana is a natural enemy of kudzu bugs on soybeans. Photo credit: Doug Mayo, UF/IFAS.

A soybean grower saw something he had never noticed before.  A white mold was growing in spots all over the stems of soybean plants in a field.  This is where you have to be careful.  Soybeans can get white mold, which is caused by the fungus Sclerotinia sclerotiorum.  If you do a google search for Soybean white mold, you will find pictures that look somewhat similar.  Upon closer inspection, at the NFREC Plant Pathology Lab, in Quincy,  the fungus was actually Beauveria bassiana which is a biological control of kudzu bugs.  The white spots in the photos are actually dead or dying kudzu bugs, and the fungus was growing on the insects, not the soybean stalks.  You can read more about this beneficial fungus at: Kudzu bugs’ decline is attributed to two factors.

The white spots are beneficial fungus Beauveria bassiana that are attacking kudzu bugs not the soybean stalks. Photo credit: Doug Mayo, UF/IFAS

Specimen #3

Slime mold found growing on a centipede lawn. Photo credit: Doug Mayo, UF/IFAS

A landowner noticed this really strange growth on her centipede lawn.  It looks hideous and destructive.  In truth, it was a relatively harmless plasmodial slime mold, named Fuligo septica.

Larry Williams, UF/IFAS Okaloosa Horticulture Agent shared the following information:

Slime molds mostly function as saprophytes, feeding on and breaking down organic matter. It should not cause any permanent problems or major damage to the lawn. One such slime mold is commonly referred to as “dog vomit” slime mold.

Here is a link to an article on slime molds that pop up on lawns, in mulch, and damp areas under trees with high organic matter: Those Mysterious Molds

Slime mold growing on the moist organic matter in a Jackson County Lawn. Photo credit: Doug Mayo, UF/IFAS.

Oklahoma State University’s diagnostic labs had gotten so may calls from concerned homeowners that they developed a YouTube video on slime molds:

Specimen 4

Harmless slime mold growing on centipede lawn after multiple rainy days. Photo credit: Doug Mayo

A similar scenario was seen on a centipede lawn at a county building in Jackson County.  This slime mold is commonly found on lawns and pasture grasses during extended rainy periods in Florida. While it looks like a serious disease, it is really just another plasmodium species that feeds on decaying organic matter.  As with the large slime mold in specimen 3, what you are seeing is actually the spore masses that will generate more slime molds when conditions are favorable again for growth.  You can knock these off with a garden hose, if you want to, but they disappear almost as fast as they form.  No real harm is done to the grass that is just serving as a platform for slime mold reproduction.

Read more about it in this article written by Matt Orwatt, UF/IFAS Washington Horticulture Agent: Frequent Rains Induce Slime Mold in Panhandle Lawns

Summary

Most of the time, when you see something that does not look normal it is a bad thing, such as weeds, fungal diseases, or damaging insects. But before you spend money on a control, it is really important to have a positive identification of the pest.  Not everything unusual is harmful.  Modern pesticides have become very target specific, so it is vital to first find out what this new thing is before you spend money trying to control it.  So the next time you see something alarming or strange in your crop, pasture, or landscape, contact your local county agent, so you can find out for certain what you are dealing with, and get some science-based advice on a plan of action, if one is needed.

New North Carolina Tomato Varieties Offer Disease Resistance and Better Flavor

New North Carolina Tomato Varieties Offer Disease Resistance and Better Flavor

Dr. Randy Gardner discussing NC State tomato varsity trials. Photo Credit: Matt Lollar

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.

New Varieties with Dr. Randy Gardner and Dr. Dilip Panthee

Dr. Randy Gardner is a retired tomato breeder from NC State with more than 30 years of experience.  Dr. Dilip Panthee is NC State’s newest tomato breeder.  Both are working on developing new cultivars with both disease resistance and an added emphasis on flavor.  The three main diseases they are focusing on for resistance and/or tolerance are Late Blight, Bacterial Spot, and Verticillium Wilt Race 2.  See the list below of some of their newest releases.  Just remember that these varieties were developed for North Carolina growing conditions, so it’s recommended that you give them a try on a small scale to evaluate them for your area.The varieties listed in the table above are available in the market.  For a sneak peak of what’s in store for the future, check out this poster developed by Dr. Panthee:  NC State Tomato Variety Replicated Trials 2018.  More details on NC State’s tomato research can be found at the Mountain Horticultural Crops Research and Extension Center website.  Thanks to NC State for an excellent field day!

Dr. Randy Gardner and Dr. Dilip Panthee, NC State tomato breeders, are working on disease resistance with an added emphasis on flavor. Photo credit: Dr. Dilip Panthee, NC State