Benefits of Nematodes in Healthy Soil Ecosystems

Benefits of Nematodes in Healthy Soil Ecosystems

The Steinernema scapterisci insect-parasitic nematode in the juvenile phase can infect and kill insects in the Orthoptera order, such as grasshoppers and crickets. Photo by David Cappaert, Bugwood.org.

The Steinernema scapterisci insect-parasitic nematode in the juvenile phase can infect and kill insects in the Orthoptera order, such as grasshoppers and crickets. Photo by David Cappaert, Bugwood.org.

Nematodes. Those microscopic, worm-like creatures that enter or attach themselves to crop roots, pierce root tissue, suck up root juices, and destroy crop yields.

Roots of a pepper plant infected by southern root-knot nematodes (Meloidogyne incognita) have extensive gall damage. Photo by Scott Bauer, USDA Agricultural Research Service, Bugwood.org.

Roots of a pepper plant infected by southern root-knot nematodes (Meloidogyne incognita) have extensive gall damage. Photo by Scott Bauer, USDA Agricultural Research Service, Bugwood.org.

But did you know, plant-parasitic nematodes are only a very small fraction of the nematodes living in your soil? And did you know most nematodes are harmless to crops – and many are even beneficial?

Although the threat of plant-parasitic nematodes damaging your crops is a concern, if a few important agricultural principles are followed – such as carefully designed crop rotations and building soil organic matter content – nematode-induced yield losses can be drastically reduced, while supporting nematode populations that will actually benefit your crops.

Nematodes are most abundant in the upper-most soil horizons, where up to 10 million individual nematodes can live per 10 square feet of soil. They subsist mostly in water-filled pore space near organic matter and plant roots.

Because of the havoc they can cause, plant parasitic nematodes, such as root-knot nematodes, have been the species most widely studied by scientists. But there are many other types of nematodes less studied, generally classified by their mouthparts and diet. Some strictly feed on either fungi or bacteria, while others are predatory, relying on other nematodes or protozoa for their diet; and others are omnivorous, able to feed on fungi and bacteria when their preferred prey is scarce, or conditions are unfavorable.

Light tillage, especially coupled with soil conservation practices and use of cover crops, can increase organic residue decomposition by bacteria and bacterial feeding nematodes, leading to more plant available nutrients for the season. Photo by Anthony LeBude, NC State University, Bugwood.org.

Light tillage, especially coupled with soil conservation practices and use of cover crops, can increase organic residue decomposition by bacteria and bacterial feeding nematodes, leading to more plant available nutrients for the season. Photo by Anthony LeBude, NC State University, Bugwood.org.

Different types of nematodes play different roles in a soil system. In row crop systems, maintaining a diversified food web through soil conservation and organic matter additions can support nematode populations that actually enhance nutrient mineralization and plant nutrient availability. This is especially beneficial in farming systems reliant on organic nutrient sources, as bacterial feeding nematodes consume nitrogen-containing bacteria and release excess nitrogen as plant available ammonium (NH4+). Nematodes can also rejuvenate old bacterial and fungal colonies and spread these microorganisms into organic residues whose nutrients may otherwise remain immobile and unavailable to plants.

Although overly intensive tillage can disturb the soil food web, properly managed tillage can actually promote healthy soil ecosystems. Light soil disturbances – especially coupled with compost and manure additions – increase the availability of organic residues to be consumed by bacteria, which in turn stimulate bacterial feeding nematodes, leading to a net increase of available nitrogen for plant uptake. And although fungal feeding nematodes are more abundant in no-till and perennial agricultural systems, bacterial feeding nematodes are better at releasing plant available nitrogen than their fungal feeding counterparts.

Thousands of Heterorhabditis bacteriophora insect-parasitic nematodes emerging out of a wax moth cadaver, ready for use as a biological control to protect crops from pests such as weevils, beetles, and flies. Photo by Peggy Greb, USDA Agricultural Research Service, Bugwood.org.

Thousands of Heterorhabditis bacteriophora insect-parasitic nematodes emerging out of a wax moth cadaver, ready for use as a biological control to protect crops from pests such as weevils, beetles, and flies. Photo by Peggy Greb, USDA Agricultural Research Service, Bugwood.org.

Another type of nematode that can be beneficial to farming systems is the insect-parasitic bacterial feeding nematode. These nematodes, such as the species Heterorhabditis bacteriophora and Steinernema scapterisci, have mutualistic relationships with bacteria, in that both the nematode and bacteria rely on one another to reproduce and grow. In their infective juvenile stage, these specialized nematodes carry within their intestines specific bacteria. The nematodes can penetrate the body of many insect hosts, such as cutworms, mole crickets, citrus weevils, sawfly and fungus gnat larvae, and many more depending on nematode species, and release the bacteria into the insect’s body cavity where it multiplies to the point of killing the insect. This allows the nematode to develop into an adult inside the insect’s body and reproduce new juveniles, which emerge from the cadaver to search for a new host. Thousands of nematodes can be produced from just one infected insect host. These types of nematodes are even available commercially as a biological insect control, most commonly applied to moistened fields as liquid suspensions at a rate of about one million per acre, depending on the crop. As they are living organisms, care must be taken not to kill the nematodes with excessive pressure, temperature, agitation, or sun exposure. It is also important to select the correct nematode species to match target insect pests.

A white grub larva infected by a Heterorhabditis bacteriophora insect-parasitic nematode next to two healthy white grub larvae for comparison. Photo by Whitney Cranshaw, Colorado State University, Bugwood.org.

A white grub larva infected by a Heterorhabditis bacteriophora insect-parasitic nematode next to two healthy white grub larvae for comparison. Photo by Whitney Cranshaw, Colorado State University, Bugwood.org.

Predatory nematodes have biological control capabilities as well, in that they can regulate populations of other nematodes – bacterial and fungal feeding – and most importantly, root-eating plant parasitic nematodes. And as part of any healthy soil food web, there are a wide variety of natural enemies that help keep in check nematode populations, such as predatory micro-arthropods and nematode ensnaring fungi. Agricultural systems designed to support a healthy soil ecosystem can therefore more successfully defend against plant parasitic nematodes and other crop diseases and pests. They can also facilitate enhanced nutrient cycling, which supports plant nutrient uptake, leading to overall healthy crop growth.

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.

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

 

Utilizing Compost to Boost Crop Productivity

Utilizing Compost to Boost Crop Productivity

Tractor front loaders make turning large amounts of compost possible for farmers. Photo by Turkey Hill Farm.

International Compost Awareness Week is May 6-12 this year. This educational initiative, promoted by the Composting Council Research and Education Foundation, was started in Canada in 1995, and has continued to grow in popularity as communities, businesses, municipalities, schools, and organizations celebrate the benefits of compost and composting. But perhaps the most important people involved in composting are the farmers who produce compost to grow the food we eat.

Compost can be produced and used on the farm as a valuable soil amendment, capable of providing not only a source of slow-release nutrients for crops, but also a way to improve soil structure, increase soil moisture-holding capacity, promote biological activity to enhance plant nutrient availability, suppress weeds, and even help combat some plant diseases.

Farmers can source compostable materials from many businesses, including fish waste from seafood markets. Photo by Turkey Hill Farm.

Although creating on-farm compost can take a lot of time and energy, it can be worth a farmer’s effort, if it keeps soil fertility costs down. One way many farmers produce enough compost to meet their fertility needs is to collect waste products generated by their surrounding community. If a system for collection and transportation can be developed, and non-compostable waste can be excluded, farmers can use waste from grocery stores, restaurants, food processing facilities, breweries, seafood markets, horse stables, dairy operations, and chipped trees collected by power line crews as they clear encroaching tree canopies.

Once a farmer has secured sources for compostable materials, next comes the step of mixing the materials to generate heat, up to 140 degrees Fahrenheit. Fortunately for the farmer, microorganisms do most of the work in the decomposition process. But it is the farmer’s responsibility to provide enough –  and the proper balance of – air, moisture, and nitrogen and carbon-rich food to fuel the aerobic microbial oxidation process. The volume needed to generate favorable composting conditions can be anywhere from about one cubic yard up to 40 cubic yards, depending on these factors.

This is why farmers, who depend on compost to supply a majority of their crops’ nutrient needs, often rely on a dump trailer and tractor front-end loader to move compost ingredients, turn compost piles, and spread the finished product on row beds. With experience, farmers learn the correct ratio of ingredients, proper volume and porosity of their piles, when temperatures plateau and piles need to be turned, and when the compost is finished and ready for use.

Spreading compost on crop rows provides a source of nutrients, improves soil structure, increases soil organic matter content, suppresses weeds, and provides many other benefits. Photo by Turkey Hill Farm.

High quality finished compost typically has an organic matter content of about 50 percent, a carbon to nitrogen ratio of around 20:1, near neutral pH, low soluble salts, and is free of weed seeds and plant phytotoxins. Compost nutrient content by volume is relatively low, and availability can vary greatly depending on soil and climatic conditions, so it is important for the farmer to monitor crop nutrient requirements and use additional amendments as needed. But when compost is used as a long-term strategy for improving soil health and building soil organic matter, its benefits can be appreciated for generations.

Interested in learning more about compost? Leon County Extension is hosting a “Got Compost?” workshop May 8, 6:00 p.m. to 8:00 p.m. EST, in celebration of International Compost Awareness Week. This workshop is tailored more for home-composters, but will also touch upon ways to up-scale compost production and will discuss small farm compost production strategies. To find out more and to register, visit the Leon County Extension Eventbrite Page.

Additionally, the Red Hills Small Farm Alliance – a non-profit organization of over 50 farmers within a 100-mile radius of Tallahassee – is promoting International Compost Awareness Week on its website and Facebook page. If you utilize compost on your farm, upload a short compost video to the Red Hills Small Farm Alliance Facebook Page for a chance to win a $50 gift certificate to the Red Hills Online Market.

 

Managing Greenhouse Insect Pests through Exclusion Techniques

Managing Greenhouse Insect Pests through Exclusion Techniques

Greenhouse vegetable production can help diversify your farm.  Florida possesses a competitive advantage during winter months, because of much lower heating costs compared to other states and Canada.  A major disadvantage, however, to producing greenhouse vegetables during the winter is the increased insect pest pressure at planting time (August – September).  A key insect pest of vegetables during the fall is the silverleaf whitefly, which transmits a number of viruses and causes irregular ripening in tomatoes.

Because a number of greenhouse vegetables are grown through May, insect pest pressure remains high throughout the season, but please do not let these risks discourage you from venturing into greenhouse production.  As you know, high risks often yield a big reward.  Greenhouse vegetables are highly valuable during winter months.  Exclusion of insect pests is the first step in implementing an integrated pest management (IPM) program in a greenhouse operation.

A well thought out IPM program includes the incorporation of cultural practices, biological controls, and reduced-risk insecticides.  With the risk of potential problems associated with the use of chemicals in a greenhouse environment, growers should rely on exclusion as their first line of defense.  Insect management should be a key consideration when designing a greenhouse.  Insect screening is available for ventilation openings, but using this strategy may result in reduced airflow.  Many screens that exclude insect pests can reduce airflow by 50% or more.  The use of ultraviolet (UV)-absorbing plastics can reduce insect populations for plastic covered greenhouses.  The UV-free light produced inside the greenhouse disrupts insect landing and feeding behavior, greatly reducing the spread of insect-vectored viruses.

Insect exclusion can be achieved through, but not limited to, four basic strategies:  1) Sanitation, 2) Air-lock entrance, 3) Insect Screening, and 4) UV Reflective Mulch.

Sanitation

The area around a greenhouse should be maintained relatively free of weeds and plant material that could harbor insect pests.  This can be achieved with nursery cloth, or a ground cover in at least a 10 foot wide barrier around the structure.  Preferably, a turf area should be maintained beyond this area.  Other plant material in the general vicinity should be evaluated for their pest harboring ability.

An air-lock entrance on the front of a greenhouse.

An air-lock entrance on the front of a greenhouse. Photo Credit: Matt Lollar, University of Florida/IFAS Extension

Air-lock Entrance

Insect pests often enter through the front entrance of a greenhouse, because it is the path of least resistance.  An air-lock entrance is critical in greenhouses with fan and pad type ventilation systems.  An air-lock can be achieved through simply installing a room enclosing the entry doorway of the greenhouse.  This extra room allows workers to close the outside door behind them reducing the chances of pests being pulled in by the ventilation suction.  The air-lock entrance room can also be utilized to house a foot-bath, hand washing area, and any other sanitation stations.

An insect screen room on the outside of a greenhouse.

An insect screen room on the outside of a greenhouse. Photo Credit: Atlas Manufacturing, Inc.

Insect Screening

Insect screening being installed on screen structure around a greenhouse cooling pad.

Insect screening being installed on screen structure around a greenhouse cooling pad. Photo Credit: Marie Arick, University of Florida/IFAS Extension

Insect screening allows for adequate ventilation while still maintaining exclusion properties.  Screens can be used in both passively ventilated and fan and pad greenhouses by either installing a screen box around the outside fan system or by

simply installing material to roof vents.  It is important to keep in mind that any size screen mesh will reduce the air flow in the greenhouse.  Improper sizing has the potential to burn fan motors or reduce cooling.  It is important to follow recommendations from the manufacturer in regards to screen size and surface area covered.

Reflective Mulch

Ultraviolet (UV) reflective mulch has been used in field grown production for quite some time.  A similar approach can be utilized in greenhouse production to help deter and confuse pests from entering through the ventilation system.  Research has shown it is important to install reflective mulch in at least a 20 foot wide, continuous barrier from the ventilation air intake end wall.  Mulch along the sidewalls may also help repel insect pests.  It is recommended that reflective mulch be used in conjunction with screening for an optimal effect.

Reflective mulch being installed near the cooling pad area of a greenhouse.

Reflective mulch being installed near the cooling pad area of a greenhouse. Photo Credit: Marie Arick, University of Florida/IFAS Extension

Greenhouse insect pests cause significant damage to foliage, blossoms, and fruit, and also vector (transmit) diseases.  It is important to develop an effective IPM strategy that involves exclusion as a first line of defense.  Very few management options are available once insect pests have entered the greenhouse.

For more information, there is a series of short videos on these topics:  UF/IFAS Greenhouse Pest Exclusion Videos

 

Panhandle Fruit & Vegetable Conference Agenda Now Available!

Panhandle Fruit & Vegetable Conference Agenda Now Available!

Join us for the Panhandle Fruit & Vegetable Conference on February 19 & 20 in Pensacola! Registration includes a farm tour, dinner after the tour, breakfast & lunch the next day, and excellent educational sessions. The complete agenda is now available.  Use your mouse or finger to “click” on the image below for full screen viewing.  Register online at:  Panhandle Fruit & Vegetable Conference Registration Page

Click your mouse on the image for full screen viewing.