Recipient Organization
UNIVERSITY OF KENTUCKY
500 S LIMESTONE 109 KINKEAD HALL
LEXINGTON,KY 40526-0001
Performing Department
Horticulture
Non Technical Summary
Since the Tobacco Master Settlement Agreement (MSA) was enacted in 1998, many Kentucky growers have turned to vegetable production as an alternative to tobacco. Vegetable crops are considered specialty crops as they are produced by people for food. They are also special in that skilled management and labor are required for their production, harvest, and proper storage. The learning curve has been high for many Kentucky growers as they transitioned from cropping systems that they knew well, such as tobacco or grain crops. However, in the 21 years since the MSA became effective there are many successful vegetable producers across the state. Like the skill level of the growers, the size and scale of the operations vary greatly. All producers, regardless of their skill level or size of operation, struggle with similar issues--pest and pathogen pressure, soil quality, and challenging weather. Regardless of the crop, production systems must continuously evolve in order to stay resilient and sustainable in an ever-changing environment, whether that environment be economic, social, or natural.One tool has been introduced to Kentucky in order to help increase farm resiliency. In 2012, the inception of the High Tunnel System Initiative within the Natural Resource Conservation Service Environmental Quality Incentives Program (NRCS EQIP) took place. High tunnels are passively heated and cooled temporary structures used to extend the growing season for high value specialty crops. They provide protection from the weather and serve as a moderately controlled environment. High tunnels have the potential to provide the grower with the ability to extend the growing season and moderate the environment with respect to precipitation and temperature. This can translate to increased income from increased marketable yields and improved produce quality. The high tunnel system has been around well before the 2012 EQIP, but in part because of the support from this program, nearly 900 high tunnels have been installed in Kentucky (Figure 1; USDA-NRCS, 2018). It is unknown how many total high tunnels exist in the state as there are many growers who purchased high tunnels with the assistance of other grants or programs, or purchased them using their own private funds.The funding available through NRCS has opened high tunnel ownership to a wider social and economic stratum; it has included people that may not normally be able to afford a high tunnel or who are not experienced growers. Many growers are unfamiliar with how to most effectively use their high tunnels and make the most out of the potential season extension. The Kentucky Horticulture Council (KHC) is a group of key industry horticulture leaders in the state. It is comprised of specialty crop growers and horticulture-related business owners. It has stated that high tunnels are one of its priority areas and that it would like to see more high tunnel resource development and training (Cindy Finneseth, KHC Executive Director, personal communication).High tunnel production is nuanced and growers face unique production challenges, including managing soil quality appropriately. There is the risk of increased soil salinity in high tunnels from over-application of fertilizer and the lack of weathering and precipitation compared to open field production. Excessive soil phosphorus (P) is also a concern. Growers often rely on animal manures for a crop nutrient source, which can be an affordable and accessible fertilizer. However, repeated use can lead to increased soil P and soil salinity, which can complicate crop production and have negative environmental impacts (Edmeades, 2003; Hao and Chang, 2003).High tunnel vegetable production does not have less pressure from pests and diseases compared to open field, but different pressure from pests and diseases. One of those particular challenges is plant-parasitic nematodes, specifically the root knot nematode (Meloidogyne spp.). Plant-parasitic nematodes are estimated to cause 14% crop loss worldwide (Mitkowski and Abawi, 2011). Root knot nematodes (RKN) are the most common and most destructive plant-parasitic nematodes. This genus of nematode is a sedentary endoparasite that invades plant roots and causes root galling. Root knot nematode possess a stylet, as do all plant-parasitic nematodes, which they use pierce the plant cuticle, consume nutrients from the plant cells, as well as inject secretions into the plant (Mitkowski and Abawi, 2011; Figure 2). This impairs root function which causes reduced water and nutrient uptake. The above ground portion of the plant may look wilted or stunted. This is because the galled roots have less ability to absorb water and nutrients from the soil and transport them to the rest of the plant. For growers who are unfamiliar with this plant parasite, they may not think to pull the plant up and observe the root system for galling. Their first assumption may be to irrigate or fertilize more. However, this is likely to have alter the infection rate or the plant's ability to resist RKN.Root knot nematode is also common in open field production. However, growers usually have the option to rotate into other land or fumigate the soil. High tunnel growers are not able to employ either of those management methods. Soil fumigation is not permitted in high tunnel environments in Kentucky. For the purposes of pesticide applications in Kentucky, high tunnels are considered greenhouses and, therefore, all the rules pertaining to greenhouses apply to high tunnels. Even so, soil fumigation is costly and would be difficult for a grower to justify on such a small area of land as what is covered by a high tunnel. Soil fumigation also is a broad spectrum approach which can negatively impact beneficial soil microorganisms (Collins et al., 2006; Gamliel et al., 2000).Meloidogyne incognita has a host range of over 1,700 plant species (Sasser et al., 1983) while M. hapla has a host range of over 550 plant species (UC-Davis Nemabase). Tomato (Lypersicon esculentum) and nearly all other vegetable crops are suitable hosts for both species of RKN making it extremely challenging for high tunnel producers to rotate to a non-host crop. Therefore, the increase in root knot nematode population density is highly probable. Tomatoes are the most high-value vegetable crop grown in high tunnels in Kentucky and the most common high tunnel crop. Growers state that they cannot afford to rotate with a lesser-value crop.Infection of nematodes into plant roots also opens up wounds in the roots that increase the likelihood of infections by soilborne pathogens, such as Verticillium or Phytophthora (Mitkowski and Abawi, 2011). This can be devastating for a tomato crop. Several Kentucky high tunnel growers have observed issues with root knot nematodes. There are nematicides labeled for use on tomatoes. However, they are either extremely costly for growers or are only moderately effective against root knot nematodes. Additionally, nematicides are not an option for certified organic growers or grower who are transitioning to become certified organic. There is a need for other management techniques that are both affordable, effective, and can be used across different types of production systems.
Animal Health Component
70%
Research Effort Categories
Basic
15%
Applied
70%
Developmental
15%
Goals / Objectives
Objective 1: Determine the level of pressure that plant-parasitic nematodes exert on vegetable cropping systems across the state.Hypothesis 1: Plant-parasitic nematodes, specifically root-knot nematodes, will be present in high densities across the state, particularly in sandy soils that has experienced continuous vegetable cropping with little non-host rotation.Objective 2: Evaluate various non-chemical methods for management of soilborne pathogens and nematodes as well as insect pests in both open field and high tunnel systems and compare those methods to viable chemical approaches.Hypothesis 2: The non-chemical methods will be as effective as the chemical methods of management and will be more widely accepted by growers because of the lower cost and the broader potential for use across open fields and high tunnels as well as their applications in conventional and organic production systems.Objective 3: Evaluate the P threshold in vegetable crops and the effects of incremental P application on their development and yield.Hypothesis 3: Excessive applications of P will not show detrimental effects to vegetable crops, but a benefit will not be observed beyond a certain rate. A threshold will be reached where P applications are no longer beneficial to the crop.
Project Methods
In order to thoroughly assess each method, each experiment will be conducted in both high tunnels and open fields. This will expand the utility of these methods to all vegetable growers, regardless of operation scale or system preference. The majority of the trials will be conducted on growers' farms across the state. Nematode identification and quantification will occur in Dr. Rudolph's lab on the main campus in Lexington.Soil and root survey of plant-parasitic nematodesA survey of soil and tomato plants around the state needs to be conducted in order to ascertain the extent of the issue (how many plant-parasitic nematodes are present and where) and identify the most abundant, problematic species in vegetables. Grower education and outreach should also be conducted in order to make growers aware of the existence of plant parasitic nematodes as well as the damage they can have on a vegetable crop. Growers should be educated regarding their management options, including preventative methods. Trainings on tomato grafting should be provided for both growers and extension agents.Soil and plant roots will be sampled from high tunnels across the state. All regions of the state will be represented and sampled. The optimal time for sampling is during the summer or early fall. This is when nematode populations are typically the highest. This will provide the most accurate evaluation of the potential damage plant-parasitic nematodes can cause. Samples will be processed by extracting nematodes from both soil and roots in my lab at UK. The population densities will be determined by quantifying the number of root knot nematodes present per gram of root or per 100 cc of soil (Ayoub, 1980). At least 100 high tunnels will be sampled across the state.Based on the data produced from this state-wide survey, I can assess which regions of the state are at the highest risk and what common factors the areas with the higher plant-parasitic nematode pressure have in common--soil type, soil moisture, cropping history, etc. This will form the information used to educate growers and extension agents in order to prevent the spread of plant-parasitic nematodes from one location to another as well as properly manage those sites that are already dealing with high plant-parasitic nematode populations.Grafting trialsOn-farm trials will be conducted with different high tunnel tomato growers who are currently dealing with root knot nematode issues in their high tunnels. Two growers have already been identified and are willing to participate with the research trials. Different rootstocks will be evaluated using the scion of the growers' choice. Rootstocks will be evaluated based on their resistance to root knot nematode (populations in both plant roots and soil will be evaluated), plant vigor, stem diameter, foliar nutrient analysis, and marketable fruit yield. The population densities will be determined by quantifying the number of root knot nematodes present per gram of root and per 100 cc of soil (Ayoub, 1980). A non-grafted control will be used in all trials for comparison. The results of the high tunnel experiments will be compared for efficacy, likelihood of adoption, and cost.Trials for evaluating other non-chemical methods for managing RKN On-farm trials will be conducted with high tunnel vegetable growers to assess other non-chemical methods for managing RKN. Different vegetable cultivars will be evaluated for their host suitability for RKN. Cultivars will be evaluated in greenhouse host assays with soil that has been inoculated with RKN eggs. Cultivars determined to be non-hosts in the greenhouse host assays will be subjected to on-farm trials with endemic RKN populations.The duration, timing, and soil temperatures reached during soil solarization will also be evaluated for efficacy in managing RKN. Data loggers to collect and record soil temperatures will be placed a 5 and 15 cm soil depth. The application of BSM to high tunnel soil will also be evaluated, including different application rates, timing, and efficacy when combined with grafting and/or solarization. The RKN population density will be monitored and quantified following the treatment applications as well as during the growing season of a vegetable crop, and at the end of the season. The RKN population densities will be determined by quantifying the number of root knot nematodes present per gram of root and per 100 cc of soil (Ayoub, 1980).Soil P threshold trialsGreenhouse studies will be conducted using field soil that is naturally low in P mixed with peat moss that is also naturally low in P. This mixture will allow for proper drainage and aeration in a greenhouse system with plants in pots. Different rates of P will be applied to the soil, starting with 0 lbs/acre and increasing up to 240 lbs/acre. Plants will be treated the same with respect to all other macro and micro nutrients. This experiment will be replicated with different crops and scaled up to field conditions depending on the results of the first greenhouse experiment.