Research Accomplishment Reports 2010

Developing Optimized Organic Production Systems for Cucurbits and Apples

M. Williams
Department of Horticulture

 

Non-Technical Summary

This project is focused on developing organically-managed production systems for select fruit and vegetable crops. A focus on two very economically important and difficult-to-grow crops is proposed. Additionally, the effects of organic soil amendments will be evaluated to determine ways to maximize and improve soil quality attributes that impact plant growth.

This project will attempt to alleviate one of the major constraints in organic melon production thereby facilitating the production of this family of crops by Kentucky growers. This project also had the potential to develop a sustainable organic apple production system for Kentucky growers, which currently does not exist.

Lastly this project seeks to scientifically show the benefits of cover cropping in a way that will direct their use in the production systems in the first two objectives. It is believed that this information would be applicable to a range of other crops and systems.

2010 Project Description

A field experiment was conducted in 2010 that focused on controlling the insect vector of bacterial wilt by using row covers over the crop to exclude the insect. Four treatments were tested:

• Control with no treatment,
• Row covers until flowering followed by pesticide application,
• Row covers until flowering with covers off for one week,
• Row covers until flowering with covers off for two weeks and then closed until harvest.

In order to track the progress of Erwinia tracheiphila as it develops, a new tool has been developed to quantitatively assess the presence of the bacteria and track disease development. Development of a Real-Time PCR screen has been obtained using extracted DNA from E. tracheiphila isolates obtained from our collaborator Iowa State University. In an effort to identify a potential organic control method for the bacteria, numerous natural compounds were screened as well as a commercially available biocontrol agent containing Pseudomonas fluorescens A506. This project is being completed by a graduate student as part of a PhD project, and he presented the results at the Kentucky Fruit and Vegetable Growers Conference in Lexington, KY in January. The field experiment was featured at daylong agent trainings in Kentucky (June 16) and TN (Aug 19), as well as at the University of Kentucky Horticulture Farm Field Day (July 22). Additionally, an on farm demonstration field day was done at Carl Benson's farm in Forkland, KY (Aug 10).

For the 2010 growing season, diseases and insects were managed in a three-year old orchard primarily by adhering to a strict spray schedule. Various sprays, pheromone traps, and bagging treatments were used to control critical pests. Additionally an organically approved thinning agent was evaluated. A presentation was made at the Kentucky Fruit and Vegetable Growers Conference in Lexington, KY in January. This project was featured in the University of Kentucky Horticulture Farm Field Day (July 22), and was used to teach organic fruit production to 14 student apprentices.

Results from this work were used as preliminary data to secure a grant from the Specialty Crops Block Grant program from the Kentucky Department of Agriculture. An 82 day incubation experiment was conducted across 3 soils collected from central Kentucky. The experiment tested the effects of 4 amendment treatments on soil structure and the soil microbial community profile. The primary hypothesis tested in this research was that amendments that stimulated greater levels of fungal biomarkers would also stimulate greater formation of soil structure. Amendment treatments: hairy vetch residue, dairy manure, vegetable compost, and a non-amended control. Samples collected on incubation days 0, 5, 12, 30. and 82 were analyzed for water stable aggregation (a measure of soil structure), microbial fatty acid methyl esters (FAMEs) and the fungal biomarker ergosterol. This project is being done by a graduate student as part of his PhD project and he presented the results at the Soil Science Society of America 2010 Annual Meetings in Long Beach, CA.

2010 Impact

The results of this work indicate that it is possible to reduce the number of pesticide treatments in an organic system by extending the duration that row covers are used to exclude the insect vector of bacterial wilt. The untreated control treatment performed poorly with a 25% - 27% yield reduction compared to the other treatments. Treatment four gave the highest yield, although it was only 2% higher then the standard organic practice of treatment two. These results will be useful to organic growers by providing a system with which they can reliably produce organic cucurbits and reduce pesticide inputs. This is significant given the difficulty of production due to extremely heavy insect pressure in the southeast, and the high cost and relative inefficiency of current organic insecticides.

Although significant strides were made in 2010 in controlling pests organically, several problems were identified that are limiting production. Trunk banding for control of codling moth had no significant reduction in the incidence of insect damage on the fruit. Codling moth pheromone traps and mating disruption ties were placed in the orchard, with some success.

Two physical barriers were used against insects and diseases, Japanese bags and deli bags. Both provided some measure of control against major diseases, including cedar apple rust, powdery mildew, sooty blotch, and flyspeck; as well as protection from codling moth and plum curculio. An organically approved thinning spray consisting of liquid lime sulfur and fish oil was used during apple bloom stage, with good results. Taken collectively these results indicate that it may be possible to grow apples organically in Kentucky but there are a handful of insects and diseases that are currently limiting production.

This experiment has shown that almost all major production practices are now feasible and 2011 experiments will focus on developing control techniques for the handful of remaining problems. As it develops, this system will help guide production decisions for KY apple growers interested in organic production.

The results of this experiment demonstrated that in all three soils vetch, and to a slightly lesser degree dairy manure, stimulated greater soil structure formation (measured as water stable macroaggregates) relative to compost and non-amended soils. Vetch and manure also stimulated higher levels of the fungal FAME 18:2ω6 and the fungal biomarker ergosterol. When macroaggregate formation was analyzed against all measured microbial biomarkers (including fungal, bacterial, and actinomycete FAMEs and ergosterol) it was most strongly related to 18:26 and ergosterol.

Thus these outcomes provide evidence that organic soil amendments such as vetch and manure can be used to influence the microbial community in such a way that it favors formation of soil structure. Given the importance of soil structure and microbial diversity to overall soil quality, these outcomes would be useful to producers, researchers and extension specialists with an interest in building or maintaining soil structure through use of organic amendments.

2010 Publications

Minter, L, and R. Bessin. 2010. Understanding cucurbit pest phenology in Central Kentucky. University of Kentucky Fruit and Vegetable Research Report PR 608: 42-43.

Caudle, R. 2010. Development of organic melon production methods to control bacterial wilt. University of Kentucky Fruit and Vegetable Research Report, PR 608: 44-45.

Scott, D., Williams, M., Archbold, D., Strang, J., and Bessin, R., 2010 Organic Apple Orchard Update. University of Kentucky Fruit and Vegetable Research Report PR 608