This project had two primary objectives:
1. To see if different amendments would affect the population of symphylans
2. To evaluate different crops response to trials and symphylans populations
Garden symphylans (Scutigerella immaculate), a soil arthropod, are an increasing problem for organic growers. Symphylans feed on young plant roots and, in high populations, severely reduce seed germination and growth of transplants. No simple or completely reliable methods currently exist to control symphylans organically. Indeed, many growers and advisors are simply unaware of them and their long-term effects.
This study tested four soil amendment regimens, compared with a control plot and a fallow plot, for their impacts on symphylans populations. The symphylans populations were isolated, identified and monitored using a potato slice in moist soil.
The one-season study showed no significant results amending the soil with micronized shrimp shell meal, farewell or sifting compost. While the mulch treatment reduced populations to one-third the level of the untreated control, the finding was not deemed to be significant. Diatomaceous earth incorporated in the soil may enable direct sown seed to produce viable crops.
Project coordinator Michelle Vesser, operator of Three Spring Gardens of North Fork, Calif., established 50-square-foot beds with six experimental applications each replicated three times:
1. The fallow beds were not cultivated, amended or planted.
2. Control beds were dug 1 foot and amended as in previous years with one-third wheelbarrow of unsifted Three Springs Compost and one-third wheelbarrow unsifted Grovers Compost.
3. The high content of organic material and carbon in organic-amended soils may provide a food source for symphylans and increase their populations. Sifting compost and applying non-carbon amendments may reduce that food source. In this application, beds were single dug and amended with one-third wheelbarrow of sifted Three Springs Compost along with 2.5 pounds of alfalfa meal and 2.5 pounds of gypsum, both non-carbon amendments.
4. Low fungal populations may contribute to high symphylans populations. Mulching could offer surface protection and support fungal populations. These beds were amended as sifted beds and mulched with straw.
5. Farewell is a microbial soil stimulant containing enzymes, whey protein, minerals and organisms that digest chitin. Considering the hypothesis that enzymes and chitinase feed on chitin-rich symphylans, these beds were amended as sifted beds with two 0.55-ounce applications of Farewell.
6. Chitin, which makes up the skin and eggs of many soils pests, is also found in shrimp shells. Adding micronized shrimp shell meal may increase chitin-feeding fungi, which could reduce symphylans populations. These beds were amended as sifted beds with two 1.5-ounce applications of micronized shrimp shell meal.
A seventh plot, not part of the study, mixed diatomaceous earth into the soil at different depths, the idea being that the sharp edges of diatoms might break the protective layer and desiccate symphylans on contact.
The project also evaluated crop response to the various trials and to the symphylans populations. A third of the beds were planted to sweet corn, a third to Swiss chard and a third to eggplant. Typically, shallow-rooted, slow-growing plants suffer damage, especially in the top 3 inches. Conversely, it is theorized, plants with fast root growth or transplants with developed roots could be productive even in high populations of symphylans.
To measure the number of symphylans in each bed, a potato is sliced, placed in moist soil and covered with a light-colored pot that has no air holes. Each bed had two samples, and counts were taken once a week for four months.
An analysis of the data indicated no significant differences among treatments, although Vesser says the data suggest that some treatments may influence symphylans populations, and that modifying them or monitoring them over several years may show reductions in symphylans. She notes that mulching did reduce the symphylans populations to an average of 60 compared with an average of 184 in the control plot. While the count for mulching is not statistically significant, it does bear further investigation. The sifting and untreated controls were virtually identical.
Harvest of Swiss chard and sweet corn shows the potential for further crop studies, while eggplant had poor results throughout the study.
Symphylan problems were first documented in 1905, and their population and damage are increasing. To date, no reliable solutions have been found. Informal research by affected growers appears to be the primary search for solutions. Creating greater links between growers and researchers will allow ongoing communication and coordinate trials in different growing conditions. The symphylans alert, created as part of this project and sent to growers and advisors, will educate them about this problem.
FARMER ADOPTION AND DIRECT IMPACT
Continued testing of specific crops, the use of diatomaceous earth and mulching will aid in understanding the problem, and this project’s elimination of amendments thought to control symphylans will help growers and researchers focus on more viable strategies.
Growers have responded positively to the dedication and focus exercised by project coordinator Michelle Vesser, both in conducting the research and setting up the education network needed for a problem of this scale.
“Wow, you are taking these symphylans by the horns,” says Jim Leap of UCSC Farm and Gardens.
Says Jon Umble, Oregon State University PhD researcher on symphylans: “Your work with connecting people/collaboration/organization is really a great asset.”
FUTURE RECOMMENDATIONS OR NEW HYPOTHESES
“I believe future studies of symphylans controls should be a high priority for sustainable agriculture research,” says Vesser, who recommends further studies in crop selection, diatomaceous earth, potatoes and California poppy rotation for symphylans control.
DISSEMINATION OF FINDINGS
This research has been shared through several venues.
· During the 2002 Eco-Farm Conference, Vesser made a slide presentation showing indicators, identification techniques and her research preceding a symphylans discussion group involving 30 participants.
· She helped create a symphylans e-mail list serve through the Appropriate Technology Transfer for Rural Areas (ATTRA) to increase grower communication and understanding of symphylans, email@example.com. The initial list included 50 growers and researchers.
· Vesser also helped create and initiate a symphylan alert, posted through ATTRA and the Sustainable Agriculture Network. ATTRA’s symphylan Web site was slated for completion in April 2002.
· Results of the work were planned for publication in the Fresno County Cooperative Extension specialty crops newsletter and for posting on the University of California, Davis, Small Farm Web page, www.sfc.ucdavis.edu.