Bio-Priming for the Control of Pythium Reemergence Damping-Off in Vegetable Crops
Many popular vegetable crops are susceptible to pre-emergence damping-off, particularly when planted in cold soil. In Montana’s Bitterroot Valley, Pythium ultimum is the primary pathogen involved. From Bitterroot Valley soil we isolated a strain of bacteria, Pseudomonas fluorescens AB254, that is antagonistic to this pathogen. In a process we have termed “bio-priming,” supersweet (sh-2) sweet corn seed was coated with this bacteria and allowed to imbibe under warm temperatures. After bio-priming, seed was planted moist or air-dried before planting. Compared with chemical pesticide treatment, bio-priming provided equal or better protection of sweet corn seeds from pre-emergence damping-off when they were planted into cold or warm soil.
(1) Determine the optimum bio-priming technique for protection of sweet corn seeds from Pythium pre-emergence damping-off.
(2) Evaluate the efficacy of the bio-priming system for protecting sweet corn seeds from damping-off in several different soils and environments.
(3) Test the usefulness of the bio-priming system for protection of seeds of peas, chickpeas, and beans.
(4) Evaluate the economic benefits of the bio-priming seed treatment.
Biological seed protection is a disease control practice that is consistent with sustainable agriculture goals. Although chemical seed treatment constitutes a low-volume pesticide use, today’s growers are considering ways to continue to control pests while reducing synthetic chemical inputs. Biological seed treatment using naturally occurring soil microorganisms has the potential to provide safe, non-polluting, and environmentally-sound disease control. The development of a delivery system for biological seed protectants that reliably furnishes the grower with a healthy seedling stand aids in making biocontrol competitive with chemical seed treatment.
Bio-priming, a seed protection system for supersweet (sh-2) sweet corn combining biological treatment and preplant hydration, was developed by Nancy Callan, Don Mathre and Jim Miller at Montana State University. Bio-priming sweet corn seeds with a bacterial biocontrol agent that we isolated from western Montana soils, provided consistent protection of sweet corn from Pythium pre-emergence damping-off. During 1989-1990, sixteen field experiments involving bio-priming protected seeds at a level equivalent to or better than did the fungicide metalaxyl. Bio-primed seed can be planted moist or air-dried before planting and storing. We feel that this research represents significant progress in the advancement of plant disease biocontrol.
This two-year feasibility study (1990-1991) was conducted to refine the bio-priming technique for sweet corn, to evaluate the usefulness of this seed treatment for seeds of other vegetable crops, and to test the widespread applicability and economic benefits of this seed protection system.
The sweet corn bio-priming system was evaluated for treatment of seeds of other vegetable crops. Sugar snap peas and chickpeas are also very susceptible to Pythium damping-off. In six or seven experiments with sugar snap peas, chickpeas, or soybeans, either bio-priming or seed coating (bacterization) with biocontrol bacteria isolated from corn seedling roots significantly increased seedling emergence over that from nontreated seed, but less than did metalaxyl treatment. No damping-off occurred in beans in these experiments. Adaptation of this biological seed treatment to crops other than sweet corn will require selection of crop-specific biocontrol agents and modification of bio-priming techniques, and we will be taking this approach in future research.
As part of our evaluation of the widespread applicability of bio-priming, we conducted parallel experiments with sh-2 sweet corn at the Southern Experiment Station in Waseca, Minnesota, by Vince Fritz, and at the Western Agricultural Research Center, Corvallis, Montana. In both locations, bio-priming with P.fluorescens AB254 protected sweet corn seed at a level comparable to metalaxyl treatment, regardless of whether bio-primed seed was planted moist or dry. Similar seed protection resulted in Idaho and in several locations in Montana.
Our Montana grower-cooperators are encouraged by the potential this research offers, and are anxious to see the treatment commercialized. Bio-priming, once available, will provide the sweet corn grower with a practical and effective alternative to either chemical seed treatment or over-sowing of nontreated seed to ensure an economically viable seedling stand. We will be working with commercial interests to examine the cost/benefit aspects of bio-priming sweet corn seed.