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1999 STEEP III Final ReportRESEARCH PROJECT TITLE: Disease Management for Annual Crops in Low-Rainfall Regions INVESTIGATORS:
COOPERATORS: STEEP III scientists in research projects near Pilot Rock and Ralston Pilot Rock Project -- ADevelopment of Conservation Farming Systems for Protecting Soil and Water Quality in Downy Brome Infested Dryland Farming Systems@ PI=s: Dan Ball (OSU, weeds), Penny Diebel (OSU, economics and risk), Don Wysocki (OSU, fertility & crop residue), Bill Payne (OSU, agronomy). Coops: Bob Adelman (NRCS, conservation compliance), Tom Golke (NRCS, technology transfer), Dick Smiley (OSU, diseases), Mike Stoltz (OSU, aphids & tours), Dale Wilkins (ARS, weeds). Grower Advisory Comm: 6 growers. Funding: STEEP III, OSU, USDA-ARS, Oregon Wheat Comm., and agribusiness. Ralston Project
-- AIntegrated Conservation Spring Cropping Systems for the Arid and Semiarid
Wheat-Fallow Region of the PNW@ PI=s: Frank Young (USDA-ARS, weeds), Kim
Kidwell (WSU, spring wheat), and Bill Pan (WSU, soil fertility, crop residue,
& water). Coop=s: Rich Alldredge (WSU, design and analysis), John
Burns (WSU, tours & meetings), Steve Clement (ARS, aphids), Ann Kennedy
(ARS, residue decomp.), Gary Lee (UI, weeds), Bob Papendick (PM-10 Coord.),
Bill Schillinger (WSU, water), Dick Smiley (OSU, diseases), Steve Ullrich
(WSU, barley), Roger Veseth (UI, education & publicity), Doug Young
(WSU, economics and risk). Grower Advisory Comm: 12 members including
representatives of the Wash. Wheat Comm. and Wash. Assoc. of Wheat Growers.
Funding: STEEP III, USDA-ARS, WSU, OSU, Wash. Dept. of Energy (PM-10),
Wash. Wheat Comm., Oregon Wheat Comm., agribusiness, and Adams, Lincoln,
& Whitman Co. Oregon ASatellite@
Experiments -- PI: Dick Smiley. Coop=s: Russ Karow (OSU, Cereals
Extension), Penny Diebel (OSU, Ag Economist), Lisa Patterson, Karl Rhinhart,
& Erling Jacobsen (OSU technical staff), and Frank & Yvonne Mader
and Tim & Shannon Rust (Farmer-Cooperators). OBJECTIVES:
KEY WORDS: Wheat, barley, diseases, cropping systems STATEMENT OF PROBLEM: Most dryland wheat
in low rainfall regions of the Pacific Northwest (PNW) is produced in
a winter wheat/summer fallow rotation. The fallow system reduces soil
quality, increases soil erosion, and is plagued with winter-annual weeds,
surface crusting, and diseases of early planted wheat. Each of these conditions
could be resolved by including spring crops in the rotation. Primary impediments
to diversified annual cropping have been more erratic crop yield due to
rainfall variability, non-profitable adapted crops, and disincentives
of previous Federal farm programs. Two STEEP III teams are examining annual
cropping systems to reduce acreage of land fallowed between winter wheat
crops. Changes in the prevalence and importance of diseases are anticipated
with changes in crop management. Diseases must be considered as new management
practices are developed. ZONE OF INTEREST: Agronomic Zones 4 and 5; low rainfall (9-16 inch) areas of Oregon and Washington, where winter wheat is rotated mostly with summer fallow. ABSTRACT OF RESEARCH FINDINGS: The spectrum and
intensity of diseases was monitored in long-term cropping system studies
at four locations in Oregon and Washington. Emphasis was given to diseases
caused by soilborne pathogenic fungi and parasitic nematodes, including
Rhizoctonia root rot, take-all, Fusarium foot rot, and root lesion nematode.
Disease-reduction benefits from crop rotation were shown in experiments
near Ralston, WA and Pilot Rock, OR. Benefits from wheat cultivar selection
and starter fertilizer placed below the seed were shown at Echo and Moro,
OR. Damage from root lesion nematode was more pronounced than anticipated
at several locations. Experiments in Oregon were concluded during 1999
and final data and economic analyses are being evaluated and prepared
for publication. RESULTS AND INTERPRETATION: Objective 1.
Diseases in the Pilot Rock and Ralston Projects: Winter and spring wheat plants were collected each year for identification and quantification of diseases on roots, crowns, and foliage. Data was submitted to the project director (Dr. Dan Ball) for incorporation into the master databank. Grain yields and other results for this project are reported in Dr. Ball=s STEEP III progress report. The focus for this pathology contribution to several larger long-term experiments was to identify differences in plant health among treatments. Data failed to provide clear differences among treatments when viewed in isolation at a single site during a single year. It was only after the majority of the experiment was completed at both sites that important trends became evident. Stress from diseases was reduced by longer-term rotations away from cereal crops, and was amplified by shorter rotations and higher amounts of surface residue. The experiment at the Shaw farm was offset one year from that at the Gilliland farm. Data for the same experimental treatments at the Gilliland and Shaw farms therefore occurred during crop years 1995 and 1996, respectively. This offset continued throughout the study. During 1995 and 1996 there was a comparison of three 3-year rotation treatments: winter wheat produced in a winter wheat/spring barley/summer fallow rotation (tillage vs chemical fallow), and in a winter canola/winter wheat/summer fallow rotation. Rhizoctonia root rot and take-all tended to be less damaging in the rotation that included canola than in rotations that only included cereals. This trend was statistically significant at the Shaw site (1996) but not the Gilliland site (1995). Other diseases were present in minor amounts but none differed among treatments. During 1996 and 1997 there was a comparison of winter wheat in three 2-year rotation treatments: winter wheat/summer fallow (tillage fallow), and winter wheat/summer fallow (tillage vs chemical fallow). The only difference among treatments at the Gilliland site (1996) was that Rhizoctonia root rot was slightly less damaging in the moldboard plow system than in the conservation tillage systems. There were no differences among treatments for any of the diseases at the Shaw site during 1997. Winter wheat was not grown on plots in 1997 and 1998 at the Gilliland and Shaw sites, respectively. All six treatments at the Gilliland and Shaw sites were planted to winter wheat during crop years 1998 and 1999, respectively. As in 1996 at Gilliland=s, take-all was less damaging in 2-year rotations where the moldboard plow was used than where conservation tillage had been practiced. As in the 3-year rotations at Gilliland=s during 1995, take-all and Rhizoctonia root rot were least damaging where canola was included as the second crop, compared to spring barley. These differences in root rots also occurred at the Shaw site during 1996 but not 1999. Strawbreaker foot rot at both locations was less prevalent in 3-year rotations than in 2-year rotations. Strawbreaker was also less prevalent in the rotation that included canola, compared to all other sequences that only included wheat and barley. Fusarium foot rot at Shaw=s was less damaging in 3-year than 2-year rotations. Winter wheat grain yield was least and numbers of lesion nematodes highest in the 3-year rotation of winter wheat, canola and summer fallow. Numbers of root lesion nematodes (Pratylenchus neglectus and P. thornei) in soil and wheat roots were inversely associated with grain yield; more information is presented in the ASpecial Nematode Sampling ...@ section. Annual spring wheat at the Shaw site was also affected by root rots that occurred on winter wheat (take-all and Rhizoctonia root rot) but was less affected or was unaffected by the foot rots (strawbreaker and Fusarium foot rot). Lesion nematodes caused more root damage in annual spring wheat than where winter wheat was rotated with fallow and/or other crops. This 6-year cropping systems study demonstrated that stresses from pathogenic fungi and nematodes were generally reduced by rotations in which winter wheat was produced once in three years rather than every other year. Stress from diseases also tended to be reduced when the amount of surface residue was kept to the minimum by moldboard plowing. Ralston Project -- Replicated on-farm research was conducted on a 20-acre site in an 11-inch rainfall zone near Ralston WA. Scientists, extension agents and growers met in 1995 to establish experimental parameters. Rotations were established with farm-size equipment during August 1995. Plots (30 x 500 ft) are in randomized complete blocks with four replicates. The experiment is duplicated so that each crop in each rotation is grown each year. Best management practices are used for tillage, residue management, fertilizers, varieties, pesticides and planting dates. Data is managed centrally to facilitate bioeconomic and risk analysis, and an integrated result. Five systems are being compared: continuous spring wheat, spring wheat-spring barley, spring wheat-fallow, winter wheat-fallow, and a grower-directed flexible cropping system (growers determine tillage, crops, and timing). The focus of this study is on conversion of the winter wheat-fallow rotation to annual cropping, over five years (1995-2000). Evaluations include all pest and agronomic considerations, profitability and economic risk, and compliance with conservation regulations. Results for the overall project are in the STEEP III report by project leader Dr. Frank Young and others. Winter wheat plants were collected for evaluation on February 22, 1998 and all spring and winter cereals were collected on May 21. Twenty plants from each replicate were used for assessments of disease identity and severity on roots, crowns, and foliage. Data will be submitted to the project leaders for incorporation into the master databank. Winter wheat -- The only treatment of winter wheat was sampled during February when plants were 6- to 8-inches tall. As in previous years, damage from Rhizoctonia root rot and take-all was present on seedlings. Damage from gray snow mold occurred in two of the four replicates. Fusarium foot rot and strawbreaker foot rot were not observed in February. Rhizoctonia root rot occurred on >90% plants, as was true in the past, but disease severity (ratings of 1.7 on a 5-point scale) was lower than in previous years. In contrast, take-all was relatively more severe than previously, with mean severity ratings of 2.1 on a 5-point scale. Plants were 22-inches high when assessed on May 21. Disease severity indices for take-all and Rhizoctonia root rot indicated relatively high levels of root damage; ratings were >2.5 on 5-point scales. Rhizoctonia root rot caused distinct patches of stunted plants during 1998 but not during 1999. Root lesion nematodes pruned branches off some main roots on 25% of the plants. Strawbreaker foot rot lesions were present on 7% plants. There was no evidence that Fusarium foot rot was present, in contrast to significant damage from this disease in 1998. Spring cereals -- Samples included hard red spring wheat (three treatments), soft white spring wheat (one treatment), and spring barley (one treatment). Rhizoctonia root rot caused more severe damage to seminal roots of spring barley (rating of 3.1 on 5-point scale) than spring wheat (ratings of 1.1 to 2.5, depending on treatment). Damage to crown roots was relatively minor, with ratings of 0.2 (on a 4-point scale) for barley and 0.3 to 0.7 for wheat. Rhizoctonia root rot ratings on seminal roots differed significantly among spring cereal treatments. Take-all damage was very minor on seminal roots (ratings of 0.4 to 0.5 for wheat and 0.1 for barley, on a 5-point scale; lsd=0.2) and was absent on crown roots. There was very little evidence of damage from root lesion nematode. Neither take-all
nor Rhizoctonia root rot were significantly more damaging in the continuous
spring wheat monoculture than in the spring wheat/chemical fallow rotation. Spring wheat was grown on both sides of the road during 1999. Rhizoctonia root rot was more damaging on the east than west side (ratings of 1.7-2.5 vs 1.1 for seminal roots, and 0.6-0.7 vs 0.3 for crown roots). Damage from root lesion nematode was also higher on the east than west side (34-51% vs 25-28% plants). Fusarium foot rot was very minor but was detected only on the east side. Field position had no effect on take-all. It is also notable that yields were higher on the west than east side of the road, opposite of what would be expected from observations of disease severity on the respective plantings. Although spring barley was produced only on the relatively Aclean@ west side of the road during 1999, the bare patch phase of Rhizoctonia root rot caused extensive damage (Fig. 1). Root rot was unexpectedly severe in apparent response to predisposition of seedlings to infection following two severe spring frosts and an occurrence of herbicide phytotoxicity. Satellite Experiments in Oregon: Satellite experiments with continuous minimum-till spring wheat have been performed at two Oregon locations since 1996. Tests to complement the work at Ralston were conducted near Moro and Echo, Oregon. Precipitation at the Oregon and Washington sites is usually comparable in amount (10-12 inches) and distribution. The goal of the satellite experiments is to determine if root disease damage can be minimized without altering the overall philosophy of a cropping system designed to stabilize highly erosive soil. Experiments were on the OSU Sherman Experiment Station (at Moro) and the 66 Ranch (operated by the Mader and Rust families) southwest of Echo. Cultivar Screening at Moro -- A group of 20 spring wheat cultivars were evaluated annually from 1996 to 1998. Eight of the cultivars were included among another selection of 20 cultivars in the 1999 trial. The 1996 experiment followed summer fallow and the plantings in 1997, 1998 and 1999 were placed over the same site to simulate 2nd-, 3rd-, and 4th-year recropping. Weeds were killed with a shallow subsurface sweep following harvest and an application of Roundup during February. The plot area was swept shallowly with a chisel plow in March to break up the stubble. Seed of three cultivars (Vanna, Westbred 936R, and ID377S) was treated with Dividend + Apron XL LS + Gaucho (1.0 + 0.0425 + 2.0 fl oz/cwt). All other seed was treated with Vitavax + Thiram. Seed was planted on April 1 into five replicates of 5 x 30 ft plots. Seed at the rate of 20 seeds/square foot was placed 0.5- to 1.5-inch deep into cool, moist soil with a plot drill equipped with four John Deere HZ openers and split-packer wheels spaced at 14-inch intervals. Soil tests indicated that no additional fertilizer was required to produce the crop. Starter fertilizer consisting of a dry blend of 16-20-0-24 (8 lb N/ac) plus 0-0-60 (8 lb K20/ac) was placed directly under the seed at the time of planting. Harmony Extra was applied to control weeds during May. Detailed disease assessments were not made on this experiment but were performed on a nearby and similar management experiment with some of the same varieties (see the next section). Grain was harvested during August. Primary contraints to yield included Rhizoctonia root rot, take-all, Hessian fly, and drought. The site had 7% less precipitation than the 20-year seasonal mean during the fall and winter, and 46% less than the 20-year seasonal mean during the spring. Precipitation for the Awinter wheat crop year@ was 30% less than the 20-year mean annual precipitation (12.1 inches). Grain yields varied from 16 to 25 bu/ac; lsd=3.1, mean=21 (Table 1). Test weights varied from 60 to 62 lb/bu; lsd=0.6, mean=61. Grain protein contents for Vanna, Westbred 936R and ID377S were 8.3%, 11.4%, and 10.1%, respectively. Integrated No-Till Management Systems at Moro -- During 1996 and 1997 we determined that yields could be improved through selection of cultivars based on results of local testing, treating seed with a broad-spectrum seed treatment, and placing fertilizer directly below the seed at the time of planting. These practices were examined as an integrated management system at Moro and Echo during 1998 and at Moro during 1999. Tests during 1998 were with the experimental plot drill described in the previous section, and refined tests during 1999 were performed with a commercial no-till drill rented by the STEEP program operated by Dr. Bill Payne. As in 1998, the experiment had a factorial design with three cultivars with or without starter fertilizer placement below the seed. The seed treatment variable examined in 1998 was discontinued because there were no differences among the four treatments. Cultivars included the Afarmers historical choice@ (WB 936; hard red spring) and the best yielding soft white and hard white types in trials at these sites during 1996 and 1997; Vanna and ID 377S, respectively. Seed was treated with Dividend +Apron XL LS + Gaucho (1.0+0.0425+2.0 oz/cwt). The experiment was
placed into standing stubble from the 1998 spring wheat crop; the 3rd-year
direct seeding without tillage. Weeds in stubble were killed by application
of Roundup in February. The base fertilizer consisted of 80 lb N as anhydrous
ammonia banded between rows. Starter fertilizer consisted of 68 lb N as
anhydrous ammonia banded between rows plus dry fertilizer mixed with the
wheat seed; a blend of super phosphate and potassium chloride delivering
12 lb N, 15 lb P205, and 10 lb K20 per acre. On March 6 seed was planted
into 10 x 50 ft plots with a JD 9600 drill with disk openers at 7.5-inch
spacings. Seed was placed 1- to Table 1. Spring wheat
yields (bu/ac) near Echo and Moro during 1996 - 1999.
1.5-inch deep into moist, cool soil. Seed was planted in three replicated plots at 100 lbs/acre. Harmony Extra was applied to control weeds during May. Diseases on roots, subcrown internodes, crowns, basal stem and foliage were assessed quantitatively on June 15. Grain was harvested during August to determine grain yield, test weight, and protein content. Emergence and stand establishment were excellent for each cultivar and fertilizer treatment. As described in the previous section, primary contraints to yield included Rhizoctonia root rot, take-all, Hessian fly, and drought. Rhizoctonia root rot occurred on 68-79% of the plants and the mean severity ratings of 2.3-2.7 (on a 5-point scale) did not differ significantly among the three varieties or fertilizer treatments, and there were not a significant cultivar by fertilizer interaction. Take-all was present on 37-48% of the plants and the severity ratings (1.8-2.2 on a 5-point scale) did not differ among cultivars or fertilizer treatments. Fusarium foot rot was also present but considered less damaging and did not differ among treatments. Hessian fly also occurred uniformly. Field mice eliminated plants in random sections of some rows. The region-wide drought during 1999 caused yields to be low (23 to 29 bu/ac; Table 2). Vanna continued to be a high yielding cultivar at this location during years when Hessian fly is not highly damaging. Starter fertilizer boosted yield by 1.5 bu/ac, which was statistically significant only at the 0.08 confidence limit this year. Test weights were 59 to 60 bu/ac and were not significantly increased by starter fertilizer. Protein contents differed among cultivars (Vanna = 8%, ID 377S = 10%, WB 936 = 11%,) and, for Vanna and ID377S, were 0.5% higher in plots receiving the starter fertilizer. Integrated No-Till Management Systems at Echo -- A commercial planting of annual no-till spring wheat was heavily damaged by Fusarium foot rot, Rhizoctonia root rot and take-all in 1995, during the fourth consecutive year of that cropping system. Experiments were initiated in 1996 to attempt to reduce damage from these root diseases in the annual no-till spring wheat system. Spring wheat crops continued to be planted annually with no tillage except a post-harvest sweep to control Russian thistle. The experiments were identical to those at Moro. Drought prevented experimental work at Echo during 1999. Soil moisture was present in only the top 12 inches of soil at the time soil samples were collected for fertilizer decisions during the spring, and meaningful precipitation was not forecast. The plot site was uniformly planted to the cultivar Alpowa during March. This was the seventh consecutive annual spring wheat crop for that site. Measurements of crop growth and disease were made during June. Plants exhibited extreme drought stress and were moderately damaged by Rhizoctonia root rot (mean disease severity rating of 2.6 on a 0 to 5 scale) and take-all (1.1 on a 0 to 5 scale). Fusarium foot rot was not present. Precipitation at the site during the September 1998 to August 1999 period totalled 6.5 inches, most of which occurred during November 1998. The crop yielded only 4.6 bu/acre (Table 2) and had a 59 lb/bu test weight and 13.1% grain protein content. This experience illustrates the high risk associated with weather as well as with annual cereal cropping in this environment. The site was abandoned when the project terminated in 1999. Special Nematode Sampling during 1999: Root damage by root lesion nematode has been observed at all three experimental sites for several years. Soil samples were periodically sent to the OSU Nematode Diagnostic Laboratory to verify the presence of nematodes but no systematic enumeration was performed until 1999. Samples were collected during July 1999 to determine numbers and species of all parasitic nematodes, and numbers of non-parasitic nematodes. Soil was taken from the top 4-inches in the crop row, except for fallow soil, at a time when the surface horizon had been very dry for at least three months and very hot during peak diurnal temperatures during the previous month. Migratory nematodes were unlikely to have been at peak numbers in the surface profile at any location at the time of sampling, and were not present at detectable levels at the time of sampling at Ralston. Table 2. Spring wheat
yields (bu/ac) in management trials near Echo and Moro, OR.
Echo: Minimum-till
annual spring wheat; the 7th and 8th years were harvested in 1998 and
1999. The plot area Moro: Spring wheat
was direct drilled into standing wheat stubble. The 3rd and 4th consecutive
crops were
Knowledge on critical levels for economic impact by parasitic nematodes is lacking for PNW dryland cropping systems. However, root lesion nematodes (Pratylenchus neglectus and P. thornei) appeared to be present in sufficiently high numbers (>500 nematodes/kg soil, and >1,000 nematodes/g root) to be considered damaging in some cropping systems at Echo, Moro and Pilot Rock, especially when in combination with additional stresses from drought and fungal pathogens. P. neglectus was the only lesion nematode species identified at Moro. The population was 1280/kg soil in the cultivar screening experiment and 580/kg soil in the integrated disease management experiment. In contrast to these annual spring wheat systems, there were only 70 lesion nematodes/kg soil at a nearby site featuring canola after winter wheat, and 10 nematode/kg in lupin following winter wheat. A mixture of P. neglectus and P. thornei was present at Pilot Rock. Numbers in the winter wheat treatments were highest in the three-year rotation that included canola (303/kg soil; 4,369/g wheat root) and lowest (7 to 25/kg soil; 127-305/g wheat root) in the three-year rotations that included barley and summer fallow. Intermediate numbers (167/kg soil; 1,059g root) occurred in annual spring wheat. Wheat yield at Pilot Rock was inversely associated with lesion nematode populations in roots (yield = 53.4 bu/ac - 11.1 logn nematodes/g root; R2=0.56; p=0.002) (Fig. 2) and soil (yield = 37.7 bu/ac - 3.6 logn nematodes/kg soil; R2=0.35; p=0.026). Stunt nematode (Tylenchorhynchus capitatus) was also present at Pilot Rock but numbers did not differ among treatments.
A mixture of P. neglectus and a species tentatively identified as P. hexincisus was present in the annual spring wheat experiment at Echo. The latter species is parasitic on a wide range of crops but has not been reported in Oregon. It is of interest that P. hexincisus was found in only one other of 33 samples collected from various cropping sequences at four locations in Oregon during this survey. The only other sighting was in another annual spring wheat monoculture at the Pendleton Experiment Station. The nematode was not identified in comparable annual spring wheat systems at Pilot Rock or Moro. Nevertheless, it appears important to determine if there is a selection process for this nematode in annual spring wheat ecosystems that does not occur in annual winter wheat, annual spring barley, or any of the crop rotation systems surveyed during 1999. The provisional identification of P. hexincisus in Oregon may represent a new dimension of plant health information of importance as additional acreage is converted from winter wheat/summer fallow rotation to annual cropping. Further evaluation of root lesion nematode populations and damage thresholds is required for these cropping systems. In particular, investigations are needed to examine the potential for damaging population surges for lesion nematodes in rotations that include alternate crop species such as canola. At the time samples were collected for this survey there was no apparent relationship between numbers of nonpathogenic nematodes and any crop management practice, including rotation, tillage, and residue management variables. Objective 2.
Develop disease management recommendations: This research and
extension activity will contribute to the determination as to whether
annual cropping systems can reduce soil erosion, improve soil quality,
and improve farm profitability. The goal of this work is to contribute
information that can be used to establish profitable and ecologically
advanced cropping systems. As such, the primary objective of this work
is to quantify diseases that have potential to limit profitability and
production efficiency, and to develop guidelines for fine-tuning cropping
systems of interest by reducing the importance of diseases as the limiting
factor in the adoption of these systems by growers. INTERACTION WITH OTHER SCIENTISTS CONDUCTING RELATED ACTIVITY: Routine interactions occurred with other STEEP III scientists participating in this project (listed at the beginning of this report) and with several other scientists located at Pullman, Pendleton and Corvallis. PUBLICATIONS AND PRESENTATIONS: Information was presented
during field tours at the Echo, Moro and Pendleton sites during 1999.
The project was discussed and written materials and data were presented
at each location. Results for work in Oregon were posted on Dr. Russ Karow=s
OSU Cereals Extension WebPage: Ahttp://www.css.orst.edu/cereals/@. Other
reports published and/or planned include the following.
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