Number 183 March 27, 2009

Transcription

1 Number 183 March 27, Wheat problems in northwest Kansas 1 2. Soybean Cyst Nematode ratings 4 3. Corn population recommendations 9 4. Should corn seeding rates be adjusted for planting dates and hybrid maturities? Wheat problems in northwest Kansas Over the last week, I have received calls from area farmers concerned about their wheat. There could be a couple of reasons for this. First, we have had some very cold temperatures that have burned back the wheat. Typically, wheat in no-till fields appears to get burned back by cold more than wheat in conventional-till fields (Photo 2). The heavier residue in a no-till field keeps the ground from warming up as quickly as in a tilled field. Once the weather warms up, the wheat should grow out of this (unless growth is limited by other factors, such as drought, nutrient deficiencies, diseases, or insect damage). In addition, there are brown wheat mites in some fields. Brown wheat mites are typically associated with dry conditions, particularly in continuous wheat. A good rain is really what the wheat needs. Once the wheat starts growing, it will thin out the mites. An insecticide treatment can control mites, but if conditions stay dry, recovering the insecticide cost may be difficult. The following information on the brown wheat mite is from an article by J.P. Michaud, Entomologist at the KSU Ag Research Center-Hays, in the March 27, 2009 issue of the Kansas Insect Newsletter: Brown wheat mites are parthenogenetic, not unlike aphids, so all individuals are female and the outbreak potential is high. Several generations may occur in the spring with populations usually peaking around mid-april. Eggs are laid in the soil and are either brick red or white in color. Spring populations begin to decline once females begin to produce the white eggs, as these will not hatch until fall, giving rise to several more generations. Adult mites generally hide in the soil to escape adverse conditions such as freezing temperatures, but can be seen feeding on the leaves of wheat plants during daylight hours on warm days. 1

2 Brown wheat mite. Photos by JP Michaud, KSU Ag Research Center-Hays Brown wheat mites have weak dispersal abilities, so they may migrate into fields from adjacent volunteer plants. They are also favored by continuous wheat that provides them with an uninterrupted food supply from year to year. Heavy rains can reduce populations very quickly, but it is not clear if overhead irrigation can cause equivalent mortality. There is also some concern that no-till conditions may favor the brown wheat mite. Less soil disturbance might favor survival of over-summering eggs and the residue may reduce mortality from rain. The threshold for treatment is considered to be several hundred mites per row foot, but if plant damage is substantial, recovery is contingent on plants obtaining sufficient moisture. Treatment options and guidelines are available in the K-State Wheat Insect management Guide 2009: The field pictured below represents a complete loss that was probably avoidable, largely because irrigation was available but not applied in a timely manner. Like so many similar situations, there appears to be a complex of problems. Wheat was poorly tillered due to late planting, making it more vulnerable to mite damage. Early in spring, the grower applied 50 lb foliar N which is slightly excessive, and then failed to follow up with irrigation that would have enabled plants to utilize the fertilizer, possibly reduced the mite population, and certainly assisted subsequent plant recovery. Low residue vs high residue and extent of freeze damage. Photo by Jeanne Falk. 2

3 Brown wheat mite damage on wheat. -- Brian Olson, Northwest Area Crops and Soils Specialist -- J.P. Michaud, Entomologist, KSU Agricultural Research Center Hays 3

4 2. Soybean Cyst Nematode ratings The 2008 ratings for Soybean Cyst Nematode (SCN) resistance of all varieties in the Soybean Performance Test are now complete, and the results are listed in the chart below. The ratings are made by the research team at K-State. The following describes how the ratings were made and how to interpret them: Each variety is rated separately for resistance to Race 3 and Race 4. The scores in the chart are the percentage of SCN production on the roots compared to the most susceptible 10 percent of the varieties evaluated. The lower the score, the better the resistance. In general terms, a score of 1-10 is considered Resistant. A score of is considered Moderately Resistant. A score of is considered Moderately Susceptible. A score of 61+ is considered Susceptible. Any score higher than 30 means that the variety may become infected with that race of SCN to a degree that it could reduce yields. SCN Race 3 is the most prevalent race in Kansas. A variety that is R or MR to SCN Race 3 will have adequate resistance in most, but not all, cases in Kansas. SCN Race 4 is also present in Kansas, but it is not as widespread as Race 3. Race 4 is scattered throughout the SCN areas of Kansas in localized fields. Race 4 is more virulent than Race 3. If a field is infected with SCN Race 4, a variety will need to have resistance to that race. There are other races of SCN in Kansas. We use Race 4 in our testing program because it has the broadest virulence spectrum. The bottom line is that the best way to make sure a soybean variety will not be injured severely by SCN is to select a variety that is R or MR to both Race 3 and Race 4. That will provide protection against both races of SCN. A variety that is R or MR only for Race 3 may be adequate in most cases, but not on fields where Race 4 is present. While Race 4 is not widespread in Kansas, it can cause significant injury in the localized areas where it occurs. Varieties with Race 4 resistance will be resistant to a broader range of SCN populations than varieties with only Race 3 resistance. However, varieties with Race 4 resistance are not as widely available K-State Soybean Performance Test SCN Ratings Brand Variety Race 3 Rating Race 4 Rating ADVANCED GENETICS AG3833NRS R S ADVANCED GENETICS AG3840NRS MR MR ADVANCED GENETICS AG4222NRS R MS ADVANCED GENETICS AG4466NRR R MS ADVANCED GENETICS AG4511NRS MS S ADVANCED GENETICS AG4780NRS R MS ADVANCED GENETICS AG5022NRS R S ADVANCED GENETICS AG5570NRS MS S ASGROW AG2906 R MR ASGROW AG3205 R MS ASGROW AG3402 R S ASGROW AG3504 MR MS ASGROW AG3602 MR MS ASGROW AG3603 R S 4

5 ASGROW AG3705 MR S ASGROW AG3803 R MR ASGROW AG3905 R MS ASGROW AG4103 R MS ASGROW AG4403 MS MR ASGROW AG4903 MS MS ASGROW AG5504 MS S ASGROW AG5605 MR MS DEKALB DKB46-51 R S DRUSSEL SEED DSS 3788RR MR MS DRUSSEL SEED DSS 3844RR S S DYNA-GRO 32C38 MR MR DYNA-GRO 32R36 MR MS DYNA-GRO 33A37 MR S DYNA-GRO 33A40 R MS DYNA-GRO 33C32 MR S DYNA-GRO 33Y45 MR MR DYNA-GRO 35D33 R MS DYNA-GRO 35D44 R MS DYNA-GRO 35G38 MR S DYNA-GRO 35Y36 MR S DYNA-GRO 36C44 MS MS DYNA-GRO 36Y48 R MS DYNA-GRO 37A44 R MR DYNA-GRO 37J34 R MS DYNA-GRO 38C42 MR MS DYNA-GRO 38P33 MR MS DYNA-GRO 39R29 MR MS DYNA-GRO DG 3399+RR S S DYNA-GRO SXO7339 MR MS DYNA-GRO SXO7531 R S DYNA-GRO SXO7737 R MR DYNA-GRO SXO7933 R MS DYNA-GRO SXO8137 R S DYNA-GRO SXO8341 R MS DYNA-GRO SXO8734STS/RR MS S DYNA-GRO SXO8831 MR S DYNA-GRO SXO8940 S MS FONTANELLE 407 NRR STS MR S FONTANELLE 454 NRR R MR FONTANELLE 478 NRR STS S S FONTANELLE 9488NRS R MS FONTANELLE 9680NRR R MS FONTANELLE 9789 NRR R MS G2 GENETICS 7333 MR R G2 GENETICS 7381 MR S G2 GENETICS 7383 MR S G2 GENETICS 7391 MR MR KANSAS AES KS3406RR S S KANSAS AES KS4404RR S S 5

6 KANSAS AES KS4704RR S MR KANSAS AES KS5306NRR R MR KANSAS AES KS5507NRR R R KRUGER K-363RR/SCN R S KRUGER K-372RR/SCN R MS KRUGER K-389RR/SCN R S KRUGER K-410RR/SCN R MS KRUGER K-417RR/SCN MR S KRUGER K-428RR/SCN MR MS KRUGER K-433RR/SCN R MR KRUGER K-439RR/SCN MR MS KRUGER K-476RR/SCN MR S KRUGER K-489RR/SCN R MS KRUGER KX3407RN R MS KRUGER KX3807RN R MS LEWIS 3698 R MR LEWIS 3909 R MS LEWIS 4009 MR MS LEWIS 4159 MR MS MIDLAND MG 3439NRR MR MR MIDLAND MG 3618NRR R MS MIDLAND MG 3738NRR MR S MIDLAND MG 3919NRR MR MR MIDLAND MG 3979NRR MR MR MIDLAND MG 4157NRS MR MR MIDLAND MG 4289NRS R MS MIDLAND MG 4329NRR MR MR MIDLAND MG 4419NRS MR MS MIDLAND MG 4477NRR R MS MIDLAND MG 4506NRR R MS MIDLAND MG 4549NRS S S MIDLAND MG 4768NRR R MS MIDLAND MG 4806NRS MS S MIDLAND MG 4829NRS MR MR MIDLAND MG 4929NRS MR MS MIDLAND MG 5197NRS R MS MIDLAND MG 9A385NRS R S MIDLAND MG 9A432NRS MR MS MIDLAND-PHILLIPS 325 NRR MR MS MIDLAND-PHILLIPS 358 NRR MR MS MIDLAND-PHILLIPS 376NRR S S MIDLAND-PHILLIPS 385NRS R MS MIDLAND-PHILLIPS 417 NRS R MS MIDLAND-PHILLIPS 439 NRS MS S MIDWEST SEED GR3832 MR MS MIDWEST SEED GR3833 R MS MIDWEST SEED GR3934 R MS MIDWEST SEED GR4133 MS S MIDWEST SEED GR4455 R MR MIDWEST SEED GR4833 R MS 6

7 MIDWEST SEED GR5331 MR MS MIDWEST SEED GR5433 MR MS MORSOY RT 4126N R MS MORSOY RT 4457N MS S MORSOY RT 4485N R MS MORSOY RT 4707N R MS MORSOY RT 4808N R MR MORSOY RT 4987N MR MR MORSOY RT 5154N R MR MORSOY RTS 4718N R MR MORSOY RTS 4824 S S MORSOY RTS 4928N R MS M-PRIDE MPG Exp.48-1NRR/ MR S M-PRIDE MPG Exp.48-2NRR S S M-PRIDE MPG Exp.48-3NRR S S M-PRIDE MPG3908NRR/STS MR MS M-PRIDE MPG4209NRR MR MS M-PRIDE MPG4509NRR/STS MS MS M-PRIDE MPG4907NRR/STS R R M-PRIDE MPG5308NRR MR MR M-PRIDE MPV3808NRR MR S M-PRIDE MPV4905NRR R MR M-PRIDE MPV5407NRR MR S M-PRIDE MPV5505NRR MR S NC+ 3A79RR S S NC+ 3A85RS MR S NC+ 3A86RS R MS NC+ 3A93RR R S NC+ 4A15RS MR MS NC+ 4A45RS MR S NC+ 4A81RS S S NC+ 4A82RS MR MR NC+ 5A03RR R MS NC+ 5A31RS MR S NK S28-B4 MS S NK S30-F5 R MR NK S32-E2 MR MS NK S34-R2 R MR NK S35-T9 MR R NK S36-B6 MS S NK S37-F7 R MS NK S37-P5 R MS NK S39-A3 R MS NK S41-R6 MR MS NK S43-N6 MR MS NK S44-D5 R MR NK S46-U6 R MR NK S47-D9 R R NK S49-H7 R MS NK S52-F2 R MS 7

8 NK S57-P1 R MS NUTECH 7316 MS S NUTECH 7324 MS MS NUTECH 7353 MR MS NUTECH 7354 R S NUTECH 7375 R S NUTECH 7386 R S NUTECH 7399 R MR NUTECH 7406 MR MS NUTECH 7417 MS S NUTECH 7438 MR S NUTECH 7443 R MS NUTECH 7445 MR S NUTECH 7475 MR MS NUTECH NT-3888CR S S NuTech/AgSource 9383 R MR NuTech/AgSource NT-3777RR MS S NuTech/AgSource NT-4444+RR/SCN R MR OHLDE O-3191 R S OHLDE O-3334NRR MR MS OHLDE O-3532 R S OHLDE O-3727NRS R MR OHLDE O-3732 R MS OHLDE O-4232 MR MS OHLDE O-4292 R MS OHLDE O-4595 R MS OHLDE X-3525 R MS OHLDE X-3927 MR MS OHLDE X-3997 MS S OHLDE X-4355 MS S PHILLIPS 358 NRR MR MS PHILLIPS 376NRR S S PHILLIPS 385NRS R S PHILLIPS 417 NRS R MS PHILLIPS 439 NRS S S PHILLIPS 486NRS S S PIONEER BRAND 95Y20 MR MS PIONEER BRAND 95Y40 MR MS PIONEER BRAND 95Y41 MR MS PRAIRIE BRAND PB-3637NRR R MS PRAIRIE BRAND PB-3796NRR R MS PRAIRIE BRAND PB-3858NRRSTS R S PRAIRIE BRAND PB-3997NRR MR MS PRAIRIE BRAND PB-4058NRRSTS R MS RENZE R3599RRcn MR MS RENZE R3788RRcn R S RENZE R4038SRcn MR MR RENZE R4439SRcn MR MR RENZE R4836SRcn MS S SCHILLINGER 457.RCP R MR 8

9 SCHILLINGER 478.RCS MR MS SCHILLINGER 495.RC R MS SCHILLINGER 557.RC MR MR SYLVESTER 3249NRR MR S SYLVESTER 3439NRR R S SYLVESTER 3618NRR MR MS SYLVESTER 3738NRR MR MS SYLVESTER 3919NRR R MS SYLVESTER 3979NRR MR MR SYLVESTER 4157NRS MR MR SYLVESTER 4289NRS R MS SYLVESTER 9A385NRS MR MS TAYLOR 353RR MS S TAYLOR 398RRS MR S TAYLOR 424RRS MR MR TAYLOR 445RR R MS TAYLOR 487RRS MS MR TAYLOR EXP 4950RR R MS TAYLOR EXP A-3920RR R S TAYLOR EXP D-3600RR R MS TAYLOR EXP D-3720RR R S TAYLOR EXP T3780RR R MS WILLCROSS RR2397N MR MS WILLCROSS RR2405N MR MS WILLCROSS RR2440NSTS MR MS WILLCROSS RR2460NS R MS WILLCROSS RR2470NSTS R MS WILLCROSS RR2477NSTS MR S WILLCROSS RR2490NSTS R MR WILLCROSS RR2498NSTS R R WILLCROSS RR2507NSTS R R WILLCROSS RR2544NSTS MR MS WILLCROSS RR2547N MR MS This work is supported by the Kansas Soybean Commission. -- Tim Todd, Plant Pathology Nematologist nema@ksu.edu 3. Corn population recommendations The optimal corn population for any situation will depend on the anticipated environment and how the hybrid responds to that environment. Producers can look back to their corn crop from the previous growing season, or wait until the current growing season is nearly complete, and evaluate whether the population they used was adequate. 9

10 If there are a number of barren plants, the populations may be too high. If the number of kernels per ear is much below 400 to 500, the population may be too high. If there are more than 600 kernels per plant, the population may be too low. Don t be concerned if a half-inch or so of the ear tip has no kernels. If kernels have formed to the tip of the ear, there may have been room in that field for more plants with additional ears. Always keep the current environment in mind. Will the environmental conditions (rainfall amount and distribution, temperatures) experienced last year likely be the same this year? What is the soil water storage capacity of the field? Does the previous crop tend to deplete stored soil water more than most crops? Will irrigation water be available in the same quantity and at the same time of year as in the past? What has been the typical germination rate and stand establishment on a given field with the planting equipment to be used? Optimal seeding rates may need to be adjusted for irrigated corn if fertilizer or irrigation rates are sharply increased or decreased. For example, research at the Irrigation Experiment Field near Scandia has shown that if fertilizer rates are increased, seeding rates also have to be increased to realize the maximum yield benefit. Consult seed company recommendations to determine if seeding rates for specific hybrids should be at the lower or upper end of the recommended ranges for a given environment. The recommended planting rates in the following table attempt to factor in these types of questions for the typical corn growing environments found in Kansas. Adjust within the recommended ranges depending on the specific conditions you expect to face. Recommend planting rates from the K-State Corn Production Handbook Suggested Dryland Corn Final Populations and Seeding Rates Area Environment Final Plant Seeding Rate* Population (plants per acre) Northeast bu/a potential 22,000-25,000 26,000-29, potential 24,000-28,000 28,000-33,000 Southeast Short-season, upland, 20,000-22,000 23,500-26,000 shallow soils Full-season 24,000-26,000 28,000-30,500 bottomground Northcentral All dryland 20,000-22,500 23,500-26,500 environments Southcentral All dryland 18,000-22,000 21,000-26,000 environments Northwest All dryland 16,000-20,000 19,000-23,500 environments Southwest All dryland environments 14,000-20,000 16,500-23,500 10

11 Suggested Irrigated Corn Final Populations and Seeding Rates Environment Hybrid Maturity Final Plant Seeding Rate* Population (plants per acre) Full irrigation Full-season 28,000-34,000 33,000-40,000 Shorter-season 30,000-36,000 35,000-42,500 Limited irrigation All 24,000-28,000 28,000-33,000 * Assumes high germination and that 85 percent of seeds produce plants. Seeding rates can be reduced if field germination is expected to be more than 85%. For more information, see the K-State Corn Production Handbook, C-560: -- Kraig Roozeboom, Cropping Systems and Row Crop Production Specialist kraig@ksu.edu 4. Should corn seeding rates be adjusted for planting dates and hybrid maturities? The seeding rate recommendations in the K-State Corn Production Handbook are a good starting point, but producers still have to decide whether to adjust those seeding rates depending on other factors, such as planting dates or hybrid maturity. Recent K-State studies conducted at Manhattan, Ottawa, and Hesston tested three hybrids of differing maturities (98-, 106-, 112-day Relative Maturity) at planting dates generally ranging from mid-march to mid-april. Each hybrid-by-planting date combination was planted at three populations (18,000, 22,000, 26,000 plants per acre at Manhattan and Ottawa; 14,000, 18,000, 22,000 plants per acre at Hesston). Results from these studies can be summarized as follows: Planting Date: * Yield response to planting date depended on year and location. * Mid-March planting generally did not reduce yield except in 2007 (0 bushels/acre), when there was a late freeze. * Mid- to late-march planting provided a yield benefit in the drought year at Hesston. * Cool temperatures often delayed emergence of mid-march plantings so that they emerged within a few days of the early April planting. * The early April planting date was most consistent across locations and years. This date avoided freeze damage in 2007 and yield reductions occasionally seen for later dates. Hybrid Maturity: * Hybrid maturity response depended on year and location. * Ottawa: The medium maturity hybrid was most consistent regardless of planting date. 11

12 * Manhattan: The fuller maturity hybrid was equal or superior to the others for all planting dates, except for the mid-may planting date in 2007 when the medium maturity hybrid yielded more. * Hesston: The fuller maturity hybrid was equal or superior to the others for all planting dates, except in the drought year of 2006 when it yielded the least for all planting dates. Population: * Higher populations generally resulted in greater yields. * Ottawa: Yields were greater with medium (22,000) or high (26,000) populations, except if planted in May or June when yield decreased with more plants per acre. * Manhattan: Yields were greater with more plants per acre; the response to increasing populations was larger in the higher-yield environments (>150 bu/a) and at earlier planting dates. * Hesston: Yields were greater with more plants per acre regardless of planting date in 2004, 2005, and There was no response to plant population in the drought year of Kraig Roozeboom, Cropping Systems and Row Crop Production Specialist kraig@ksu.edu -- Larry Maddux, Agronomist-in-charge, Kansas River Valley Experiment Field lmaddux@ksu.edu -- Mark Claassen, Agronomist-in-charge (retired), Harvey County Experiment Field mclaasse@ksu.edu These e-updates are a regular weekly item from K-State Extension Agronomy and Steve Watson, Agronomy e- Update Editor. All of the Research and Extension faculty in Agronomy will be involved as sources from time to time. If you have any questions or suggestions for topics you'd like to have us address in this weekly update, contact Steve Watson, swatson@ksu.edu, or Jim Shroyer, Research and Extension Crop Production Specialist and State Extension Agronomy Leader jshroyer@ksu.edu 12