News-- Nov/Dec 1999 -- Oklahoma Alfalfa

Results of Alfalfa Variety Tests conducted in Oklahoma are available on the web at alfalfa.okstate.edu/var-test/alf-var.html. A hard copy print out will be available in January. In addition to these detailed reports on variety tests, we publish a summary in July, in time to help finalize alfalfa variety choices for fall planting.

The 1999 results include 14 tests: three at Stillwater, three at Perkins, two at Chickasha, and one each at Lahoma, Cherokee, Haskell, Tipton, Cordell, and Goodwell.

New Varieties Need Seed Producer

I will be proposing the release of four new alfalfa varieties for Oklahoma to the Plant Materials Naming and Release Committee at Oklahoma State University. Assuming these varieties are released next spring, we will need help producing seed and marketing them.

The general plan for these varieties is to make an exclusive release to an individual, a company, or a group working together. There will be few restriction on where the seed is produced or how it is marketed as long as a solid plan is presented to and accepted by the Oklahoma Agricultural Experiment Station.

The purpose of this article, at this time is to make those interested in alfalfa seed production aware of our plans. Hopefully there are several alfalfa hay and seed producers who will devise interesting plans. If there are ideas, questions and or suggestions, I would like to hear from you.

A brief summary of each of the new varieties is located on page 5.

John Caddel
Forage Agronomist
Plant & Soil Sciences Dept., OSU

Dry weather this fall has made it difficult to spray to remove weeds from fall planted alfalfa. Emergence of alfalfa and weeds was somewhat erratic and plants that came up became drought stressed during October and much of November. Now that most areas have received some moisture, it is time to scout fall-planted alfalfa and decide if it needs to be sprayed for weeds.

Most weeds emerged at the same time as alfalfa and they should be actively growing again. These growing weeds can still be controlled this fall as long as we continue to have mild weather. For best results, spray weeds on a sunny warm day. Also do it before temperatures get too cold (10 to 15 degrees F) and weeds go dormant for the winter.

Poast Plus (1 ½ pt/A) or Select 2 EC (6 fl. oz/A) applied this December before weeds go dormant is the best choice for controlling volunteer wheat seedlings and other grasses in fall-planted alfalfa. For control of most broadleaf weeds (including seedling dock), use Butyrac 200.

It is very important to spray weeds in the fall before they go dormant due to cold temperature because most of the cool-season broadleaf weeds and grasses are not controlled with spring applications. Shepherdspurse and treacle mustard are seldom controlled with spring spraying of Butyrac, and producers are usually very disappointed with spring spray results.

January and February is the time to apply herbicides like Sinbar and Velpar L for control of cool-season weeds in established stands. If the first cutting of hay last year had more than 3% weeds, then need to spray those fields this coming January or February. Once alfalfa stands thin to less than 30 stems/sq. ft., then weeds are able to grow in areas not occupied by alfalfa. When weeds are able to have growing room, they start competing with alfalfa, and each year the percentage of weeds in the hay will increase. More on weed control in the January issue.

-- Jim Stritzke
Alfalfa Weed Control Specialist,
Plant & Soil Sciences Department, OSU

alfalfa.okstate.edu

We have had quite a bout with spotted alfalfa aphids this fall, very much like many of the falls in the 1970's and 1980's. Until this year, conditions were not favorable for spotted alfalfa aphid development and reproduction. Maybe it’s one of those El Nino or La Nina things we get so tire of hearing about.

Dr. Richard Berberet and his colleagues were on the ball and produced "ALERTS" based on frequent field scouting. In case you have not been checking the Web for alfalfa alerts recently, the following includes a reprint of what was posted on the web to help get information to producers and consultants as quickly as possible.

The Insect Alerts ( below) were written by R.C. Berberet, Department of Entomology and Plant Pathology, Oklahoma State University. Alerts were posted on the web at the Oklahoma Alfalfa Page alfalfa.okstate.edu

If you have information that should be posted in the Alfalfa Alerts contact John Caddel at caddel@okstate.edu

Alert Posted 10-25-99

SPOTTED ALFALFA APHIDS ARE ON THE INCREASE in alfalfa fields across most of Oklahoma. The most severe infestations at this time appear to be in southwestern Oklahoma, however, populations are building throughout central and western areas of the State. The dry weather has created ideal conditions for population increase in the spotted aphid. Some established fields of alfalfa in the southwest are already showing stunting, chlorosis, and dying plants due to aphid feeding. Although the season has ended for alfalfa forage production, it will be necessary to spray heavily infested fields to prevent loss of stands.

The spotted aphid is even more damaging to newly planted alfalfa than to established stands. Farmers should check all fields planted this fall at weekly intervals to detect infestations. If numbers of spotted aphids average 1 or more per plant, spraying is advised. Problems with this aphid in both seedlings and established stands may continue into the winter unless heavy rainfall and temperatures well below freezing occur.

Alert Posted 10-29-99

SPOTTED ALFALFA APHIDS CONTINUE TO INCREASE in alfalfa fields throughout central and western Oklahoma. Many established stands in the southcentral and southwestern parts of the state are being seriously damaged and should be sprayed. Although populations have increased somewhat more slowly in the northcentral area because of heavy rains received in September, aphid numbers are reaching damaging levels. Unless weather patterns change dramatically, with much colder temperatures and heavy rainfall, the potential for damage by the spotted aphid will continue to increase. Even though most fields have been cut for the final time this year, this aphid can destroy stands by feeding on the limited foliar growth that is typically present in winter.

It is even more important to check newly planted alfalfa stands on a weekly basis. The small plants in these stands can withstand relatively little feeding by spotted aphid. If numbers on seedlings average 1 or more/plant, spraying is advised. On larger plants with several trifoliolates, insecticide should be applied if numbers average 3 or more/plant.

Alert Posted 11-9-99

SPOTTED ALFALFA APHID NUMBERS HAVE BEEN REDUCED in many areas of Oklahoma by the heavy rains received October 29-31. The greatest reductions have been found in north-central areas of the State where rainfall exceeded 3.00 inches. Aphid numbers in fields checked since November 1 are well below the levels that require insecticide application to avoid damage to alfalfa stands. However, populations may still be much higher than is typical for this time of year in many fields, and it is recommended that fields be checked at 1-2 week intervals unless additional rainfall and much colder temperatures occur.

In southern areas of the State, aphid numbers were much higher over the last 2-3 weeks than in the north and rainfall amounts tended to be lower. Although it appears that numbers were reduced where 1-2 inches of rain were received, damaging populations are still possible, and it is important that fields be checked weekly. This is particularly true for new stands, where the small plants cannot withstand more than 2-3 aphids per stem before suffering damage.

Alert Posted 11-20-99

SPOTTED ALFALFA APHID POPULATIONS CONTINUE AT HIGH LEVELS in some areas of Oklahoma, particularly in the southcentral and southwestern counties. The rainfall received at the end of October reduced populations somewhat, but many fields again have numbers well above the economic threshold. Although fields are not producing forage for harvest at this time, it is important to remember that stand loss can occur due to feeding on crown growth throughout the winter. As long as weather stays mild and dry, the potential for aphid damage exists. In established fields where there is little foliar growth, sample weekly by placing a light-colored card on the soil surface below crowns, and brush the foliage to dislodge aphids. Check at least 30 crowns per field. When average numbers exceed 20-30 aphids per crown, application of insecticide should be considered in order to prevent death of plants.

Weekly sampling in new stands of alfalfa should be conducted to detect spotted aphid infestions and prevent serious damage. Newly established alfalfa plants have much less tolerance for aphid infestations than older plants. Insecticide applications should be made in new stands if numbers of aphids exceed 3 per plant.

Alert Posted 12-2-99

SPOTTED ALFALFA APHIDS ARE STILL PRESENT at high numbers in some fields of western Oklahoma. Heavy infestations and damage to alfalfa has been found in Grady County as recently as December 1. The potential for damage to stands will continue unless aphids are killed by abundant rainfall (several inches) and very cold temperatures. IT IS IMPORTANT to remember that these aphids can kill plants during mild winter weather, even though little foliar growth is present.

Check fields weekly. To sample short, crown growth in established stands, place a light-colored card on the soil surface below crowns, and brush the foliage to dislodge aphids. If average numbers exceed 20-30 aphids per crown, application of insecticide should be considered. In new stands planted this fall, insecticides should be applied if numbers of aphids exceed 3 per plant.

OK 169 is a broad gene base cultivar resulting from an equal blend of seed from seven strains, each of which was the result of interpollination of the best cultivars and experimental strains in a series of evaluations. The cultivars and experimental strains were selected for yield and persistence.

Parentage of OK 169 traces to 26 released cultivars and germplasms and 20 unreleased experimental strains.

Flower color of OK 169 is 95% purple and 5% variegated. Fall dormancy for OK 169 is approximately 4.6, more fall dormant that OK 49. Winter hardiness has been good enough for the strain to survive winters in Oklahoma with no lost due to cold.

OK 169 has produced forage yields as good as any other well-tested cultivar. Forage yield production in Oklahoma for OK 169 was evaluated for four generations. In 3 years OK 169 averaged 4% better than average.

Standard pest resistance tests indicate OK 169 has high resistance to fusarium wilt, resistance to bacterial wilt, and the spotted alfalfa aphid. It exhibits moderate resistance to phytophthora root rot and low resistance to anthracnose and the blue alfalfa aphid.

OK199, a moderately wide gene base cultivar, was derived by strain crossing plants of three cultivars and an experimental strain (Cimarron VR, WL 320, OK 49, and OK 177) all well adapted to the southern Great Plains. Equal quantities of each of the four components were blended and sown in wide rows for seed production at Chickasha, OK, in 1992. Plants were allowed to intercross, and seed was harvested in bulk in summer 1993.

Flower color of OK 199 is predominately purple with less than 10% of the plants having variegated flowers. Fall dormancy of OK 199 is similar to that of OK 49, but not much less dormant than Cimarron VR and WL 320. Winter hardiness has been good enough for the strain to survive many winters in Oklahoma with no stand loss due to cold.

OK 199 averaged about 3 % higher yield than the average in our tests, which is as good as any well-tested cultivar from public or private breeding programs. OK 199 should possess resistance to fusarium wilt, bacterial wilt, and spotted alfalfa aphid. It should be moderately resistance to phytophthora root rot, anthracnose, blue alfalfa aphid, verticillium wilt and pea aphid.

OK 200, a moderately wide gene base cultivar, is the result of indirect selection among and within adapted alfalfa cultivars and germplasms for pest resistance, tolerance to environmental stress, seed production, and general adaptation. It was derived by crossing 9 well-adapted, multiple-pest resistant cultivars and experimental strains for the southern plains with KS 219 as the female (a multiple pest resistant strain from Kansas). KS 219 was sown in a single row around a forage yield evaluation test.

Flower color of OK 200 is predominately purple with rare variegated ones. OK 200 is somewhat more fall dormant than OK 49. Winter hardiness has been good enough for the strain to survive many winters in Oklahoma with no lost due to cold. OK 200 has produced forage yields as good as any other well-tested cultivar. Yield for OK 200 has been stable over generations, and OK 200 averaged about 4 % above the test mean.

OK 200 should have adequate resistance to fusarium wilt, bacterial wilt, the spotted alfalfa aphid, phytophthora root rot, anthracnose, the blue alfalfa aphid, verticillium wilt, and pea aphid.

OK 201, a moderately wide gene base cultivar, was derived from strain crossing surviving plants of cultivars adapted to the southwest Oklahoma. The parent cultivars included Buffalo, Cody, Cimarron, WL 318, and 555. OK 201 is the result of selecting among and within well adapted alfalfa cultivars for production and persistent in Washita Co., OK. This development scheme allows for simultaneous indirect selection for pest resistance, tolerance to environmental stress, seed production, and general adaptation to southwest Oklahoma while maintaining a broad gene base of old (1940's and 1950's) alfalfa cultivars and infusing genes from cultivars developed for the 1980's and 1990's.

Flower color of OK 201 is purple. Fall dormancy of OK 201 is somewhat less than OK 49. All of the parental cultivars are moderately fall dormant and possess more winter hardiness than necessary for the coldest winters in Oklahoma. OK 201 has produced forage yields as good as any other well-tested cultivar.

OK 201 performed well in all yield tests but produced somewhat less than the test mean in irrigated tests in Chickasha and Stillwater. Its performance in other tests at Chickasha and tests in drier areas of the west was well above average and comparable to the best alfalfa cultivars available from private and public programs.

Alfalfa Variety Tests	Weed-It Tips	Insect Alerts
New Varieties		Meetings in Oklahoma
	OTHER LINKS
Oklahoma Alfalfa	Alfalfa Hay & Seed Assoc.	Return to Newsletters
Other Web Pages	Current Directors List	Membership Form

368 Ag Hall OSU Plant & Soil Sciences Department Stillwater, OK 74078
November/December 1999	Volume 23 No. 10