NEWS--June1997--Oklahoma Alfalfa

ALFALFA'S IMPORTANCE TO OKLAHOMA

Alfalfa is definitely important to the state of Oklahoma. Many people, even some alfalfa producers, don't really know its importance to their area and to the state. Most think alfalfa is just something that is grown on a piece of land to grow hay and has to be cut every once in a while. A few people also know that a lot of bugs and worms eat alfalfa, and it has to be sprayed.

The graph in Figure 1 shows alfalfa hay is worth about $120 million each year to the state of Oklahoma. These data are from the Oklahoma Agricultural Statistics Service, using five-year averages that tend to smooth out much of the year to year variation.

Figure 1. Annual Value of Alfalfa Hay, 1977 to 1995.

It is pretty easy to see that alfalfa's value to the state has been increasing steadily from $74 million in 1977 to a high of $129 million around 1992. The graphs in Figures 2 thru 5 may also be surprising to many of us. Yields have increased from 3.2 to 3.6 tons/acre (Figure 2). The individual year of 1995 was estimated at 3.8 tons/acre.

Figure 2. Alfalfa Hay Yield (tons/acre) from 1977 to 1995.

The five-year average price has gone from less than $60/ton in the late 1970's to more than $91/ton during the last several years (Figure 3).

When the average price is more than $91 (which includes some fairly bad hay) those producers doing a good job of making high quality hay and using good marketing skills are getting much more.

Figure 3. Average Price of Alfalfa Hay ($/ton) 1977 to 1995.

Acreage has been fairly steady around 400,000 (Figure 4) except for a dip in the mid 1980's and a jump around 1990. Total production for the state has also been fairly steady -- around 1.3 million tons (figure 5).

Figure 4. Alfalfa Acreage in Oklahoma from 1977 to 1995.

Figure 5. Total Production (millions of tons/yr.), 1977-1995.

Total income to the state for alfalfa hay is more than 1/4 the income from wheat for grain, and the alfalfa is produced on well less than 1/10 the acreage. More specifically, it takes 18 times as much land with wheat to produce only 4 times as many dollars for the state

Economists multiply the value of a product by a factor of 7 to 10 to get a more meaningful measure of something's impact on the economy of the state or region. We know that the money earned by alfalfa production helps many people in addition to the individual producers and their families. Equipment, fuel, repairs, chemicals, labor, etc., are purchased with the money earned from alfalfa in addition to how the family uses its net income. So the alfalfa industry in Oklahoma is creating about $1 billion of spending power in the state, going through many hands.

Maybe we should brag about it a little more. It's not just hay! And it is certainly not chicken feed!!!!

-- John Caddel,
Forage Agronomist

This has been another difficult year to know what to do about controlling summer weeds. Some of the early emerged summer weeds were frozen back, then the standing alfalfa shaded the area enough to prevent emergence of more seedlings. Then a big crop of weeds (primarily crabgrass and foxtail) germinated after the delayed first cutting due to the wet soil conditions at harvest.

POAST PLUS at 1½ pint/acre applied on these grasses gave excellent control, but wet conditions at second harvest resulted in another flush of weeds in many fields. This means that you will need to spray again if you want to keep weeds under control. If grasses and pigweeds are still small and growing conditions are good, then control should still be possible.

You need to scout fields about 1 week after hay is off, and decide what to do about weed control. Here are your summer weed control options:

1. Do no weed control: This may be the most profitable option, especially if you have a good stand and need hay for your beef cattle or you have a beef producer who will give you a fair price for it. If it turns dry in July, these summer weeds may not be highly competitive with alfalfa during the rest of the summer.

2. Herbicide options now: Good soil moisture now, means that we probably will have two more good cuttings of alfalfa, and continued rain would result in a lot of summer weeds, so it may be profitable to control weeds with herbicides.

PURSUIT (4 oz/acre) should still control most pigweeds less than 4 inches tall and actively growing. Do not expect good control of pigweeds more than 4 inches tall or if they are drought stressed.

Important note: certain pigweeds such as waterhemp are resistant to PURSUIT. In addition, resistance in palmers pigweed has been reported in the northwestern part of Oklahoma. Do not expect any grass control from PURSUIT applied this late. Pursuit has good residual activity, so expect summer-long weed control of susceptible weeds applied now. Be aware of rotational crop guidelines after using PURSUIT. It is 4 months for wheat and 18 months for sorghum (see label for other crops).

BUTYRAC 200 (2,4-DB) at 2 pints/acre can be used now, in third cutting of alfalfa, to get good control of 2- to 4-inch tall pigweeds that are actively growing. Do not expect to kill large pigweeds that were clipped during swathing. Some suppression of 6-inch regrowth from 6-inch tall pigweeds clipped at harvest was possible last year with good moisture conditions.

POAST PLUS at 1½ pint/acre can still be used in third cutting to control emerged summer grasses less than 4 inches tall. It is essential that 1 quart of crop oil concentrate/acre be added to the spray mix.

For weed-free hay at next cutting, scout your fields and spray BUTYRAC for pigweeds and POAST PLUS for grasses. If both grasses and pigweeds are present, apply a mixture of BUTYRAC and POAST PLUS. Expect good control of emerged weeds but no control of weeds that emerge after application. For this reason, it is important to time applications of BUTYRAC and POST PLUS just before canopy closure of alfalfa to maximum emergence of weeds .

For both BUTYRAC 200 and POAST PLUS, weeds need to be actively growing (good soil moisture and temperature) when herbicide is applied. Neither of these herbicides has residual activity, so it is necessary to scout fields for newly emerged weeds and respray in each cutting if season-long weed control is desired.

-- Jim Stritzke
Alfalfa Weed Control Specialist

Potato Leafhopper Economic Thresholds in Alfalfa

After a brisk round of southerly winds and rains, some insects that are not year-round residents find their way to Oklahoma. Normally, potato leafhoppers are year-round residents of the Gulf coast states and gradually migrate northward with spring winds. Because of wind dispersal, potato leafhoppers are likely to be a pest of alfalfa from June to October. The potato leafhopper poses the greatest threat (if any) in the higher rainfall and humidity areas of the state. In western Oklahoma, high potato leafhopper populations are rare because hot, dry conditions normally prevail.

The potato leafhopper adult is a light green, wedge-shaped insect about 1/8 inch long. The nymphs closely resemble adults; however, they are smaller, yellow, and wingless. Both adults and nymphs are very active; they can move sideways and backward as rapidly as forward when they are disturbed.

Damage: Both adults and nymphs use their piercing-sucking mouth parts to feed on alfalfa; however, the most serious damage is caused by the nymphs. Initial feeding damage is characterized by a wedge-shape yellow area formed on the leaf tip known as "hopper burn". (Sometimes confused with drought.)

Heavy feeding causes the entire leaf to turn yellow and heavily infested fields take on a yellow color. Usually damage is greatest along field margins. Mowing

ditches next to alfalfa meadows can increase chances of sustaining leafhopper damage because the leafhoppers move into the alfalfa.

Due to their minute size, the best means of detecting leafhoppers before damage can be seen is a sweep net. Sample at least four areas across a field. In each area take at least 20 sweeps before counting the number of adults and nymphs. Treatment is justified at these combinations of alfalfa height and leafhopper numbers:

Alfalfa height (inches)	Leafhoppers per sweep
3	.2
6	.5
12 or taller	1.0

Besides height and leafhopper density, one needs to consider yield potential and stand age before deciding to treat or not. Insecticides recommended for control include: Dimethoate, Methoxychlor, Parathion, Lorsban, and Furadan.

-- Phil Mulder
Alfalfa Entomologist

Scouting alfalfa fields, taking precautions while harvesting, spraying fields or infested areas, and inspecting baled hay all help prevent toxicity in horses from consumption of alfalfa containing blister beetles.

Blister beetle adults emerge from the soil in late spring or early summer, and large numbers normally will congregate in small areas of fields, usually within 50 yards of a field margin. The predominant species found in Oklahoma is the yellow and black striped blister beetle.

The first alfalfa cutting of the year normally is free of blister beetles problems because they are not normally in alfalfa fields in large numbers that early.

Blister beetles contain a toxic blistering agent, cantharidin, which can cause irritation or serious damage to the stomach lining and other organs of the digestive and urinary tracts of horses.

According to some reports, ingestion of as few as 15 beetles can cause illness, and consumption of 50 to 100 can cause death.

Because of their congregating nature, remains of beetles killed during the alfalfa harvesting process are likely to be concentrated in a few hay bales or small portions of bales. Cantharidin is a stable compound that retains its toxicity to livestock even when dried remains of the beetles are fed along with the forage.

When infesting alfalfa, blister beetles prefer to feed on blossoms. Swarms of beetles often are crushed by crimper rollers of the swather and are trapped in the windrowed hay.

If beetles remain alive in the windrows, most of them will crawl out. They also can be trapped and killed in hay if windrows are driven on before beetles have had time to escape.

Two of the best ways to avoid blister beetle problems in hay from an infested field are swathing without crimpers and avoiding wheel traffic on freshly cut windrows.

Application of a short-residual insecticide to infested areas, entire fields, fence rows, and borders can kill beetles just before harvest. Sevin has given good results under Oklahoma conditions. Methoxychlor also is registered for blister beetle control. Both products have a seven-day waiting period before harvest.

Parathion also can be effective, but it has a 15-day waiting period before harvest. Malathion and the permethrin products have no waiting period, but their labels don't list blister beetles as a target pest, and effectiveness of their blister beetle kill in Oklahoma hasn't been tested thoroughly.

Livestock owners buying alfalfa should know their supplier well and find out what precautions were taken to avoid blister beetles in hay. If presence of beetles is suspected, hay should be inspected thoroughly before feeding.

Purchase of alfalfa harvested before May or after September reduces blister beetle risks significantly.

If toxicity symptoms are seen in horses, a veterinarian should be called immediately. If a large amount of cantharidin is consumed, a horse may die within six hours. Small amounts consumed cause mild colic. A frequent symptom of cantharidin illness of a horse is placing the muzzle in water and playing in the water with the lips and tongue.

Severe poisoning may result in low blood calcium and magnesium, which can cause stiffness and an exaggerated goose-stepping gait. Horses that survive 24 hours may strain frequently, and small amounts of blood may be seen in the urine.

In addition to having a veterinarian examine a horse showing symptoms of toxicity, remaining hay also should be inspected for presence of blister beetles.

O.S.U. Extension Facts No. 2072 has photos and additional information about blister beetles.

-- Phil Mulder
Alfalfa Entomologist

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