Welcome to the Spring 1998 issue of The Forager

UPCOMING EVENTS
Wisconsin Forage Council Forage Expo	July 1, 1998 Arlington Research Farm, Arlington, WI
National Alfalfa Improvement Conference	August 2 - 6, 1998 Bozeman, MT
American Society of Agronomy Meetings	October 18 - 22, 1998 Baltimore, MD
Wisconsin Forage Council Annual Meeting	January 26-27, 1999 Paper Valley Hotel, Appleton, WI
American Forage & Grassland Council Meeting	Feb. 21-26, 1999 Omaha, NB

In This Issue:

Facts About Potato Leafhopper Damage In Alfalfa, pages 2 & 3

Hay Dessicants and Preservatives, page 4

What is Bloat?, pages 5 & 6

1999 Wisconsin Forage Council Forage Spokesperson Contest, page 6

We would like to thank Dairyland Seed Co., Inc. for sponsoring this issue of The Forager.

Facts About Potato Leafhopper Damage In Alfalfa

The potato leafhopper is reported to be the most common and most destructive insect affecting alfalfa stands in North America. Leafhopper damage reduces alfalfa yield, hay quality and in severe cases, stand life. At one time or another, almost every alfalfa field in the Midwest and eastern areas of the U.S. and Canada has suffered from leafhopper infestation. It is common for alfalfa growers to mistake leafhopper damage for moisture or heat stress, or Boron deficiency due to the characteristic yellowing symptom caused by leafhopper damage.

To aid you in the process of leafhopper identification and control, here are some facts about potato leafhoppers which may prove helpful:

· Adult potato leafhoppers are yellowish or lime green, and about 0.13 inch long and 0.03 inch wide.

· The nymphs are similar in appearance, but lack wings. Both adult and nymph stages cause damage to alfalfa.

· Leafhoppers normally jump or crawl rapidly sideways when disturbed.

· Leafhoppers are sucking insects and feed on the sap from alfalfa plants and cause yellowing and stunts plant growth.

· Very young alfalfa plants and plants in early stages of regrowth are the most susceptible to leafhopper damage.

· Infestation is most likely to occur prior to the second and third cutting of alfalfa in most areas, and in the first cut if it has been delayed.

· Warm, dry spring weather is much more conducive to leafhopper infestation than is cool, wet spring weather.

· Damaging populations may be more likely when temperatures are between 70 and 90°F., and particularly when harvest is delayed.

· Leafhoppers typically migrate from the edge of the field inward.

How much damage can leafhoppers cause?

Simply put - very significant and extremely costly damage. Literally millions of dollars are stolen from alfalfa growers each year by leafhoppers in terms of lost yield and quality.

1. Established Stands

Studies have shown the average loss from an existing stand of alfalfa is 500 pounds per acre per harvest where infestation exists. Based on a hay price of $90.00 per ton, that would calculate to a loss of $22.50 per acre per cutting.

2. New Stands

The loss from new seedings is even more substantial than that from established stands. Leafhoppers can rob up to 1,300 pounds per acre per harvest, or cost a producer $50.00 per acre per cutting.

The loss is not limited to just annual yield reduction. For example, when leafhoppers are controlled, other factors which affect income and profitability are positively impacted:

Quality is improved - alfalfa contains more protein when leafhoppers are controlled.

Recovery is improved - plants are more vigorous and regrow faster after each cutting.

Stand life is improved - plants which are not damaged are more healthy and better able to survive the winter.

Yield the following season is improved - plots have shown alfalfa stands produce 0.5 ton more hay the following season if leafhoppers were controlled the previous year.

Where are leafhoppers present?

Potato leafhoppers are believed to overwinter in a large area across the southern U.S. Traditionally, it was thought that the insects overwinter in areas of Mississippi and Louisiana and migrate annually from there to areas of the mid- and upper-midwest. Recent research has shown that leafhoppers also overwinter on pine trees in Georgia and Tennessee, and migrate from there to the northeast each spring.

What are the signs of leafhopper infestation?

Two primary symptoms of leafhopper infestation are most common:

1. Yellowing or Hopper-Burn

Because the leafhopper removes juices from the alfalfa plant and blocks vascular tissue as it feeds, it causes a wedge-shaped yellow area to occur in the leaf tip. As damage increases, the entire leaf turns yellow, giving a yellow or burned tint to all the plants in the field.

2. Stunted Plant Growth

When infestations are at threshold or above, alfalfa plants also are noticeably stunted in their growth, sometimes more than half that of a normal plant. Use a sweep net to detect leafhopper infestation before significant damage occurs:

For alfalfa fields of 10 acres or larger, it is recommended to take 10 sweeps in at least five different locations and count the number of adults and nymphs collected per location. As a rule of thumb, if the number of leafhoppers collected from 10 sweeps per location equals or exceeds the height of the alfalfa stand, measured in inches, control steps should be taken.

What are leafhopper control options?

1. Biological Control

Under cool and wet conditions, a naturally-occurring fungal pathogen may reduce the number of leafhoppers. However, the fungus does not appear every year or on every plant. Other leafhopper predators have been shown to only slightly reduce leafhopper infestation levels.

2. Cutting Schedule Control

When an alfalfa field is cut, adult leafhoppers will leave. The wingless nymphs will remain in the field, but soon die due to lack of foliage. Control by cutting, however, usually means harvest will be done much earlier than it should be, which significantly reduces yield. Damage often has occurred prior to even an early cutting, which means quality as well as yield loss.

3. Chemical Control

Treatment of the alfalfa crop with insecticides is an effective way to control potato leafhoppers once a need to spray has been determined. Several insecticides are registered for leafhopper control and have been used effectively.

The downside to chemical control, of course, is the cost and the required time delay between application and harvest. Chemical control costs can range between $10.00 and $12.00 per acre per spraying. Each chemical varies in the amount of time required between application and harvest, but one week to ten days may be necessary. Insecticide labels should be read and followed carefully. Producers are encouraged to follow integrated pest management practices.

4. Plant A Resistant Variety

Planting a variety with true potato leafhopper resistance allows growers to harvest when they choose, and to reduce the cost and hassle of insecticide application.

Much interest has been expressed in compounds to reduce field curing time of forages.

First, it is important to recognize that two totally different types of products with different modes of action are sold: one is a desiccant which is a compound applied to the hay at cutting to increase drying rate, and the other is a preservative which is applied to hay as it is baled to allow baling of wetter than normal hay without spoilage during storage. Both products are usually applied through a spray system, which costs $600 to $1,000, either on the mower (for dessicants), or on the harvesting equipment (for preservatives).

Forage drying rate curves indicate that moisture is lost rapidly at very high moisture contents (right after cutting) and less rapidly as the hay becomes more dry. This means that hay, as we all know, initial drying is rapid and loss of the final few percentages of moisture before harvesting takes considerable time.

The desiccants that are effective contain potassium or sodium carbonate. This compound disturbs the waxy cuticle of the alfalfa stem to allow it to dry faster. Desiccants work only on legumes such as alfalfa, trefoil and clovers. Effectiveness varies with climatic conditions. Desiccants reduce drying time, most when drying conditions are good. Thus, they tend to work better on second and third cuttings in Wisconsin. They are recommended for hay making and are of less usefulness when forage is harvested as haylage.

Preservatives are applied to the hay as it is harvested and prevents heating and spoilage of hay baled at high moisture contents. Preservatives are cost effective if used only when needed to prevent rain damage to hay, and if applied uniformly to windrow as it is entering the baler. The most effective preservatives for alfalfa are organic acids, (primarily propionate and acetate) and their derivatives such as sodium diacetate.

Propionate (propionic acid) has been most commonly used, and any product containing a high percentage of this compound will be effective. Use of ammonium propionate (also called buffered propionic acid), rather than propionic acid, is recommended because the product is less caustic - therefore safer to handle and less corrosive to machinery. When purchasing preservatives, compare cost on a per pound of propionic acid basis. Other additives do little, if anything, to preserve hay. Some hay preservative products dilute the proponic acid and require greater product use rates.

Rates of propionate required vary with moisture content of the hay and are 10 lb/ton for hay at 20-25% moisture, 20 lb/ton for 25-30% moisture and 30 lb/ton for 30-35% moisture. Note that rates are for pounds of propionate, not product. Therefore, a product with 50% propionate would need to be applied at twice the above rates.

Use of preservatives for hay above 35% moisture is not recommended.

Anhydrous ammonia is an effective preservative for grasses. It can be injected into bales or released into a stack of bales covered and tightly sealed with plastic. Ammonia should be applied at the rate of 20-40 lbs/ton with higher rates used for hay near 35% moisture, and lower rates used when moisture is near 20%.

Currently, evidence is not sufficient to indicate that microbial hay preservatives are effective in preserving hay.

Bloat is a digestive disorder characterized by an accumulation of gas in the first two compartments of a ruminant's stomach (the rumen and reticulum). Production of gas (primarily carbon dioxide and methane) is a normal result of the fermentation processes. The gas is usually discharged by belching (erutication), but if the animal is unable to remove the excess gas, pressure builds up in the rumen-reticulum exerting pressure on the diaphragm which prevents the animal from inhaling, and bloat occurs. The most common type of bloat is frothy bloat where gas builds up in a foam or froth above the rumen contents and normal belching is inhibited.

Observable bloat can occur after as little as 15 minutes of grazing. Often the animal bloats only mildly and stops eating. The discomfort is eventually relieved. In more severe bloat, the animal's rumen is distended by ballooning of the rumen, it urinates and defecates frequently, bellows and staggers. Death, due to restricted breathing and heart failure follows unless action is taken.

When is it likely to occur?

Bloat can occur on any forage that is low in fiber and high in protein, but is most common on immature legume pastures. Bloat has been observed on alfalfa, white clover and red clover pastures, but is rare on trefoil, sainfoin and vetch pastures. It usually occurs when cattle or sheep are first turned onto legume pastures. It seldom occurs on grasses, (or pastures with at least 50% grass), coarser pastures or hay. Bloat usually follows a heavy feeding or grazing period. Animals that are hungry or greedy feeders are most susceptible. Frost, dew or rain on the field often increase the likelihood of bloat. Bloat incidence is likely to be increased during periods of rapid plant growth in the spring or following a summer rain.

Thus, most bloat occurs:

· when cattle are first turned onto pastures in the spring

· when cattle are moved to new pastures

· if the previous pasture was grazed too short so that cattle are hungry

· in late summer, during periods of rapid plant growth

· after rain following a period of drought.

How do I reduce the occurrence of bloat?

Begin grazing in the spring on pastures that are grass or grass-legume (at least 50% grass) mixtures. This will allow the animal time to adjust to the pasture.

Make sure that the animal is full when first put onto pasture in the spring. This reduces the intake of the fresh pasture until the rumen has had time to adjust to the new feedstuff.

Do not start animals grazing when the forage is wet from dew or rain. Start animals on legume pastures gradually. For example, leave cattle on pasture 1 hour the first day and gradually increase grazing time to 4 hours by the third day and day-long grazing by day 5. Be sure that fiber is maintained in the animal ration during initial grazing periods. Feed some dry hay or corn silage to grazing animals prior to turning them out to pasture.

Check animals for bloat carefully every 2 hours when beginning grazing. When rotating cattle or sheep among pastures, be sure that animals are moved fast enough so that they are not excessively hungry when going onto fresh pastures.

Animals with supplemental feed will be less likely to bloat. For example, a dairy cow, where 40 to 50% of the intake is pasture will be less likely to bloat than beef cattle, dairy heifers and sheep, where pasture comprises 100% of the diet.

Where bloat has been a problem, consider seeding using birdsfoot trefoil as the legume because it is non-bloating.

Consider using Bloat Guard® (Poloxalene) during periods where bloat is likely. Poloxolene can be mixed with grain supplement or drinking water, drenched or fed as a pasture block. Effectiveness of this product depends an daily intake. Thus, mixing with a daily supplement is more effective than feeding in blocks on pasture.

Some animals are chronic bloaters. If a particular animal frequently shows signs of bloat, it may be best to remove that animal from the herd.

What do I do if bloat occurs?

When bloat is observed, immediately remove all animals from pasture and offer dry hay. This will reduce the bloat problem in all animals that will eat. Causing bloated animals to walk is also helpful. Bloat can cause death in as little as 1 hour, so it is important to be prepared to render emergency treatment. Materials and directions for use can be obtained from the local veterinarian.

WISCONSIN FORAGE COUNCIL Field Day Tours (July 1, 1998)

What's New with Forages?

More mileage from corn silage: management options. (Joe Lauer)

Kura clover: a new legume for pasture and hay. (Ken Albrecht and Rob Zemenchik)

Alfalfa blotch leafminer: a new pest of Wisconsin alfalfa. (John Wedberg)

Influence of plant maturity on mineral composition of forages. (John Peters)

What's New in Grain Crop Production?

Soybean management with transgenetic varieties. (Ed Oplinger, Mike Bertram and John Gaska)

Management strategies for white mold control in soybean. (Craig Grau, Ed Oplinger and Jim Kurle)

Postemergence weed control effects on soybean yield. (Chris Boerboom)

Winter wheat variety performance and selection. (Ed Oplinger, Mark Martinka and Heidi Kaeppler)

Weed Management in Forage and Field Crops

Finding, identifying, and controlling new weeds. (Jerry Doll)

Weed management in direct seeded alfalfa. (Gordon Harvey)

Factors that affect weed-crop competition. (Dave Stoltenberg)

Preventing or delaying development of herbicide resistant weeds. (Gordon Harvey)

Soil Fertility and Management

Nitrogen management for winter wheat. (Larry Bundy)

Composted manure as a soil amendment. (Leslie Cooperband)

Field verification of soil K buffering. (Keith Kelling)

Effect of subsoiling on corn and soybeans. (Dick Wolkowski)

Grazing and Pasture Topics

Palatability of orchardgrass. (Dan Undersander)

Selecting the right orchardgrass variety. (Dan Undersander)

Stockpiled forage. (Janet Riesterer)

Nitrogen cycling in pastures. (Michael Russelle)