Might be time for endophyte test

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By Dave Barker

In the United States, interest in endophyte has focused almost totally on its infection of tall fescue.

Although tall fescue is the most common forage grass species in the eastern United States, it is possibly second to ryegrass on grazing dairy farms.

My time in New Zealand taught me that endophyte can also infect perennial ryegrass, however, I’m unable to find any information on endophyte in U.S. perennial ryegrass.

Correction: The turf industry publishes endophyte levels for its turf ryegrasses. There is no information on endophyte in forage ryegrass.

Grass fungus. Endophyte is a fungus that grows in the intracellular spaces of some grasses.

It has the potential to impair livestock production (milk and meat) by toxic alkaloids produced during hot dry conditions.

Endophyte is abundant in tall fescue in Ohio, with an average of 58 percent of the plants in a pasture being infected. Studies have reported losses in beef gains of one pound/day while grazing toxic tall fescue.

These alkaloids can also cause spontaneous abortions in cattle and horses, as well as reduce milk production.

During the fall of 2003, we surveyed 46 ryegrass pastures (predominantly dairy) in Ohio, for endophyte. These pastures represented 31 farms from 10 counties, and varied in age, fertility, management and composition.

Approximately 20 tillers were sampled from each field and tested for presence of endophyte, using an antibody method. Of the 46 ryegrass fields measured, 30 (65 percent) had negligible (<5 percent) infection; 11 (24 percent) had moderate (5 percent to 40 percent) infection and five (11 percent) had high (>40 percent) infection.

The bad news. Ryegrass in Ohio can contain toxic levels of endophyte;

* Moderate (5 percent to 39 percent) endophyte levels were also found for several commercial forage cultivars;

* We do not know the effect of the wet summer of 2003. We will be repeating measurements on these same fields during the fall of 2004 to determine if endophyte levels are varying due to the effects of season or farm management.

We have never seen endophyte levels go down – so the extent of increase (or not) in endophyte will be of considerable interest.

The good news. All the fields with high (>40 percent) endophyte levels had unknown genetic history – or, if you plant varieties known to be endophyte-free, you can probably avoid most problems with ryegrass endophyte;

* There were no definitive effects due to fertility, grazing management or ryegrass cultivar.

Check your stands. Endophyte levels in perennial ryegrass pastures should be measured within the first few years after establishment.

If you planted endophyte-free seed, you probably have little reason for concern, however, a minority of these fields did show endophyte present and a test would be prudent.

The greatest risk of endophyte occurred in fields with unknown genetics or endophyte status – in these cases, an endophyte test is essential.

(Dave Barker is a specialist within the department of horticulture and crop sciences at Ohio State. Lanny Rhodes, Tom Noyes and Dean Slates also contributed to this research work. Rhodes is a plant pathologist at Ohio State; Noyes and Slates are OSU Extension ag agents in Wayne and Holmes counties, respectively.)

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