In Your Turf: June 1997, Endophytes: The Inside Story

Endophytes are microorganisms which exist naturally inside several species of turfgrass. As part of their existence, they emit chemical compounds that discourage pests and diseases from consuming the turf, creating a kind of natural resistance.

Endophytes have proven that they are a benefit — so much so that turf breeders as a matter of course breed endophytes into as many varieties as possible, which include varieties of perennial ryegrasses, fine fescues and tall fescues. Although a breakthrough may be coming in the near future, so far no commercially viable varieties of bluegrass have been successfully produced with endophytes.

The question is, if endophytes are such a benefit, then why aren’t seed producers and marketers making more noise about it?

BRIEF HISTORY. Endophytes were first discovered in the 1930s and, at that time, were labeled a bane of agriculture. In pasture grass, endophytes make livestock extremely sick.

It wasn’t until the early 1970s that the organisms were found to have a positive effect controlling pests and diseases, according to Doug Brede, director of research with Jacklin Seed, Post Falls, Idaho.

We know that chemicals called alkaloids affect either the feeding or reproductive cycle of insects, said Brede.

We’re not sure whether it’s more of a toxic effect or if the ‘taste’ of the turf with endophytes is what affects the insects, but it’s probably a combination of both.

In addition, there is an unknown positive affect.

Whether it’s other chemicals produced by the endophytes or some other reason, turf with endophytes seems to be more fit to resist environmental stresses such as drought and heat than noninfected plants, added Brede.

The varieties of endophytes impregnated in turfgrass today are generally the same across varieties, so there was some concern about insects gaining resistance, noted Brede. However, it doesn’t seem as though it will be a problem.

The compounds produced by endophytes seem to present multiple problems for the insects, rather than affecting only one part of the insect. Resistance should not become an issue, he said.

THE PROBLEMS. One of the biggest issues with endophytes and turfgrass is ensuring that the seed in the bag contains viable endophytes once the end user makes his or her purchase. Not being able to guarantee viability is a big limiting factor in the marketing of endophytes, noted Brede.

The endophytes are greatly affected by the handling of the seed from the time it leaves our hands, he explained.

High temperatures and humidity can greatly reduce endophyte content. Spending a long time on the shelf can also hurt viability. After 12 months of storage, endophyte viability is greatly reduced, and after two years it may be completely gone.

In addition, endophytes cannot be applied to an existing stand of turf, nor will the endophyte move from an infected plant to a neighboring plant.

When overseeded with a noninfected stand of turf, said Brede, the endophytic varieties will eventually take over the stand.

The other limitation of endophytes is that they are only effective on leaf feeding insects, such as cutworms and armyworms. While some varieties of endophytes reside in the crown area, one has yet to be found that lives in the roots where troublesome grubs and mole crickets destroy turf.

ONE STEP FURTHER. At least one researcher is exploring ways to harness the power of the endophyte to develop a new class of pesticide chemistry. Mike Richardson, assistant professor in the department of plant sciences at the Cook College of Rutgers University, New Brunswick, N.J., is trying to separate and classify the compounds that endophytes produce.

There are many compounds that are not alkaloids that have not yet been identified, noted Richardson.

We know they work — the question is, ‘What are they?’

Richardson is currently collecting compounds from the endophytes and testing their effectiveness on a variety of pests. It takes about six to eight weeks to draw out substantial quantities of material to test.

Once an active compound is found and identified, Richardson will have to determine if it can be made synthetically or if it must be naturally derived.

If the chemistry has a simple structure, we may be able to synthesize it in the laboratory, he said.

If not, it may require us to biosynthesize it through fermentation.

Richardson expects that a compound or chemical class will be identified within a year, and the viability of manufacturing the compound should be determined within two years. He predicted that one or two classes of compounds could result from the research.