Reducing grasshopper infestation using animal impact

Joel Herrmann herded cattle for Joe Black and Sons out of Bruneau, Idaho, for eight years. In 1995-96, on a BLM winter range southeast of the Bruneau Sand Dunes, Joel was operating with a holistic goal that he had written, and a biological grazing plan that he worked with on a computer. The plan was carried out by herding, control of water points, and some fencing. During this time Joel did a fair amount of photographic monitoring, as well as several monitoring transects.

"Monitoring is one of the best ways to learn your ground," says Joel. "I've put a lot of time in it, and gained a lot. Monitoring taught me more about what's happening biologically out there, than any reading or anything else I've done. It's got me down to scratch the ground and really look at what's going on. It has done more to make me realize that we're not anywhere near the potential that this land has to offer."

"The enterprise is not real estate. It is taking care of the land and producing from it," says Joel. "What Allan Savory threw out was off the wall compared to a lot of the traditional thinking. I didn't agree right off--oh, you can only improve the water cycle so much, there's only so much rain. Of course the more I monitored, the more I saw. I thought, my God, what are the possibilities? Whether he has got it right or not, we have to rewrite our own beliefs."

"Science breaks things down into parts. But if you want to make something work, you better always put it all back together. If you're going to make the system work, you're not going to do it by understanding all these little broken-up parts. Just go out and try something, and see what happens."

Grasshoppers were often a problem on the allotment, at times consuming nearly all the green grass. Spraying was not an option because of the Sand Dunes tiger beetle, curlews, and hawks. Joel talked to Tommie Martin, who referred him to books about the grasshopper's life cycle, and other animal impact experiments.

Joel put his Sand Dunes monitoring information in a binder, with extensive photo captions giving time, date, and management contexts. The following is excerpted from Joel's Sand Dunes book.

This summary follows the experimental use of cattle as a tool for controlling grasshopper infestations within the Sand Dunes Cell. This experimental project was based on the findings that bare, capped soil provides an excellent habitat for the protection and incubation of grasshopper eggs, and furthermore, on information from the successful use of animal impact for grasshopper control in Montana, Nevada, and Arizona. Also taken into consideration were the photographic and monitoring records from the Dickshooter Operation [another BLM allotment leased by Joe Black and Sons, on which Joel herded yearlings] that show animal impact, especially trampling, is an effective tool for cultivating capped soil and for improving ground cover.

To control the amount of time that any given grass plant was exposed to grazing and to control and intensify trampling, the [500] steers were kept bunched in a relatively small area. Each morning the steers were gathered into a single herd. On an average day, the steers would continue to drift and graze until late morning before stopping to rest. They would bunch more tightly during these rest periods which usually lasted two to three hours. When a significant number of the steers began to show signs of wanting to move, the entire herd was stirred and set into a grazing pattern that would take them to water. In some areas, the steers were breaking for water twice a day, while in areas where water was not as accessible, the steers broke for water only once a day, usually around 5 or 6 o'clock in the evening. The steers were given plenty of time to water, usually 45 to 60 minutes, and then they were drifted as a herd back into a specified area, where they would be easy to gather the next morning.

Bare slopes were impacted by herding the steers across the slopes rather than trying to push them up and down the incline. By cutting across the slopes, it was much easier to keep the steers in a more effective pattern, plus the method produced a moderate amount of terracing, which helps reduce erosion and provides a surface where plants can more easily establish.

Although the steers did provide moderate impact as a result of being handled in a single herd, the most effective trampling was achieved through the feeding program, where alfalfa hay was used as an attractant.

The species of grasshopper which is of most concern within the Sand Dunes Cell is commonly known as the migratory grasshopper. Like most other grasshoppers, this species deposits its eggs in the ground in clusters called egg pods, made from a glue-like secretion that holds the eggs together and also binds soil particles around the eggs. In this way, the eggs are in part protected from outside elements.

Stimulated by the warming of the surrounding soil and by spring rains, the eggs hatch over a period of 4 to 6 weeks. The timing of the hatch can vary by as much as two months, depending on the weather. The grasshoppers emerge as small nymphs and feed on the nearby vegetation. Unless forced by hunger, they are selective eaters. Most species relish small grains, such as grass seeds, and in the open range, they tend to clip the finer-stemmed bunchgrasses.

The grasshoppers go through five or six nymphal stages in 35 to 50 days before becoming adults. About two weeks after mating, the female deposits her first cluster of eggs. Rodents and the larvae of certain bees, wasps, and beetles all feed on the eggs, but where the soil is moist and mulch is plentiful, fungi and microorganisms play the chief role in the destruction of grasshopper eggs. This is why capped, bare soil surfaces and frosted subsurfaces favor the survival of grasshopper eggs, since these conditions keep the eggs dry.

One concern was the effects that the trampling could have on the tiger beetles, a rare species that occupied the sandy basin behind the Bruneau Sand Dunes. For this reason, while using the pond behind the sand dunes, the steers were allowed to file into water to minimize the impact. [Note: the tiger beetle occupies sandy, relatively unvegetated, low-successional environment near the Dunes; Joel's photo shows the steers filing singly across the sand to a water point.]

Feeding was used to implement herd effect in areas where there was little ground cover. In some of these areas, straight alfalfa was fed; in others, a combination of alfalfa and grass straw. The grass straw was used as a litter base, which the cattle trampled into the soil while competing for the alfalfa.

In early 1996, Joel again used herding and feeding to create animal impact, this time attracting cows with wheat hay.

This little knoll on the northern slope is an east-southeast exposure [above, left]. It is gravelly and has a light cover of cheatgrass. This slope is prime habitat for grasshopper eggs. The steep slope, bare ground, gravel, frosted subsurface and capped surface provide a poor water cycle and a poor habitat for microorganisms (fungi) that decay egg pods. The angle of the slope and semi-southern exposure, in conjunction with the bare ground, provides an excellent incubator for the eggs during a dry spring and summer.

A small group of cattle was fed wheat hay on the slope. The hay was used to attract the cattle onto the steep slope and to provide litter. In an excited state, the cattle trample indiscriminately, mulching the hay into the soil.

The photo [above, right] shows the feed ground a little less than two months after treatment. The seed source for the green is wheat that was used as an attractant and mulch source. Note the growth within hoofprints.

Egg pod counts were not tabulated scientifically before and after, as was hoped for. Jay Black inspected the area the following summer, and noted that grasshoppers were far less abundant near where the animal impact had occurred than elsewhere. Joel's photographs during the following year show at least a temporary advance in succession on the treated sites.

A sand dunes monitoring summary

Succession: Despite the relatively high percentage of basal cover, the percentage of litter is low, resulting in a high percentage of bare or unprotected soil in the spaces between the plants. There is also a lack of diversity, where 90 percent of the perennial plants are Sandberg's poa and 9 percent are crested wheatgrass. Almost all of the seedlings were Sandberg's poa, and although poa can be expected to do well in a cold, wet year, a greater diversity in seedlings could also be expected.

Water cycle: The insufficient amount of ground cover and canopy have contributed to capping and frosting, greatly inhibiting the soil's ability to absorb and retain moisture.

Mineral cycle: There is a high percentage of dead plant material, some two years old, still standing. Of the material that has become litter, very little is being incorporated into the soil.

Energy flow: Sandberg's poa is good forage and provides good ground cover, but it is a cool-season plant that normally only produces in cold, wet springs and quickly stops during dry, warm weather.

Thirty-six percent of the plants were resprout or recovering plants. Almost all of these were poa that showed evidence of being overgrazed in the past. Perhaps the biggest concern is that two out of three crested wheatgrass plants are overrested.

Patterns of Choice, 1998.