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Cause and Effect

Posted Sep. 1, 2000

As agricultural producers, we are confronted with persistent production problems that cost us much time and money. Have you ever asked yourself if you are dealing with only the symptom of a problem or why you want the problem to go away? We often attack symptoms and never get to the nitty-gritty of the land resource management that's causing the problem.

Pasture weeds, insect outbreaks, and parasite infestations in cattle are common in the cattle industry. We spend thousands of dollars each year in attempts to control these problems. The following are examples of how some producers are looking at the causes and eliminating them.

Weeds in Pastures
I have visited with you about our work at the Coffey Ranch, where we monitor plant species composition each year. When we first took over the ranch in 1987, pastures had an average of 26 percent western ragweed. The infestation was way above the economic threshold (15 percent) for good grass production. We had to decide whether to spend the money to spray the ragweed and kill it or determine what was causing such an infestation and try to do something about it. To solve the problem, we initiated time control with cattle in a rotational grazing system to stop overgrazing of grasses and allow them to dominate the weeds. Our solution wasn't quick, nor did it eradicate ragweed, but in three seasons the weeds were under control (figure 1).

Southern Oklahoma and much of Texas have experienced major grasshopper population outbreaks and drought for the past four seasons. These conditions have made national news several times. I don't have to tell you how grasshoppers can damage plants. I know that if we could get past the drought, the grasshoppers would go away. But why? We have to ask why grasshopper populations explode during drought. Are grasshoppers responding to the conditions caused by the drought? Think about the life cycle of the grasshopper. The insect lays eggs in the fall, which determines what the population is going to be the following year. Egg laying requires bare soil so the grasshoppers can deposit many eggs. Also, bare soil and sparse vegetation aid grasshopper nymphs as they emerge the following spring.

It is in drought that pastures are overgrazed, plants are weakened, vegetation becomes sparse, and ground cover becomes nonexistent. In 1998 we measured grasshopper population and ground cover on two adjacent ranches. The ranch with the higher bare ground percentage had higher grasshopper populations (figure 2).

The photo below shows a high population of dung beetles disposing of a recent deposit. Now why do I bring up a subject like this? Do you know how many pests and parasites of livestock require dung to complete their life cycle? The face fly, horn fly, and stomach worm are among them and are major pests of livestock. Dung beetles (many species) can destroy a dung pile within four hours. In doing so, they destroy the medium or host for the pests.

When we view and solve problems by looking at the cause and not the symptoms, we can save money in production costs and increase our opportunity for profit. Developments in technology allow us to attack symptoms, but we need to remind ourselves that management may cause the problem, and if it does, then we need to change how we manage land resources.

There is a new informational bulletin from the USDA's Sustainable Agricultural Network: Naturalize Your Farming System: A Whole-Farm Approach to Managing Pests. This bulletin is filled with colored photos, cutting-edge research examples, and anecdotes from farmers using strategies like those I mentioned. You can order the bulletin by going to the Sustainable Agricultural Web page, http://www.sare.org, and then the publication page.