Method: Orchard Management

Integrated Pest Management Program

One important feature of the park's landscape is a 35-acre pecan orchard. Its canopy provides shade and comfort on hot summer days. The orchard also acts as a buffer between agricultural fields, the historic Johnson farm area, and the LBJ Ranch house. It is believed to have been planted in the 1930s and is now composed of five or six varieties of trees, some historic and others developed more recently. During the 1950s and 1960s, the orchard was managed with a multitude of agrochemicals, the accepted practice of the day. When the National Park Service assumed management of the property, the use of pesticides and herbicides was no longer acceptable, and an intensive integrated pest management program was developed working with IPM specialists from Texas A&M University and the NPS Santa Fe Support Office for the Intermountain Region. The IPM program at Lyndon B. Johnson National Historical Park was started in the late 1970s and was one of the first serious IPM programs in the country within the national park system. Although the park's orchard is managed for saleable and sustainable crop production, park managers determined that minimizing the use of pesticides and their effects on non-target organisms was more important than maximizing profitability.

Every wild pecan tree is genetically distinct from its neighbors, which provides considerable protection from pathogens. Orchard trees, on the other hand, are propagated vegetatively, creating many genetically uniform trees that are highly susceptible to epidemics of pecan scab. The park's relatively dry environment limits vulnerability to this fungus to times of rapid leaf growth after early spring rains, or the period shortly thereafter when there is nut growth. This allows park staff to limit the spraying of fungicides to these narrow time periods.

Because orchard trees are grown to produce a nut crop each year and do not follow the "boom and bust" cycle of their wild relatives, they are also very susceptible to the pecan nut casebearer, which seeks out orchard trees during bust years in the wild. Park staff use pheromone traps to monitor the number of casebearer moths, then target the spraying of an endotoxin to specific time periods. As part of the park's IPM program, staff have also developed a monitoring protocol for the pecan weevil, which feeds on mature nut cropsⁱ.

A groundwater monitoring protocol and routine surface water monitoring to detect runoff and leaching of pesticides are also extremely important aspects of the park's IPM program. In order to reduce their effect on the natural environment, the chemicals used on the orchard have been chosen because they are biodegradable, not biologically magnified, and not readily leached through the soil.

Orchard Thinning

In 1999, park staff worked with county field agents and Texas A&M University to establish a thinning regime for the orchard. The orchard had become extremely overcrowded, making it more susceptible to pecan scab, and the consensus was that every other tree should be removed. Before doing so, park staff worked with the state historic preservation officer and a landscape architect at the NPS Santa Fe Support Office for the Intermountain Region to carefully document the orchard in accordance with the National Historic Preservation Act. This record will allow any changes made to be reversed in the future if necessary.

One of the most difficult elements in the thinning process was to find someone willing to cut the trees, which were too small to be valuable for lumber. Eventually, park staff worked out a cooperative arrangement in which a logger agreed to do the cutting in exchange for the firewood, and park staff was responsible for the cleanup. The tree removal could potentially have created a public relations problem with visitors, but the park's interpretive staff became an important public relations tool. Interpreters were kept abreast of management decisions regarding the thinning process, and were able to explain the process and address visitors' concerns during interpretive bus tours that pass by the orchard.

Eventually trees that have been removed as a result of death or disease rather than the thinning program will need to be replaced. The park's internal management decision has been that maintaining the historic appearance of the landscape is more important than maintaining the historic genetic stock of individual trees. By planting more recently developed disease-resistant varieties, park staff believe that the reduction in pesticide use and its benefits to the environment will outweigh the loss of historic accuracy.

ⁱHarris, Marvin. "Taming the Wild Pecan at Lyndon B. Johnson National Historical Park." Park Science 19, no. 2 (December 1999): 1, 20-21.