Integrated Pest Management System for Peas in the PNW

Chapter 4 – Disease Control, No. 7, Fall 1988

Don Wysocki

Weeds, diseases and pests influence the production of most crops. This is particularly true for the production of green peas in the Pacific Northwest. These pests are one reason that yields of green peas have remained the same or slightly declined over the past 20 years. Root diseases alone may reduce yields by 10 to 50 percent. A system of controlling pests while sustaining plant vigor and yields is being researched cooperatively by a group of STEEP and other scientists. This system incorporates the combined use of pesticides, resistant varieties, biological ‘controls and proper soil and plant management to control pests and provide an environment that is minimally stressful to growing plants. This broad, multi-faceted research project began in 1985 and is given the name of Integrated Pest Management (1PM).

According to research leader, John Kraft, USDA-ARS plant pathologist, Prosser, WA, the strategy is to develop a management system for the control of diseases, weeds and insects in a winter cereal-green pea cropping system with emphasis on the peas. Green peas are an excellent rotational crop with fall grains where rainfall is adequate. Peas decrease the incidence of diseases in the following cereal crop, supply a portion of the cereal’s nitrogen needs and provide better protection against erosion than does summer fallow. However, the risk of low yield often discourages the use of peas into continuous cereal or cereal fallow rotations. The objectives of the 1PM research are to: (1) develop through soil management and pest control strategies, a system that reduces plant stresses and increases yields, (2) determine the effects of production, harvest and pest management practices on the quality of processed and seed peas and (3) investigate the effect that 1PM systems have on the succeeding cereal crop.

Emphasis in this research program is placed on improving growth early in the season. Stresses such as inadequate fertility, high temperature, low moisture or soil compaction during this stage of growth frequently intensify the problems with soilborne root diseases. Stressed plants are more susceptible to disease, and once infected their roots begin to rot and die back, This restricts water and nutrient uptake and can drastically reduce yields, Organisms responsible for these root diseases include species of Pythium, Fusarium and Rhizoctonia. The goal of 1PM is to lessen the impact of these early stresses and reduce the occurrence of soilborne diseases.

The broad nature and complex objective of this project requires the cooperative effort of several scientists from Idaho, Oregon and Washington. Cooperating on the project in addition to Kraft are USDA-ARS scientists Betty Klepper, plant physiologist; Dale Wilkins, agricultural engineer; Paul Rasmussen, soil scientist, all at Pendleton, and Alex Ogg, weed scientist, Pullman. And cooperating from the state agricultural experiment stations of Idaho and Oregon, respectively, are Larry O’Keeffe, entomologist, Moscow, and Vance Pumphrey, agronomist, Pendleton.

Description of the Research

Four experimental sites located in growers’ fields serve as the research base for this project. Two of these sites are located in Walla Walla County, WA, and two are located in Umatilla County, OR. At each site, eight different management systems are applied to a wheat-pea rotation. These systems are shown in Table 1. The scientists are evaluating the effects that these systems have upon plant diseases, weeds, insects, soil properties and quantity and quality of yield. At each location, measurements are made on plant development, density and distribution of pathogen inoculum, weed infestation, insect populations, soil water status, soil physical properties, soil and plant nutrient status and yield.

The tillage practices used in these systems address the management considerations of residue distribution and soil compaction.

Table 1. IPM systems for wheat-pea rotations at research sites in Walla Walla County, WA, and Umatilla County, OR (Kraft et al. 1985).

Moldboard plowing incorporates the highest percentage of residue and it does so in the top 7 to 10 inches of soil, but probably produces the most compaction (plow pan). Chisel plowing incorporates a lesser amount of residue, but concentrates it into the upper few inches of soil, However, chisel plowing is less likely to cause compaction than is plowing. The paraplow is a tillage tool that is designed to lift and shatter the soil. It is similar to a plow but it does not invert the soil. The paraplow penetrates the soil more deeply than a moldboard plow and destroys compact tillage layers. It incorporates very little residue, thus most residue remains on the surface. The differences in residue incorporation and soil loosening caused by the tillage methods are important from the standpoint of soil water status disease propagation.

It is hoped that this research will result in the development of a management system that will permit maximum economic return in a wheat-pea rotation without adverse environmental impact. The IPM project is attempting to integrate biological controls,’ climate, resistant varieties, proper cultural practices and the judicious use of pesticides to provide the best condition achievable for the development of vigorous pea plants. This research should help maintain peas as a viable alternative crop in rotation with cereal grains for areas of the Pacific Northwest.

Use of Trade Names

Research results are given for information only and are not to be construed as a recommendation for an unregistered use of a pesticide. Always read and follow label instructions carefully. To simplify the information, trade names have been used. Neither endorsement of named products is intended nor criticism implied of similar products not mentioned.