A Multidisciplinary Approach to Evaluate and Aid the Transition From Conventional to Low-Input Pest Management Systems in Stone Fruits

1991 Annual Report for LW91-028

Project Type: Research and Education
Funds awarded in 1991: $299,814.00
Projected End Date: 12/31/1993
Matching Non-Federal Funds: $68,868.00
Region: Western
State: California
Principal Investigator:
Kent Daane
Division of Insect Biology, UC Berkeley

A Multidisciplinary Approach to Evaluate and Aid the Transition From Conventional to Low-Input Pest Management Systems in Stone Fruits


1. To develop management guidelines for stone fruits by comparing the economics and the effectiveness of environmentally safe, low-input systems for stone fruits to conventional pest management systems.
2. To determine the levels of brown rot disease in low input and conventional stone fruit orchards and the effects of nitrogen levels on stone fruit susceptibility to brown rot fungus, Monilinia fructicola.
3. To determine the "best suited" combination of cover crops species and methods for managing cover crops, with respect to suppression of nematodes in the soil and enhancement of beneficial arthropods in the trees.
4. To determine control achieved and comparative costs of non-toxic control strategies (e.g. pheromone confusion and Bacillus thuringiensis) for oriental fruit moth, Grapholita molesta; peach twig borer, Anarsia lineatella; and omnivorous leafroller, Platynota stultana.
5. To evaluate the postharvest life and quality attributes of selected stone fruit varieties growing under conventional and low input pest management systems.
6. To compare orchard blocks having conventional versus low-input pest management systems with regard to differences in percent organic matter, nitrogen rates, root development, and water retention.

Abstract of Results
During the past three years we have been working in four peach orchards owned by two large farming operations, assisting them in the transition from conventional to sustainable management systems. In each orchard, half of the block has been left under conventional management for comparison. Initially, we concentrated on insect pest management since several "sustainable" tools are available.

These tools, which replace broad spectrum pesticides, include oil sprays in the dormant season, a very specific insect bacteria spray (Bacillus thuringiensis) and mating disruption using pheromone confusion. We have also been slowly bringing down the nitrogen level in the trees to help in insect and disease management and using composts, manures and/or cover crops to supply nitrogen where feasible. The results have demonstrated insect control in all four sustainable blocks to be as good or better than conventional blocks. There have been some minor problems in one of the sustainable orchards with secondary insect pests. An economic analysis indicates the sustainable approach costs about $100/acre more than the conventional approach. One of the cooperating growers has been so pleased with the results that he will convert all his stone fruit orchards to the sustainable system in 1996.

Good progress was made towards a more sustainable approach to brown rot (the major fruit disease of peach) management. Three tools have shown promise: maintenance of moderately low tree nitrogen level, addition of organic composts to the soil and cleaning up of diseased, mummified fruits in the trees. Additionally, we observed a negative correlation between a yeast on the fruit and levels of brown rot. Methods of manipulating this yeast will be studied in greater detail in the future. In addition to less fruit disease, the application of compost to the soil has also shown a tendency towards better fruit quality and less fruit damage from insects.

Many side studies are being conducted to develop additional sustainable tools. These include cover crops for weed control on the berms, cover crops for nematode control and pheromone confusion for mating disruption of some secondary pests. Finally, a new planting was established on University property where numerous sustainable techniques are being evaluated and will be demonstrated to large numbers of visitors.

Economic Analysis
An economic comparison of the plots in 1993 and 1994 showed higher costs in the sustainable plots ranging from $40 to $200 per acre compared to conventional plots. On average, the difference was less than $100 per acre. This small increase in production costs should not be a significant barrier to the adoption of sustainable practices by peach growers.

Potential Contributions
The greatest benefit of this work is the reduction of broad spectrum (and generally more toxic) pesticides in the orchard. These have been replaced with more specific pesticides or non-toxic treatments thus protecting the ecosystem and providing for greater worker safety. As many as three separate sprays applying a total of six lbs/acre of organo-phosphate insecticides were eliminated in our test plots.

Areas Needing Additional Study
As we move towards more sustainable systems where we are trying to live with and manipulate pests rather than eliminate them, it is obvious we need to better understand the overall ecology of the whole orchard. In other words, we need more information on how all the organisms in an orchard interact with each other. In particular, the soil ecosystem deserves more attention. We need to better understand how soil microorganisms affect tree health & nutrient availability and how cover crops and soil amendments affect the microorganisms.
Reported in 1995