Potato Leafhopper Resistant Alfalfa: The Potential for Improving Organic and Traditional Farming Systems

View the project final report

• 2004 annual report

Commodities

• Agronomic: general hay and forage crops, grass (misc. perennial), hay

Practices

• Animal Production: feed/forage
• Crop Production: application rate management
• Education and Training: demonstration, display, farmer to farmer, on-farm/ranch research
• Farm Business Management: agricultural finance
• Pest Management: biological control, chemical control, field monitoring/scouting, integrated pest management
• Production Systems: agroecosystems

Alfalfa is the least expensive and consequently a primary source of protein on dairy farms in the northeast U.S. However, Potato Leafhopper (PLH) infestations lower the yield, quality and persistence of alfalfa if they are not controlled. Traditionally, PLH control involves an insecticide application, which means that organic dairy producers suffer the full negative effects of PLH if they include alfalfa in their farming system. This can explain why there are only 2700 acres of organic alfalfa (0.3% of total alfalfa acres) in the northeast when there are more than 17,000 dairy cows (increasing at 27% each year) producing organic milk. Insecticides that control PLH also kill beneficial or non-target insects (e.g. honey bees, lady-bird beetles, wasps that control alfalfa weevil). Killing these beneficial insects destroys the natural insect balance which can cause subsequent outbreaks of harmful crop insects in alfalfa and other crops. In 1997, PLH-resistant alfalfa varieties were developed, using traditional breeding technology, and introduced to the market. The initial PLH-resistant varieties were about 35% resistant and current varieties have over 75% levels of resistance. It is not clear if these newer PLH-resistant varieties are able to improve the economic and environmental sustainability of dairy and hay crop farming systems. This project will couple on-farm research that will quantify benefits of adopting PLH-resistant alfalfa varieties with outreach programs that demonstrate the potential for these new varieties to enhance the sustainability of their farming systems and reduce or eliminate the amount of insecticides applied annually in alfalfa production.

PLH-resistant and PLH-susceptible varieties of alfalfa will be planted on 6 farms located in Mercer (western) or Centre (central) counties in Pennsylvania. Producers have been selected based on their strong interest in managing alfalfa for high yields and quality. They are eager to try innovations in forage management. Each farm will provide field space (approximately 3 acres) for one replication of the two-treatment comparison. Preference will be given to fields that have minimal soil variability and are located where field days can easily be attended. The three acres will be divided and the PLH-resistant variety planted in half and the susceptible variety planted in the other half. Plantings will be made in spring 2004 with the farmer’s drill or cultipacker seeder.

This project, which aims to provide information to farmers employing organic practices, does not initially involve organic growers because of the potential risk associated with failure of the PLH-resistant trait. Failure to control PLH feeding in an organic situation presents high financial risk to an organic grower while non-organic growers have insecticide options. If PLH-resistant alfalfa performs well on these “non-organic” farms then it will be evaluated on “organic” farms.

Throughout each growing season, each alfalfa variety at each farm will be scouted and numbers of PLH, other pests and beneficial insect species will be determined twice per month by the local Crop Management Association (CMA) personnel. The PLH-resistant variety will not be treated with insecticides. During the both years, chemical PLH control will be applied to the PLH-susceptible variety when the CMA personnel determines that the PLH threshold for economic damage (per Penn State University Entomology Department Extension guidelines) has been reached. Broadcast spray applications of cyfluthrin (Baythroid 2) or lambda-cyhalothrin (Warrior) insecticides will be used for control.

The alfalfa will be harvested twice during the establishment year and three or four times during subsequent years. Crop consultants, extension agents, and farmers will work together to determine yield (see procedure detail in Appendix A) of each variety at each harvest. Forage dry matter determinations will be used to correct field fresh weights to 12 % moisture (standard for dry hay).

Statistical analysis of forage yield, PLH and beneficial insect populations will be conducted to determine possible differences between the two alfalfa varieties. To analyze financial benefits to the farming system, costs and net returns associated with crop production and management of varieties will be determined and analyzed in partial budgets. Of greatest importance to organic dairy farmers and the community at large will be an assessment of the opportunity for alfalfa production without the use if insecticides. The analysis will also include estimates for regional and state-wide benefits from reducing insecticide usage if this new technology were to be widely adopted.