Reducing leafhopper damage with alfalfa intercrops

2007 Impact statement
  • Hansen, Julie Lynn

abstract

Potato leafhopper (PLH) often is the most damaging alfalfa insect pest in the Northeast (NE). Forage grasses in mixture with alfalfa can cause PLH to emigrate and are environmentally beneficial. In the seeding year, a visual rating of damage from PLH to conventional alfalfa when planted with a grass was significantly less than for alfalfa seeded alone, and damage ratings to PLH-resistant alfalfa with or without a grass were similar, and were significantly less, than for the conventional alfalfa. The alfalfa-grass mixtures shifted toward more grass in the mixture when the alfalfa was not protected from PLH damage by insecticide treatment or genetic resistance.

submitted by

issue being addressed

In most years, potato leafhopper (PLH) is the most damaging alfalfa insect pest in the Northeast (NE). This insect significantly reduces alfalfa yield and forage quality. Forage grasses in mixture with alfalfa can cause PLH to emigrate and are environmentally beneficial, but may reduce forage quality. Producing high quality forage is a key to profitability in livestock production systems. Some recent alfalfa varieties have glandular hairs and PLH-resistance, yet are not immune to damage from PLH. Potato leafhopper-resistant alfalfa cultivars intercropped with perennial forage grass could be an IPM strategy that would have environmental, agronomic, and economic benefits to forage producers. The objectives are to compare PLH damage to the alfalfa, and forage yield and quality of a conventional alfalfa variety and a PLH-resistant variety both in monoculture and intercropped with grass, to conduct an economic analysis, and to share results in extension outreach.

response

Research trials were established in Pennsylvania and New York. For each trial site, half was treated with insecticide to control potato leaf hopper (PLH), and half was not treated with insecticide to allow natural infestations of PLH. Within these treatments, a PLH-resistant alfalfa variety and a conventional alfalfa variety were each seeded alone (monoculture), and each seeded with a variety of timothy, orchardgrass, or tall fescue. Intercropping PLH-resistant alfalfa varieties with grass could minimize risk of PLH damage and eliminate insecticide use for PLH control.
The PLH damage to alfalfa was rated visually on a 1 to 5 scale where a rating of 1 was no apparent damage and 5 was severe damage. In the seeding year, damage from PLH to conventional alfalfa when planted with a grass was lower than in monoculture, and this difference was statistically significant at two of four locations. For PLH-resistant alfalfa, PLH damage levels were similar when planted in monoculture and with a grass. Potato leafhopper damage to alfalfa was less for the PLH-resistant variety (average 2.1) than for the conventional variety planted with a grass (average 3.3). The alfalfa-grass mixtures shifted toward more grass in the mixture when the alfalfa was not protected from PLH damage by insecticide treatment or genetic resistance. Results from forage quality analyses and first production year will be available at a later date.

impact assessment

Alfalfa is a high value, high quality forage for Northeast agriculture, and potato leafhoppers (PLH) reduce both yield and forage quality. Forage producers and associated agribusinesses will benefit from development of recommendations for the Northeast concerning alfalfa variety selection, alfalfa-grass mixtures, and chemical PLH control. Insecticides are effective, but add input costs and are detrimental to beneficial insects. Potato leafhopper-resistant alfalfa varieties are mostly effective against PLH damage; however, PLH still feed on these types of alfalfa varieties. Both conventional and PLH-resistant alfalfa varieties are often planted with a grass, which impacts forage quality and may reduce PLH damage to alfalfa. Research data will be used to model economics of controlling PLH damage to alfalfa based on input costs and output value of forage yield and quality. Expected changes in forage yield, quality, and resulting net benefits associated with combinations of PLH resistant varieties, insecticide treatments, and alfalfa-grass mixtures will be used to identify optimal pest management strategies to reduce pesticide use and maximize forage crop value.

academic priority area

topic description

Reduce pesticide use.

has geographic focus

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funding source description

  • Special Grants
  • New York State Department of Agriculture and Markets

collaborators

  • New York State Agriculture Experiment Station
  • The Pennsylvania State University

key personnel

  • J. Keith Waldron
  • Dr. David Johnson
  • Dr. Marvin Hall
  • John Hanchar
  • Dr. Donald R. Viands
  • Dr. John E. Losey

mission focus

From CALS annual faculty reporting. Imported on August 5, 2008