Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If you need an accessible version of this item please contact JSTOR User Support

The Effects of Refuge Size and Number on Acarine Predator-Prey Dynamics in a Pesticide-Disturbed Apple Orchard

P. J. Lester, H. M. A. Thistlewood and R. Harmsen
Journal of Applied Ecology
Vol. 35, No. 2 (Apr., 1998), pp. 323-331
Stable URL: http://www.jstor.org/stable/2405131
Page Count: 9
  • Read Online (Free)
  • Download ($18.00)
  • Cite this Item
If you need an accessible version of this item please contact JSTOR User Support
The Effects of Refuge Size and Number on Acarine Predator-Prey Dynamics in a Pesticide-Disturbed Apple Orchard
Preview not available

Abstract

1. In apple orchards, the use of pesticides such as pyrethroids for the control of lepidopteran and dipteran pests can severely disturb natural equilibria by killing or repelling acarine predators. After spraying, phytophagous mite populations will often subsequently increase to densities which are above economic thresholds. To conserve predator populations we manipulated the size and number of predator refuges. Refuges were made with various sizes of polyethylene sheeting placed over 0, 10, 30, 60 or 100% of the leaves on trees before spraying with the pyrethroid permethrin. 2. At the time of spraying the phytoseiid predator Typhlodromus caudiglans and the stigmaeid predator Zetzellia mali were present in similar densities. The main phytophagous mites present were the tetranychid mites Panonychus ulmi and Tetranychus urticae. After spraying, Typhlodromus caudiglans was virtually eliminated from sprayed leaves, but not from refuge leaves. Recolonization of sprayed leaves by T. caudiglans was slow, probably due to toxic or repellent effects of the pyrethroid residue. Densities of Z. mali were only slightly affected by the pyrethroid, but this species was unable to control tetranychid densities on sprayed leaves in the absence of T. caudiglans. After spraying, P. ulmi and Tetranychus urticae increased on sprayed leaves to densities well in excess of crop economic thresholds, while densities remained low on refuge leaves. 3. The major effect of refuge size was a high positive correlation between entire-tree densities of T. caudiglans and refuge size, and a high negative correlation with P. ulmi densities. The refuge size necessary to control P. ulmi to below economically damaging densities was predicted to be in excess of 60% of each tree. Thus, only 40% of each tree would receive a pyrethroid spray. This is not practical for management purposes as the reduced spray coverage is unlikely to control target lepidopteran and dipteran pests. No significant effects of refuge number were observed. 4. The application of a pyrethroid spray resulted in a major disturbance to natural acarine population dynamics in this orchard for up to 11 weeks after spraying. While refuges were useful in conserving a population of the predator Typhlodromus caudiglans and reducing entire-tree densities of phytophagous mites, the use of refuges may be more valuable when using pesticides with a lower residual effect.

Page Thumbnails

  • Thumbnail: Page 
323
    323
  • Thumbnail: Page 
324
    324
  • Thumbnail: Page 
325
    325
  • Thumbnail: Page 
326
    326
  • Thumbnail: Page 
327
    327
  • Thumbnail: Page 
328
    328
  • Thumbnail: Page 
329
    329
  • Thumbnail: Page 
330
    330
  • Thumbnail: Page 
331
    331