 |
ProCrop |
Potato Leaf Hopper-Tolerant "Alfalfa Varieties and Economic Thresholds
Although several advancements have been made in the past three years regarding alfalfa with some level of resistance to PLH, it is probably more accurate to classify these varieties as tolerant vs. resistant to PLH damage. Several field tests, and on-farm observations continue to show (at least in large scale tests) that these varieties can tolerate considerable PLH damage, and still yield well. In a more moderate, or even "average" PLH year, selected "PLH-tolerant" varieties may yield well and save one or more insecticide applications/yr. However, in a high pressure year such as this year (and in 1997), most of the varieties, to date, will still harbor PLH adults and/or nymphs, and may therefore still benefit from a timely insecticide treatment for PLH.
Given, the tolerance of these varieties, recent research at Iowa State University found that the traditional PLH thresholds could be increased 10-fold to account for the value of this tolerance. Thus, for a typical threshold of 12/ten sweeps at the 8" height, the threshold would be 120/ten sweeps for a PLH-tolerant variety.
IF you are seeing stunting injury on a "PLH-tolerant" variety, that you believe is due to PLH, AND the PLH counts are less than the threshold (e.g. at 50/ten sweeps), our observation reflects a difference between the response of the varieties used in the Iowa State study, and the variety in your particular field. As with most thresholds, therefore, use these as a GUIDE in making your final treatment decision. If you are seeing damage, and/or other pests such as plant bugs are also present (threshold = 3-5/sweep then an insecticide treatment may be warranted.
Back to Potato
Leafhoppers - Insects Menu
Back to Insects Menu
Back to Main ProCrop Index
