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Potato Leaf Hopper Host Range and Feeding Injury
PLH will feed on over 200 hosts, reflecting a variety of field and vegetable crops, weeds, shrubs and trees. Primary crops affected include: alfalfa, snap (green beans), soybean and potato. In Minnesota, PLH has also damaged young maple and apple trees.
PLH, uses "piercing-sucking" mouthparts (stylet) to cause direct damage, feeding primarily on stems or petioles. Based on recent work of Dr. Elaine Backus, University of Missouri, the injury has been characterized as a "localized, saliva-enhanced wound response." Although some of the earlier descriptions have suggested that PLH "injects a toxin" into the host plant, this is not an accurate description.
PLH injures alfalfa by repeatedly probing and feeding, with their stylets, into stem phloem tissue, injecting saliva to aid in the uptake of cell contents. Plant fluid must be drawn up the stylet before it can be tasted by leafhoppers. MECHANICAL damage from the probing activity is greatly enhanced by the flushing of cells with injected saliva. This localized activity kills pholem vascular cambium, which stimulates uneven division of new cells that eventually crush xylem elements. Thus, PLH salvia is clearly involved in aiding the digestion process of cell contents. However, the injury is due to a combination of the saliva, the probing process, and the wound response by the plant. The wound response subsequently creates the barriers to normal flow of nutrients via xylem and phloem tissue.
The most noticeable symptoms include "hopperburn" (apical yellowing of leaves) and shortening of internodes (stunting). Initial yield losses are due to the stunting effect; by the time yellowing is noticeable, quality losses (reduced crude protein) are also underway. Typical yield losses in MN on-farm trials have ranged from 400-600 lbs/ac/cutting for established stands (2nd or 3rd cuttings). Losses in a two-year new seeding study (direct-seeded) averaged 1500 lbs/ac, for 2 cuttings combined.
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