Submitted to: American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 1, 1998
Publication Date: N/A
Interpretive Summary: The USDA's Agricultural Research Service maintains the only pecan breeding program in the world, and produces improved cultivars for all growers, especially in the U.S. 'Pawnee' is a pecan cultivar released by this program in 1984. This improved cultivar was tested for resistance to yellow aphids, and found to be more resistant than any other cultivar or clone ever tested. Yellow aphids are a major problem in pecan production since they suck huge quantities of nutrients from the leaves. Also, they reproduce very fast since they can give birth to progeny and have short life cycles. 'Pawnee' has natural genetic resistance or what scientists call host plant resistance to these pests. In tests in the greenhouse and field, 'Pawnee' had lower natural population levels of these insects. Growers should be interested in planting this cultivar since it should experience less damage from this insect complex, and should produce more profit than susceptible cultivars.
Technical Abstract: Putative resistance to the yellow aphid complex (Monellia caryella Fitch and Monelliopsis pecanis Bissell) in the 'Pawnee' pecan (Carya illinoinensis (Wangenh.) K. Koch) cultivar was first noted in greenhouse tests by rating cultivars for relative amounts of honeydew on adaxial leaf surfaces. This resistance was confirmed in two field tests monitored from mid-June to mid-October. 'Pawnee' supported significantly lower aphid populations during every rating period when relatively large numbers of these insects were present. 'Navaho' also showed resistance, with 'Desirable' having intermediate resistance and 'Stuart' being very susceptible. Insect populations were also monitored on the four quadrants of each tree, with this quadrant effect being significant in only one test. This test had the highest populations on the West and lowest populations on the East.