Evaluating selected yield parameters of glyphosate-tolerant sugar beet varieties subjected to sugar beet root aphid (Pemphigus betae Doane) infestation

The sugar beet root aphid, Pemphigus betae Doane (Hemiptera: Aphididae), is a pest of sugar beet in all the major sugar beet production regions of the United States. Apart from physical damage to the host plant, large populations of P. betae can induce significant reductions in yield, sugar content, and recoverable sugar. Unfortunately, control of this insect is complicated by its subterranean biology and by having no pesticides registered for its management. In 2010, a study was initiated at Scottsbluff, Nebraska to better understand P. betae resistance in several glyphosate-tolerant sugar beet varieties (Beta66RR50, Beta66RR60, CRR714, HM9042RR, HM9024RR, HM9027RR, HM4093RR, and Beta37RR22) subjected to two different tillage practices (conventional till vs. zone-tilling). Prior to this study, side-by-side comparisons of the reaction of these varieties to P. betae primarily had been studied in the laboratory. The study was conducted at four different aphid infestation levels (no infest, low-, medium-, and high infest) to test for the impact of varying aphid numbers on several yield parameters (sugar yield, sugar loss to molasses, top weight, and root weight) and to account for differences between varieties regarding these yield parameters. We also compared varieties based on the level of root aphid infestation (as indicated by a root rating index ranging in scale from 0-5) in order to validate the resistance against this pest in production fields, to help in managing this insect on sugar beet, and to better understand the yield reductions cause by P. betae in the field.