Evaluation location: Texas, United States
Each entry was replicated 15 times. Three seeds of each entry were planted in 4-inch square pots using a 2:1 topsoil: sand mix. After germination, each pot was reduced to one healthy plant. These plants were allowed to grow until they reached the four true leaf stage. Each pot was then infested with five sugarbeet root aphids. Aphids used for infesting the plants were taken from a bulk greenhouse culture reared Chenopodium quinoa. Potted, infested plants were arranged randomly in groups of three in flats with a row of empty pots separating each group of three. Greenhouse temperature was approximately 20 degrees C and plants were manually watered as needed to keep the soil moist and prevent aphids from drowning before colonies established. Plants were allowed to grow undisturbed for six weeks.
After six weeks the infestations were evaluated. Plants that died from causes other than sugarbeet root aphid damage, before the evaluations were made, were not included in the analyses. Plants were removed from the pots, and the severity of the infestation was determined by floating aphids out of the root mass in 12 cm diameter x 8 cm deep bowls filled with water. Level of infestation was rated between 1-4 for each plant. Classifications are as follows: 1 - no nymphs or adults present; 2 - nymphs present, no adults present; 3 - nymphs present, few adults present; 4 - nymphs present, many adults present. Aphids were classified as adult using the presence of the sub-genital plate as an indicator of maturity.
Data were analyzed by analysis of variance and the Student-Newman-Keuls test was used to separate significantly different means (p=0.05). The results of the 1-4 rating.
For an Excel (xlsx) file of Michels screening data from 1995 to 2010