–by Dr. Jeff Whitworth
Alfalfa weevils have been actively feeding and developing quite rapidly throughout south central and north central Kansas during the last 7-10 days. However, infestation levels have not increased very much. The most significantly infested fields monitored during this period reached the 55% level, i.e. just over 1 larva/2 stems. Most fields were between 25-35% infested, with about 75% of the larvae at least in the late 1st- 3rd instar stage. Some fields have been sprayed and it seemed to provide good knockdown (see fig. 1 of dead larvae). All fields not treated had prepupae and pupae (see fig. 2). Alfalfa weevil larval sampling/monitoring should continue for at least another 10-14 days.
Pea aphid populations have decreased significantly in the last 7-10 days in the untreated fields.
Figure 1: Dead Larvae (photo by Cody Wyckoff)
Figure 2: Alfalfa Weevil Pupa (Photo by Cody Wyckoff)