Alfalfa Growth May Outpace Weevil Damage

Some tip feeding and a few small alfalfa weevil larvae were apparent in Fayette County alfalfa on May 4 (Figure 1).  However, plant growth in established alfalfa fields should be far enough along that it would take substantial numbers of weevils to cause significant damage. Continue to monitor fields because larvae are still small; but assess situations carefully before making an insecticide application.

Figure 1. Alfalfa weevil larva and tip feeding damage. (Photo: Lee Townsend, UK)

Figure 1. Alfalfa weevil larva and tip feeding damage. (Photo: Lee Townsend, UK)

The cool, rainy spring has been ideal for aphid buildup in alfalfa. The pea aphid (Figure 2) is present in every field but rarely reaches damaging levels (50 or more per stem). While numbers drop off during the heat of summer, this aphid is present from April to November.

Figure 2. Pea aphid. (Photo: Lee Townsend, UK)

Figure 2. Pea aphid. (Photo: Lee Townsend, UK)

Light to moderate populations provide a host or food source for beneficial wasps (Figure 3) and predators such as lady beetles. Unneeded insecticide applications can knock out beneficial insects.

Figure 3. A small wasp will emerge from this swollen, tan, mummified pea aphid. (Photo: Lee Townsend, UK)

Figure 3. A small wasp will emerge from this swollen, tan, mummified pea aphid. (Photo: Lee Townsend, UK)

 

by Lee Townsend, UK Entomologist

 

Posted in Forages