The following update was prepared by Clemson Peanut Specialist Dan Anco.
What is the treatment threshold for threecornered alfalfa hopper? Good question. At this point we don’t really have a good answer linking insect or girdling counts to economic yield impact. Still, most of the products labeled for threecornered alfalfa hopper (TCAH) are broad spectrum insecticides.
Threecornered alfalfa hopper
While more of a concern during periods of hot dry weather, products like these have the potential to kill beneficial insects and flare spider mites. Because of this I would probably err on the side of caution in most cases where the risk of damage from TCAH may be questionable. Fields with large to excessive amounts of vine growth (irrigated fields, most Virginia types or some of the larger runners) probably can tolerate more TCAH than fields with less growth.
Vine girdled by threecornered alfalfa hopper. Photo by Dan Anco.
If peanuts are starting to show signs of manganese deficiency near 95 to 100 DAP (about 20% of plants), would it payoff to apply additional manganese if it previously went out at 60/75 DAP? At this point I would not add additional manganese. Some of the new growth may currently be showing manganese deficiency, and adding more Mn may green the leaves up some, but at this point in the season more Mn hasn’t been linked to improved returns. As we get closer to the tail end of the season, peanut leaves can start to show signs of nutrient stress when they are supporting a large crop, since more of the nutrients are flowing to the developing seed.
Most of the crop continues to look good. As these next few weeks roll out, keep an eye out for late leaf spot lesions and then pod maturity.
Source: Clemson Cooperative Extension PeeDee, Peanut Update – Threecornered Alfalfa Hopper and Late Season Mn