Below are a few words from Dr. Mark Abney, UGA Entomologist, on managing thrips in peanut.
Most of the insect questions we receive from growers in May are going to be about thrips. Usually thrips
questions in May mean something went wrong (or at least someone thinks something went wrong).
“The thrips are eating me up. Should I spray them?” The answer is: “It depends”.
When were the peanuts planted? Thrips injury is almost always most severe around 28 days after
planting, but spraying them then is generally not a good idea. By that time, the damage is done, and if
growing conditions are favorable the plants will begin to “grow out” of thrips injury within a week. If it is
hot and dry and/or the peanuts have herbicide injury, spraying might be justified, but it will still be late.
What insecticide was used at plant? There will almost always be some adult thrips on peanut seedlings
regardless of insecticide use. Peanuts treated with phorate (Thimet) or aldicarb (AgLogic) rarely require
any additional insecticide. Thrips injury is often worse in fields treated with imidacloprid in-furrow than
those treated with either of the granular insecticides, and the decision to spray fields treated with
imidacloprid can be tough. By the time we think a field that was treated with imidacloprid needs a foliar
insecticide, it is usually too late to do much good (we should still consider the weather and any herbicide
injury). I think most fields that are not treated with an insecticide at plant will benefit from an
automatic acephate application around 14 days after planting.
How many thrips are on the plants? Recently completed research at UGA suggests that the threshold
for thrips on untreated peanuts is 2 adult tobacco thrips per plant at 14 day after planting. It is not
uncommon to find two adult thrips per plant on treated peanuts, but we expect reproduction to be low
in treated fields. Immature thrips cause most of the injury. In fields where an insecticide was applied atplant, the presence of large numbers of immature thrips can indicate a problem with the in-furrow
application. When this happens, we have to go back to the first and second questions and consider if it is
too late to benefit from a foliar application.
When the decision is made to spray thrips, most growers will be using acephate. It is important that the
“peanut rate” is used…the “cotton rate” will not be effective in peanut. Cutting the acephate rate IS NOT
the place to save some money.
Another question is, “Will this foliar spray help reduce tomato spotted wilt?” Sometimes this is phrased
more as a statement: “I am going to spray thrips because I’m concerned about tomato spotted wilt”.
There are no foliar applied insecticides that reduce the incidence of TSWV.