Slow Growth, Fast Growth: Peanuts and Thrips
The recent cooler weather, especially the nights, slowed down peanut growth. This means it also reduced the uptake of in-furrow, at plant insecticides designed to provide thrips protection. As a result we get kicked while we are down. The peanuts are slow growing so it gives the thrips a chance to really “work ‘em over” and the plant doesn’t have the ability to outgrow the feeding injury. While this is happening, the reduce rate of the roots picking up the insecticide and moving it to the upper portions of the plant allows the thrips to keep feeding without ingesting a lethal dose of the insecticide. That’s a double whammy.
What to do? That’s a hard question to answer. Here’s my generic response. If you got some rain in the last day or two, the warm temperatures will result in a big jump in growth and move the insecticide throughout the plant so good control should be the result. If you didn’t get much rain, then the plant will take up less of the insecticide even with the warmer temperatures and control won’t be quite a s good. Does this mean any and all fields that have received limited rainfall need to be treated? No, only those fields that are suffering from a lot of thrips injury should get a spray if soil moisture isn’t real good right now. . There’s a good chance we’ve reached the peak of thrips activity, so giving the plant a little kick in the pants will put it right where it needs to be this time of year. Even some fields that have good soil moisture may be taking a beating from thrips and you might feel a spray would really help get the peanuts moving along much faster.
Thrips sprays are cheap and if you’ve got a lot of damage, you aren’t throwing money away with an application. If you want to make sure, take a white piece of paper or board and pull off some unopened leaflets and slap them against the white surface. If you see a lot of tiny, yellow, almost wormlike bugs on the surface, then you have a lot of immature thrips feeding and these will continue to cause damage for several more days. If you have damage, but don’t see any thrips on the white surface, then either the population has dropped or your insecticide has kicked in and is protecting the plant now. The bottom line is to not treat if you can’t find any thrips in the unopened leaflets. Don’t worry about the thrips spray flaring mites since April wasn’t particularly hot and a warm April always creates concerns about early spider mite outbreaks.
Article first appeared as North Carolina Peanut Note (PNNC-2012-023)