We’ve done a lot of insecticide evaluation in the last two weeks, and the common theme is that the best treatments are still providing good control. Our go to treatments of Bidrin (6-8 oz), Acephate/Orthene (0.75 lb), Transform (1.5 oz) are top performers, providing 75 percent to 80 percent control.
Other top performers are Acephate or Bidrin tank-mixed with a pyrethroid insecticide. I lean toward these mixes as we progress into the bollworm window. Diamond also has added some consistent improvement in plant bug control when mixed with just about anything. Of course, tank-mixing any decent plant bug insecticide with another should improve control, but putting the unique mode of action of Diamond to use makes sense in our high pressure areas.
Bad treatments still stink. Do not use a pyrethroid insecticide applied alone for control of tarnished plant bug. By themselves, these products are providing less than 30 percent control after two applications. Imidacloprid products such as Admire Pro or imidacloprid + pyrethroid pre-mixes (e.g., Brigadier) are not providing acceptable control of tarnished plant bugs. I’ve also seen a slip with Endigo over the last two years, although control with this product is still acceptable.
Our pyrethroid resistance is now so complete that pre-mixes that include a pyrethroid have lost some of their punch. Avoid the neonic/pyrethroid pre-mixes during peak bloom when plant bugs are the primary pest. This includes Leverage, Endigo and Brigadier which I think will have a better fit at the tail end when bollworm and stink bugs become a greater concern.
Corn earworm flight expected soon
I’m expecting our corn earworm flight to start kicking off this week. Given the fair amount of late-planted soybeans in the state, we need to be alert for infestations in soybean during August. Normally, our worst infestations of corn earworm in soybeans occur in the Mississippi River bottoms, but they can potentially occur anywhere. The recommended treatment threshold for corn earworm in soybeans is 9 larvae per 25 sweeps.
Against high infestations, Belt SC, Prevathon, or Besiege will provide extended residual control. I’ve also had good results with Steward and Tracer, although you should expect less residual control. Avoid the pyrethroid insecticides if infestations are well above threshold. Their performance has been inconsistent in recent years, and they do not provide effective residual control more than 7 days (less if it rains).
A new product, Intrepid Edge, may be worth looking at on a limited basis. It is a pre-mix of Intrepid and spinetoram (e.g., Radiant). However, I’ve not tested this product against corn earworm. It is labeled at a rate of 4 – 6.4 oz/acre. This should be an excellent treatment for soybean loopers, but I’m concerned the spinetoram rate is too low for corn earworm.