Column for June Issue of Peanut Grower Magazine Peanut Notes No. 41 2019
This is a little early, but June will be here before we know it.
In June effective weed management continues to be an important element of successful peanut production. Depending on planting and emergence dates paraquat (various formulations) may not be an option. Applications must be made within 28 days after peanuts emerge. Applying paraquat (along with Basagran and residual herbicides) is more effective when applied 2 to 3 weeks after peanut emergence. It is important to be as timely as possible with PPO-inhibiting herbicides for several reasons. First, they (Cobra, Ultra Blazer, and Storm) are more effective when applied to smaller weeds (less than 3 inches tall.) Secondly, when we apply these herbicides to larger weeds we often get incomplete control and that pushes us to resistance more quickly. We also need to optimize performance not only by being timely but also by applying higher spray volumes (20 GPA provides better coverage than 15 GPA, and 15 GPA provides better coverage than 10 GPA.) Coverage is important with contact herbicides like the PPO inhibitors. Reducing groundspeed is also helpful regardless of carrier volume.
By late June it is important to have developed a solid fungicide program for leaf spot and stem rot. Some of the fungicides we are using have slipped in their performance compared with control they provided for leaf spot in previous years. Rotating chemistry (sites of action) and being timely and achieving adequate coverage are important as we move into some unknowns relative to leaf spot control. Pathologists in all states in the peanut belt have excellent information on how to approach developing effective fungicide programs.
The general recommendation for Virginia market types is to apply gypsum at or shortly before peak flowering. This is often in late June and into July, although a significant amount of gypsum goes out in early June. In terms of thrips, populations are often lower and injury from feeding is less when peanuts are planted in early May than in late May or June. However, if thrips numbers are high and injury is significant, an application of acephate is warranted even with later plantings. There is some debate about the impact of thrips injury on yield and some are questioning the performance of acephate. As with leaf spot programs, consult local experts to know how to approach thrips in June. The further north one goes in the peanut belt the more important it is to make sure thrips populations are suppressed because of the truncated growing season in northern areas.
As you move later into June it is important to use caution when applying any insecticide as they can cause an increase spider mites. Hot and dry conditions and overuse of fungicides and insecticides can create conditions that escalate this pest. This is especially true for rootworms, and growers are advised to look closely at the southern corn rootworm advisory index when deciding on use of chlorpyrifos.
Late June is also a good time to consider boron and manganese applications. Manganese deficiencies are obvious in most cases while boron deficiencies are observed in pods at harvest. Most folks are applying these micronutrients across the board. Make sure you consider the actual amount of elemental boron and manganese when you select products. While some products are easier to handle and mix, they may not supply what is needed to correct a deficiency.
June is a good time to look closely at nodulation, especially in new peanut fields. If there is an issue with biological nitrogen fixation the sooner it is addressed with nitrogen fertilizer the better.
In June and July there will be a lot of questions about mixing products. Regardless of what you decide to do with mixes, it is important to avoid mixes that settle out and create problems with spray equipment. We also need to avoid excessive injury and marginal pest control.