Peanut Pointers: June 2023

Be Timely With Fungicides

Hopefully, everyone has finished up planting or is almost done by now. I know we didn’t get an early start to planting this year because of the cooler temperatures in April, which has seemed to be the trend the past few years. Still, here’s hoping everyone has a solid stand of peanuts and that the crop is off to a good start. 

Now’s the time to scout around for those early season weed escapes and clean them up while they are small and easy to control. 

Then, we need to begin our fungicide program. Disease control is one of the most expensive inputs in peanut production. Everyone wants to make the highest yield and save money by reducing the number of sprays. My advice is to start spraying peanuts for leaf spot when they are around 40 days of age. We don’t want to get behind and spend more money trying to play catch up, then still suffer yield losses in the end. 

You must get the fungicides on the plants before the disease gets established with the recommended rate and volume of spray for good canopy coverage. Also, I think banding some of the high-end fungicides early is an excellent way to cut costs and still provide good protection. There may be times to delay sprays later in the season that in the end wind up saving a trip across the field, but the first one is not the one to skip or delay. 

One last tip is to pull a pegging-zone sample about 2-3 inches deep in the row to ensure we have adequate calcium levels for pod fill. Gypsum is a great product when you have a high pH but a low calcium level. Also remember, gypsum is important on dryland acres since it is water soluble enough to allow it to enter the soil solution faster than lime when rains are scattered and sparse.

Look At Pegging-Zone Soil Test And Ca:K Ratio

A majority of the peanut crop is planted and off to a good start; however, growers did face a few obstacles along the way. Cool, wet conditions caused some stand issues in late April- and early May-planted peanut. The good news is that a majority of the crop was planted once temperatures finally warmed up, allowing peanuts a better chance to germinate and emerge. As we move into June, growers need to start transitioning from planting to managing the crop to ensure high-yield potential. Therefore, growers need to form a plan to protect the crop from pests and weeds and to provide peanuts with needed fertility. 

The No.1 way to protect the crop from pests is to hire a consultant or scout to provide feedback needed to make effective management decisions. This is especially helpful for insects and weeds. I know growers already have their fungicide programs in mind, but having someone scouting the crop can also help with changes in plans or chemistries if severe outbreaks occur. 

When it comes to needed fertility, calcium and boron are two important fertility components to be mindful of in June. Decisions on calcium and boron applications need to be finalized over the next few weeks. Currently, about a third of the crop is moving into the 40-to-60 days after planting range. If your soil test results indicate at least 500 pounds per acre calcium in the top 4 inches of soil (the pegging zone), AND a Ca:K ratio of 3:1 or higher, then you are not likely to see a yield response to calcium fertilization. However, all seed peanuts should automatically receive 1,000 pounds per acre of gypsum, no matter the calcium level in the soil. If you are unsure about a calcium product, put your fertilizer dollars into gypsum rather than an unproven or untested product. 

For boron, growers need to apply 0.5 pounds per acre. Boron applications can be achieved in a number of ways. The easiest method is foliar feeding at 0.25 pounds per acre tank-mixed with your first two fungicide sprays. Make product decisions wisely. Beware of products recommended at very low rates. For example, 6 ounces of a 5% liquid boron solution only gives you 0.025 pounds of boron per acre.  

If you need help in any way, call your county Extension agent. I hope everyone has a great production year.

Count Active Nodules To Determine Nitrogen Fixation

Four to five weeks after planting is a good time to scout for nodulation. Research has shown that nitrogen fixation of peanuts can occur with a broad range of Bradyrhizobium and other rhizobia strains. Nodulation and nitrogen-fixation activities of peanuts can vary widely depending on the storage of the inoculum, liquid versus powder, soil temperature, status with regard to salinity, fertility and acidity, water availability, crop rotation, fertilization practices, pesticide application, etc. 

In addition to the abiotic factors, nodule size also has direct impact on effectiveness and activity of nitrogen fixation. The highest nitrogen-fixation activity is correlated with medium size nodules (0.06-0.08 inch or >1.5-2.0 mm), compared with the smaller (<0.06 inch or 1.5 mm) or larger (>0.08 inch or 2.0 mm) size nodules. When scouting nodulation on your peanuts, it is a good idea to check nodule size as well as the color of internal tissue. Carefully dig plants and count the number of active nodulations. Active and healthy nodules should appear reddish-pink inside due to the reaction of leghemoglobin. Supplemental nitrogen is not required if an average of 20 active nodules per plant is observed. It is not common to apply additional nitrogen in the properly inoculated peanut fields. If supplemental nitrogen is required, 10 to 20 pounds per acre of  N should be sufficient, depending on the number of active nodules per plant and residual N in soil and irrigation water. 

Prevent Weed Competition And Interference

In the Virginia-Carolina region, I often consider June a transition month, especially as we move to the last week of the month. We have dealt with weeds and thrips as high priorities in May. I hope that our residual herbicides at planting, and likely paraquat and Basagran applied with additional residual herbicides, have been effective. Weed scientists often refer to the “critical period of weed control” as the first three to six weeks of the season. If we can keep the crop clean during that period, we have likely protected it well enough to optimize yield. 

Preventing early season weed interference is where we get the most out of our herbicide programs. However, peanuts are unique compared to some of our other crops. Because they never get very tall, it does not take much for a weed to get above the canopy. That fact, along with the need to dig and invert vines and because we make numerous fungicide applications, requires us to keep fields weed-free for the balance of the season. Our window for paraquat often ends in June (spraying within four weeks after peanut emergence) and we’ll need to shift to PPO inhibitors (Storm, Ultra Blazer, Cobra, 2,4-DB, selective grass herbicides, or Cadre/Impose). 

Our insect control needs to also shift from suppressing thrips to addressing rootworms, spider mites and foliar-feeding insects. We have good options for spider mites — if we are timely — and foliar-feeding insects. Pyrethroids are about 60% effective on corn earworms, while the more expensive products are almost completely effective and do not flare mites, in most cases. 

We do not have a chemical option for rootworms. There is a void in the absence of chlorpyrifos (Lorsban). In our research, we have not seen value in multiple postemergence sprays of insecticides to control adults. Some of these products are expensive when you consider three sprays. 

We encourage growers to apply gypsum later in the month, although I suspect by the time this column comes out, a lot of gypsum will have already been applied. My concern on early applications is big rain events we often get in early to mid-June when peanut plants are small. I hate to see soil and gypsum wash down to the middles. 

Planning for leaf spot and stem rot sprays is high on the list in June. Further south, many growers begin their fungicide sprays 30 days after planting. In the mid- and upper- V-C region, we recommend starting at about 45 days after planting but no later than July 10. Generally, temperatures are higher further south and peanuts have likely come up more quickly after planting, but inoculum for leaf spot can also be higher. This is why we can often get by with a five-spray program in North Carolina and Virginia compared with more sprays in Alabama, Florida, Georgia and South Carolina. We also refer to the R3 stage of growth as the starting point in North Carolina. This would be the case unless peanuts were planted late, and in that instance, we need to initiate sprays no later than July 10. 

As we move into July, do not forget to include manganese and boron. In most cases, these products can be applied with herbicides, fungicides and insecticides. Prohexadione calcium (Apogee or Kudos) will come later, well into July. PG