Jordan Column April 2021 Issue Peanut Grower Magazine IPM Peanut Notes No. 19 2021
As we move into the season we often think in terms of preventive treatments versus reactive treatments to address agronomic issues and pests. In reality we use both approaches. This is in part based on logistical constraints and the ability to be timely with inputs needed to correct a problem. We also may need to incorporate effective practices that prevent or minimize a problem ahead of time because we may not have a tool that is corrective once something develops. Our ability to address issues rapidly and completely is important for us to protect peanut yield. If we are unable to do that we better do something ahead of time that keeps the issue from exploding and causing yield and financial loss.
I recently read a “letter to the editor” in the periodical Science titled, Stay True to Integrated Pest Management. The discussion was general and not specifically related to peanuts. The letter implied, based on my understanding, that using seed treatments of insecticides was not consistent with the goals of integrated pest management (IPM.) This got me thinking about how we decide if a practice should be defined as a principle of IPM. This is important for me because I think managing pests using IPM principles is critical (and because I teach the IPM course at NC State University and want to get it right.) We often think of IPM with respect to monitoring pest populations during the crop cycle once it has emerged, most often insects, and then treating based on economic thresholds that are established (based on numbers of the pest or levels of injury caused by the pest in relation to the impact on yield, crop price, and cost of the treatment.) This is certainly a core component of IPM. But knowledge and monitoring occurs well before the crop is planted, especially with peanuts. What happened in the field years ago needs to be considered.
Effective fungicide seed treatments are essential in protecting peanut seedlings from pathogens and the diseases they cause to get an adequate stand. There is no substitute other than an in-furrow application of fungicide. Our stands will be low if we do not treat, even when seed quality is good. We also know in North Carolina that if insecticide is not applied to suppress thrips we will get a yield hit in most fields. One can certainly wait until peanuts have emerged to apply insecticide, but a more effective way from a logistical standpoint is to apply a systemic insecticide in the seed furrow at planting.
For both seedling diseases and thrips, we know fields will exceed the economic injury level if a control practice is not used, and an effective way to suppress these is to use a preventive treatment as the crop is being planted. Even deciding to use a resistant variety for a disease is done when we plant and not after the peanuts emerge. This too is a core component of IPM because we are using knowledge from the past and making a decision based on the economic impact. We also have to take into account the yield of a resistant variety versus a susceptible variety if the pest is either controlled in some other way (in the case of a susceptible variety) or the pest does not develop (in the case of a resistant variety.) What is the financial impact in both of these scenarios? Just because we don’t automatically plant the resistant variety does not mean we are ignoring IPM principles. And of course, we would have major yield losses in peanuts if we did not use PPI and PRE herbicides. We just know our weed populations will be high enough in most fields to justify herbicide use, and practical knowledge informs us that relying only on POST herbicides is not always (and in fact seldom) completely effective.
There is nothing wrong from an IPM standpoint with using herbicides in a preventive manner. There are many risks to peanut yields and we have many tools to address these risks. The more we know about the history of fields and production in those fields, the more effective we can be with IPM. Preventive treatments are just as much a part of IPM as the reactive treatments. IPM depends on our knowledge of the pest both historically and contemporarily and the availability and effectiveness of the tools at our disposal.