Peanuts have responded well to the mild temperatures that have been experienced this season. While warm temperatures have been experienced intermediately, temperatures in mid-July were unseasonably cool. Accompanied by overcast conditions and high relative humidity, flowering, pegging and early pod set are excellent. These conditions have also helped reduce the evapotranspiration rate allowing for the peanut canopy to fully develop.
As a result, many of the row middles for runner and virginia-type peanuts have lapped. Planting patterns of more upright growing types, such as Spanish, are more obvious, especially in fields with wider row spacings.
Peanut Disease Update
While the environmental conditions are generally good for peanut growth and development, these same conditions favor the development of many of the peanut diseases seen in the Southwest. There have been reports of early leaf spot since the middle of June, however this disease has been easily maintained with fungicide applications targeting pod rot, or applications made directly for leaf spot.
In addition to leaf spot, reports of Sclerotinia blight have been coming in from both the High Plains and the Rolling Plains. While most fields with a history of the disease have either been rotated, planted to a resistant variety, or previously treated, it is important to remain diligent and continue to scout and manage in order to minimize potential losses.
Another disease to be mindful of at this time is the pod rot complex, caused by Pythium spp. and/or Rhizoctonia solani. Many fields with a history of this disease have received preventative applications that were made anywhere between 60 and 75 days after planting. Subtle differences, such as the appearance of the infected pods (greasy or dry rotted) can be used to differentiate the two pathogens. This is important when it comes to selecting the proper fungicides to apply.
Several factors including pathogen pressure or field history, fungicide selection, as well as application timing and application method may effect disease control.
Other diseases that have been observed within the last 2 weeks are Southern blight, caused by Sclerotium rolfsii, limb rot, caused by R. solani, and root-knot nematode (Meloidogyne arenaria). The two former diseases are fungal diseases which often cause inconspicuous symptoms but are easily managed with fungicide applications made to control Rhizoctonia pod rot.
Root-knot nematodes are less widely distributed than the other diseases mentioned. Above ground symptoms consist of poor growth and severe stunting, but infections may go unnoticed. Roots of infected plants exhibit abnormal growth or galls.