And there we go again in Georgia. “Feast or Famine”. Too much rain or we can’t buy a rain. Cool and wet soils to hot and dry soils. Feast or famine.
Environment plays a key role in the treat of diseases to our row crops. For example, in my now 25 field seasons in Georgia I do not ever remember finding Pythium on peanut seedlings; this year Laxmi Pandey, the new sherif in the diagnostic lab in Tifton, has found it on a handful of peanut samples you have submitted. In conversations with Dr Tim Brenneman Saturday night, he too has been seeing Pythium on young peanut roots and agrees it is all about the cool, wet early season.
Jump ahead to now- pic 1 is from Cale Yarbrough in Grady Co. The peanut seedling in his hand is on its way to a certain death from Aspergillus crown rot (note the ring of sooty black spores just at the top edge of the lesion.) Aspergillus crown rot is more severe during periods of hot, dry soils as the these damage the tender young shoot and allow for infections to develop. Quality seeds, effective seed treatments, Velum in-furrow, irrigation and rainfall to cool the soil, and control of lesser corn stalk borers all help to reduce stand loss to Aspergillus crown rot and subsequent increase risk to tomato spotted wilt.
Pic 2 is from Jeremy in Colquitt Co. While these are “spots on leaves” they are not early leaf spot or late leaf spot diseases. These symptoms are most likely associated with use of Thimet in-furrow at planting, or could also be “leaf scorch” caused by the fungal pathogen Leptosphaerulina crassiasca. Either way, neither is typically anything more than cosmetic. HOWEVER anything which leads to early-season defoliation of a peanut crop can fuel and early outbreak of white mold. The decay of the leaves can trigger germination of sclerotia of the white mold pathogen until recently known as “Sclerotium rolfsii”.
Peanut situation: hot and dry increases risk to Aspergillus crown rot, decreases risk to leaf spot diseases, and COULD increase risk to white mold.
Pics 3 and 4 were sent to me by a consultant scouting corn in Baker Co over the weekend. Southern corn rust could be anywhere across the Deep South of Georgia now but we have NOT seen a jailbreak north yet. Please keep the samples (corn, kudzu, and soybean samples coming)
Pic 5 and pic 6 are screen shots this morning of national monitoring efforts for southern corn rust and for soybean rust. Thanks to so many of you for your efforts.
