Sclerotium rolfsii (White mold) and Rhizoctonia solani are soilborne pathogens that cause white mold and limb rot, major diseases in peanut production. The most effective control of these diseases has been with good crop rotation and fungicides. Fungicides cost Georgia’s peanut farmers an estimated $80 to $100 per acre each year. Release of new varieties and promising fungicides could offer growers improved management options for white mold and limb rot. The objective of this research was to compare the economic return when either a reduced cost fungicide program or a premium fungicide program was applied to three different varieties (Georgia-06G, Georgia-07W and Georgia-12Y). The trial was established at the Vidalia Onion and Vegetable Research Center in Lyons, GA. The experimental design was a split-plot and each combination of treatments (fungicide program X variety) was replicated four times. Both programs included seven fungicide applications. The reduced cost treatment was developed around a 4-block tebuconazole (7.2 fl oz/A)/chlorothalonil (1.5 pt/A) program. The premium treatment was developed around a 3-block Fontelis (16 fl oz/A) program with a single application of tebuconazole/chlorothalonil as above. Peanuts were planted on May 28, dug on October7 and harvested on October 13. Plots were rated for leaf spot, TSWV, Rhizoctonia limb rot, and white mold. The most important diseases in the trial were Rhizoctonia limb rot and tomato spotted wilt virus.
This trial began as a white mold trial. However, no white mold was found in the trial. Rhizoctonia limb rot and TSWV became the most significant disease.
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Peanuts were sprayed 30 days after planting (DAP), 45 DAP, 60 DAP, 75 DAP, 90 DAP, 105 DAP, and 120 DAP with the fungicide. The premium program was Bravo, Bravo, Fontelis, Fontelis, Fontelis, Bravo + Tebuconazole, Bravo. The reduced cost program was Bravo, Bravo, Teb + Bravo, Teb + Bravo, Teb + Bravo, Teb + Bravo, Bravo. The previous crop was soybeans. Fertility and weed control was based on UGA Extension recommendations. The plot was irrigated 1 inch per week and increased to 2 inches per week after bloom and during pod fill.
-Three out of four of the top yielding fungicide programs were the reduced cost program Bravo/Tebuconazole.
-12Y has been previously documented to have a high yield potential. This research proves that 12Y also has a high susceptibility to Rhizoctonia limb rot. A premium fungicide program with 12Y may be a good investment.
-The highest yielding variety was O6G sprayed with the reduced cost program. The lowest yielding was O6G sprayed with the premium Fontellis program. The reduced cost program yielded 1,458 lbs. higher than the premium program in the O6G variety and had the least amount of Rhizoctonia limb rot in the trial.
-Under these conditions where limb rot was severe, varieties with less susceptibility to limb rot in combination with the reduced cost fungicide program would be the most profitable choice for growers.
-The only statistical correlation of disease and yield was with TSWV.
-The big question was the low yield on GA-O6G with Fontellis. We have never seen this, and there is no disease data to explain it here.
-The peanuts in the trial graded 73% and 75% SMK. Loan value was $358.79 and $363.03. For comparison, out of 2,055 loads at Southeastern Gin and Peanut, the average grade was 72.19% and loan value was $351.33. The peanuts in the trial were dug at 132 days based on the UGA Extension peanut maturity profile board. While other factors do contribute to peanut grade, I think more focus on digging dates based on using the peanut profile board needs to be followed. There’s no sense in losing money from digging early or late.
-Comparing the trial loan value to the average, there is a $12 per ton difference. $12 dollars per ton may not seem like a lot of money, but that could easily be $24 per acre, $12,000 across 500 acres and $24,000 across 1,000 acres. I strongly encourage growers to do a maturity check on peanuts on a regular basis next year during the digging season. Be sure the sample is pulled correctly and checked correctly if someone outside Extension is doing it.