Effects of Pesticides on Red Rot of Planted Sugarcane

Abstract

Red rot, caused by Colletotrichum falcatum, is an important constraint to sugarcane production. In Louisiana, red rot primarily affects planted seed-cane and is more severe when billets (stalk sections) are planted rather than whole stalks. At planting, application of seed-treatment pesticides, particularly a combination of a fungicide and the insecticide thiamethoxam, has improved stand establishment and increased yields in billet plantings in Louisiana. However, information on the effect of chemicals on disease development is lacking. Greenhouse experiments were conducted to evaluate stalk rot symptom severity and initial plant growth for billets dip-treated with a combination of the fungicides azoxystrobin and propiconazole, thiamethoxam, a combination of both fungicides and the insecticide, and, as a control, untreated billets. Reductions in disease severity recorded for different treatments were similar for billets inoculated with the fungus or exposed to natural inoculum. Disease severity was consistently reduced by the combination treatment, while reductions resulting from treatment with fungicides and insecticide alone were variable. Reductions occurred for both internode and node rot severity. The effects of pesticide treatments on plant growth after 6 weeks were minor; however, there was evidence of disease adversely affecting germination, particularly for nontreated billets exposed to natural inoculum, where germination was reduced by one third. The treatments that reduced disease severity prevented this reduction. The results provide evidence that reduction in disease severity is an important contributor to the stand establishment and yield improvements observed for treated billets in field experiments.

QTL Mapping and Candidate Gene Mining for Stem Diameter Using Genetic Basis of Cultivated Soybean and Wild Soybean

“…Lodging results in poor light penetration, reduced photosynthetic activity, worse dry matter accumulation, and decreases in nutrient absorption and transport efficiency [3,4]. When soybean varieties that exhibit severe lodging are susceptible to fungal diseases, this can result in greater than 60% yield reductions in severe instances [5,6]. Plant height is a key metric that is often used to assess plant lodging resistance [7], and areas Agronomy 2024, 14, 1019 2 of 16 with superior growing conditions can influence plant height, ultimately aggravating the challenges posed by lodging [8].…”