Dry Heat and Exposure Time Influence Divine Nightshade and Itchgrass Seed Emergence

In Louisiana, growers remove sugarcane ( Saccharum spp. hybrids) residue following green‐cane harvesting by prescribed burning. Divine nightshade [ Solanum nigrescens (Mart. & Gal)] and itchgrass [ Rottboellia cochinchinensis (Lour.) Clayton] are problematic weeds in Louisiana sugarcane production. The objective of this study was to determine the effects of dry heat and exposure duration on divine nightshade and itchgrass emergence. Divine nightshade and itchgrass seeds were exposed to three temperature levels (100, 150, and 200°C) for seven exposure timings (0, 5, 10, 20, 40, 80, and 160 s). Exposure to 150 and 200°C for 5 to 20 s reduced divine nightshade emergence 6 to 29%. Divine nightshade emergence was not completely inhibited at 200°C for 160 s. However, itchgrass exposed to 150°C for 40 s or longer or to 200°C for 20 s or longer failed to emerge. Results from this study showed itchgrass seed could be controlled with dry heat, but prescribed burns that produced temperatures below 100°C or temperatures greater than 150°C for short durations may not control all divine nightshade seeds. The aforementioned temperature and exposure duration that allowed divine nightshade to survive introduced the potential for divine nightshade to become more abundant. Core Ideas Itchgrass seed exposed to 150°C dry heat for 40 s or more did not emerge. Divine nightshade seed was more tolerant to 150 and 200°C than itchgrass. Dry heat was an effective control strategy for surface deposited weed seeds.