Effect of depth of flooding on growth and fecundity of fall panicum (Panicum dichotomiflorum)

Abstract

Fall panicum is the most prevalent and problematic weed in rice in Florida. Outdoor studies were conducted in 2021 to determine the effect of flooding on fall panicum growth and ability to produce and develop panicles. Fall panicum at the two- to four-leaf and four- to six-leaf stages of development were flooded in stock tanks maintained at flooding depths of 0, 10, 15, 20, and 30 cm for 56 days. Plant height, number of tillers and leaves, leaf area, shoot biomass, root biomass, and panicle branches for both fall panicum leaf stages of development decreased with increasing flooding depth. Fall panicum flooded at two- to four-leaf stage survived flood depth of 15 cm while plants flooded at the four- to six-leaf stage survived and emerged from flood depth of up to 20 cm. The 10 cm flood depth resulted in the tallest plants with more leaves, tillers, and leaf area for both growth stages. The probability of fall panicum survival and ability to produce panicles decreased as flood depth increased. Flood depth required for 50% survival for four- to six-leaf stage plants was estimated to occur at 14 cm while that of two- to four-leaf stage plants occurred at 12 cm. The flood depth required to reduce panicle branch production by 50% was estimated to be 15 and 20 cm for two- to four-leaf and four- to six-leaf stage plants, respectively. These results show flooding >10 cm is required to significantly reduce fall panicum survival and ability to produce panicles. Since flood level in rice is usually maintained at averagely 10 cm, chemical weed control will be important to supplement flooding for effective control of fall panicum in rice.

Tolerance to drought and flooding events provides a competitive advantage for an invasive over a native plant species

“…Each water‐level treatment was replicated 15 times. The experimental period (111 days) was chosen to accurately assess the performance of U. mutica and P. dichotomiflorum as both plant species have rapid vegetative growth and can complete their life cycle within 60–90 days ( P. dichotomiflorum : Chiruvelli et al., 2023; as shown for two congenerics of U. mutica : Macedo et al., 2019).…”