Sources of Recurring Outbreaks of Lythrum salicaria (Purple Loosestrife) Near the Mouth of the Mississippi River
USGS researchers are examining germination of Purple Loosestrife to determine if the seed bank can reestablish this invasive species in the Mississippi Delta.
Science Issue and Relevance: Recurring outbreaks of Lythrum salicaria (purple loosestrife) may be linked to dispersal and long-term seed bank storage (seeds in the soil) on the Birdfoot Delta of the Barataria Estuary of Louisiana. This Eurasian invasive species could damage waterfowl, wildlife, and microbial habitats. While the species is common in northern wetlands, it has seldom been reported in freshwater wetlands of the Gulf Coast. However, one to five individuals were discovered in three locations near the mouth of the Mississippi River in 2018. The soil will be reexamined for loosestrife during 2024. This work will determine the distribution of seed bank storage in the Delta.
Methods for Addressing the Issue: Seed banks of Lythrum salicaria in former outbreak areas were lifted with a shovel by airboat on the Birdfoot Delta of Louisiana in October 2023. The former outbreak occurrences of loosestrife are near Pass-a-Loutre, south of Venice, Louisiana. The soil was transported to a greenhouse, where germination is being examined for one year to check if the seed bank can reestablish this invasive species. This work will determine the distribution of seed bank storage in the Delta.
Future Steps: Based on the findings of these studies, further work will be proposed to determine the routes of entry of Lythrum salicaria seed into the Delta (water, wind, animal). If a seed bank is not found, then it is likely that the invasion is recurring by dispersal. If seeds are stored in the soil, then alternate methods of removal will be recommended. It is likely that the invasions are made possible by soil disturbances created by hurricane or dredge spoil deposition, so that methods of restoring disturbed soil might be explored.
USGS researchers are examining germination of Purple Loosestrife to determine if the seed bank can reestablish this invasive species in the Mississippi Delta.
Science Issue and Relevance: Recurring outbreaks of Lythrum salicaria (purple loosestrife) may be linked to dispersal and long-term seed bank storage (seeds in the soil) on the Birdfoot Delta of the Barataria Estuary of Louisiana. This Eurasian invasive species could damage waterfowl, wildlife, and microbial habitats. While the species is common in northern wetlands, it has seldom been reported in freshwater wetlands of the Gulf Coast. However, one to five individuals were discovered in three locations near the mouth of the Mississippi River in 2018. The soil will be reexamined for loosestrife during 2024. This work will determine the distribution of seed bank storage in the Delta.
Methods for Addressing the Issue: Seed banks of Lythrum salicaria in former outbreak areas were lifted with a shovel by airboat on the Birdfoot Delta of Louisiana in October 2023. The former outbreak occurrences of loosestrife are near Pass-a-Loutre, south of Venice, Louisiana. The soil was transported to a greenhouse, where germination is being examined for one year to check if the seed bank can reestablish this invasive species. This work will determine the distribution of seed bank storage in the Delta.
Future Steps: Based on the findings of these studies, further work will be proposed to determine the routes of entry of Lythrum salicaria seed into the Delta (water, wind, animal). If a seed bank is not found, then it is likely that the invasion is recurring by dispersal. If seeds are stored in the soil, then alternate methods of removal will be recommended. It is likely that the invasions are made possible by soil disturbances created by hurricane or dredge spoil deposition, so that methods of restoring disturbed soil might be explored.