Seeds that float in the air can hitchhike in unusual places – like the air-intake grille of a refrigerated shipping container. This is the finding of a team of researchers from the USDA Forest Service, Arkansas State University, and other organizations, from a study that involved vacuuming seeds from air-intake grilles over two seasons at the Port of Savannah, Georgia.
The viability of such seeds is of significant interest to federal regulatory and enforcement agencies, and the project required a shared stewardship approach.
The team’s findings were published in the journal Scientific Reports. Seeds from 30 plant taxa were collected from the air-intake grilles, including seeds of wild sugarcane (Saccharum spontaneum), a grass on the USDA Federal Noxious Weeds List.
Federal noxious weeds pose immediate, significant threats to agriculture, nursery, and forestry industries. Although a lovely grass and useful in its native range, wild sugarcane has the potential to join cogongrass, stiltgrass, and other nonnative species that have become extremely widespread in the U.S.
During the two shipping seasons, we estimate that over 40,000 seeds from this species entered the Garden City Terminal at the Port of Savannah. This quantity of incoming seeds is more than sufficient to cause introduction and establishment of this nonnative invader, even If the escape rate from the shipping containers is limited
says Rima Lucardi, a Forest Service researcher and lead author of the project.
To estimate the chance that seeds would survive and establish in the U.S., Lucardi and her colleagues analyzed and modeled viable seeds from four plant taxa. All are prolific seed producers, wind-pollinated and wind-dispersed, and able to persist in a wide range of environmental conditions and climates.
The researchers propose several possible strategies for reducing risk to native ecosystems and agricultural commodities. For example, instead of labor-intensive vacuuming of air-intake grilles, a liquid pre-emergent herbicide could potentially be applied to containers while in port.
Prevention and best management practices, from the farm to the store, reduce the probability of nonnative seeds establishing in the U.S. Inspection for exterior seeds hitching a ride on shipping containers at their points-of-origin or stops along the way would also reduce risk of invasion.
Preventing nonnative plant invasions is much more cost-effective in the long run than trying to manage them once they have spread and become widely established.
The team had previously shown that the Port is a hotspot of nonnative plant diversity and richness.
