Under threat of attack, people rally in defense of their homeland.
That is exactly what the Missouri Department of Conservation is asking citizens to do as they head to the great outdoors for Independence Day weekend.
"Not too many years ago, you could travel around the country without too much thought about spreading pests that could devastate our natural world," said Invasive Species Coordinator Tim Banek. "Today, we need everyone to be aware of invasive species when they travel, even short distances."
Two prime examples, said Banek, are the zebra mussel and the emerald ash borer.
Neither was found in Missouri 20 years ago.
Both now have footholds here and require constant vigilance by boaters, anglers, hunters and campers to limit their spread.
In the case of the zebra mussels, preventive measures start by knowing where the fingernail-sized, black and white mollusks already are established.
Lake Taneycomo, Bull Shoals Reservoir, Lake of the Ozarks, Pomme de Terre Lake, Lake Lotawana, the Osage, Missouri and Mississippi rivers and the mouth of the Meramec River all are known to harbor the prolific mussels.
Boaters and anglers who use their boats in more than one lake or stream are urged to remove any clinging vegetation, drain and inspect boats and trailers for zebra mussels and allow them to dry for at least five days before relaunching in a new location.
Flushing live wells, bilges and motor cooling systems with hot water or chlorine bleach also is important.
The emerald ash borer is a green beetle that has caused millions of dollars of damage in forests across the Northeastern United States and the Upper Midwest.
Its habit of tunneling beneath tree bark, coupled with Americans' love of camping and campfires, has caused the pest to spread more rapidly than it might have otherwise.
Campers who take firewood with them from one campsite to another can carry emerald ash borer larvae, which emerge and infest new areas.
Campers can avoid spreading emerald ash borers -- along with other forest pests or diseases like the gypsy moth and the thousand-cankers disease of black walnut trees -- by obtaining firewood in areas where they camp and burning it all before leaving.
Even moving firewood from one campground to another in the same neighborhood can spread parasites and diseases.
Campers who accidentally move firewood should burn it immediately.
Even Missourians who plan close-to-home "staycations" can unwittingly contribute to invasive species problems. An excellent example is taking fishing bait from one place to another.
"Most people would never dream that catching crayfish in a pond or stream near home and taking them to a fishing spot a few miles away could cause serious ecological problems, but it can," said Banek. "Different crayfish species have very specific distributions. Moving one species into the next watershed can put larger, more aggressive crayfish in competition with the native crayfish and crowd them out. Over time, that leads to loss of biological diversity and undermines the stability of aquatic ecosystems."
Worms, minnows, crickets and other bait purchased from bait shops also pose potential threats to Missouri's wild resources. Banek urges anglers never to dump leftover bait.
"Just about everyone has thrown live worms or minnows into the water at the end of a fishing trip, thinking they will feed the fish, but we know better now. Invasive species sometimes slip into the bait supply chain and once they are loose, they can multiply."
He said the same is true of worms, which sometimes are imported from as far away as Canada.
You can find more information about how to prevent the spread of invasive species at mdc.mo.gov/landown/invasive.htm.