It turns out that horses are a primary spreader of invasive weeds.

Some national forest districts do not allow hay fed horses into the forest. The horses must have a diet of native grasses and the like.

As for tires. It turns out that mosquitoes love old used tires. When it rains used tires end up holding nice little puddles of water that are ideal for mosquito breeding.

A few decades back, tire dealers would sell the tires and send them around the country for processing. This would spread the mosquitoes and any disease carried by the mosquitoes.

To contain the West Nile virus, governments restricted the sale of used tires. HEre is a page from Illinois. There are pages like this for every state.