Industrial hemp farming is facing growing pains in its first year as a legal agricultural product at the federal level.
Now, farmers and police have identified another of these possible headache areas. They call it cross-pollination, the process by which seeds are exchanged between outdoor hemp and marijuana fields, causing legal and labeling ramifications for both the farmers, manufacturers and consumers of both products.
The cross-pollination problem may also cost thousands of dollars in unusable yields for both producers, according the New York Daily News. 
When retailers see the THC content of marijuana flower is reduced because the yield is cut with accidental infusions of industrial hemp, they may be less likely to buy it or even to trust the farmer.
Likewise, when law-enforcement detect that levels of THC, the active ingredient in marijuana, exceed 0.3% in a given hemp crop, they will be rendered illegal and liable to seizure. In a cross-pollination scenario, both hypothetical farms would be out tons of product and profit from no fault of their own.
New U.S. Dept. of Agriculture rules allow for a grace window of up to 0.5% THC before the hemp becomes an illegal sample, but that doesn’t mean police always know how to handle confusing substances.
This summer, a Colorado hemp driver was arrested in South Dakota hauling hundreds of pounds of what he called hemp and CBD, but which police claimed tested positive for THC at illegal levels.
The USDA guidelines explicitly recommend that police allow hemp shipments to pass between states unmolested. South Dakota has not legalized CBD at the state level.
According to the Arkansas Democrat Gazette, New York police bragged recently about a similar bust in which they claimed to have seized over 100 pounds of marijuana.
A store-owner accused in the case claims that the entire trophy consisted of industrial hemp. 
“The farm's lawyer, Timothy Fair, said that before the hemp shipment left Vermont, it was tested at FedEx's request by a local police department,” the Democrat Gazette reports. “The level of THC was less than half the allowable threshold, he said.” 
There are fixes to the problem of open-air cross-pollination. Distance is a relatively reliable method, though not avoidable in existing farms. Likewise, hydroponic systems that allow for indoor hemp and marijuana cultivation are already highly popular (no pun intended).
Still, the best medicine for this confusing and frustrating side-effect of the increasingly liberal state and federal laws toward marijuana and hemp is likely to emerge over time as farmers, retailers and police work to smooth out the rough edges.