While there have been lots of studies looking at the effect of greenhouse gasses on increasing temperatures around the planet, my question is what are the effects of emissions on food production.
Quantitatively hydrogen fluoride is insignificant, except when it is emitted from volcanic sources, in which case it is extremely toxic to crops - far more than any other natural gas. Possibly the worst recorded case was from Iceland when the volcanic eruption of 1783-1794 killed most if not all the crops and livestock downwind. The combination of fluorine poisoning and ensuing famine eventually killed some 10,000 people, or 22% of Iceland's population.
Strictly HF itself is not a 'greenhouse gas', but it reacts rapidly in the upper atmosphere to form other greenhouse gasses, such as CFCs, perfluorocarbons, and the extremely potent GHG, sulphur hexafluoride.
To add to Trevor's answer, FACE experiments have shown that elevated CO2 can affect grain quality and the food product.
Specifically looking at carbon dioxide, there's been a series of field experiments that involve artificially raising the local
CO2 levels for different plant species and seeing how they reallocate this carbon and develop. Results from the Free Air Concentration Experiments (FACE) have been published for the past 25 years and can be found in some pretty major journals.
Some major findings are that the expected yields from carbon enriched plant species aren't as high as previously estimated, and that the rise of ground level ozone associated with higher carbon levels is damaging plant capacity for photosynthesis.