Netting can confound the retrieval of spectral properties of the crop. If the net is in between the crop and the camera then it could cause tremendous issues but it may depend on the netting method you are using.
If the netting is elevated and taut above the crop, then it may not make a huge difference. However, if the netting is not stretched perfectly and evenly across the crop then areas where it sags more or less will show differences due to the netting, not the crop. For an example of how netting can affect reflected light, look at the maps below of an apple orchard. There is a gap in the middle where the net does not cover. As you can see, areas with the net have drastically lower NDVI values. If you use the histogram slider, it is possible to focus on NDVI values within the netting; however, it is difficult to know whether these values are accurate since the net is mediating the light. Therefore, we can't guarantee accurate results for any application if nets are present.