Field locations can often be many miles from the nearest source of supplies or drinking water. Many supplies used by nematologists may not be easily available at local stores.
It's a wise idea to take extras of everything that is reasonably possible. Plastic bags and labels, for example, have a way of taking wings and although it's more environmentally sensitive to chase them down, this may not always be feasible.
A recent television commercial taught many of us the importance of duct tape to the success of lunar exploration. It also seems to be useful in many ways for field trials. If it isn't needed to repair equipment or keep something in place, the roll is likely to be in use to prop something up at a critical angle or height.
Just making a list is often not enough. It's a good idea to check off items as they are placed in the vehicle to be certain they are not left behind on the laboratory bench.