Back 4 Blood brings in a variety of new objectives for you to complete on your path to reaching the next safe room. In Act 1, Bad Seeds, you are directed to investigate a biomass form that has grown over some farmland. This tissue has also blocked your path from moving forward, so there is no choice but to get rid of it. This is an objective you will have multiple times through the campaign, but we will explain the first instance since it is very similar in all following iterations. Here is how to destroy the Nest Nodes in Back 4 Blood.
Before you begin looking for Nest Nodes to destroy, take a chance to scavenge the area for supplies. The small shed to the left when you first get to the farmland often has a First Aid Cabinet, and the house here can be entered to find items as well. When you are ready, make your way to the bridge.
At the bridge, you will see a bunch of wormy tentacles spreading from the main node. You need to destroy three smaller nodes before you can break this one. While there are no UI markers of where the nodes are, you can follow the golden strands of tentacles directly to them.
When you find them, you will notice some yellow balls poking out of the mounds of flesh. Destroy those, and a horde will be called in, but you will finish one of three.
From there, continue the same process of following the yellow in the tentacles to find the nodes you need to destroy. They can swap locations, but the barn is a pretty safe bet to find at least one of them (check the roof!). When you have all three destroyed, go back to the main node on the bridge, and you will see a big ball to shoot at. Destroy this node, and a trailer will drop into the river and float to an area where you can use it to cross. On the other side is a small cabin, and up the road is the safe room in an RV.