Is it even an issue at this point?
There was absolutely no information in March and April warning against radioactive fallout in the countryside in Fukushima, where many residents ate the wild mountain vegetables - seasonal delicacy. On the contrary, as we all know now throughout the world (I hope), the national government and the Fukushima prefectural government were busily dispatching the two Nagasaki University professors (Yamashita and Takayama) to brainwash the residents.
Now the Fukushima prefectural government says it will test wild mushrooms. About the only reason I can think of is that the prefectural government just wants to make sure they are contaminated beyond 500 becquerels/kg level, so that they can send the bill to TEPCO for non-sales. If they are contaminated but with less than 500 becquerels/kg level and people still don't buy the mushrooms, they will send the bill to TEPCO anyway for damages from "baseless rumor", also known as "radiation".
The testing probably has nothing to do with safety for the consumers. Remember, they, and everyone in the government or with strong ties with the government have been saying all along that if you eat food that contains radioactive cesium well exceeding 500 becquerels/kg, it is safe.
From Yomiuri Shinbun (8/3/2011):
Fukushima Prefecture announced on August 3 that it will test wild mushrooms in Fukushima for radioactive materials. The harvest season for wild mushrooms will start soon.
The testing will start within this week.
According to the prefecture's Agriculture, Forestry and Fisheries Division, the testing will done on 45 types of mushrooms sold at shops within the prefecture including direct sales depots.
If radioactive materials exceeding the provisional safety limit are found in a mushroom, the prefectural government will ask the municipality where the mushroom was harvested to voluntarily stop the shipment of the same mushrooms.
Still no information as to what caused the hothouse mushrooms to become radioactive.