Fukushima silk contamination?

I'm afraid that a major radiation exposure pathway could have been overlooked by not paying
attention to silk production after the Fukushima nuclear accident. I have read that the prefectures of
Fukushima and neighboring Gunma are renowned for silk production and thus understand that silk
cocoons are produced there. Silkworms feed on mulberry leaves. How has the radioactive fallout from the nuclear accident that has landed on these leaves and on the earth affected the silk cocoon production and how has it been controlled? The silkworms eat huge amount of leaves which suggests that the radioactive elements in Mulberry leaves enrich in the process. I have read studies on the effects on forests but nothing on sericulture. I'm afraid of silk contamination and its effects on end-users (plus workers in the process).

Does anyone have any facts or opinions to share?