Not a Customs but rather an Agriculture issue (generally same inspection station). No, you may not bring the item in. If you declare it, will be seized. If you don't and get caught, it's a whopping fine. And, before you feel bad, there is a very good reason. One item can cause millions of dollars of damage to US agriculture. And, feel good - because if you like coconut, you can buy them at a local super market in the USA.