Adjust your tone
Serious, worrying or bad news needs to be presented in the right tone. Not over-dramatic, certainly not flippant but with the tone of voice you would want to hear or read if you were presented with bad news.
Acknowledge the concern/distress/worry of those affected. Show your concern speaking/writing with clarity and brevity to explain the news honestly and clearly. Explain what is being done to resolve the situation. If you know when there may be more news and from who then advise on when this will be. Mention your role and professional capacity and authority to be giving the news. For example, “As a farmer affected by this disease outbreak, I know that …” or “As the leader of the research group working on this, I can say that since it was known …”
Direct your audience to further sources of information.
Make sure you are aware and follow your company procedure for breaking bad news. If you are unsure, speak to the relevant person within your company.