Dog owners are being advised not to let their animals jump into the lakes and ponds at Windsor Great Park after a toxic blue-green algae started to appear. A spokesperson for Windsor Great Park said: "Blue-green algae is a toxic, but naturally occurring algae, which blooms in warm, dry weather. It presents a danger when ingested. Following the recent milder weather, Windsor Great Park has been affected by blue-green algae in Obelisk Pond (Englefield Green), Wick Pond (Egham) and, now also, Virginia Water Lake." The spokesman said that signs had been put up in affected areas warning visitors about the algae and advising them not to allow their dogs to enter the water. He said measures had been implemented, including the use of barley straw extract to break down the algae. He added: "We continue to monitor the waters. However, the most effective treatment for the removal of blue-green algae is a period of cold or wet weather."