The risk for blowfly strike in sheep is currently high throughout the country, warns Elanco Animal Health and the National Animal Disease Information Service (NADIS).
The two bodies have produced an interactive map, updated monthly, which predicts the emergence of blowflies based on Met Office data.
Professor Richard Wall of Bristol University said: "While blowflies are very active in the recent hot weather, the risk of strike is lower than might be expected, particularly for shorn ewes, because it is too dry for the maggots to survive.
“It is also too hot and dry for the parasitic worm larvae on pasture that lead to scouring in lambs. Scouring is one of the main factors that increase lamb susceptibility to blowfly strike.
“However, the strike risk will increase quickly once the dry weather breaks and so high levels of vigilance will be required."
The map can be found at alerts.nadis.org.uk/
Elanco also runs a blowfly tracker service which is automatically updated as blowfly strike cases are reported.
It is encouraging farmers, vets and SQPs to record any new cases on the tracker at farmanimalhealth.co.uk/tracker .