North Island farmers are being advised to take precautions to protect their stock from facial eczema as muggy weather conditions raise the risk levels.
The fungal disease affects mainly North Island farms in late summer and autumn as the spores that spread it to livestock multiply in the base of dried-out pasture.
Infected animals suffer liver and skin damage which in severe cases can kill them.
Leo Cooney of AsureQuality, which monitors the facial eczema risk, says spore counts have spiked across most of the North Island over the past week.
He says the risk is much lower compared with the same time last year because wet weather has kept the infection at bay.
But he says farmers should still take precautions because spore counts are expected to increase further over the next few weeks due to warmer weather.