South East Local Land Services is advising Monaro producers who are grazing livestock on lucerne to check their animals and their lucerne plants following numerous reports of severe photo sensitisation in ewes and lambs last week.
Local Land Services was contacted by graziers from across the district who described their animals showing inflammation and scabbing around the eyes, ears and muzzles consistent with photosensitisation.
“Investigation of these reports has identified the presence of cowpea aphids in very high populations on lucerne plants within each of the paddocks” said Senior Agricultural Advisor Jo Powells.
“Cowpea aphids are shiny black with white and black legs. The nymphs are a dull grey and non-winged nymphs are black and shiny.
“They congregate along plant stems and under their leaves where they suck on the sap of the plant” said Jo.
It’s believed that cowpea aphids contain a photodynamic fluorescent pigment that can cause phototoxic effects in stock that are exposed to the plants they are feeding on. Whilst commonly reported on vetch crops as well as faba beans, chickpeas and lupins, medics including lucerne are also affected by the aphid.
“We are strongly encouraging land managers to check their lucerne for the presence of these aphids.
“If significant numbers are present, we recommend removing stock from these paddocks until the aphid numbers can be controlled or begin to reduce” said Jo.
Dr Petrea Wait, District Veterinarian for the Monaro is concerned by the rapid onset of the photosensitisation.
“We are seeing cases of a very severe form of photosensitisation in these sheep. The effects are being seen in all classes of sheep, including very young lambs, and we urge producers to check any sheep grazing lucerne.”
“The signs of disease include inflammation of the areas not covered by fleece, particularly the face, but also the udder of lactating ewes.
“These areas of inflamed skin progress to thick, crusted lesions of the muzzle, around the eyes and the ears.”
“Some sheep are being blinded by the extreme swelling of their eyelids, are unbale to eat due to lip lesions or develop mastitis secondary to udder inflammation.
“Lamb mortalities are also increased in these mobs.”
Affected sheep appear to recover quickly if they are promptly removed from the lucerne crop and provided with shade. Some severely affected sheep might need further veterinary treatment including pain relief if they are unable to eat, or antibiotic therapy if they develop secondary infections.
Aphid control options are available, consult your local agronomist. You can find more information about the symptoms and treatment options in the NSW DPI Prime Fact.