THE release of the new subterranean pasture variety, Narrikup, at the Dowerin GWN7 Machinery Field Days last week was too little too late for many pasture growers in the Esperance region whose farms' stock carrying capacity has fallen by up to one-third.
During the winter and early spring months since 2007 growers in the Jerdacuttup and Munglinup districts have reported distressed subterranean pasture crops suffering from reddened leaves which often resulted in the death of patches of pasture.
Originally thought to be a red clover leaf virus, some pasture experts including Department of Agriculture and Food WA (DAFWA) senior research officer Brad Nutt don't believe this to be the case.
Affected clover plants were readily found with stunted growth, deep red or orange-red leaf edges and necrosis and red coloured petioles.
In a large number of cases many plants also had bronzing and flecking on the surface of the leaves.
Clover plant deaths also occurred in a large number of Esperance paddocks ranging from five to 10 per cent of paddocks in some of the less affected paddocks to 100pc in others.
This year the condition made a resurgence and pastures as far north as Salmon Gums and Cascade were now affected.
In 2007 none of the tested samples gave a positive response to Subterranean Clover Red Leaf Virus and no symptoms of root rot were found in any live plants.
The sod samples with red leaves that were collected in the field recovered their green colour and vigour after about three weeks in a DAFWA glasshouse which indicated some nutritional deficiencies may have been present in the paddock and overcome in the glasshouse with fertiliser application.
But Mr Nutt believed the condition was prevalent in the Esperance region this year due to a combination of factors.
He said this time around the Red Clover Leaf Virus had again been ruled out as a leading cause.
"It seems to be occurring because of the compounding of a number of stresses," Mr Nutt said.
"Much of the red pasture was found to be growing in soil with a pH level below five.
"As far as I can tell the combination of acidity, root rot and an extended period of dry have much to answer for."
Mr Nutt recently travelled to Esperance to carry out tests and get a scope of how widespread the situation was.
"The plants just couldn't absorb any nutrients, phosphorus in particular," he said.
"In some parts near Cascade entire paddocks were covered with red clover.
"It has happened intermittently for some years throughout the Wheatbelt but for such a high rainfall zone as Esperance it is a very unusual occurrence."
Mr Nutt bought samples of plant specimens back to his Perth lab and replanted them in a range of different soil conditions to find that most samples recovered well.
"It has an immediate impact on the amount of stock many farmers can carry but it also has a flow-on effect," Mr Nutt said.
"Those clovers aren't setting seed and paddocks aren't receiving the rotational benefits because they aren't fixing nitrogen back into the soil."
He suggested serious liming programs could be the answer to the problem and growers should think seriously before committing to clover-on-clover rotations.
In the short-term he suggested growers switch to a variety with more acid tolerance like some of the Serradella breeds.
"I wouldn't be keen to plant any variety of sub-clover until the problem is fixed," Mr Nutt said.
"Otherwise it will just be like a dog chasing its tail."
Esperance's Association for Sheep Husbandry Excellence, Evaluation and Production (ASHEEP) is currently working with DAFWA to establish the prevalence of red and dying clover in the region.