White heads and stem borer in wheat

Every year we receive reports of white heads in wheat, and while there are sev­eral pos­si­ble causes of this symp­tom, one sus­pect impli­cated in the crime is a small stem bor­ing larva called Ephys­teris silig­ni­tis (Turner) belong­ing to the moth Fam­ily Gelechi­idae.

Rod Collins and Hugh Brier did some inves­tiga­tive work back in 1998. They reared a cou­ple of lar­vae through to the adult moths and had them iden­ti­fied by ANIC.

Rod Collins made the fol­low­ing obser­va­tions: “The dam­age was usu­ally con­fined to a sin­gle tiller per plant at a rel­a­tively low inci­dence through fields. Infected tillers seemed to have flow­ered nor­mally, but soon after flow­er­ing the stem upwards from the last node (and includ­ing the head) died and was white in colour with no grain in the head. From a dis­tance, these symp­toms appeared to be the same as those of crown rot. How­ever, infected tillers were green and appar­ently healthy from the last node (includ­ing the flag leaf) down. On closer exam­i­na­tion, a small entry hole about the size of a pin­head was evi­dent usu­ally at or just below the first node up from the base of the plant. In some cases an exit hole was noted just above the last node.”

When the stem was split open, you could fol­low where the larva had been up until the last node, where it was often found feed­ing on the tip of the stem just above the last node. In some cases, the larva had chewed through the tip and con­tin­ued to move upwards towards the head. It appeared that once the stem began to dry out, the larva would bore a hole in the stem and exit. Only one larva was found per stem in all the plants that I saw.”

It seems not much is known about this species. It is believed to be a native species, one of three in this genus found in Aus­tralia. Ephys­teris promptella is recorded as a pest of sug­ar­cane in Aus­tralia. Ephys­teris silig­ni­tis occurs widely in Aus­tralia south to about 35 degrees south and is thought to be con­fined to Aus­tralia. It is in the wettest parts e.g. Bris­bane and Mt Bel­len­den Ker and the dri­est. It is com­mon at Alice Springs. It was sug­gested that it may feed on grasses but there was no evidence.

Stem borer larva in wheat (Photo by Iain Macpherson)

At this stage the reports of iso­lated ‘white heads’ do not rep­re­sent eco­nomic loss, but this stem borer is some­thing to be aware of if those scat­tered white heads are observed in fields. There is no reg­is­tered chem­i­cal control.

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2 Comments

  1. Kieran O'Keeffe
    Posted November 11, 2009 at 1:05 pm | Permalink

    We have seen for many years a few white heads on the edge of wheat and rice crops and on closer inspec­tion it is caused by Bathytricha trun­cata (Sug­ar­cane and maize stem borer). Last sea­son we had a few maize crops that started to lodge and in split­ting open the stems it was being caused by Bathytricha. We are keep­ing a close eye on maize crops near wheat this sea­son but have drawn a blank on what we can do if the prob­lem occurs again. I have some inter­est­ing pics from last year

  2. Warwick Nightingale
    Posted September 19, 2012 at 9:45 pm | Permalink

    Is any­one see­ing these in south­ern NSW this season?

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