No concern for tell-tale holes

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Corn ear­worm lar­vae on veg­e­ta­tive sorghum crops pro­duce char­ac­ter­is­tic holes in the leaves after feed­ing in the throat of the plant. These tell-tale signs are of no great con­cern as this type of feed­ing will not affect crop yield.

Cap­tion: BEB alias Austin McLen­nan show­ing a char­ac­ter­is­tic holey sorghum leaf.

The recent pres­ence of high num­bers of corn ear­worm, Heli­cov­er­pa armigera, on win­ter cere­als and chick­pea could her­ald the begin­ning of a busy time ahead for grain sorghum in south­ern Queens­land.

As lar­vae on cere­al crops mature, they climb down the plant and bur­row into the soil to pupate. Moths emerge from these pupae 2 to 3 weeks lat­er, and start the next gen­er­a­tion by lay­ing eggs on suit­able host plants.

Veg­e­ta­tive sorghum is attrac­tive to egglay­ing moths, and lar­vae hatch from new­ly laid eggs in 3 to 4 days. Sur­vival of lar­vae on veg­e­ta­tive crops may not be high, but veg­e­ta­tive sorghum can be an impor­tant inter­me­di­ate host that bridges the gap between win­ter and sum­mer.

Army­worm lar­vae may also be present in veg­e­ta­tive sorghum. Army­worm lar­vae cause sorghum plants to look ‘ragged’, but again this leaf feed­ing does not result in any yield loss in advanced and active­ly grow­ing seedling crops.

Con­trol of lar­vae on veg­e­ta­tive sorghum is gen­er­al­ly not rec­om­mend­ed as the dam­age is cos­met­ic and unlike­ly to affect yield.

While corn ear­worm lar­vae are adver­tis­ing their pres­ence in south­ern Queens­land grain sorghum crops, of great­est impor­tance are lar­val infes­ta­tions after flow­er­ing and dur­ing grain fill.

Egglay­ing by corn ear­worm moths and lar­val man­age­ment on sorghum heads will be the sub­ject of a future post­ing.