Armyworms or Corn Earworm in Whorls of Sorghum

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I am getting multiple call about whorl feeding in milo. Fall armyworms or corn earworms are the likley culprits. The photos below were texted to me today by a client. It may look bad, but both sorghum and corn can tolerate a lot of leaf injury without affecting yield (especially when it is calf high or taller). It can make for an ugly and poopy mess, but infestations must be pretty extreme to cause economic injury.

The recommended treatment threshold for whorl feeding caterpillars is 75-100% infested plants. It is more common for this to occur with fall armyworm in late planted milo. It is difficult to achieve excellent coverage and control because the larvae are in the whorl and often relatively large when noticed. My suggestion is to scout and don’t get too excited unless you reach the threshold level above. Keep in mind that you can’t reverse injury that is already done. It is very possible the larva has already dropped to the ground to pupate from whorls with a lot of feeding sign. I would suggest Belt (2 oz/acre), Besiege (7 oz/acre) or Prevathon (14 oz/acre) if treatment is needed.

Hint – You can and should pull whorls to identify the larvae. However, there is a good chance you are dealing with fall armyworm if there are hot spots of infested plants or a very high percentage of plants are infested. With corn earworm, infested plants will usually be more randomly scattered across the field.

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