Virginia Cotton: Planning for Insect Buildup

    Bollworm moth - corn earworm cotton square. Photo: Kate Harrell, County Extension Agent- Integrated Pest Management

    I’ve been hoping this buildup would wait coincide with the third week of cotton bloom which will occur during first half of August, but corn is looking mature and it could be close. I hate to spray anything right in front of a moth flight.

    • Bollworm moth trap are just being set out.
    • I was in a field with a lot of moths yesterday but the overall buildup should not be occurring yet.
    • The main 2 Bt gene variety is 1646 and will have some susceptibility to worms, but the 3 Bt gene toxin varieties should remain below economic concerns. We need to consider strategies now to help the technology last.
    • Selection for resistance occurs in corn. Planting corn refugees is the best strategy to protect our cotton crop.
    • Second, protect the beneficial insects in the field just prior to the moth flight by not spraying or delay spraying for bugs until you can also include a worm product.
    • Thirdly, include a pyrethroid during moth flights on 3-gene as well.

     Bollguard 2

    • If heavy moth flight – Prevathon/Besiege in conjunction with a bug product.
    • If low moth flight, a pyrethroid approach with automatic second trip if eggs continue .
    • 3-gene varieties, use a pyrethroid in that 3rd week of bloom spray.  Plan A is using Orthene as your primary plant bug material, then adding a better bollworm pyrethroid like Baythroid makes sense.  Plan B is using just a pyrethroid with no tank mix, then Bifenthrin is the best choice.
    • Some populations of plant bugs are resistant to pyrethroids so check behind it to be sure you get them if not using Orthene.
    •  Spider Mites are present but have not been flared yet.  Hopefully some soaking rain is on the way and the beneficial insects will finish them off.  Avoid Orthene until the rain pattern returns.
    •  Stink bugs present and will be coming out of corn as it matures or dries down.  They are rarely a concern until the third week of bloom when high numbers of susceptible bolls are present.
    • Either Orthene and pyrethroid or a mix of both will take care of them when you go out for that clean up spray.
    • Plant bug numbers are increasing. With low boll numbers, it is still about fruit retention.
    • It looks like maybe a third to half the fields that have never been sprayed are borderline to slightly above threshold but continue to have high fruit retention.
    • If threshold fields are not blooming, I would use AdmirePro now. If they started blooming last week, and you have high bug numbers, use Transform, or if borderline, I am thinking we might drag our feet slightly and go a little early with the cleanup spray.
    • That would look something like spraying the second week of bloom (around July 25-30) and again a couple weeks later or keep it scouted.



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