Texas Sorghum: Harvest Nearing but Don’t Count Insects Out Yet

    Our earlier sorghum ranged in stage from dough to hard dough. I made note of one of our producers greasing up the combine this week getting ready for sorghum harvest. He might not be too far off but no field was quite past economic insect concerns yet.

    For the first time in a few weeks we had no field reach ET for spider mites in sorghum this week. We also found just a few headworms, all bollworms in this case, in a few fields. These worms were well below ET.

    Our most consistent find was yellow sugarcane aphids (YSCA) on lower leaves and Lygus in maturing sorghum heads with just a touch of stink bugs intermingled with the Lygus from time to time. Our highest YSCA rating was 3-4 and nearing economic concern. We rated most YSCA fields 0-1 or 1-2. Our highest Lygus / stink bug count was 7.9 per head.

    Under the Reed Consulting banner, I conducted a Lygus in sorghum ET study in 2001 under a pressing need to know at the time. To my knowledge this is the only effort made toward this pest in sorghum. The results of that one-year study indicated that the ET for Lygus in sorghum should be about 12-14 per head crop value depending. By default this is a useable threshold for this pest until a full multi-year study can be conducted, hopefully soon.

    All of the pest ‘excitement’ is falling to the late sorghum again this season. Our late sorghum ranges in stage from flag to soft dough with the majority of fields falling between boot and 15% bloom. The fields in bloom are now within the sorghum midge window and the midge have reached ET in a number of our program fields this week. The highest level of midge we have found is 2.11 midge per head but others were over the midge ET of 1 per head and required treatment.

    Not all fields we checked required treatment and most of our fields ranged from 0 to 0.32 midge per head. This underscores the need to check in bloom sorghum midge daily. While midge only live as adults for a short time, they are quite mobile and can infest a previously clean field within a day causing economic damage.

    We have also picked up some headworms in these blooming fields. In this case, the majority were small FAW. So far these worms have been below ET. Gary Cross’, CEA-Hale, FAW moth traps increased this week and I feel we can expect the FAW larva finds to increase rapidly soon. These FAW should be a consideration for any field reaching ET for sorghum midge. I would urge producers to choose their midge control products carefully.

    Pyrethroids have proven to give excellent midge control with substantial residual that can last throughout bloom. These pyrethroids will not control FAW and certainly will not cover any FAW egg lay with residual, but will take out any predators that could lessen the soon to be coming FAW.

    For this reason we are recommending in our program acres requiring midge treatment a mix of a pyrethroid and a good FAW product or perhaps and maybe preferably a premix of the two products.

    Our other sorghum pests in the later sorghum were very similar to the older sorghum. This could be another consideration in product choice when targeting the midge or FAW. The spider mite population has been slowly growing in the later sorghum. Almost all later fields have some level of mites present.

    If the predators were removed, we would have potential secondary pest issues, such as spider mites or YSCA on the increase. There are some excellent FAW products that are very predator friendly available now. In situations like these, those type products should look very attractive.

    Melanaphis Aphid – The ‘White’ Sugarcane Aphid

    For most of the season I have avoided mentioning the white sugarcane aphid from a desire not to stir up panic over a pest that may or may not even visit this area. It is also one that I feel can be economically controlled if we maintain a good scouting program and utilize sound IPM strategies.

    This tropical aphid pest invaded sorghum along the gulf coast region up through Louisiana and some of Oklahoma last season. Unlike the green bug or YSCA, it does not inject a nasty toxin into infested sorghum leaves killing them outright. It does attack with a remarkable reproductive capability that can outpace predation and parasitism and suck the life from whole sorghum plants.

    It appears to attack very late in sorghum’s life cycle and caused a tremendous amount of harvest trouble through gumming up machinery in the lower Rio Grande Valley up to Corpus Christi during 2013. Nonetheless, we have kept a vigilant lookout for this species in our area sorghum fields and Johnson grass patches.

    Treatments of the product Trans-form have proven to be affective and economical against this invasive pest through Texas A&M AgriLife product trials in South Texas and Louisiana over the past two seasons. The success of Transform against this aphid prompted a section 18 release for Transform in Texas grain sorghum.

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