Texas Plains IPM: Insects All Over but Few at Economic Thresholds

Bollworm burrowing into cotton boll. Photo: University of Tennessee

General Status

Still very dry, with several things to scout and consider in triple digit temperatures. Some additional rains have come in the past week, but these too have been spotty and limited in benefit. Most of our scouting program fields are on the back side of peak water use with needs still quite high with others just coming into this ‘crunch time’ and still a handful of others with it on the near horizon.

We are picking up some level of just about every usual pest imaginable in our respective crop fields. Just a few have become economic requiring treatment. These are spotty and scattered with the number of fields being literally just a few. The exception is with the sugarcane aphid on grain setting sorghum.

It seems difficult to state, but there is so much threatening and happening we need to stay engaged and alert with scouting and many other crop management areas. Yet, there are so few fields with pests actually reaching economic levels it is easy to become complacent.

If a pest or intense management need missed around ‘crunch time’ the consequences are dire. But, the end of a crazy season is in sight, likely nearer than an elusive soaking rain.

Cotton

About 60% of our program cotton reached absolute cut-out this week of less than 3.5 NAWF (nodes above white flower). Our latest field, wildcat cotton, should be in first bloom today, but is being scouted during this writing. We also have a grouping of fields hovering at or just under 5 NAWF.

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I can safely state that all fields are holding as much fruit as environmentally possible and moisture available. Many fields are short statured and thus have fewer overall fruiting sites than we would like but have been im-pressed with retention despite conditions.

That being said, many fields are experiencing heavy natural drop. This typically does happen shortly following absolute cut-out with the plants dropping everything they cannot hold as they bloom out. While we do need to make sure this drop is natural and not pest related, this is normal and irreversible.

If there are any intended inputs for these fields in terms of fertilizer, etc., it is honestly too late and could do more harm than good. Water needs are still high for cut-out fields as they still need to fill multiple bolls, but there is a danger of overwatering and causing regrowth if the heavy irrigations are carried too far into the post cut-out timing.

On the pest side, we did have another 1 field reach ET for Lygus this week. This was a field at 4.9 NAWF and not experiencing natural drop yet with most drop being caused by Lygus feeding. Last week we had an increase in bollworm egg lay but did not find enough worms to treat any of our fields this week with beneficials lending a solid hand.

This week, eggs were a little harder to find in cotton and our moth trap numbers are down considerably. While we can easily find worms and eggs in susceptible grain crops, we did not find any eggs in cotton unless the field was at least somewhat lush, and no grain crop was within miles.

Even in this situation , our highest numbers were only 853 eggs per acre. We are picking up very light aphid populations in fields with left over and high nitrogen content due to an early cut-out and we can find a few spider mites (two-spotted) in a few dry fields that have been at cut-out a while.

The driest of our fields are just a few weeks away from being passed most economic pest damage. Despite light numbers, we should still be on the lookout for the odd Lygus field and our peak average bollworm egg lay is still around the corner next week. We will see if the population of worms will be enough to fill the ‘sink’ of late corn and sorghum to threaten cotton.

Corn

Our oldest program corn is in full dent and our youngest is just now in green silk. All of our intended corn fields are in some stage of dent now, with most in a race with the Banks grass mite (BGM). Morning dews, pathogens, and beneficials have played a vital role in holding most of our mite populations in check surprisingly well.

Now that the sugarcane aphid is active and spreading in sorghum fields and the temperature has returned to triple digits, mites are making a comeback surge. As fields reach about 25% starch line, the plants need to start a natural dry down process and a touch more mite damage might be tolerated.

Our ET for BGM in field corn is 3.5-4 on the 0-10 damage rating system. Please consult the Texas Corn Pest Management guide for exact details, but I strongly suggest keeping with the 3.5-4 mite threshold for as long as the grain is filling and not pushing that envelope past 4.5 for any reason.

Stalk integrity could be at risk if mites are allowed to desiccate the plant prematurely. Hopefully, more morning dews will help the establishment of mite pathogens to regain control before thresholds are reached wholesale like some regional fields have over the past month. Diseases remain a minor issue in corn so far.

Sorghum

Our sorghum ranges in stage from VX to dough with most falling about soft dough. Sugarcane aphids increased and reached ET in 75% of our fields in dough stages this week triggering several treatments. Meanwhile, the SCA remain hard to find in whorl stage sorghum fields still.

Beneficials are making a large impact on the pest this year but it is not likely they can hold them alone. We were still finding fall armyworms (FAW) in all whorl stage sorghum fields, but the feeding remains well below ET. Our highest FAW rating showed about a 5% foliage loss to 100% of the plants.

This looks very impressive and we have fielded many questions this week over the issue with economic concerns. Plants can tolerate a large amount of foliar damage without it becoming economic.

Our current ET remains 25-30% foliage loss to 100% of the plants before a foliar application for any foliar pest would return expenses. We should be very watchful of these worms ‘riding’ the head out through boot stage, or feeding down into the growing point and damaging the future head.

We found headworms, mostly bollworms, with regularity again this week. Our highest numbers were 0.8 worms per head with most of these worms being small. The Sorghum headworm calculator can be found here.

If any field needs to be treated for another pest, I urge and remind producers to salvage and make use of the beneficial populations to aid in SCA control. Our experiences show us that we cannot control this aphid without their help. Our choices of predator friendly pesticides for other pests can help with this goal more than any other factor.

The BGM increased in our sorghum fields similarly to the corn. The 0-10 damage rating scale can be utilized in sorghum also. Our highest BGM damage in sorghum came in at a 2.2. We also found a few sorghum midge again this week but only up to 0.05 per head.




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