General Status
For most of our fields, things are winding down rapidly. For late fields or the minority that are still lush and setting fruit, pest pressure still seems to be heating up. A long-awaited substantial rain for just about every acre finally came last weekend or the week before depending on your location.
While I still feel all surviving fields not harvested yet is receiving some benefit from the rains, unless the muddy fields are delaying harvest. Make no mistake, this benefit is a fraction of what benefit fields could have reaped a few weeks earlier. Today most fields are still muddy five days after the rainfall and for the majority of surviving acres the volume of rain this late in development was far excess.
We are very likely to have regrowth issues in most cotton fields while older sorghum could sucker head and older corn’s dry down is delayed. One area crop that will receive 100% benefit from the heavy rains should be wheat. With so many open and failed summer recently plowed fields, the rains went a long way towards establishing some moisture into the soil profile, hopefully for later use if it can be conserved or made use of.
Cotton
Our Plains Pest Management cotton acres this week seemed like two totally separate crops. The majority of our fields have been in absolute cut-out for quite some time with the last harvestable boll being set weeks ago. Boll counts are a bit disappointing in these fields with little to no insect activity in them at all this week.
In these fields even the youngest bolls have accumulated just about all of the 450 heat units that would put their development past even stink bugs and certainly the 350 heat units to put them out of reach for Lygus and bollworms.
On the other hand, we have a full 1/3 of our cotton fields that for ease of discussion I will call lush fields. 100% of our pest populations of all species were found in these fields and are the only situation I will be referring to for the remainder of this pest update section.
These fields mostly have a decent yield goal in sight (for the year) and either had a predetermined realistic acre to irrigation capacity acre size with irrigations intensely scheduled for ideal fruiting impact, have a higher irrigation capacity to begin with, or even in two cases, are simply late planted.
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One thing all of these fields had in common were that they were still blooming and setting bolls with realistic chances of maturing in time for harvest earlier this week, just now reaching cut-out. With our average last effective blooming date of August 24th and a plant structure capable of hanging onto these bolls as long as moisture is available, counting on them making and adding to harvest is a safe bet. At least for blooms on or before the 24th.
Following that date, the odds start stacking up against a boll maturing after that very quickly. Thankfully, even for our lushest fields, I don’t think this will be an issue but regrowth following the heavy rains could be a problem soon.
Of these lush fields, we have had to treat the vast majority for Lygus recently, mostly last week, but a few fields increased in population requiring treatment behind the rains. This makes around 80% of these type of fields we had to treat in the last 14 days. In all cases treated last week, control looked outstanding with fruit set returning to normal.
From this date forward on fields falling into this category, we need to make sure any potential Lygus feeding occurring are actually occurring on bolls that have a chance of maturing in time. With most of our fields in this situation reaching cut-out will settle the issue with most young-junk fruit being naturally shed.
We also continue to see an increase in bollworm activity in these lush fields. None of our fields has reached economic levels for the worms yet but all have serious and continued egg lay that started 2-3 weeks ago and continues this week. All of these fields held be-tween 5,000 and 17,000 eggs per acre.
We are still seeing a pretty high worm mortality rate with even our highest bollworm field only holding 1,500 small worms this week. This high mortality rate might be a result of solid beneficial numbers clustering into the same lush fields at the same time as the pests. We are seeing respectable to good beneficials in the form of assassin bugs, minute pirate bugs, Nabids, and lacewing larvae. Hopefully this trend will continue.
We are also seeing some light stink bug populations in these lusher fields. So far, this population pressure is light and scattered. I am seeing no or very limited boll damage ( about 1% or less) from those still susceptible bolls. Please refer to our Managing Insect Pests in Texas Cotton for all recommended stink bug thresholds and ‘stink bug safe fruit development’ stages.
There has been quite a bit of discussion on the turn-rows following the rains and just what can be done about cotton and the expected regrowth. This has sparked the same conversations among many Texas A&M AgriLife IPM and Agronomy personnel. Let me share some of our professional conclusions.
First let me set the stage for just the situation we are in. I do not think we have any fields in the area, and we certainly do not have any in our scouting program, even those that can be described as lush, not at cut-out as of this week. So, I do not feel we are talking about any late, and rank fields that are overshooting the proverbial cotton harvest landing.
That being said, applying plant growth regulators to cut-out cotton has never officially proven to have any benefit in preventing cotton regrowth. PGRs cannot prevent regrowth, although they might make the regrowth shorter, which is very likely pointless in terms of helping keep the plant manageable or easier to harvest.
Unfortunately, we will most likely have re-growth to deal with, particularly on the lower yielding fields that have been cut-out for quite some time. These fields, if regrowing, will be very tough to kill in harvest aid season just when and where we need the crop to be economical.
Several of us have noted that under demonstration style trials a conditioning treatment or managed maturity treatment has looked to be the best economical method of managing regrowth, but this has not been in widespread use either.
We will have to cross this regrowth and harvest aid bridge when we get there. So, for all but the odd and hidden, lush, and rank cotton field that is not at cut-out yet we probably should be recommending that we leave the PGRs out of the sprayer for now.
Sorghum
Our older sorghum is in hard dough, very near black line while our younger sorghum is between flag and 5% bloom stage. I currently consider our later sorghum fields as lush, and they also seem to be attracting quite a bit of insect activity.
We now have sorghum aphids (formerly sugarcane aphids) in all of these fields but all at sub-threshold levels. This pressure ranged from 3% up to 18% plants infested with thumb sized colonies (50 per colony) with the post boot ET at 30% infested and 20% infested for pre-boot sorghum. It is very unlikely that our older field will reach ET for the sorghum aphid with just weeks left in its development and the level of beneficials we are seeing there.
We now have Lygus in our older sorghum, but only at 1.36 Lygus per head with a suggested threshold of around 12 per head. There were no other pests of note in our older sorghum.
Fall armyworms remain in the sorghum at flag leaf, but at a greatly reduced level from the whorl stage pressure the fields had been experiencing. We had no headworms of any species in any late field head.
In the blooming sorghum field, we did find 5% of the heads infested with sorghum midge, which should also be well below ET. We will need to keep a close eye on all three of these potential pests sorghum aphid, sorghum midge, and all species of headworms over the next month or so in this late sorghum while the older sorghum should be ready to harvest in the same amount of time.
