Pest numbers low in Texas cotton, but stay on guard

The following Integrated Pest Management (IPM) report was just released by Texas AgriLife Extension County Agent Blayne Reed. The report gives a great overview of pest concerns affecting Texas right now.

This week crops are advancing well although most fields still fall into the ‘late’ category, but not too late for careful management to bring in safely with an average fall. There were not many fields that needed pest treatment this week, but we are tracking several pests on the rise in several of our crops.

As we struggle to put weeds to bed, again, and manage a late crop for maturity we have a lot of pests to keep an eye on. I expect to be making several treatment recommendations over the next few weeks on our Plains Pest Management scouting acres.

Our youngest PPM cotton field is just now coming into first bloom. With blooms not very common on this late field, the fleahoppers were well over threshold and had begun to cause an increase in square drop that we just could not afford this week. This field required treatment but was the lone cotton field we treated for pests this week.

Most irrigated fields came in between 6 and 8 NAWF and were well past fleahopper issues and well on their way of setting a promising boll load. A few irrigated fields were nearing the critical 5 NAWF stage and peak water use/peak boll set but most of our dryland fields were hovering around that critical stage with some already at 4.7.

Without a decent rain, some of these dryland fields will be at an absolute cut-out of 3.5 NAWF by next week with all yield potential set.

Although much of our irrigated fields were still coming in with relatively high NAWF counts, they were also showing signs of drought stress. With good boll set ongoing, we felt the need to start pushing several fields with needs rising and future rainfall looking far off.

Our PGR treatments were very selective and only to fields still showing growth plant measurements with higher irrigation capacities.

We found more bollworm eggs in our cotton this week than we found in all fields over the last two years combined. Still this was only in about 2/3 of our fields with most fields holding less than 6,000 eggs per acre. There were a few fields with over 30,000 eggs per acre.

In West Texas we never recommend spraying for eggs. This is due to the likelihood of high mortality. This could come from a multitude of factors but environmental and predation on smaller plants when compared to other cotton growing regions are likely to be the main reasons. Indeed, on our highest egg count fields we were seeing signs of poor egg viability such as darkening eggs or multiple eggs laid on the same leaf.

We will have to scout and see what worms actually emerge from these eggs, but all indications from corn show that the worm pressure should increase over the next few weeks. So far, our highest worm counts have been less than 1,000 per acre. If we need to make decisions on bollworm treatment in the near future, our ET remains at 8,000 to 10,000 bollworms per acre or the newer 6% harvestable bolls damaged threshold.

All Bt types should be scouted, especially if the upcoming flights are as large as expected, but the same thresholds can be applied to all fields.

We are picking up a few aphids in the area. Our highest per leaf counts are in our southern scouting areas or where a harsher on beneficial product was used in fleahopper control. Still, most fields were coming in at less than 1 per leaf with pre-open boll ET at about 50 or more per leaf.

We are picking up several true armyworms and cabbage loopers in non-Bt fields. All of these foliage feeders ET is about 50,000 worms per acre unless there is an increase in incidental fruit feeding from these pests. Then the 6% harvestable boll damage can be applied here too. Our highest combined count in any field for these ‘foliage’ feeders came in at about 3,000 per acre with much less than 1% ‘incidental’ fruit damage.

Our oldest PPM corn is in the late dough stage and should be moving into dent soon. Our youngest is at V9. We have a fairly large grouping of our ‘earliest’ late corn moved into tassel and silk this week. We found a southwestern corn borer this week, but it was a lone egg and the first I have seen in some time, but this should be peak timing for them to move into tasseling corn, especially if it is a non-Bt type.

We noted an increase in Banks grass mite and diseases this week. Both are still well below ET with our highest BGM rating coming in at 2.5 on our Texas A&M AgriLife 0-10 damage rating scale with 3.5-4 being the threshold.

For the diseases, after noting a sharp increase in southern rust in a few fields a few weeks ago that has since held fairly steady, we only began to note ratable common rust in most fields this week.

We also started finding some light, but usual corn smut in our older fields.

Our oldest PPM sorghum fields are in soft dough while our youngest are up to a V5, but we have fields scattered everywhere in between. The biggest news remains the sugarcane aphid, but several pests are active in our area sorghum that deserve attention.

The SCA remains thankfully absent or hard to find in our younger whorl stage sorghum but pretty easy to find in our post boot sorghum. We have not treated any of our fields yet, but some are fields that required treatment. Several of our fields are nearing SCA ET with the predators giving a solid effort in checking all the advancing aphids.

We currently have all four major sorghum aphid pest species in our area fields including thegreen bug, corn leaf aphids, and green bugs. I do not expect the beneficials to win the battle against the SCA and expect to recommend treatment very soon.

In our still finding fall armyworms in our whorl stage sorghum fields. While the damage remains noticeable and constant, we have had no fields go anywhere near our 30% foliage loss ET for this stage sorghum. In most of our blooming sorghum fields we are also finding sorghum midge at sub-economic levels.

This can change quickly and fields in bloom should be checked daily for midge until bloom is past. In most of our fields we are also finding notable head worm populations. Our highest so far has come in at 0.42 medium to large worms per head and 0.6 small worms per head.

Most fields are coming in with less than 0.16 worms per head of any size. Much like cotton, this could change soon as more moths move into flight and choose their next host crop. Of our head worm populations this week, about 75% have been bollworms and 25% have been the fall armyworm.

For treatment decisions, species should not come into play, but for product selection it could as some products availa-ble will not control FAW, but I urge producers to choose products that are soft on beneficials in order to save these allies for the SCA. Most of the beneficial soft Lep products will control both.


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