Texas Blacklands: Widespread Wheat Rusts; Cotton Planting Mostly Finished

    Wheat leaf rust. Photo: Stephen Harrison, LSU AgCenter

    GENERAL

    Wheat across the area is progressing nicely and ranges from just finishing pollination in some of the earliest planted fields to head emergence is some of our later planted field and/or later maturing varieties. Drought stress is starting to become apparent in fields west of I-35 where our soil texture is a little lighter.

    Rust is still active in the area despite the lack of rainfall, and currently most of the rust issues is still stripe rust but I did find a leaf rust pustule in the Malone area on the 9th of April. Aphids are also still being found in area wheat fields, but thanks to our beneficial I nsect populations are currently not a cause of concern.

    Corn is growing nicely despite the lack of rain, and much like our wheat crop areas west of I-35 and area with lighter rockier soils are starting to exhibit signs of drought stress.

    Cotton planting is complete except for some fields that were not planted in hopes of rain replenishing soil moisture at the seeding depth instead of dry planting. Some of the first planted cotton fields are starting to emerge, and now is the time to start assessing stand establishment and scouting for thrips.

    WHEAT

    The area wheat crop needs a widespread rain event without the H-word but is still progressing nicely. In Hill and Northern McLennan Counties stripe rust is still active in fields not recently treated with a fungicide, and untreated fields of both hard red and soft red winter wheat should be monitored closely.

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    Leaf rust is active in the Hill County UVT trials and with the strong winds we had last week (5-9 April) could have easily move leaf rust pustules into the area. I have also found a few pustules of leaf rust in other fields around the Malone area.

    The moisture that moved through late this week will help both leaf rust and stripe rust infections to grow and spread to new leaves in the same or nearby fields, so fields not treated with a fungicide lately should be scouted for leaf and stripe rust.

    Aphids are still being found in area wheat fields and consist mostly of English grain aphids. Fields with aphids present are still below the economic threshold, and thanks to a good beneficial insect population in these fields I expect they will not reach the economic threshold by the hard dough stage.

    If fields are treated for aphids we need to read the label closely and understand the products maximum use rate per acre per year as well as the products pre-harvest interval. Chlorpyrifos (Lorsban) is probably the most used insecticide for aphid control in wheat, and these insecticides have a maximum use rate of 2 pints per acre per year (1 lbs. chlorpyrifos per acre) and carries a 28-day pre-harvest interval.

    Dimethoate is also commonly used in wheat and has a maximum use rate of 1 pint per acre per year and carries a 35-day pre-harvest interval.

    Now is the time we typically start dealing with armyworms in wheat, but currently I am not nor have I heard of reports of armyworms in wheat fields in the area. The dry weather pattern may help to explain why we have not had armyworm issues this year, as armyworms are favored by coot damp weather.

    Fields should continue to be scouted for armyworms with the moisture that moved through the area this week as it may help armyworms get started.

    COTTON

    I would estimate that about 90% of the cotton crop in the area has been planted, and some of the first planted fields were starting to emerge earlier this week. As the crop starts to emerge now is the time to start evaluating stands and scouting for thrips. Insecticide seed treatments typically provide control of thrips for 2-3 weeks after planting, however, this dry weather pattern may affect their efficacy.

    These insecticide seed treatments need soil moisture to solubilize the insecticide in to the soil water solution for the plant to uptake the insecticide and control thrips, and the drying soil moisture profile may reduce the amount of these insecticide absorbed by the plant.

    Thrips are an important early season pest of cotton as damage can reduce leaf size, slow the rate of growth, delay maturity, and in the worst cases kill the plant. Fields should be treated for aphids when the field averages 1 thrips per true leaf, and during the cotyledon stage the threshold is 1 thrips per plant.




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