Texas LGRV Cotton: Heavy Whitefly, Aphid Populations

    Whitefly adults and eggs. Photo: James Castner, University of Florida

    General Situation

    Very hot and dry in the Valley this week with scattered traces of rainfall in some areas. The heavy rainfall from this past weekend was mainly on the west side of the Valley in Starr County. In Hidalgo county they received 0.3 to 0.5 inches in McAllen, Pharr, Edinburg, and Donna areas. McCook received a couple of inches of rainfall in some areas. There were reports of hail in McAllen/Mission areas, but very isolated areas saw that.

    As for the rest of the Valley; Willacy and Cameron counties received no rain this past weekend but did receive some scattered showers this week on Thursday that gave trace amounts of precipitation that disappeared as soon as it hit the ground.

    As we continue to scout in Cameron and Willacy counties many more dryland acres have been zeroed out due to the severe drought conditions.


    In irrigated cotton many growers were applying plant growth regulators (PGRs) such as Mepiquat Chloride this week. In most irrigated cotton along the Rio Grande growers were applying both a growth regulator along with an insecticide to control both whiteflies and cotton aphids. We saw many whiteflies (adults, nymphs, and eggs) this week building up fast along the river and seeing many more adult whiteflies in the Mid Valley as well.

    Some growers along the river (Progreso, Donna, Pharr, and Mission areas) were on their second application for whitefly and cotton aphid control, while many others were just beginning to apply their first. Whiteflies will feed on plant sugars and then excrete honeydew that glistens on the leaves.

    When high infestations of whiteflies are present, they can quickly excrete large amounts of honeydew that is then an excellent food source for sooty mold to develop causing leaves to turn black. It is important to manage whiteflies early to avoid rapid populations to build as sooty mold can develop quickly and will cause black stained cotton once cotton bolls open.

    Cotton aphid pressure was heavy along the river and found heavy in a few fields through the Mid Valley but most fields had a sharp decline of cotton aphids due to predators (ladybugs larva and adults), parasitism (aphid mummies) and a natural occurring fungus Neozygites fresenii, a fungus that infects and kills aphids.

    Still picking up on hotspots of fleahopper in some fields but majority of cotton fields were little to no fleahopper pressure.

    Grain Sorghum

    Lots of grain sorghum fields in the Valley in hard dough stage as today one of the first fields in the Harlingen area was being harvested. Still finding high sugarcane aphid populations in some sorghum varieties across the Valley this week as many fields were sprayed last week into this week. Some sorghum is also being sprayed for headworm pressure but many fields are generally clean.

    Late planted sorghum flowering needs to be checked and sprayed for midge as they are certainly abundant in presence in flowering sorghum we saw here at the station in Weslaco.

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