Nutrient deficiency symptoms reported

This information was summarized from the June 12 teleconference with ISU Extension field specialists in crops.

Crop conditions

  • Many areas of the state received rainfall in the past week. However, parts of southwestern, west central, and northwestern Iowa missed recent rains and are showing increased drought symptoms.
  • Corn is typically at the V6 to V8 growth stage (6- to 8-leaf collars visible). Soybeans are generally at the V2 to V3 growth stage (fully developed leaf nodes) with reports of R1 (beginning flowering) soybeans in southern Iowa.
  • Warm, sunny conditions have allowed for excellent haying, with 90 percent of the first cutting completed.
  • Oats have headed in most parts of the state and wheat has started turning.
  • Pastures in the dryer areas are still under drought stress.

Soils

  • Potassium deficiency symptoms (yellowing and browning along leaf margins, beginning at the tips and edges of the lower leaves) were reported statewide.

Diseases

  • Southern Iowa continues to report fields with Stewart's wilt. In some situations other disease problems such as corn leaf anthracose, Fusarium crown rot, or nutrient deficiencies are being misidentified as Stewart's wilt.
  • Field specialists and the Plant Disease Clinic report seeing Rhizoctonia, Phytophthora, and Fusarium in soybeans.

Insects

  • European corn borers are taking flight in fields. Initial scouting reports indicate low numbers of egg masses.
  • Moderate-to-heavy infestations of corn leaf aphids in several cornfields were reported by Jim Jensen (southeast).

Weeds

  • Postemergence herbicide applications are in full swing but have been hampered by recent high winds. Early-morning and evening applications are common to take advantage of calmer winds. Unfavorable application conditions have delayed postemergence applications, resulting in larger, more difficult-to-control weed populations and increased crop competition.
  • Herbicide carryover injury continues to be reported and includes buggy-whipped or wrapped corn and excessive leaf burn from postemergence products.
  • Herbicide drift complaints continue statewide.

This article originally appeared on pages 107-108 of the IC-484(14) -- June 19, 2000 issue.

Updated 06/18/2000 - 1:00pm