Corn
Why is my young corn falling down?
Several fields have recently had young corn plants falling over.
Corn sometimes has problems developing its nodal root system which causes plants to fall over when the plants get one to two feet tall. Normal shoot development often precedes this scenario, although nutrient deficiency symptoms may be observed, due to poor root exploration. This condition is often referred to as rootless corn syndrome. The ability of corn plants to recover from this condition depends upon favorable environmental conditions and why the nodal roots are failing to develop.
Corn
has a two part root system consisting of seminal roots and nodal roots.
The seminal root system consists of the radicle and lateral seminal roots
which develop below the seed. These roots temporarily anchor the seedling
and take up water and nutrients during and shortly after emergence. The
seminal roots cease growth by the V3 growth stage. The nodal roots begin
developing at emergence and provide structural support and the bulk of
nutrient and water uptake during the remainder of the plant's life.
When nodal roots do not develop, the only structure anchoring the plant is the mesocotyl (the shoot from the seed to the crown of the plant). Thus, when the plants develop substantial size, they will fall over, since there is no lateral support for the stem.
There are several reasons why nodal roots may not develop, including shallow planting, poor seed-furrow closure and soil erosion. Corn planted less than one inch deep will move the nodal root origination point up to or above the soil surface, subjecting these roots to many factors that can retard growth (hot, dry and/or compacted soil, herbicide injury or carryover, and surface-feeding insects). Corn planted at the recommended seeding depth (one and a half to two inches deep) will develop the nodal roots below the soil surface, avoiding these potential problems. Corn planted in fairly moist soil may also compact the soil around the seed-furrow, especially on heavy clay soils, causing the furrow to open and present the same problems as shallow planting. Heavy rainfall or wind erosion may also move soil away from the crown of emerged corn plants, especially on light textured soils with raised beds, exposing the nodal root system as well.
Some
herbicides labeled for use on corn can inhibit nodal root development.
Prowl/Pendimax (pendimethalin) applied preemergence may inhibit nodal
root development, often causing considerable root swelling, especially
at the tips. Clarity (dicamba) or 2,4-D applied early postemergence may
also cause nodal roots to be short and/or fused together.
Rootless corn syndrome is often erroneously blamed on chinch bug damage. Chinch bugs are capable of inhibiting nodal roots, but injury is nearly always the result of sustained, large, and easily observed populations of chinch bugs.
Herbicide carryover may also inhibit root development. However, shoot stunting is normally evident accompanying the root stunting. Herbicide carryover problems typically are more pronounced along field borders where overlapping and applicator slowing occurs.
Corn should likely recover if rainfall or irrigation water is received, which should promote nodal root development. However, dryland fields could sustain considerable stand loss, if rainfall doesn't promote root growth soon. Cultivation may also promote root development, if soil can be moved around the base of plants without knocking them down.
