Scouting crops is important not only for identifying and remedying any threats, but also for identifying the corn plant’s growth stage. Stage identification helps farmers know what’s going on developmentally and what they should be doing from a management standpoint, whether that’s applying fertilizer, spraying pesticides or helping the crop live up to its potential. Crop stage can also help a farmer identify when certain diseases, pests or nutrient deficiencies are likely to appear.

There are two methods used to stage corn plants: leaf collar and droopy leaf. This guide is based on the leaf collar method, which counts the number of leaves on a plant that have visible collars, starting with the rounded “thumb-shaped” leaf near the bottom of the plant. From there, each vegetative stage is determined and labeled (e.g., V1, V2, V3, etc.) by counting visible collars until the tassel emerges.

As the corn kernel germinates, the first root (the radicle) extends from the tip end of the seed. 

• Vulnerabilities: Fertilizer burn, and prolonged exposure to cold rain, snow melt or soil temperatures below 50 degrees Fahrenheit
• Management tip: Wait for soil temperatures to climb above minimum thresholds, and make sure to place seed 1.5 inches to 2.0 inches deep. 

The corn spike, known as the coleoptile, pushes through the soil surface roughly a week after planting (though emergence can range from four days to several weeks after planting). Within the coleoptile are the first five sets of corn leaves. When the coleoptile meets sunlight, it opens/splits. The corn plant’s growing point, also known as the crown, is roughly 1.0 inch to 1.5 inches below the surface. 

• Disease: Pythium, Rhizoctonia, Fusarium, Phytophthora
• Insects: Black cutworm, white grub, seed corn beetles, wireworms
• Other vulnerabilities: Cloddy soil, soil crusting, chemical injury, a hard freeze
• Management tip: Take population estimates, making note of abnormal germination, runts, planting depth, and any emergence or planter issues. Noting issues can help you improve next season. 

Roughly three to four days after emergence, the first leaf emerges, and the leaf collar is visible. The V1 leaf typically has a more rounded tip than subsequent leaves. During this period, the seminal root system continues to grow, and the initial bumps of the nodal root system may be visible. The growing point remains below the surface, which means the plant can be cut off or hailed upon with little lasting impact. 

• Disease: Pythium, Rhizoctonia, Fusarium, Phytophthora
• Insects: Black cutworm, white grub, seed corn beetles, wireworms
• Other vulnerabilities: Weeds, nutrient deficiencies causing purpling, yellowing or striping
• Management tip: Scout fields soon after emergence, keeping in mind your field’s history and likely threats for a given season. Early season pest damage like that from black cutworm may not be evident from the road.  

The seed is no longer the corn plant’s main food source. The plant begins to rely on its nodal root system roughly 10 to 20 days after emergence, launching its photosynthetic process. The corn plant’s above-ground height is typically around 8 inches, and its growing point remains below the surface where root hairs are growing. 

• Disease: Pythium, Rhizoctonia, Fusarium, Phytophthora
• Insects: Black cutworm, white grub, seed corn beetles, wireworms
• Other vulnerabilities: Flooding, cold soils, weeds, nutrient deficiencies
• Management tip: Weeds compete with your corn crop for light, water and nutrients. Keep your fields clean.

Roots are elongating and the growing point is nearing the surface, limiting the impact of hail, wind, frost or cut off plants. The tassel has started to form. 

• Disease: Eyespot, Stewart’s leaf blight, Goss’s Wilt, common rust
• Insects: Corn rootworm, European corn borer
• Other vulnerabilities: Flooding, weed competition, nutrient deficiencies
• Management tip: Herbicides can be applied during these stages, so make sure to note weed height and coverage when scouting fields. 

The crown, or growing point, reaches the soil surface. The stalk begins to elongate and ear shoots are visible. Potential kernel rows are being determined. This is a critical period when nitrogen uptake begins. 

• Disease: Goss’s Wilt, Stewart’s leaf blight, common rust, gray leaf spot, northern leaf blight, eyespot
• Insects: Corn rootworm, European corn borer, common stalk borer, fall armyworm, southwestern corn borer, corn leaf aphids
• Other vulnerabilities: Nutrient deficiencies, hail, freeze, flooding
• Management tip: Be on watch for nutrient deficiencies during this timeframe and take steps to correct them. This is an optimal time to side-dress nitrogen. 

This is a period of rapid growth, with stalks lengthening, tassels quickly developing and plants showing ear shoots. The number of kernel rows will be set by V8 and the process of determining potential kernels per row begins. During this period of rapid development, the lower leaves may die if a plant is stressed. The plant will likely be around 2 feet tall. 

• Disease: Stewart’s leaf blight, Goss’s Wilt, common rust, gray leaf spot, northern leaf blight, eyespot
• Insects: Common stalk borer, corn rootworm, European corn borer, fall armyworm, southwestern corn borer, corn leaf aphids, Japanese beetles
• Other vulnerabilities: Nutrient deficiencies
• Management tip: Side-dressing nitrogen is a great option for getting plants this key nutrient as the plant needs it, but farmers should be aware that doing so after V8 can damage roots. 

The period from V10 forward is one of rapid growth and dry matter accumulation. The cornstalk elongates, and tassels grow quickly. The plant’s moisture and nutrient requirements are high during the V10-V15 period. Potential kernels per row are determined in the V12 to V15 stages. Silks begin to grow from the upper ears. Ear development is rapid from V16 to V18. By V17, the tips of the upper ear shoots may be visible atop leaf sheafs, along with the tip of the tassel. Brace roots grow from the nodes above the soil surface to support the plant and take in water and nutrients. Most hybrids grown in the Corn Belt will have 19-20 leaves prior to tassel.

• Diseases: Goss’s Wilt, gray leaf spot, eyespot, southern corn rust, Stewart’s leaf blight, common rust, northern leaf blight, Fusarium stock rot, Gibberella stalk rot
• Insects: Corn rootworm, European corn borer, fall armyworm, southwestern corn borer, corn leaf aphids, Japanese beetles
• Other vulnerabilities: Nutrient or moisture deficiencies from the V10 to V15 stages can slash kernel numbers and ear size. Hot, dry conditions are especially detrimental from V16 to V18. Hail and greensnap are also threats.
• Management tip: Anything you can do to reduce plant stress and allow for adequate nutrient levels can help maximize yield potential, as the plant is utilizing major amounts of nitrogen, phosphorous and potassium during these stages.

The last branch of the tassel is completely visible, extended outward and not held in by the upper leaves. Silks will emerge in two or three days. The corn plant is at full height and all leaves have emerged. 

• Diseases: Goss’s Wilt, tar spot, northern leaf blight, gray leaf spot, eyespot
• Insects: Corn rootworm, corn earworm, Japanese beetles, European corn borer
• Other vulnerabilities: Hail, drought, heat
• Management tip: If you are using fungicides, your first application should be around the time the crop is tasseling.  

Silks emerge two to three days after tassels, and fields generally shed pollen in the morning and evening for around a week. That pollen shed is a major determinant for whether potential kernels are fertilized, and hot, dry conditions reduce fertilization. Nitrogen and phosphorous uptake are rapid. 

• Diseases: Eyespot, gray leaf spot, northern leaf blight, southern leaf blight, tar spot, Goss’s Wilt
• Insects: Corn earworm, corn rootworm, European corn borer, Japanese beetles, western bean cutworm
• Other vulnerabilities: Hail, dryness, heat
• Management tip: Be especially vigilant in scouting for disease and insect damage from VT through the reproductive stages. Loss of leaves and damage to silks during these stages will clip yields.

White, blister-like kernels form on the cob roughly 10 to 14 days after silking, and starch begins to accumulate. Silks darken and dry out. Drought stress at this stage can result in aborted kernels. 

• Diseases: Eyespot, Goss’s Wilt, common rust, gray leaf spot, northern leaf blight, Fusarium stalk rot, Gibberella stalk rot, tar spot
• Insects: European corn borer, southwestern corn borer, Japanese beetles, western bean cutworm, corn earworm
• Other vulnerabilities: Drought stress
• Management tip: Additional water at or after this stage won’t improve yield; in fact, it can slow dry down and may encourage stalk or grain diseases.

Kernels are yellow and filled with white, milky liquid, while the silks of the corn ear are dry and brown. Dry matter is rapidly accumulating. 

• Diseases: Goss’s Wilt, tar spot, gray leaf spot, northern leaf blight, Fusarium stalk or ear rot, Gibberella stalk or ear rot, anthracnose top dieback, diplodia ear rot, common rust, eyespot
• Insects: European corn borer, southwestern corn borer, Japanese beetles, western bean cutworm, corn earworm, corn rootworm
• Other vulnerabilities: Heat or drought stress
• Management tip: Limit drought stress, as this can lead to small, shallow kernels, tip back, lodging or stalk cannibalization. 

Inner kernel fluid begins to thicken as starch accumulates. At this point, kernels have obtained around half their total dry weight, and they are becoming more yellow and consistent in terms of size. Stress during this stage will affect kernel weight.

• Diseases: Goss’s Wilt, Fusarium stalk or ear rot, Gibberella stalk or ear rot, anthracnose top dieback, Diplodia ear rot
• Insects: European corn borer, southwestern corn borer, Japanese beetles, western bean cutworm, corn earworm
• Other vulnerabilities: Environmental stress, particularly drought; nutrient deficiencies
• Management tip: Assessing late-season intactness, plant health and harvestability, including use of a simple push or squeeze test, can help you prioritize fields and can inform hybrid selections for the following season.  

Kernels begin to dry down and harden from the top of the kernel toward the cob, resulting in a dent on the top of each kernel and the retreat of the milk line toward the kernel tip. Kernels will continue to fill and add weight for another 20 days. Frost during this stage can result in premature black layer, lowering test weights and slowing dry down. Conversely, overly hot, dry weather during this stage can cut yields. 

• Diseases: Goss’s Wilt, anthracnose top dieback, Diplodia ear rot, Fusarium ear rot, Gibberella ear rot
• Insects: European corn borer, southwestern corn borer
• Other vulnerabilities: Frost, heat, drought
• Management tip: Keeping your corn plants green and healthy through the final maturity growth stage can help pack as much starch as possible into that kernel, building yield.   

Kernels continue gaining weight until the milk line disappears and a black layer forms where the kernel attaches to the cob, generally around 60 days after silking. Kernel moisture is around 30% to 35% at black layer. Frost will have no impact on yield. The husks and many leaves of the plant are no longer green. 

• Diseases: Anthracnose stalk rot, Diplodia ear rot, Fusarium ear rot, Gibberella ear rot, Physoderma stalk rot 
• Insects: European corn borer, southwestern corn borer
• Other vulnerabilities: Excess rain or wind, snow, hail
• Management tip: Prioritize corn fields for harvesting by maturity, standability, grain moisture and ear retention; take notes on hybrids and pull samples from problem areas so you can avoid repeat issues next season.