Corn

Comprehensive IPM Plan for Corn: Optimizing Pest Management Year-Round

Toxicity of insecticides to corn pollinating insects and bees

Common Corn Field Pests and Recommended Control Measures

1. Seedling Emergence Stage

Key Pests & Their Impact

• Soil Pests (Wireworms, White Grubs, Seedcorn Maggot) – These pests feed on seeds and roots, causing poor germination and weak plant establishment.
• Cutworms (Black Cutworm) – Nocturnal feeders that sever young plants at the soil surface, leading to plant loss.
• Mole Crickets – Burrow in the soil and damage underground parts of seedlings, prevalent in tropical regions.
• Shoot Fly – A major pest in warm regions, lays eggs in the whorl, leading to plant death (deadheart symptoms).

Recommended Insecticides

• Seed Treatment: Thiamethoxam, Clothianidin, Imidacloprid
• Soil Treatment: Chlorpyrifos, Terbufos, Tefluthrin
• Foliar Sprays for Cutworm: Lambda-cyhalothrin, Chlorantraniliprole
• Bait & Soil Applications for Mole Cricket & Shoot Fly: Fipronil, Phoxim

Resistance Management

• Rotate neonicotinoids with other systemic insecticides to reduce resistance development.
• Implement crop rotation and soil tillage to disrupt pest life cycles.

2. Vegetative Growth Stage

Key Pests & Their Impact

• Thrips – These tiny insects suck plant sap, causing leaf distortion and plant stunting.
• Chinch Bugs – Feed on plant sap, leading to wilting and yellowing, especially in dry conditions.
• Oriental Armyworm – Highly mobile caterpillars that can cause complete defoliation.

Recommended Insecticides

• Thrips Control: Thiamethoxam, Chlorfenapyr, Spirotetramat
• Chinch Bug Management: Bifenthrin, Deltamethrin
• Armyworm Control: Lambda-cyhalothrin, Emamectin Benzoate, Lufenuron

Resistance Management

• Use insect growth regulators (IGRs) like Diflubenzuron alongside contact insecticides.
• Preserve beneficial insects by reducing broad-spectrum insecticide use.

3. Whorl Stage

Key Pests & Their Impact

• Fall Armyworm (FAW) – Highly destructive, attacking leaves and whorls, leading to yield losses.
• Corn Borers (Asian & European Corn Borers) – Larvae bore into stalks, weakening the plant.
• Stem Borers – Found in tropical and subtropical regions, feed inside stems, reducing plant vigor.
• Corn Rootworms – Larvae damage roots, leading to lodging and nutrient deficiency.

Recommended Insecticides

• FAW Control: Chlorantraniliprole, Flubendiamide, Spinetoram
• Corn Borer Control: Indoxacarb, Methoxyfenozide, Lambda-cyhalothrin
• Stem Borer Prevention: Beta-cyfluthrin, Carbaryl, Azadirachtin
• Corn Rootworm Management: Terbufos, Clothianidin, Spinosad

Resistance Management

• Rotate different insecticide classes following IRAC guidelines.
• Use biological control where applicable, such as Bt corn hybrids.

4. Tasseling & Silking Stage

Key Pests & Their Impact

• Corn Earworm / Bollworm – Attacks developing kernels, causing direct yield losses.
• Corn Leaf Aphid – Reduces plant vigor and interferes with pollination.
• Silking Beetles – Feed on silks, leading to poor pollination.

Recommended Insecticides

• Earworm Control: Emamectin Benzoate, Chlorantraniliprole, Indoxacarb
• Aphid Management: Malathion, Flonicamid, Pymetrozine
• Silking Beetle Control: Lambda-cyhalothrin, Acephate, Thiamethoxam

Resistance Management

• Rotate contact insecticides with systemic alternatives.
• Implement refuge strategies when using Bt corn varieties.

5. Grain Filling Stage

Key Pests & Their Impact

• Late-Stage Corn Earworm / Armyworm – Continued kernel feeding reduces grain quality.
• Stink Bugs – Piercing-sucking mouthparts damage kernels and lower market value.
• Stored Grain Pests (Weevils, Maize Beetles) – Infest post-harvest grains, causing storage losses.

Recommended Insecticides

• Late-Stage Earworm & Armyworm Control: Chlorantraniliprole, Emamectin Benzoate, Novaluron
• Stink Bug Control: Lambda-cyhalothrin, Beta-cyfluthrin, Thiamethoxam
• Stored Grain Pest Prevention: Malathion, Aluminium Phosphide, Deltamethrin

Resistance Management

• Reduce late-stage pesticide use to prevent residues in harvested grains.
• Adopt integrated storage pest control (fumigation, aeration, and temperature management).

Corn Field Diseases and Fungicide

Seedling Stage (Emergence to V5)

Common Diseases & Their Impact

• Damping-Off & Seedling Blight (Fungal) – Caused by Pythium, Fusarium, Rhizoctonia, and Diplodia. Leads to seed rot, poor emergence, and weak seedlings.
• Downy Mildew (Oomycete) – Peronosclerospora spp. cause systemic infection, leading to yellow streaks and plant stunting.
• Stewart’s Wilt (Bacterial) – Pantoea stewartii, spread by corn flea beetles, causes wilting and slimy stalk rot.

Recommended Fungicide Solutions

• Seed Treatment (Preventive): Metalaxyl, Mefenoxam, Azoxystrobin, Fludioxonil, Thiram
• Resistance Management: Rotate fungicide classes and use disease-free, high-quality treated seeds.

Vegetative Stage (V6 to Pre-Tassel)

Common Diseases & Their Impact

• Northern Corn Leaf Blight (NCLB) – Exserohilum turcicum, cigar-shaped gray lesions spread under humid conditions.
• Gray Leaf Spot (GLS) – Cercospora zeae-maydis, rectangular gray lesions block photosynthesis, reducing yield.
• Common & Southern Rust (Fungal) – Puccinia sorghi (common), Puccinia polysora (southern). Southern rust is more aggressive in warm, humid climates.
• Anthracnose Leaf Blight – Colletotrichum graminicola causes leaf lesions, later leading to stalk rot.
• Goss’s Wilt (Bacterial) – Clavibacter michiganensis, causes severe leaf blight, spreads through plant wounds.

Recommended Fungicide Solutions

• Preventive & Curative Fungicides: Azoxystrobin, Pyraclostrobin, Propiconazole, Tebuconazole, Fluxapyroxad, Benzovindiflupyr
• Application Timing: Best applied at V10–V14 or before tasseling for foliar disease protection.
• Resistance Management: Rotate QoI (Strobilurin), DMI (Triazole), SDHI fungicides to prevent resistance.

Tasseling & Silking Stage (VT–R1)

Common Diseases & Their Impact

• Southern Rust – Wind-spread Puccinia polysora can cause severe leaf loss, reducing kernel fill.
• Common Smut & Head Smut – Ustilago maydis (common smut), Sphacelotheca reiliana (head smut) infect silks and stalks.
• Anthracnose Top Dieback & Stalk Rot – Early leaf infections by Colletotrichum lead to premature death.
• Ear & Silk Molds – Fusarium, Gibberella, Aspergillus, and Diplodia infect ears, leading to mold and mycotoxin contamination.

Recommended Fungicide Solutions

• Preventive Sprays at VT/R1: Azoxystrobin, Pyraclostrobin, Propiconazole, Tebuconazole, Metconazole
• Application Benefits: Protects against rusts, GLS, NCLB, and helps minimize stalk rot risks.
• Resistance Management: Rotate modes of action and avoid unnecessary fungicide applications.

Grain Filling Stage (R2–R6)

Common Diseases & Their Impact

• Stalk Rots (Anthracnose, Fusarium, Gibberella, Charcoal Rot) – Weakened stalks cause lodging and grain losses.
• Ear Rots (Diplodia, Gibberella, Fusarium, Aspergillus) – Lead to moldy, lightweight grain and mycotoxin contamination.
• Tar Spot (Fungal) – Phyllachora maydis, black specks on leaves cause premature death and lodging.

Recommended Fungicide Solutions

• Late Fungicide Sprays (If Needed for Tar Spot & Late Rusts): Tebuconazole, Metconazole, Benzovindiflupyr
• Harvest & Storage Management: Prevent mycotoxins by drying grain to ≤15% moisture and using proper aeration.

Preventative vs. Curative Fungicides

• Preventative (Before Infection): QoI (Azoxystrobin, Pyraclostrobin) blocks spore germination.
• Curative (Early Infection): DMI (Propiconazole, Tebuconazole) inhibits fungal growth inside plants.
• Best Strategy: Apply dual-action fungicides (QoI + DMI) at VT for the best disease control.

Cornfield weed control

Pre-Planting Stage (Before Corn Emergence)

Common Weeds

• Grass Weeds: Bermudagrass (Cynodon dactylon), Volunteer cereals, Johnsongrass (Sorghum halepense)
• Broadleaf Weeds: Horseweed (Conyza canadensis), Field pennycress (Thlaspi arvense), Giant ragweed (Ambrosia trifida), Kochia (Kochia scoparia)

Recommended Herbicides

Pre-Emergence (Soil-Applied) Herbicides:

• Atrazine → Controls broadleaf weeds like pigweeds, ragweed, morningglories.
• Acetochlor, S-metolachlor, Dimethenamid-P → Effective on annual grasses (foxtails, barnyardgrass) and some broadleaf weeds.
• Pendimethalin → Prevents annual grasses and broadleaves like pigweed.
• Isoxaflutole, Mesotrione → Controls broadleaf weeds with extended soil activity.
• Flumioxazin, Saflufenacil → Targets pigweeds and resistant broadleaf species.

Burndown (Non-Selective) Herbicides:

• Glyphosate → Broad-spectrum weed control, used before planting (non-GMO corn only).
• Paraquat → Fast-acting burndown for emerged weeds before planting.

Best Practice: Apply pre-emergence herbicides immediately after planting to stop weeds before they emerge. Ensure proper soil moisture for activation.

Early Vegetative Stage (Emergence to V4)

Common Weeds

• Grass Weeds: Foxtails (Setaria spp.), Barnyardgrass (Echinochloa crus-galli), Itchgrass (Rottboellia cochinchinensis)
• Broadleaf Weeds: Velvetleaf (Abutilon theophrasti), Common ragweed (Ambrosia artemisiifolia), Pigweeds (Amaranthus spp.), Common lambsquarters (Chenopodium album)

Recommended Herbicides

Post-Emergence (Foliar-Applied) Herbicides:

• 2,4-D → Broadleaf control (ragweed, morningglories, pigweed). Apply early to avoid corn injury.
• Dicamba → Controls tough broadleaf weeds like kochia and pigweed.
• Mesotrione, Tembotrione, Topramezone → Controls broadleaf weeds like lambsquarters, pigweed.
• Nicosulfuron, Rimsulfuron → Selective grass weed control (foxtails, barnyardgrass, johnsongrass).
• Atrazine → Used in combination with other herbicides to enhance residual control.

Best Practice: Apply post-emergence herbicides when weeds are small (2–4 leaves) for best results. Use tank mixes for broad-spectrum control and resistance management.

Mid-Season Stage (V5 to Tasseling)

Common Weeds

• Grass Weeds: Fall panicum (Panicum dichotomiflorum), Crabgrass (Digitaria spp.), Johnsongrass (Sorghum halepense)
• Broadleaf Weeds: Waterhemp (Amaranthus tuberculatus), Palmer amaranth (Amaranthus palmeri), Striga (Striga hermonthica), Nutsedges (Cyperus spp.)

Recommended Herbicides

Post-Emergence Herbicides for Late-Emerging Weeds:

• Mesotrione, Tembotrione → Extended control of late-emerging broadleaf weeds.
• Halosulfuron → Effective on nutsedge species.
• Glufosinate → Used only in LibertyLink corn hybrids.
• Glyphosate → Used in glyphosate-tolerant corn (Roundup Ready) for grass and broadleaf control.

Best Practice: Apply herbicides before weeds exceed 6 inches to prevent competition with corn. Avoid herbicide drift onto sensitive crops.

Late-Season Stage (Tasseling to Maturity)

Common Weeds

• Grass Weeds: Johnsongrass, Volunteer cereals, Tall foxtail
• Broadleaf Weeds: Morningglories (Ipomoea spp.), Cocklebur (Xanthium strumarium), Velvetleaf

Recommended Herbicides

Spot Treatments & Harvest-Aid Herbicides:

• Paraquat → Desiccates late-season weeds before harvest.
• Glufosinate → Used in glufosinate-tolerant corn for late-season clean-up.
• Dicamba → Used for post-harvest weed suppression.

Best Practice: Remove weed escapes before seed set to prevent future infestations. Consider mechanical removal for weeds like morningglories that interfere with harvesting.