8.1 Agricultural Plant & Animal Pest Control (Field Crops & Livestock)

8.1 Agricultural Plant & Animal Pest Control (Field Crops & Livestock)

Quick Answer: North Dakota's agricultural pest control — crop and agricultural pest control — livestock classes (NDAC 60-03-01-05(1) and (2)) govern commercial chemical applications across North Dakota's production landscapes. Key agronomic mandates include scouting soybean aphids to the 250 aphids/plant (80% infested, R1–R5) threshold, scouting wheat midge at twilight to the 1 midge per 4–5 heads benchmark, and combating 4-way resistant kochia with layered soil residuals. For Fusarium head blight (scab), triazoles must be applied strictly at Feekes 10.51 (50% flowering), while strobilurins (Group 11) are strictly prohibited at flowering because they increase DON (vomitoxin) levels. Under the livestock class, systemic treatments for cattle grubs (Hypoderma spp.) must be applied BEFORE November 1 in North Dakota to prevent lethal host-parasite tissue reactions (esophageal bloat or spinal paralysis).

North Dakota Agricultural Cropping Systems

North Dakota features one of the most diverse and climatically demanding agricultural production regions in North America. Commercial applicators operating under the agricultural pest control — crop class must calibrate chemical programs to distinct crop rotations, regional soil classifications, and short northern growing seasons (90 to 120 frost-free days):

• Small Grains: Hard Red Spring Wheat (HRSW), Durum Wheat (concentrated in the north-central and northwest regions), and Feed/Malting Barley. Small grains dominate the prairie landscape and are susceptible to cool-season foliar blights, root rots, and head blights.
• Row Crops: Soybeans (prevalent throughout the Red River Valley and central plains), Field Corn, Sunflowers (oilseed and confection varieties centered in central and western North Dakota), and Dry Edible Beans (pinto, navy, black, and kidney beans, where North Dakota leads national production).
• Oilseeds & Pulses: Canola (Brassica napus, dominant across the cooler northern tier counties), Field Peas, Lentils, and Chickpeas.

Because these crops are frequently grown in close geographic proximity, applicators must constantly guard against herbicide drift, vapor volatilization during high-temperature inversions, and sprayer tank contamination.

Key Agronomic Insect Pests: Scouting Protocols & Action Thresholds

Integrated Pest Management (IPM) in North Dakota requires rigorous field scouting rather than calendar-based chemical sprays. Applying insecticides prior to reaching established economic thresholds increases production costs, eliminates beneficial predators, and accelerates insecticide resistance.

Troublesome Northern Plains Weed Species & Resistance Biotypes

Herbicide-resistant weeds represent the single greatest operational challenge to agricultural crop class applicators in North Dakota. Decades of single-site chemical selection pressure have produced biotypes capable of surviving multiple herbicide mechanisms of action (MOA):

1. Kochia (Bassia scoparia)

Kochia is an aggressive, drought-tolerant, and salt-tolerant summer annual adapted to germinate at soil temperatures just above freezing. Upon maturity, the stem snaps at ground level, forming a tumbleweed that disperses up to 30,000 seeds across miles. In North Dakota, kochia biotypes have documented resistance to four distinct herbicide groups:

• Group 2 (ALS Inhibitors): Chlorsulfuron, thifensulfuron, imazamox (near 100% resistance statewide).
• Group 9 (EPSPS Inhibitor): Glyphosate (widespread via target-site mutation and gene amplification).
• Group 4 (Synthetic Auxins): Dicamba and fluroxypyr (documented across western and central ND).
• Group 14 (PPO Inhibitors): Saflufenacil and sulfentrazone (emerging resistance). Management Mandate: Control requires layered pre-emergence soil residuals (metribuzin, pyroxasulfone) combined with multi-MOA post-emergence tank mixtures applied to weeds under 3 inches in height.

2. Palmer Amaranth (Amaranthus palmeri) & Waterhemp (Amaranthus tuberculatus)

Palmer amaranth is on the North Dakota state noxious weed list; waterhemp is a widespread and aggressive pigweed in the state but is not a listed state noxious weed. North Dakota does not use "Class A prohibited" terminology — the legal duty comes from NDCC 4.1-47-02, which requires every person to do all things necessary and proper to control the spread of noxious weeds, enforced through county and city weed officers. Suspected Palmer amaranth should be reported to the county weed officer. Characteristics of both species include:

• Immense growth rates (up to 2–3 inches per day under hot conditions) and prolific fecundity (>500,000 to 1,000,000 seeds per female plant).
• Dioecious reproduction (separate male and female plants), forcing obligate outcrossing and rapid transfer of resistance genes across Groups 2, 4, 5, 9, 14, 15, and 27.
• Identification: Stems are completely hairless; Palmer amaranth features a petiole longer than the leaf blade and occasional white chevron watermarks.

3. Grasses and Perennials

• Wild Oat (Avena fatua) & Green Foxtail (Setaria viridis): Prevalent cross-resistance to Group 1 (ACCase inhibitors, 'fops' and 'dims') and Group 2 chemistries.
• Canada Thistle (Cirsium arvense): Creeping perennial with an extensive horizontal root system. Foliar applications must be timed at the bud stage or post-harvest fall rosette stage when carbohydrates and systemic herbicides (clopyralid, glyphosate) translocate downward into root crowns.

Critical Small Grain & Oilseed Disease Management

Fusarium Head Blight / Scab (Fusarium graminearum)

Fusarium head blight is the most economically damaging fungal disease of wheat and durum in the northern plains. In addition to yield loss, the fungus produces deoxynivalenol (DON), commonly known as vomitoxin. DON contamination leads to severe elevator dockage, rejection of human milling grain, and toxicosis/feed refusal in non-ruminant livestock (especially swine).

• Application Timing Window: Triazole fungicides must be applied strictly at Feekes 10.51 (50% head flowering / early anthesis) in HRSW and durum. In barley, which flowers within the boot, application is timed at full head emergence.
• THE ABSOLUTE STROBILURIN PROHIBITION: Strobilurin fungicides (Fungicide Resistance Action Committee [FRAC] Group 11 / QoI, e.g., azoxystrobin, pyraclostrobin) are strictly prohibited at heading or flowering. University research demonstrates that strobilurin application during heading or anthesis dramatically increases DON vomitoxin concentrations in the harvested grain, even if the field appears cosmetically clean. Only labeled Group 3 triazoles (prothioconazole, metconazole) or triazole-SDHI premixes may be used.

Sclerotinia White Mold (Sclerotinia sclerotiorum)

Overwinters as black resting sclerotia in the soil. Under cool, wet conditions, sclerotia produce apothecia that release airborne ascospores. In canola, fungicide protection must be applied at 20% to 40% bloom before senescing flower petals fall into leaf axils, where they serve as the nutrient base for fungal colonization. In sunflowers, Sclerotinia causes wilt, mid-stalk rot, and catastrophic head rot.

Agricultural Pest Control — Livestock

The livestock class (NDAC 60-03-01-05(2)) authorizes commercial chemical applications to beef cattle, dairy herds, swine, sheep, and livestock facilities to manage debilitating ectoparasites:

• Horn Flies (Haematobia irritans): Small blood-sucking flies that remain clustered on the backs, shoulders, and withers of cattle. The economic injury threshold is 200 flies per animal. Heavy infestations cause blood loss, reduced grazing, and significant weaning weight deficits.
• Face Flies (Musca autumnalis): Non-biting flies that feed on ocular, nasal, and salivated secretions. They serve as the primary vector for Moraxella bovis, the bacterium causing infectious bovine keratoconjunctivitis (pinkeye).
• Stable Flies (Stomoxys calcitrans): Severe blood-feeders that attack the lower legs of livestock, causing defensive bunching and heat stress. They breed in decaying straw-manure mixtures around round-bale feeders.
• Lice (Bovicola bovis chewing lice; Linognathus vituli sucking lice): Cold-weather parasites proliferating during winter confinement, causing intense pruritus, hair loss, and unthriftiness.
• Sheep Keds (Melophagus ovinus): Wingless blood-feeding dipteran parasites that stain and damage wool fleece.

Cattle Grub Host-Parasite Biology & the November 1 Treatment Cutoff

Cattle grubs represent the larval stage of heel flies: the Common Cattle Grub (Hypoderma lineatum) and the Northern Cattle Grub (Hypoderma bovis).

Summer: Heel flies oviposit on leg hair → Larvae bore through skin into connective tissue
  ├── H. lineatum migrates to the ESOPHAGUS (gullet) by autumn
  └── H. bovis migrates to the SPINAL CANAL (epidural fat) by autumn

TREATMENT CUTOFF (LABEL AND NDSU EXTENSION GUIDANCE): DO NOT TREAT AFTER NOVEMBER 1
  ├── Treated BEFORE Nov 1: Larvae killed safely in non-critical connective tissue.
  └── Treated AFTER Nov 1: Risk of severe host-parasite tissue reactions:
        ├── Dying H. lineatum in esophagus → Esophageal edema, salivation, choking, and fatal BLOAT
        └── Dying H. bovis in spinal canal → Epidural pressure, ataxia, and permanent PARALYSIS

Systemic organophosphate and macrocyclic lactone (ivermectin, doramectin, moxidectin) pour-on treatments must be completed prior to November 1 in North Dakota. If cattle are not treated before November 1, systemic grub applications must be withheld until spring (March/April), when surviving grubs have migrated to the subcutaneous tissue of the backline forming noticeable breathing pores (warbles), where they can be treated safely.

Livestock Application Delivery Methods

• Dust Bags & Backrubbers: Self-treatment devices placed in forced-use mineral lanes or water gates. Highly effective for horn fly and face fly suppression.
• Pour-Ons & Spot-Ons: Systemic or contact liquid formulations dosed precisely according to individual animal body weight and applied along the dorsal midline from withers to tailhead.
• Insecticide Ear Tags: Polymer matrix tags providing continuous slow-release delivery of pyrethroids, organophosphates, or macrocyclic lactones. To prevent rapid horn fly resistance, applicators must rotate chemical classes annually and remove tags at the end of the fly season.
• High-Pressure Sprayers & Dips: Used in feedlot or dairy operations for complete coverage against winter lice or mange mites.

Independent Preparation Notice

This study guide is an independent educational publication developed by OpenExamPrep. It is not affiliated with, sponsored by, endorsed by, or produced in partnership with the North Dakota Department of Agriculture, North Dakota State University Extension, or the EPA.