Field guides
Short, sourced answers to the questions growers and crop advisers ask during the season: what a symptom is, when a spray pays, how much nitrogen, how to stage a crop. Written for the US and Canada, with the label differences called out.
Diseases
- Canola · June–August · 7 min
Blackleg of canola: scouting and variety rotation
Leaf lesions vs stem cankers, the pre-harvest stem clip survey on the 0–5 scale, and how to rotate Rlm/LepR resistance groups to keep blackleg in check.
Updated October 19, 2026 - Canola · July–October · 7 min
Clubroot of canola: symptoms, resistance erosion and field hygiene
How to confirm clubroot galls, why first-generation resistance is failing in tight rotations, and the rotation and sanitation rules for Prairie fields.
Updated October 19, 2026 - Corn · July · 6 min
Corn fungicide timing (VT–R2): a decision guide
A step-by-step guide to deciding whether a corn fungicide at VT–R2 will pay: disease pressure, hybrid rating, weather, price, break-even math and PHI.
Updated October 19, 2026 - Soybeans · July–August · 7 min
Frogeye leaf spot and fungicide resistance
How to identify frogeye leaf spot in soybeans, why strobilurin (FRAC 11) fungicides no longer control it in much of the Corn Belt, and what to use instead.
Updated October 19, 2026 - Wheat and small grains · June · 7 min
Fusarium head blight in wheat: fungicide timing at anthesis
Spray FHB at early anthesis (Feekes 10.5.1, Zadoks 61): which FRAC 3 and 3+7 fungicides rate well, why not strobilurins, nozzles, the risk tool and DON.
Updated October 19, 2026 - Corn · July–August · 6 min
Gray leaf spot vs. northern corn leaf blight vs. southern rust
Side-by-side identification of gray leaf spot, northern corn leaf blight and southern rust: lesion shape, colour, position, conditions and management.
Updated October 19, 2026 - Canola · July · 7 min
Sclerotinia stem rot in canola: spray timing at 20–50% flower
How to count main-stem flowers to stage bloom, run the sclerotinia risk checklist and decide whether one or two fungicide passes pay in Prairie canola.
Updated October 19, 2026 - Soybeans · August · 7 min
Sudden death syndrome vs. brown stem rot: telling them apart
SDS and brown stem rot both yellow soybean leaves between the veins in August. The split-stem test separates them, and the management is different.
Updated October 19, 2026 - Corn · July–August · 6 min
Tar spot of corn: identification, look-alikes and when a fungicide pays
How to confirm tar spot (Phyllachora maydis), tell it from rust and frass, and decide whether a VT–R3 fungicide will pay in the Corn Belt and Ontario.
Updated October 19, 2026 - Corn · May–August · 6 min
What's wrong with my corn leaves? 12 common causes
Differential diagnosis for corn leaf symptoms: yellowing, purpling, bleaching, striping, firing, holes, lesions, twisted whorls, and how to confirm each.
Updated October 19, 2026 - Soybeans · July–August · 7 min
White mold in soybeans: risk, timing and fungicide ROI
When white mold (Sclerotinia) pays to spray in soybeans: risk factors, the R1–R2 window, FRAC groups that work, the CPN ROI calculator and Sporecaster.
Updated October 19, 2026
Insects and nematodes
- Canola · May–June · 6 min
Flea beetle thresholds in canola
How to assess the 25 per cent leaf-area-loss threshold for flea beetles on canola cotyledons, the seed treatment window and foliar IRAC options in Canada.
Updated October 19, 2026 - Soybeans · September–October · 7 min
Soybean cyst nematode: how and when to sample
Fall is the time to soil sample for SCN. Core count, depth, pattern, where to send it, how to read egg counts and HG types, and what to do with the number.
Updated October 19, 2026
Weeds and herbicides
- All crops · October–May · 7 min
Kochia management on the Northern Plains and Prairies
Kochia biology, Group 2/9/4/14 resistance surveys, fall and spring residuals, tillage, patches and harvest weed seed control on the Plains and Prairies.
Updated October 19, 2026 - Soybeans · February–June · 7 min
Waterhemp control in soybeans: layered residuals and sites of action
How to build a soybean waterhemp program: full-rate pre residual, overlapping Group 15, post by trait before 4 inches, and seed control at harvest.
Updated October 19, 2026
Fertility and nitrogen
- Corn · January–June · 7 min
How much nitrogen for corn after soybeans (MRTN explained)
MRTN gives a profitable N range for corn after soybean, not a yield-goal number. Typical ranges, the price ratio, Ontario's method and product conversions.
Updated October 19, 2026 - All crops · October–March · 7 min
How to read a soil test report
Line by line: pH and buffer pH, organic matter, CEC, P and K by extractant, interpretation categories, micronutrients, nitrate tests and common misreadings.
Updated October 19, 2026 - Corn · June · 7 min
Sidedress nitrogen on corn: timing, rates and tools
When to sidedress corn (V4–V8, later with high-clearance), how to read a late-spring nitrate test, estimate N loss after rain and pick UAN, Y-drop or urea.
Updated October 19, 2026
Planting and stands
- Canola · April–May · 6 min
Canola seeding rate: hitting 50–80 plants per square metre
The canola seeding rate formula in kg/ha and lb/ac, thousand seed weight and emergence inputs, a worked example and the hoop method for counting the stand.
Updated October 19, 2026 - Corn · March–April · 6 min
Corn seeding rate: how to set population and seed drop
Turn a target corn stand into seed drop: the germination and emergence formula, seeds per foot at 30- and 20-inch rows, population ranges and metric units.
Updated October 19, 2026 - All crops · May–June · 7 min
Should I replant? Corn and soybean stand decisions
Count the stand (17 ft 5 in at 30-inch rows), compare its yield with a later replant using extension tables, subtract replant cost. Corn and soybean steps.
Updated October 19, 2026 - All crops · April–May · 7 min
Soil temperature for planting corn and soybeans
Plant corn and soybeans when soil at seed depth is 50 °F (10 °C) and rising, with no cold rain in the first 48 hours. How to check, data sources and frost.
Updated October 19, 2026
Growth stages
- Corn · May–September · 7 min
Corn growth stages V1–R6 with a scouting checklist
Stage corn with the leaf-collar method, what to scout at each V and R stage, rough GDD timing, herbicide and fungicide label cut-offs, and black layer.
Updated October 19, 2026 - Soybeans · June–August · 7 min
Soybean growth stages and the R3 fungicide decision
How to stage soybeans from VE to R8 using the Fehr and Caviness system, recognise R1, R3 and R5 in the field, and why R3 is the usual fungicide timing.
Updated October 19, 2026 - Wheat and small grains · March–July · 7 min
Wheat growth stages: Feekes and Zadoks side by side
Feekes 1–11.4 against Zadoks 10–92 in one table, how to find jointing, flag leaf, boot, heading and anthesis, and which decisions hang on each stage.
Updated October 19, 2026
Harvest and storage
- Corn · September–October · 7 min
Corn harvest: black layer, drying costs and stalk rot checks
Black layer at about 30% moisture, field drydown by weather, the push test for stalk rot, harvest moisture, drying cost per point and storage targets.
Updated October 19, 2026 - All crops · September–November · 7 min
DON (vomitoxin) in corn and wheat: testing, limits and storage
Where DON comes from, FDA and Canadian levels, why sampling drives test results, drying below 15%, segregating loads and what cleaning can and cannot do.
Updated October 19, 2026
Labels and regulation
Calculations and tools
- All crops · all · 6 min
Bushels per acre to tonnes per hectare, by crop
Convert bu/ac to t/ha with the right factor for corn, soybean, wheat, barley, oats and canola, plus lb/ac, gal/ac, inch and °F conversions.
Updated October 19, 2026 - All crops · April–August · 7 min
Tank mix order and compatibility basics
Label first, then the jar test, WALES and APPLES loading order, water pH and hardness, AMS, adjuvants, the mixes that fail, and what to write down.
Updated October 19, 2026