Successfully managing pests and diseases is one of the biggest challenges for farmers who want to run their operations sustainably. Regularly checking crop growth and development makes it possible to recognize whether nutrient deficiency or another crop health problem is developing, and whether anything can be done to correct it. Early detection is key to success as it provides for more time to react and allows the crop a chance to recover.
Field scouting provides information needed to make the best possible in-season crop management decision. Regular and planned field scouting provides information on pest pressure, crop injury, crop growth stage, and soil and plant nutrient conditions. Field scouting, along with good field records, provides a resource for future management plans. An understanding of the local soil, climate, and awareness of disease and pest pressures all contribute to identifying the presence of plant health problems.
The frequency with which scouting must be done will vary according to the type of crop grown and pests present or expected. Scouting should be done regularly, if not daily, during the growing season or when weather conditions favour rapid development of specific pests. With some plant diseases, daily scouting is necessary when it is warm and humid. With weeds, competition is normally most critical during the seedling stage, but this can vary with the species.
The shape of the field, its ease of access, and the nature of the pest’s typical distribution pattern all play a part in deciding how to scout a field. For efficiency’s sake, an “M” shaped walking pattern is best used on square or rectangular shaped fields. For irregularly shaped fields scouts must keep in mind that they must cover a representative area of the field. it is a good idea to break a field into sections of 15 to 20 hectares that have similar field characteristics and management systems. Thorough sampling procedures allows producers to make sound decision, and perhaps save money.
Do not sample field borders, fencerows, ditch banks, or other non-typical areas of the field unless specific pest protocols suggest this. The exception, of course, is contour strips, where the whole strip can be considered edge. You cannot scout one edge of the field and expect pest populations to be the same in other areas. Often pest populations found on the field edge do not indicate what is present in the rest of the field.
Weed Scouting Procedure
The goal of weed scouting is to assess the infestation level of known pest weeds and detect new weeds that may be at very low levels so action can be taken to control or prevent them from becoming an economic concern. Begin scouting as soon as weeds appear in the field. Record growth stages of both broad-leaf and grassy weeds and the numbers per square metre of each weed. Scouts can group individual weed populations into these three categories:
Scattered – Weeds are present but very few plants within the field. Enough plants to produce seed but not likely to cause economic loss in the current year.
Moderate – Uniform concentration of weeds across the field. Average concentrations of no more than 1 plant per meter of row or scattered spots of severe infestations. Economic loss likely unless control measures taken.
Severe – More than 1 plant per meter of row for broadleaf weeds and 3 plants per meter of row for grasses, or large areas of heavy infestations. Economic loss certain unless weeds controlled.
Rules of Thumb for Scouting
- Sample 5 locations within an area with a maximum size of 15 to 20 hectares, sample “like with like.”
- Follow standard protocols when collecting information.
- Scouts need to be familiar with the growth and maturity stages of the crop.
- To determine the crop growth stage, scouts should collect a random sample of 10 plants around each sampling point. (The sampling sites should be evenly distributed across the field excluding obvious influencing factors such as field edges, hills, and low-lying areas)
- Scouts need to be familiar with the pest life cycle.
- Archive information for later assessments.