Time for Field Detective Work

Start scouting your crops early in the season to evaluate stands and check for potential problems. Otherwise, over time the “evidence” often disappears as seeds or plants rot away, or when weeds take over. A simple windshield observation or drive-by will not do. Walk each field individually.

Keep your scouting simple. Basic field scouting equipment should include a clipboard to record information, a pocketknife, plastic bags to collect specimens, a hand lens, a measuring tape, and a hula-hoop for population counts. While scouting, look for things that will affect yields, such as plant population, emergence, soil compaction, crusting, diseases, insects, weed escapes, herbicide injury etc.

Your scouting pattern must be representative of the whole field!

• Include changes in variety/hybrid, soil type, past cropping history, fertilizer/manure application and any other factors that can affect plant growth.
• Avoid scouting outside rows and headlands unless there are specific reasons for sampling these areas.
• For uniform pests, or problems for which the distribution pattern is not known (e.g. corn rootworm, stalk rots, weeds), the sampling locations should be evenly distributed across the field.
• For problems expected to occur on headlands or in outside rows (e.g. armyworm, spidermites or soil compaction), the sampling locations should be evenly distributed around the edges of the field.
• For problems expected in particular parts of a field (Phytophthora Root Rot in damp clay soils or black cutworms in weedy patches), sampling locations should be concentrated in areas where the problem or pests are most likely to be found.

To calculate plant population in row crops, count the number of plants in 1/1000 of an acre and then multiply the count by 1000 to obtain the number of plants per acre. Table 1 below lists the row length equal to 1/1000 of an acre at various row widths.

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Table 1. "What's 1/1000 of an acre"

To determine plant population and pest infestation levels in narrow row crops, a sampling frame with a known area can be placed on the ground for the counts. This is done using a square frame (e.g. 50 cm x 50 cm equal 0.25 m²) or a circular frame (e.g. a Hula-hoop). The Hula-hoop method is displayed in Table 2. Using the Hula-hoop, determine the number of plants per acre by counting the number of plants found inside the hoop and multiplying that number by the predetermined factor for the diameter of your hoop, which is listed in Table 2.

Table 2

Regardless of the method used to determine plant population and pest infestation levels, at least 10 random counts should be taken in each field to determine an average.

The starting point for diagnosing problems is to look for patterns. Look for areas where the problem occurs and where it is absent.

• Crop problems that are consistent with the topography or the soil type of the field are more likely to be soil related than caused by pests or field operations.
• Problems which are worse on one side or edge of the field are likely to be related to spray drift or to the movement of insects into the field from one side.
• Problems, which occur on isolated plants throughout a field, may relate to diseases such as root rots.
• Problem areas within a field, which have sharply defined boundaries or appear in strips, are often related to field operations. Nematodes, however, are immobile enough that the edge of a nematode-infested spot may also be very distinct.
• Problems that are concentrated in one row but do not appear in an adjacent row are usually equipment or starter fertilizer related. The distance between affected rows will provide some insight into the width of the piece of equipment involved. At times, crop patterns may also relate to old field boundaries which could be up to ten years old or more.

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