Crop Scouting Report Template Form – Fill Out and Use This PDF

J. Doll, C. Grau, B. Jensen, J. Wedberg, J. Meyer

Introduction

Field monitoring, or scouting, is the backbone of all pest management programs. Before appropriate pest control decisions can be made, a detailed assessment of pest populations must be obtained. Efficient pest scouting requires a thorough knowledge of pest and crop biology, pest identification and habits, correct sampling methods, and economic thresholds (when available).

The goal of scouting is to give a complete, accurate and unbiased assessment of pest populations. The field scout is the link between the consultant and grower. Scouting report forms must be comprehensive enough so control decisions can be made directly from the report form. These forms not only serve as a record of current pest populations but should be saved by the growers or consultant as part of the field history records.

Scouting Frequency

The frequency with which visits must be made depends on the type of crop grown and pest(s) present or expected. Field visits must be scheduled such that increases in pest populations are detected as soon as economic thresholds are reached.Field corn should be monitored at weekly intervals until pollination is completed, at which time scouting frequency can be relaxed to approximately once every ten days. At this time there is little danger of pest levels exceeding the economic threshold level between visits. The field scouts, however, should always have flexible schedules to allow revisiting problem fields.

Scouting Patterns

Before a scout enters a field an appropriate route must be planned. For efficiency sake, an M-shaped walking pattern is best used on square or rectangular shaped fields. In irregularly shaped fields scouts must keep in mind that they must cover a representative area of the field. Consult Figure 1 for suggested field patterns.

You cannot scout one edge of the field and expect pest populations to be the same in other areas. Do not sample the edge of a field unless it is specifically recommended (i.e. stalk borer or weed scouting). Often pest populations found on the field edge do not indicate what is present in the rest of the field. The exception, of course, is contour strips, where the whole strip can be considered “edge.” When

Figure 1: Suggested field patterns

scouting contour strips, walk the middle of the contour and zig-zag back and forth. Each individual strip must be scouted separately because the types of pest found as well as degree of infestation may vary from strip to strip.

The number of times a scout must stop to make specific counts will vary according to the type of pests found and will be discussed later in this bulletin.

For large fields (greater than fifty acres), the scout’s accuracy diminishes to the point where a field of this size or larger should be split into two separate fields. Separate fields according to geography, previous cropping history or soil type.

Field History Forms

Before the scouting season begins, growers should com- plete a Field History Form (Appendix A). It should contain such information as field location, cropping history, crop yields, pesticide use, fertilizer and lime applications, soil type, soil test records, major pest problems, and anything else that could make scouting more effective.

Scouting Report Forms

Whenever a field is scouted, a field report form (Appendices B or C) should be filled out and a copy left with the grower. Even if damaging levels of pests are not found, farmers are still interested in general crop health and growth stage. These forms should be filled out in triplicate with copies given to the grower, scout supervisor, and a copy should stay with the scout. As scouts prepare to walk individual

fields, they should familiarize themselves with past reports so problem areas can be closely monitored.

feet of row by the appropriate conversion factor (Table 1) to determine plant population.

Equipment

When monitoring corn a scout should carry the following equipment:

µscout report forms and clipboard pencil(s)

µpocket knife (for splitting stalks and cutworm scouting)

µmagnifying glass or hand lens for accurate pest identification

µbags, plastic vials and labels (for collecting plant and insect specimens for future identification)

µmechanical hand counter

µmeasuring tape

In addition the scout should have available in their vehicle:

µreference materials (in case problems are encoun- tered in the field)

µspade (for digging entire plant for pest identifica- tion)

µcooler with ice (to keep unknown weed, insect and disease samples fresh until accurate identification can be obtained)

Stand Counts

Stand counts should be made the second week after emergence. Count the number of plants in 20 linear feet of row from five randomly selected areas of a field. Measure the distance between rows in several locations within the field. Multiply the total number of plants counted in the 100

Row Width	Conversion Factor
30 inches	174
36 inches	145
38 inches	138
40 inches	131

For example, if you have counted a total of 145 plants and the row width was 30 inches, multiply 145 (plants) x 174 (conversion factor) = 25,230 plants per acre.

Table 1: Conversion factors to determine corn populations

Weed Scouting Procedure

The first weed survey should occur shortly after corn emergence and continue at weekly intervals until control options are no longer available. Scouts should record the relative weed abundance and growth stages at ten randomly selected sites. When moving between sites always look for pockets of problem weed infestations. Mark their location on a weed map (Appendix D) so growers can spot treat these areas if necessary. Continue adding to this weed map as the season progresses. This map should be as accurate as possible and include field boundaries and other points of reference (i.e. waterways, access roads and buildings).

Scouts can group individual weed populations into these four categories:

Scattered-Weeds present but very few plants within the field. Enough plants to produce seed but not likely to cause economic loss in the current year.

Slight-Weeds scattered throughout the field, an average of no more than 1 plant per 3 feet of row, or scattered spots of moderate infestations. Economic loss unlikely but possible in certain areas.

Moderate-Fairly uniform concentration of weeds across the field. Average concentrations of no more than 1 plant per foot of row or scattered spots of severe infestations. Economic loss likely unless control measures taken.

Severe-More than 1 plant per foot of row for broadleaf weeds and 3 plants per foot of row for grasses, or large areas of heavy infestations. Economic loss certain unless weeds controlled.

We do not have exact threshold numbers on a species by species basis at this time. Common sense and intuition should be the guides to determine the course of action in a given field.

Perennial broadleaves like Canada thistle, hemp dogbane, bindweeds, and Jerusalem artichoke usually occur in scattered patches. Yield loss in these areas can be very serious. The decision of what action is appropriate will be based on the percentage of the field infested, weed and crop growth stage, and distribution pattern of the patches.

In addition to yield losses, certain weeds can interfere greatly with harvest. Bindweeds and giant ragweed are examples of weeds that should be controlled regardless of

their impact on corn yield as they can greatly reduce harvest efficiency and increase machinery repair costs.

A comprehensive weed survey/map should be completed by the end of the scouting season. Growers can then develop a preventative weed control program, if necessary, based on weeds most likely to be present next season.

Corn Disease Scouting

Corn should be monitored for evidence of disease during each field visit. If seedling blights are present during the early season scouting, determine percent of plants infected by looking at 20 plants in each of five randomly selected areas within a field.

For leaf diseases, general remarks should be noted as to crop stage, percent of plants affected, percent of foliage infected, whether the disease is above or below the ear, and the location of the infestation within the field. Stalk rots evaluation should be treated differently. Use either the “squeeze test” (squeezing the lower internodes between thumb and forefinger, if tissue collapses then stalk rots are likely to be present) or the “push test” (pushing the plant 6-8 inches off vertical center, if it breaks between the ear and lowest node then stalk rots are likely present) to determine if plants are infected. Conduct either test on 20 plants in each of five randomly selected areas of a field. Report to grower which of the stalk rots are likely the cause and an average percent infestation. Stalk rot tests should begin about four weeks after tasseling. If a fall scouting is conducted, examine for ear rot infestation. Strip back husks from 10 consecutive plants. Record percent infested and color(s) of mold. Repeat 10 times in a 25 acre field, including represen- tative areas.

Sampling For Corn Nematodes

A nematode assay can be valuable to: 1) confirm a sus- pected nematode problem or 2) eliminate nematodes as one of several possible causes of poor plant growth.

The best results are obtained when soil and root samples are taken 6 to 10 weeks after planting. Nematode popula- tions at this time appear to correlate best with grain yield.

However, late summer or fall samples can also be useful in predicting next year’s problems.

Nematode damage to corn often appears in circular or oval pockets in the field. Rarely does an entire field show symptoms. Sample the suspected areas.

There are several ways to take a soil sample for nematode analysis. The following is a general guide.

1.Use a soil probe, narrow-blade trowel or a shovel. Take samples close to plants and to a

depth of 8 to 10 inches. Discard the upper 2 inches of soil, especially if it is dry. Be sure to include plant roots.

2.One sample is adequate per 10 acre field or suspected area within the field. Sample soil and roots from 10 plants and mix into one compos ite sample - 2 pints of soil is adequate. Sample from plants in the margins of suspected areas and not from their centers.

3.Place samples in sturdy plastic bags. Fasten the open end securely and accurately label samples. Keep the samples from becoming overheated. Mail samples early in the week to avoid delays in transit.

Corn Insect Scouting

Scouting methods for insects vary according to species present. The following are scouting guidelines for the major insect pests of Wisconsin field corn.

Seed Corn Maggot and Seed Corn Beetles

Scheduled scouting for seed corn maggots and seed corn beetle damage is unnecessary. However, if you find wilted, yellowed or stunted plants during seedling stand counts, or during cutworm or other soil insect scouting activities, check for damage from these insects. If numbers justify it, check 50 plants in 5 randomly selected areas of the field (250 plants) to determine percent damaged plants. Dig up and examine damaged seedlings and search for seeds in areas that have no plants to determine if skips are insect or planter related. Unlike the spotty nature of wireworm damage, damage from these insects will usually cover most of the field.

Wireworms

Like seed corn maggot and seed corn beetles, scheduled scouting for wireworms is not suggested. However, symp- toms of their activity may be observed during seedling stand counts or cutworm scouting. If wireworm damage is sus- pected, check 50 plants in 5 areas of the field to determine average percent of plants damaged. Dig up several dam- aged plants along with a 4-6 inch core of surrounding soil. Check for wireworms in the soil surrounding the roots, the underground portion of the stem, and in the remains of the seeds (if still present). Search for seeds in areas where plants are missing.

White Grubs

Routine scouting is not suggested. However, damage may be observed during seedling stand counts or cutworm surveys. If signs of white grub damage are found, make counts on 25 plants in 5 areas of the field to determine

percentage of damaged plants. Dig up suspect plants and examine the roots for signs of pruning; search for grubs in the soil immediately surrounding the root zone. Record the percent of damaged plants and number of grubs found.

Stalk Borer and Hop-Vine Borer

Start scouting for plant damage at emergence and until approximately mid-June. Examine 5 sets of 50 consecutive plants for signs of damage and record the percent of plants damaged by each species. Infestations will typically be found in the first 4-6 rows around field margins, grassy waterways, and alfalfa/grass strips. However, damage can be found field-wide if grassy weeds were present the previous year. If the infestation is localized, make detailed maps of infested areas so spot treatments can be made.

Cutworms

As corn plants emerge, check 5 groups of 50 plants. Cutworm infestations are already started by the time corn is planted. Low, wet fields or low, wet areas within fields have a greater probability of attack from black cutworms. Re- duced tillage, weed growth prior to tillage, and late planting are also suspected of contributing to cutworm problems. Some Wisconsin farmers have experienced severe cutworm damage in first year corn following spring plowed sod or alfalfa/grass sod.

Check for cutworms on and below the soil surface adjacent to damaged plants. Occasionally cutworms will be found under crop residue, soil clods, or in soil cracks. Count and record the number of damaged plants (leaf feeding, cut, or wilting), the number and size of cutworms and crop stage.

Corn Leaf Aphid

Examine 10 sets of 5 consecutive plants for corn leaf aphids during the late whorl to early tassel emergence stages. The aphids initially will be found in the whorl of younger plants and later on the tassel.

Start scouting for aphids just prior to or during the tassel emergence period. You will, of course, have to pull the whorl leaves, unroll them, and search for aphids.

Because parasites, predators, and diseases will often keep aphids under control, it is important to note and record their presence. Look for lady beetles and lady beetle larvae, lacewing larvae (aphid lions) and syrphid fly maggots. The aphid colonies may have brown or golden aphids; these are diseased or parasitized.

Corn Rootworms

Make three counts of both species of beetles at 7-10 day intervals between mid-July and Sept. 1. Count the total

number of western and northern rootworm beetles on 50 plants (10 sets of 5 plants) each time. Do not select adja- cent plants at each location; approach plants with caution because the beetles are easily disturbed. Leave a space of about 3-4 plants between each sampled plant.

Count the beetles on the entire plant, including the ear tip, the tassel, the leaf surfaces and behind leaf axils. When approaching a plant, grasp the ear tip firmly with one hand while you use the other to search for beetles on the rest of the plant. When you are ready to examine the silks and ear tip for beetles, open your hand carefully so none of the beetles escape unnoticed. Expose the ear tip as some beetles may be feeding on developing kernels.

The purpose of this scouting is twofold. First, accurate counts are necessary to determine if the silks need insecti- cide protection against beetle feeding. Because of this, one of the counts must be made at the onset of silking. The second purpose is to determine the potential for rootworm larval damage to corn planted the following year in the field.

European Corn Borer

First Generation. Scouting activity for first generation European corn borer must begin at 700 borer degree days (base 50 degrees Fahrenheit). In southern Wisconsin, this can occur as early as the first week of June .

Examine 10 random sets of 10-20 consecutive plants each. Record the number of plants that show signs of whorl feeding. Dissect one infested plant per set and record the number of larvae found on the leaves or in the whorl. The usual range is 1-5 larvae per plant. More mature larvae (3/8 inch or larger) will be found within the stalk and are no longer susceptible to chemical insecticide treatments. These mature larvae should not be included in the larval counts.

Larvae are susceptible to chemical control for only 7-10 days after eggs hatch depending on temperatures. It is important that scouting visits are timely to make sure that larvae are not feeding within the stalk.

Second Generation Scouting. Egg scouting is necessary after tassels emerge; leaf-feeding is no longer a valid indicator once tassels emerge. Begin to look for second generation borer eggs at 1250 borer degree days (mid to late-July in southern Wisconsin). Examine 10 random sets of 5 consecutive plants each. Egg masses are usually laid on the undersides of leaves. Examine the undersides of all leaves for unhatched masses or the remains of hatched masses. Record the number of egg masses found. When an egg mass is found, record the egg’s stage of development according to the following categories:

•White (W) - eggs are newly laid

•Cream (C) - intermediate