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(BASIC) Guide for Monitoring Arthropods


Guideline for Monitoring Arthropods for the Cotton Project


We, like our funders, are interested in effectively training growers to permanently reduce or eliminate the use of polluting agrochemicals. The primary object of monitoring in this project is to help growers make spray/no–spray decisions based on the status of biological control in their fields. The monitoring reports that help them reach those decisions begin with the work of the Field Scouts who make the observations and collect the arthropod samples required to decide if biological control is working or not.


Observations made on small pest hotspots, dusty field edges, or other atypical areas, are frequently crucial to assessing the status of biological control. But, randomized sampling, averaging, and related statistical treatments are specifically designed to insure that “anomalous” samples do not “bias” the results that are intended to apply to the whole crop. Consequently, the formal data gathering protocols that are most familiar to people trained in scientific investigation, tend to “average out” and obscure the very information needed to assess biological control.

Moreover, in our experience, communication with growers is most useful when modeled after the style used by pathologists when reporting to attending physicians. Such reports provide general impressions and qualitative findings, and judgements based on experience, rather than numbers. Quantitative data are presented in simple discrete classifications such as “rare”, “common”, etc. It is of little use to be informed, for example, that the average cell in a biopsy was 99.12% non–cancerous.

Although we will still be making some counts and gathering some numeric data, we want to emphasize qualitative information as more efficiently and effectively reflecting the complexity of living systems.


The special problems of monitoring for biological control have two consequences. First, they rule out the possibility of a sampling protocol that can be completely specified in advance. MONITORING IS A PROCESS NOT A PROCEDURE. Scouts cannot mechanically follow a cookbook, but must chose the specific sample locations and, out of the thousands of details that could be noted, they must record those observations that are most significant to biological control. Such choices can only be made in field, not planned in advance. Second, the scout must learn what to look for; i.e. they must learn what conditions are likely to provide the crucial information on the status of biological control. A partial list of these field marks will be provided to scouts, but a checklist can never completely substitute for alertness, experience, and biological intuition.

The discretion of the scout is also important in making sure that the adequate information is gathered within existing budgetary constraints. We need to have enough time to spend in the fields where we are not sure if biological control is working well enough. But we will not have adequate time for these potential trouble spots if we waste it gathering non–critical data. The scout must learn to use monitoring time wisely


Although it is impossible to plan every detail of a monitoring procedure in advance, there is a repeatable sequence of steps that has proven effective through many years of biological control monitoring


The ease and quality of the field observation reports is enhanced when the scout tape records observations into a tape recorder for transferring later to the report form. This helps when scouts are working with trainers to remember new information. Always tell the date, time and location before speaking. With small tape recorders if the trainer says something, repeat it, because the microphone may not pick it up. Use shortened words and names so that it doesn’t take too long to listen to the recording. Watch out that you don’t push the wrong button and erase important information. Have battery and tape supply.


Field maps may be divided into any number of sections that make sense for monitoring. If we learn that the field is homogeneous, then division may be unnecessary. It may make most sense to divide a particular field in half (i.e. sections that are either near to or farthest from an alfalfa field). Field maps will have whatever divisions for each field marked that the team decides. Each section will be monitored according to the guidelines below


The Inspection and Sweep Net Report (for observations in the field) and the D–Vac Vacuum Sample Report (for observations from the vacuum samples) use a 4–point rating system as follows. The number of organisms that makes it a medium or a high level relates to the possible damage threshold or the potential for biocontrol. It is going to be different for different organisms in the situation. If numeric counts are meaningful for the evaluation, such as leaf counts for mites and predators, or trap counts for moths, or sticky traps for parasites, then include them. However, in general for field crops like cotton and alfalfa, numeric counts from sequential sweep and vacuum samples are not meaningful in themselves without the evaluation of whether it is a low, medium or high level within the given situation.

0 = none,

L = low level of presence,

M = common and/or present at a significant level (i.e. this could be between 5 and 10 in 30 sweeps for midges or beetles at effective levels to contribute to biocontrol)

H = high level in the direction of being out of balance. A high level could be between 10 and 20 in 30 sweeps for some pests, predators or parasites, but may be more. There is a column to refer to location on the field map and a column. The right–hand column allows for reporting any additional information that helps explain how biocontrol is working.


Scouts must pay attention to more than the immediate findings. They must be alert to patterns and trends. They must scout for information and continuously develop their intuitive powers to guide them in where to look. Past, present and possible future populations in the crop and surrounding area run through our minds as we determine where to sample for how long.


Before sampling, record (on tape) a general assessment of the farmscape (location date time weather–temp, cloud cover, wind direction), crop status–stage , abnormal growth & health, status of adjacent crops–harvesting or spraying, habitat status, irrigation, grower practices–herbicide or fertilizer use, irrigation, and activity of other wildlife–birds eating worms, syrphids, moth flight ant activity, and review findings from the previous monitoring report..


The purpose is to locate hotspots and be reasonably sure you didn’t miss any. Sweep in sets of 10 sweeps at a time, then look. After each set of 10, look and decide if you want to take another set of 10 sweeps, and then a third. After 3 sets of 10 sweeps, record the location, time and observations from the sweep net. We are sampling in steps according to three kinds of findings:

1. If there are pests in the initial 3 sets of 10 sweeps, continue hunting around taking 5 sweeps at a time that are not recorded. Then take another set of 10 sweeps from the hotspot and record the findings. The purpose of this is to find out if there are "hotspots", places in the field with high populations especially of pests. Once the hotspots are found, the purpose of the sweeping is then to assess the amount of biological control for those pests. Take as many sets of 10 sweeps needed to draw a conclusion–should only be one from the ‘hot spot’ in that section.

2. If pests are present with few beneficials, take a D–vac sample of the area. Combine this sample with any from no–pest spots in the same field to get an idea resources available to natural enemies.

3. If there are no pests in the initial 3 sets of 10 sweeps, take 20 more sweeps from a larger area to see if you can find any. If there are no pests in this sample of 20 sweeps, record it and move on to the next section. If pests are found follow A or B above.


Use the above process (1&2) for taking leaf samples during the season when mites, aphids and whitefly are anticipated pests on an as needed basis. Plant map when it will provide information about impact of biological control (i.e. square retention/shed, rank growth). Incorporate leaf counts into field log and inspection and sweep net report. Append plant map data and conclusions.


Vacuum the hotspots as needed: Use the D–Vac samples when it can provide significant additional information about tiny forms, relationships between the life stages of pests and beneficials and ratios of pests and natural enemies in hotspots based on sweep net sampling. Mark the position in the field so that a sample can be taken the next time the field is sampled. Take a D–Vac sample of last week’s hottest spot. Note date time location and number of sucks (brushing up one side of the plant=one suck). Use the vacuum only as needed.

Vacuum the habitat: Take a composite D–Vac sample from the surrounding habitat; annuals (adjacent crops, annual habitat planting, weeds, wildflowers); perennial (planned habitat, trees, bushes). Take a separate sample of neighboring alfalfa.


Compile observations on the report form with locations on the field map. It may help to have a log sheet and field map for transcribing information off the tape recorder and then combine the information for the report forms.


Inspection and Sweep Net Report: describes the actual observations of levels of organisms in the field and habitat. It is not the place to record explanations, forecasts or other activity in the field. Fill out 1 for each section of field. Completed by field scout and submitted to grower ASAP.

D–Vac Vacuum Sample Report: describes the findings from the sample in light of the observations from the field giving more in–depth information about the relationships of the life stages of the pest and a more complete assessment of the tiny forms of pests and beneficial species. Completed by DI staff after analysis. Submitted to grower within 7 days of sampling.

Field Observations Report: compiles relevant observations in the farmscape, farm activity and monitoring reports and includes background biological information, other activity of the scouts, forecasts and suggestions. When the D–Vac samples from crop hotspots and from habitat are viewed in the context of the field monitoring, an analysis is possible about the chances for biological control to succeed. Completed by field scout and submitted to grower ASAP.

Field Map: shows location of sweeps, hot spots, releases and significant observations in the surrounding area. Location of sweep spots should be numbered to correspond with sweep log (see below) and inspection and sweep report. Completed by field scout and submitted to grower ASAP.

Field Log: is an OPTIONAL transcript of the tape–recorded observations in each field. Number of insects and observations that document the progress of biological control. From this you should be able to fill out the field map and inspection and sweep net report. Completed by field scout and NOT submitted to grower

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