The Nuts and Bolts of Scouting
by Julie Newman
Scouting is the backbone of integrated pest management (IPM) programs. It involves the regular inspection of plants, surrounding areas, and detection tools such as sticky traps for pests and other problems. Pests that are monitored in scouting programs include insects and other invertebrates, weeds, pathogens, nematodes and vertebrates. Natural enemies (beneficial organisms) may also be monitored. The scout is the person who does the monitoring, keeps records and summarizes monitoring information. The scout locates specific sites of infestation and identifies the type of problem, pest levels and stage in the life cycle. Monitoring data collected by the scout over time is used to determine if pest populations are increasing, decreasing, or staying the same. This data is used along with threshold levels to time the application of pesticides and other control actions. A threshold is the level at which plant injury or pest population size is sufficient to warrant control action; below this level the presence of pests and the amount of damage can be tolerated. After applying a pest management control action, monitoring data is used to evaluate the effectiveness of the treatment.
In this introductory article, I will describe the benefits and economics of scouting, qualities of a good scout, the relationship between scouts and the IPM team, and scouting methods that generally apply to all types of pests and beneficial organisms. In the subsequent feature articles of this newsletter issue, specific methods for scouting insects and other invertebrates, diseases and weeds will be described.
Benefits of Scouting Programs
Provides early warning of pest presence. Early detection of pests by regularly monitoring allows growers to implement appropriate control strategies before pest populations escalate, which may include the use of slower-acting methods that are more environment-friendly and safer for workers. This limits the spread of pests, including invasive species, within the nursery. Early detection and control action also reduces pest infestations on harvested plants that are sold and moved to other areas, helping nurseries comply with shipping and quarantine regulations.
Reduces pesticide use. Basing pest control strategies on scouting information along with specific pest threshold levels generally reduces pesticide use. Pesticide reduction results in improved plant quality, less problems with pesticide resistance, fewer disruptions in cultural practices and lower production costs. Additionally, reduced pesticide use improves worker safety and reduces environmental risks and potential liability issues.
Most California growers have implemented scouting programs in their nurseries, primarily in response to reducing lost revenue caused by pest and disease damage (Matthews 2013), but also to comply with pesticide, quarantine and runoff regulations. For example, a UC survey that my staff and I used in Ventura County to demonstrate practices that flower and nursery growers have implemented to reduce pesticide runoff found that 95% of the 65 nurseries sampled regularly monitored for pests and used this data in deciding when to apply pesticides.
When considering whether or not to implement a scouting program, labor costs are a primary factor. Generally, the cost of labor for applying pesticides in nurseries is greater than the cost of labor for scouting; further, the highest cost in pest management is the cost of pesticide materials, as illustrated in fig. 1 (Matthews 2013). Thus scouting is cost effective when it is offset by reductions in pesticide use.
Fig.1. Costs per acre of chemical treatments and scouting across four cases. The labor costs of applying chemical treatments are significantly higher than the labor cost of scouting labor, and as much as over three times higher in the Nursery #3. Source: Matthews 2013
Reduced pesticide use in nurseries as a result of implementing scouting programs has been documented in studies conducted by researchers and extension agents in various states. In California, a 5-year UC Cooperative Extension project involving five different types of ornamental plants demonstrated that scouting programs reduced pesticide use up to 40 percent (Newman 2014), resulting in an average overall cost savings of 20% (fig. 2). Additionally, this project demonstrated that reduced insect and disease damage (from properly timed treatments) and less phytotoxicity (from reduced pesticide use) resulted in healthier crops.
Fig. 2. Comparison of overall pesticide management costs per acre per month across five types of ornamental corps using the grower's standard practice and IPM scouting. The scouting programs reduced overall costs by an average of 20%.
Qualities of a Good Scout
The scout must have thorough knowledge of the pest complex for the specific crop varieties of the nursery and be trained in data collection techniques. The ability to identify the signs and symptoms of pests and diseases on plants and to distinguish between pests and beneficial organisms is critical. Ongoing scout training is recommended. If in-house employees are used in the nursery for scouting, they must be able to scout regularly and consistently. A limitation of in-house scouts with multiple responsibilities is that during busy periods in the nursery scouting is neglected in lieu of more immediate duties.
The Scout and the IPM Team
The scout is usually part of a team of players in the overall pest management program. In addition to the scout, other members of the team include the person responsible for making pest control decisions, such as the grower or PCA (unless decision-making responsibilities are directly assigned to the scout), and those involved in spraying pesticides and applying other control actions.
Developing a Monitoring Plan
Monitoring methods include the visual inspection of plants in crop areas, as well as plants outside the growing area that can serve as a source for pest infestations. The entire production area should be inspected for pests and for potential issues that could contribute to plant problems and information concerning previous pest history and other potential pest problems should be collected. In addition, monitoring methods include the use of tools such as insect traps, disease detection kits, and instruments for determining soil pH and conductivity. See Integrated Pest Management for Floriculture and Nurseries (Dreistadt 2001) for a more complete list of tools used in scouting and table 1 for more monitoring methods.
Insects and Mites
|visual inspection of crops||1||2||1||2||1|
|visual inspection fo growing
area and surrounding areas
|environmental monitoring compared with optimal conditions||1||1||2||3||2|
|cultural care compared with recommended practices||1||1||2||2||2|
|on-site tools and tests(e.g.,
ELISA kits, traps, and water chemistry meters
|off-site laboratory tests||1||1||2||1||4|
|historic records compared to
current scouting results
Floriculture and Nurseries (Dreistadt 2001) for a more complete list of tools used in scouting and table 1 for more monitoring methods.
KEY: 1=very important method for that problem; 2=somewhat important method; 3=not important method, 4=not used or very rarely used.
Table 1. Monitoring methods and the types of pests they detect. Source: Adapted from Dreistadt 2001.
A written monitoring plan should be developed that clearly spells out what monitoring methods are to be used and how they will be employed. Monitoring methods chosen should be appropriate to the target pests (table 1) and the crop. For crops with quarantine pests, there may be protocols that must be followed. The monitoring plan should develop a protocol for the collection and inspection of samples for each pest of interest to estimate overall pest population. The number of samples and the sampling unit should be constant over time.If the plants are small, the sample unit may be an entire plant; for larger plants the sample unit may be a set number of shoots and leaves or flower buds. The number of plants to sample depends on the value of the crop and the budget, as well as crop susceptibility to insect or disease problems. It is important that the site be sampled the same way each week to make results comparable among sample dates.
For more information on sampling methodology, see the UC Container Nursery Production and Business Management Manual (Newman 2014). Specific methodology used for insects and other invertebrates, diseases and weeds is also discussed in the subsequent feature articles in this newsletter.
Implementing the Monitoring Plan
It is critical that propagation areas and incoming shipments from other nurseries be intensely monitored to insure that plants are free from pests and diseases when they are planted out. The scout should also inspect outgoing shipments of plants from the nursery to insure that life stages of pests, especially invasive species, do not move to other areas along with the shipment. Scouting should occur at least once a week, following the procedure outlined in the monitoring plan. Foliage and other plant parts for pests should be examined by using a using a 10 to 15X hand lens or optivisor (fig. 4)
beneficial populations, conditions that promote pest
problems and for evaluating the effectiveness of pest
control actions. The scout in this photo is wearing an
optivisor, a visor with a built in magnifying lens, similar
to a jeweler’s magnifying visor. Photo: J. K. Clark.
Keep in mind that pests are rarely distributed uniformly over all parts of an individual plant, and not all areas of the nursery will be infested. Although it is important to randomly select plant samples, it also helps to target hot spots where pests tend to be a problem. In addition to collecting samples using the monitoring plan protocol, be alert for any sign of pest or natural enemy presence anywhere in the nursery while scouting. Also, look for plants that are damaged by pests, adverse environmental conditions, or incorrect use of agricultural chemicals, such as pesticides and fertilizers. Record the specific location of infested plants using maps and flags so that control actions can clearly target that location. Reinspect these plants after taking action to determine if control was effective.
Record Keeping and Summarizing Data
The scout should keep written records of pest counts or degree of injury. Records of environmental conditions such as temperature and relative humidity are also important, as these can be used to predict the growth of pest and pathogen populations. See the UC Container Nursery Production and Business Management Manual and Jim Bethke’s article in this newsletter for examples of recordkeeping forms for plant inspections. If the scout is not the pest management decision maker, he or she will need to summarize the data for those involved in pest management decision making. From such data collected over time, the scout may prepare a graph to illustrate pest population trends or compare current data with the previous collection period.
Julie Newman is Emeritus Floriculture and Nursery Crops Advisor, UC Cooperative Extension, Ventura and Santa Barbara Counties.
Dreistadt SH. 2001. Integrated Pest Management for Floriculture and Nurseries. Oakland: University of California Division of Agriculture and Natural Resources Publication 3402.
Matthews WA. 2013. Use of Scouting as a pest management practice by California nurseries. University of California Agricultural Issues Center. http://ucnfa.ucanr.edu/files/251424.pdf.
Newman JP, Wilen C, Robb K, Bethke JA, Kabashima J. 2014. Integrated pest management, Chapter 12. In: Newman, J. (ed.). Container Nursery Production and Business Management. Oakland: Univ. of California Division of Agriculture and Natural. Resources Publication 3540.