GLOBE and Integrated Pest Management:
A Case Study for Developing Science Partnerships

David R. Brooks, Principal Investigator, GLOBE Haze/Aerosol Monitoring Project
Drexel University, Philadelphia, PA
Katherine Schanbacher, Research Assistant W. B. Saul High School of Agricultural Sciences, Philadelphia, PA
David Suchanic, Extension Agent, Horticulture
Penn State Montgomery County Extension Service, Collegeville, PA

4th Annual GLOBE Conference, Durham, New Hampshire, July 18-23, 1999

Introduction

The motivation for this project comes from considering some questions about the state of GLOBE science. How can we motivate participating GLOBE schools to be more diligent about their data collection? How can we convince schools to try new protocols? How can we reach schools that are not collecting GLOBE data at all? How can we leverage GLOBE's resources to help teachers and students meet the scientific challenges of understanding our environment? How can we provide more feedback and involvement from scientists who could use GLOBE data? How can we bridge the gap between many of GLOBE's essentially physical measurements and the living world more typically described by students?

One way to address these questions is to develop partnerships beyond GLOBE, in which scientists, teachers, and students can participate as equals. All too often, scientists provide teachers with access to data and teaching materials, but expect nothing in return. No matter how sophisticated, such programs are too one-sided to function as partnerships. In the GLOBE model, true partnerships develop when scientists define their needs and schools provide high-quality data that are otherwise difficult or impossible to obtain. However, this ideal arrangement is rarely realized in practice even within GLOBE. In order to develop indispensable partnerships, we must actively seek ways to use the resources GLOBE has to offer. The purpose of this paper is to describe a project that we believe defines such a partnership.

Integrated Pest Management: A Brief Background

Integrated pest management (IPM) is an area of agricultural science that is currently very much in vogue in the United States. The goal of IPM is to minimize the use of pesticides and other chemical controls in all areas of agriculture, ranging from huge agribusiness operations to individual homeowners treating their lawns and ornamental plants. IPM is important both in developed and developing countries. In countries such as the United States, the widespread use of chemical pest controls has imposed a heavy burden on the environment and agricultural scientists are seeking ways to reverse the escalating dependence on toxic chemicals. In developing countries, there is pressure to "solve" the problem of feeding rapidly growing populations by increasing the use of chemical fertilizers and pest controls. However, this choice not only degrades the environment, but is expensive and ultimately futile.

The quantitative data required to implement IPM programs include growing degree days (GDDs) -- a cumulative measure of air temperature that starts at the beginning of the local growing season -- and related information about, for example, soil temperature and precipitation. The GDD for one day is the average air temperature minus a base temperature. It is common to define the average simply as the average of the daily maximum and minimum temperature. In northern temperate climates, a typical assumption is that the growing season starts March 1, with a GDD base temperature of 50F. (The use of Fahrenheit degrees is an accommodation that must be made to serve the needs of the agricultural community in the U.S.) The raw data required to calculate GDDs and related values are already part of GLOBE protocols. Because GDDs are cumulative, a continuous air temperature record is a primary requirement.

Integrating GLOBE into Integrated Pest Management

In the United States, agricultural extension programs exist in every state. They are managed by state departments of agriculture through "land grant" universities such as Penn State University in Pennsylvania. There are agricultural extension offices throughout the country, serving virtually every county. Many of them have extensive public outreach programs and many extension agents are enthusiastic about IPM. In Pennsylvania, new environmental education guidelines require that schools include IPM as part of their environmental education curriculum. However, extension agents typically have never heard of GLOBE and they often have no experience in writing experiment protocols and learning activities directed at specific age groups.

This extensive network of agricultural extension agents constitutes a natural audience for GLOBE. They need GLOBE's expertise and infrastructure. In return, extension offices can help schools focus on problems of local interest and can provide the kind of professional interaction that leverages GLOBE's limited human resources.

In early spring of 1999, the lead author of this paper approached entomologist David Suchanic at Penn State's Montgomery County Extension Service, who leads an active IPM research program serving commercial horticultural interests in the predominantly suburban counties around Philadelphia. We then contacted the IPM Coordinator at Pennsylvania's Department of Agriculture and secured summer salary support for a student at Philadelphia's W. B. Saul High School of Agricultural Sciences (Kate Schanbacher) to work with us. Because of Suchanic's interest in updating pest emergence tables for ornamental plants, we planned a project to compare various methods of collecting temperature and calculating GDDs at Saul HS (SHS). This school (a non-reporting GLOBE school) has a large campus on the edge of a municipal park in a part of Philadelphia that is more suburban than urban. There is a working farm with livestock, open pastures, and a variety of ornamental plants around the classroom buildings.

Air temperature sources used for this project include manual measurements made at (but never reported by) SHS, automated collection with temperature sensors and a data logger, values reported from the Philadelphia International Airport, temperature data from SkyBit, Inc. (a commercial provider of agricultural meteorology forecasts), and a biophenometer (an instrument that monitors air temperature and continuously calculates GDD). GDD calculations for predicting pest emergence require reliable local air temperature data. Because the calculation is cumulative, systematic errors in modeling, interpolating, or extrapolating air temperature, in lieu of actual measurements, can result in large errors as the growing season progresses. It is well known that differences in terrain and elevation can produce significant and even dramatic air temperature differences over very short distances. These differences affect the local ecosystems within which agricultural pests develop and, hence, affect how controls should be applied.

The environment surrounding SHS, with its gently sloping terrain, open fields, pastures surrounded by trees, and buildings surrounded by ornamentals, is more typical of a small farm or commercial nursery than of an urban high school. Temperatures there are certainly more representative of conditions in the surrounding suburban counties than temperatures taken 10 km away at Philadelphia International Airport, which consists of acres of paving and buildings in a highly urbanized area. It is important to realize that this project can be replicated in other environments. In fact, although GLOBE emphasizes "natural" settings, the needs of the IPM community encompass any environment where things grow. Although it might be argued that GLOBE air temperature measurements are not essential for routine weather forecasting, the same argument cannot be made for IPM. The network of meteorological weather stations is simply too sparse to meet the highly localized needs of IPM modeling.

Comparing Temperature Sources

Figure 1(a). Air temperature data for Saul High School, May 1999.
Figure 1(b). Air temperature data for Saul High School, June 1999.
Figure 1 summarizes some of the air temperature data collected at SHS during May and June: air temperature readings collected with a data logger at 15-minute intervals (shown as a continuous line), hourly temperatures from the National Weather Service station at Philadelphia International Airport (PHL), interpolated values from SkyBit, Inc., and (a very few) manual measurements. The sensor for the logged values is located just below the bottom of a GLOBE-standard thermometer enclosure rather than inside. This is because the instructions for using the biophenometer calls for the sensor to be in the shade but not in an enclosure. PHL values are reported in the Philadelphia Inquirer newspaper for the previous day. Typically, these values start at 1:00 am and continue hourly to 9:00 or 10:00 pm. The SkyBit values are taken from summaries of what a computer model believed the maximum and minimum temperatures were based on interpolation or extrapolation from existing weather stations.

An unfortunate gap in logged temperatures from June 10-22, the end of which can be seen in Figure 1(b), demonstrates the importance of maintaining manual measurements along with automated data collection. The SHS temperature collection site is located in a sheep pasture. Despite the consensus among students and teachers that sheep are not very curious animals, it is clear that on several occasions they pulled up the soil temperature sensors and chewed on them. This problem finally was solved by putting a rabbit cage over the area where the sensors were buried. However, when students reconnected the sensor cables, their order was inadvertently reversed and it was learned only later that the air temperature sensor, which previously had been a soil temperature sensor, was no longer functioning. Note that during the 10-day period from June 21 through June 30, at the end of the school year, there were no manual temperature measurements made at SHS.

Sheep attacks aside, there are several features of interest in Figure 1. The PHL temperatures tend often to overestimate the nighttime minimum temperatures and sometimes to underestimate the daytime maximum temperatures at SHS by a few degrees. The systematically lower nighttime temperatures at SHS, relative to PHL, are consistent with an "urban heat island effect" argument. Because PHL is in a heavily urbanized area, it is not surprising that it cools more slowly in the evening than a more suburban environment. PHL is also next to the Delaware River, which may produce a moderating effect on daytime temperatures.

Figure 2. Comparison of suburban and urban (PHL) air temperatures.
For an additional comparison, consider Figure 2. In this case, the PHL temperatures are compared to data logged temperatures recorded during May 1999 in Brooks' backyard a suburban setting about 25 km from PHL; a similar systematic overestimate of nighttime temperatures is evident. These nighttime temperature differences could lead to significant differences in GDDs at sites that are actually quite close to each other. Some climate scientists believe that global warming trends are most clearly evident not in average temperature, but in rising nighttime temperatures. The data presented here show that, in order to make this argument, differences in temperature patterns between urban and less developed areas must be studied carefully. In areas where there GLOBE schools are spaced along an urban-rural interface, there are many opportunities for making valuable contributions.

Soil Temperatures

Figure 3. Soil temperatures at Saul High School.
Figure 3 shows some air temperatures, and 5 cm (2") and 10 cm (4") soil temperatures from the SHS site, along with 2" soil temperatures reported by SkyBit. The data show the expected decrease in temperature with depth, as well as the insulating properties of soil that are evident during record-setting air temperatures in early July. The diurnal cycle makes single manual soil temperature readings difficult to interpret; Figure 3 shows that single soil temperature measurements should be made at the same solar time every day. The 2" max/min soil temperatures from SkyBit, Inc., are based on computer models and bear little resemblance to the measured values the maximum values are much closer to air temperature than to 2" soil temperature. This is perhaps an unfair comparison because the ground cover assumed for the interpolated value is unknown it could be bare soil, for example, rather than the short grass at the SHS site. These data show again the importance of actual measurements at a local site. A study of how soil temperatures differ as a function of ground cover would make an excellent science project.

Growing Degree Day Calculations

Figure 4. Growing Degree Day calculations.
One of the goals of this project has been to compare different methods of calculating GDDs. This may be important because differences due to temperature sources or algorithms can produce significant differences in this cumulative value. Figure 4 shows GDD data from the SHS site based on max/min logged, PHL, and SkyBit temperatures, and the biophenometer placed at the site. The microprocessor-controlled biophenometer accumulates GDD continuously rather than calculating a daily value based just on the previous max/min temperature. As automated data collection at SHS started on May 7, GDD is assigned a value on May 7 of 201.5 based on calculations from the PHL max/min temperatures back to March 1. For the same reason, the biophenometer was set to 0 on May 10 and the PHL value of 257 for May 10 was added to subsequent biophenometer values. The cause of the lack of agreement between the biophenometer and GDDs based on logged temperatures is currently unknown, but appears to be related to a systematic downward bias of nighttime temperatures reported by the biophenometer. The relatively good agreement between logged and PHL GDDs can be attributed to the fact that the PHL values tend to underestimate daytime high temperatures and overestimate nighttime lows, a condition that reduces discrepancies in GDD calculations. We look forward to repeating this project next year, when we will start all measurements on March 1 and produce completely independent GDD records from each source.

Entomology

This project started too late in the spring to follow the full life cycle of many pests. However, we have identified some pests that infest common ornamentals and trees. These are listed in Table 1. Although it is tempting to think of flying insects as free to roam over large distances, this is not actually the case. Many agricultural pests spend all their lives in the same local area, passing through their developmental stages on or near the same plant. Hence, again, local measurements are critical to understanding how and when to control these pests.

Table 1. Ornamentals and pests observed at Saul High School.
PlantLocationPestCurrent status
Betula papyrifera(Birch)in front of gym (full sun)leaf miner (larvae and adults)residual damage only
Pinus mugho (Mugo pine)behind fence on Henry Avenue (full sun)sawfly (larvae)residual damage only
Ilex opaca (American Holly)in front of building (partial sun)leaf miner (larvae)residual damage only
Pieres japonica (Andromeda)in front of building (shady)lace bug (larvae, nymphs, adults)heavily infested with extensive damage

Discussion

We believe this project is important because it provides a real-world example of how to work with partners outside the GLOBE family. In this case, GLOBE temperature protocols are a starting point for meeting the needs of a potentially large community of users who already have both scientific and educational mandates. From the perspective of the agricultural community, the location of a collection site is of less interest than having a high density of sites with complete data records. Thus, a connection with IPM programs provides excellent opportunities for GLOBE schools that may feel hampered by lack of access to a "natural" area.

Taken just by themselves, the data we have presented show that even apparently simple quantities such as air and soil temperature are actually very interesting, scientifically valuable, and worthy of more careful attention than they get from the thousands of schools who have provided sporadic and, therefore, essentially useless reports. It is discouraging to note that even though air temperature is the most widely made GLOBE measurement, it is rare to find a temperature record that is suitable for GDD calculations. Soil temperature, which is important for IPM and also for studies of global climate, is rarely reported; a total of a few dozen measurements per week is typical. Considering the fact that soil temperature measurements are easy and inexpensive to make, we believe that they have the highest scientific benefit-to-cost or benefit-to-effort ratio of any neglected GLOBE measurement. Some features of air and soil temperature variation that are of interest to the agricultural community cannot be observed even with a complete manually collected GLOBE data record. Automated data collection can provide a better picture, but there is a significant price to be paid in the extra effort required to maintain and process those data. It is essential to continue an active program of manual data collection both as a backup source of data and to provide younger students with a record that is easier to process and understand.

Finally, we believe some broader lessons can be drawn from this project. In general, GLOBE protocols are only starting points for doing meaningful science. When GLOBE teachers learn protocols and teach them to their students, they are preparing to do real science, but just doing the protocols is not science. We believe it will be helpful for teachers to guide students toward asking appropriate questions so that following GLOBE protocols can be viewed as a necessary part of answering those questions, rather than as an end in itself. Our project suggests several ways that GLOBE protocols can be part of real science investigations; two have been mentioned elsewhere in this paper. To cite just one more example, cold air and soil temperatures are important for many plants and trees in temperate climates. The same kinds of measurements we have been making this summer can be continued through the winter to search for links to bud break and other markers of the beginning of a new growing season.

Finally, when scientists tap into the resources GLOBE has to offer, in search of data for their own research, they must explain their objectives as thoroughly as possible to as large an audience as possible. We have not been successful at engaging a larger community of students and teachers at Saul High School and this is an endeavor that will require more effort as we continue our work there.

Acknowledgments

We greatly appreciate the encouragement and support provided for this project by Lee Bentz, IPM Coordinator for Pennsylvania's Department of Agriculture.