Weather monitors as part of your IPM program

LOW-COST WEATHER MONITORS CAN BE A GREAT TOOL FOR YOUR IPM PROGRAM

Have you ever stopped to consider how many things the weather will affect as you grow your fruit crop? Obviously the temperature and rainfall will affect the physical growth of your crop, but it will also affect the growth of the diseases and insects that can cause problems.

Research has shown that the life cycle of many insects is determined by the temperature. Pest phenology is the study of this relationship between the activity of insects and the number of accumulated heat units or degree days. For example, researchers have shown that each year you can expect the first flight of codling moths to start showing up in your traps when your area has accumulated somewhere between 141 and 491 degree days(DD) base 50. The peak of this first flight occurs when somewhere between 307 and 824 DD have been accumulated. Knowing information like this can give you an idea as to when you need to start monitoring for pests, whether it be through the use of traps or direct visual observation.

Environment is also one of the three main factors that will determine whether or not a disease will occur in your crop (the other two being the presence of a susceptible host and the disease causing agent). If the weather is not right, the disease won’t occur. Weather conditions that may need to be considered, depending on the disease, can include rainfall, temperature, humidity and the number of hours of leaf wetness. Often times it is a combination of these factors that can determine whether or not conditions are suitable for disease development. A good example would be primary apple scab infections during the first half of the growing season. Apple scab can occur anytime the temperature is above 34 degrees (F). However, at 34 degrees you would need 41 hours of leaf wetness for the disease to develop. But raise the average temperature for the period to 61-75 degrees and the length of time required goes down to only six hours of leaf wetness.

In the past, researchers as well as some growers have used fairly expensive instruments or weather stations to measure these weather conditions. Once the data was accumulated, calculations had to be made or the data had to be compared to charts to determine the likelihood of a disease causing event or the accumulation of enough degree days to affect the life cycle of an insect. More recently however, less expensive equipment has become available that makes it more affordable and practical for monitoring weather conditions. In addition, the data collected from this equipment is downloadable to a computer that has the software to do all the calculations and storage of the data for you.

In 2000, the OSU Extension, Wayne County IPM program conducted a research project that compared the accuracy of these less expensive units to the standard units based at the OARDC in Wooster. The project also compared the growing conditions for the same period of time at several different locations or "microclimates" throughout the county. Results showed that the accuracy of these units was comparable to that of the more standard units. More important though was the difference in microclimates within the county, especially for disease prediction. By monitoring for disease favorable conditions, the involved growers knew whether or not an infection period had occurred. For one grower that meant delaying the first fungicide application for scab for almost a week because even though the leaves were wet for more than 12 hours one rainy night, the average temperature during this period of time was too low for disease development. However, a grower at another location in the county knew he had to apply a fungicide right away because his temperature had been a few degrees warmer. In this case, temperature made the difference. If the microclimate of your orchard is on a hillside with little windbreak verses being in lower area or having windbreaks, the amount of leaf wetness time could make the difference.

In 2003 and 2004, these same weather monitors were used in targeting spray dates for insect pests in orchards being used for on-farm research plots. Codling moth eggs are known to hatch approximately 250 degree days (base 50) from the bio-fix date (the day that a sustained moth flight occurs). Depending on the pesticide being used, applications were made at either 200 DD or 250 DD following biofix to allow for the best protection and most efficient use of these pesticides.

Monitors that were included in these projects included the Watchdog leaf wetness/temperature logger (provides enough information for apple scab monitoring) and the Watchdog Model 450 data logger purchased from Spectrum Technologies, Inc. (www.specmeter.com). With the model 450, which has internal monitors for temperature and relative humidity, we also purchased a rain gauge and leaf wetness meter that plug into two additional ports so that we could also monitor for fire blight. Each of these units will down load onto a computer equipped with Specware-software that allows you to view your data as well as incorporate your data into models that help you determine what is going on in your orchard. In addition to tree fruit, the company has disease and insect models that allow monitoring for grape, tomato and potato pests. Since conducting these research projects, several area growers have purchased their own monitoring equipment noting that the cost of the equipment could be paid for by eliminating 2-3 unnecessary spray applications.

Another monitor offered by the same company this year is a stand alone unit that avoids having to down load the data to a computer. Instead the unit has a digital read out that indicates the daily highs and lows, hours of leaf wetness and whether or not a scab infection period has occurred. In addition you can also use it to track degree days. Other producers of monitors on the market include Onset Computer Corporation (www.onsetcomp.com) and Davis Instruments (www.davisnet.com).

In summary, including the use of monitoring equipment in your IPM program can be a way of protecting your crop and saving you money in the long run. With the price of the equipment coming down, the wait may not be so long! And as one grower stated, using this equipment can take a lot of the guess work out of knowing when to apply a pesticide.