V.) Predictive Tools Flashcards
Phenology Models
Phenology: The study of the relationship between weather and cyclic events such as flowering, growth, and reproduction in the life of an organism.
Phenology models predict when such events will occur.
This is particularly useful for invertebrates, including insects and nematodes, since they cannot regulate their own internal temperature and therefore depend on external temperatures (require heat) in order to develop from one point in their life cycle to another e.g. from egg to larva, from larva to an emerged adult.
Because of yearly variations in weather, Calendar dates are not a reliable basis for predicting pest control in and of themselves.
Phenology models (continued I)
Most pest organisms have temperature thresholds above and below which growth does not occur.
A.) Lower Developmental Threshold (LDT):
B.) Upper Developmental Threshold (UDT):
A.) The lower developmental threshold:
For a species is the temperature below which development stops.
B.) The upper developmental threshold:
Can be defined as the temperature at which the rate of growth of development is at its maximum.(not used as frequently).
It is important to note that each stage of an organisms has its own total heat requirements and therefore changes thresholds.
Phenology models (continued II)
The average amount of heat above the lower developmental threshold required to complete an organisms stage, is referred to the physiological time, and can be determined through research.
Through a combination of temperatures and time, a measurement unit called degree-days (DD) is formed.
DegreeDays (DD):
Degree-day:
Is the amount of heat that accumulates when the avg. temperature is 1° above the lower developmental threshold of an organism over a 24 hour period.
Estimating
The simplest way to estimate the number of degree days accumulated in one day is to use an average temperature for that day.
-Either by adding hourly markers and dividing by 24
Or
- Through the subtraction of the lowest temperature from the highest temperature and dividing by 2(may be inaccurate if there is a large temperature gap)
Phenology models (continued III)
Example
…Degree-day: Is the amount of heat that accumulates when the avg. temperature is 1° above the lower developmental threshold of an organism over a 24 hour period.
If a species has a lower developmental threshold of 52°F, and the temperature remains 53°F for 24 hours, this is equal to 1° degree-day (°F).
Similarly on a day of constant 60°F temperature(8°F above the lower developmental threshold of 52°F), it only takes three hours to accumulate 1degreeday; therefore 8 degree days are accumulated through out a 24 hour period.
Phenology models (continued IV)
Biofix date:
Biofix date:
The date to begin accumulating degree days; varies with species. Usually based on specific events such as planting dates, first trap catch, first occurrence of pest, or a specific developmental stage of the pest or crop. (Sometimes January 1st is used as default.)
Based off the biofix date, pest stages can be estimated by accumulating the degree days on a daily routine, and compared against the organisms LDT throughout the season.
Degree day calculators can be found at UC IPM program’s weather data base.
Disease forecasting:
Disease forecasting systems use Weather, host, and pathogen data to predict times when disease outbreak is likely.
Expert systems:
In agriculture, integrated expert systems combine the expertise of various disciplines such as plant pathology, entomology, weed science, nematology, and crop production to address specific on site concerns.
Plant mapping:
Plant mapping is a useful tool for certain growers or PCAs to monitor the developmental status of plants in their fields including indications of crop health.
Precision farming:
Precision farming systems use global positioning systems (GPS) to collect data and geographic information systems (GIS) to manage it.
How to keep monitoring records
Sampling records Permanent samples Graphs Data sheets and files Field maps Electronic databases
