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R.F. Line and R.M. Cu
USDA-ARS
Wheat Genetics Physiology
and Disease Research Unit
P.O. Box 646430
Pullman, WA 99164-6430
 Comments and questions about MoreCrop send email to:
morecrop@listproc.wsu.edu
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Managerial Options for Reasonable Economical Control of Rusts
and Other Pathogens. An Expert System for Managing Wheat Diseases
in the PNW.
By Roland F. Line and Ramon M. Cu
INTRODUCTION
The computerized system for managing diseases of wheat was
developed for the Pacific Northwest (PNW). The program is referred
to by the acronym MoreCrop (Managerial Options for Reasonable
Economical Control of Rusts and Other Pathogens) and is designed
to provide disease managerial options in different agronomic
zones of the PNW. MoreCrop provides information, options, and
suggestions to help the user make decisions regarding management
of wheat diseases. It predicts diseases and provides control
information based on geographical regions, agronomic zones, crop
managerial practices, cultivar characteristics, and prevailing
weather. MoreCrop can use past managerial decisions to reconstruct
disease conditions, help you decide what disease control option
to select, and provide disease and cultivar-related information
for research, extension, and education.
MoreCrop uses the classical disease triangle as the overriding
principle in predicting a disease outcome. This means that a
susceptible host, a virulent pathogen, and favorable environmental
conditions must exists for the disease to develop and cause damage
to the crop. MoreCrop is an expansion of earlier guidelines for
integrated control of rusts and other diseases, and it is based
on more than 30 years of data on crop management, epidemiology,
and control of rusts, smuts and other wheat diseases. Information
from other plant pathologists and crop scientists was also utilized.
The program was developed specifically for the PNW, but the principles
and concepts should also apply to other regions of the world
and to other crops, and the program should serve as prototype
in developing a total crop managerial program for wheat.
INTEGRATED MANAGEMENT OF WHEAT
DISEASES IN THE PNW
The Pacific Northwest (PNW) is a region of great environmental
diversity. It has the widest range of environmental Conditions
in North America. Because of this diversity, most wheat diseases
can be found in the PNW, and have caused severe losses. The occurrence
and severity of diseases depend mostly on the geographical region,
agronomic zone, crop managerial practices, prevailing weather
conditions, susceptibility of wheat cultivars, disease history
of the field, and presence of virulent species, races, or strains
of the pathogens. MoreCrop considers the environmental diversity
of the PNW in giving a predictive output for the region and the
agronomic zone in which wheat is grown. It is, therefore, important
that you determine the region and the zone where the wheat field
is located.
Stripe rust, leaf rust, and stem rust are indigenous to the
PNW and are potentially the most widely destructive diseases
of wheat in the region. The environment in some specific areas
of the PNW is always favorable for stripe rust and leaf rust,
but in most areas, the environment is favorable for stripe rust
in 3 out of 4 years and favorable for leaf rust in 2 out of 4.
Stem rust is less frequently severe. Models have been developed
for predicting the rusts, and guidelines for their integrated
control have been developed based on more than 30 years of laboratory
and field research.
Common bunt, dwarf bunt, and flag smut have been unique problems
in the PNW. They are both seed-borne and soil-borne, and are
affected by the date of planting. Crop and soil management as
well as resistant cultivars can be used to reduce disease severity.
Seed treatment with fungicides is the most effective control
method for common bunt and flag smut. Loose smut and Karnal bunt,
two smut diseases that are usually unimportant in the PNW, were
added because of interest by growers in the region.
Cephalosporium stripe, strawbreaker foot rot (Pseudocercosporella
foot rot or eyespot), dry land root and foot rot (Fusarium root
and foot rot), Pythium root rot, Rhizoctonia root rot, and take-all
are all soil-borne diseases that infect underground plant parts
or the basal stem. These diseases are affected by crop and soil
managerial practices. Also, strawbreaker foot rot is controlled
by using resistant cultivars, and take-all and Pythium may be
reduced by seed treatment. Since these diseases are soil-borne,
previous occurrences of the diseases (disease and field history)
are important aspect of disease management.
Barley yellow dwarf, wheat streak mosaic, powdery mildew,
the snow molds and the Septoria diseases occur under certain
conditions in some zones and regions of the PNW, and each has
a unique epidemiology and control method. Barley yellow dwarf
is common in zones where wheat is planted in early fall and late
spring. Barley yellow dwarf is transmitted by aphids. Consequently,
severity of the disease is affected by aphid activity and population
size. Using insecticides to control aphids has potential for
control of the disease. Like barley yellow dwarf, wheat streak
mosaic is also affected by early fall planting and adverse weather
such as hailstorm during production of the previous crop. Like
the rusts, powdery mildew is an obligate parasite, widely distributed
throughout the PNW, and can be controlled by fungicides. However,
Powdery mildew seldom causes severe damage to wheat in the PNW.
The snow molds develop during the winter especially when there
is an extended period of snow cover. Conditions that favor extensive
plant growth in the fall reduce the severity of the disease.
Snow molds can be controlled by growing resistant cultivars.
The Septoria diseases are most prevalent in regions where there
are long wet periods, especially in the late spring. Resistant
cultivars and / or foliar fungicides will control the disease.
Management options for scab, tan spot, bacterial leaf blight,
and seedling blight are included. These diseases are more important
in regions outside of the PNW, but can sometimes occur under
certain managerial conditions. Physiologic leaf spot and hessian
fly are two noninfectious diseases that occur in the PNW and
are influenced by management and cultivar selection. Physiologic
leaf spot is managed by the use of chloride fertilizer, while
hessian fly is controlled by insecticide.
Guidelines for the managing each disease have been developed
and used in the PNW. Factors considered in developing the guidelines
were: (1) crop and soil managerial systems (regional and local),
(2) weather conditions (seasonal, local and regional), (3) kind
of diseases and their charateristics, (4) disease and pest interaction,
(5) virulence of races and host susceptibility, (6) kind and
degree of host resistance, (7) severity of disease at different
growth stages, (8) yield loss in relation to disease severity,
(9) effectiveness of fungicides at rates and schedules, (10)
potential yield, and (11) economics (cost versus benefits of
control). These factors were used to develop the MoreCrop system
for wheat disease management.
DESCRIPTION OF MoreCrop
The graphical user interface of MoreCrop allows
the user to interact with the system through the graphical screen
and icons. MoreCrop allows you to easily define a managerial
scenario using the following variables: geographical regions
of North America, agronomic zones of the PNW, crop managerial
practices, wheat cultivars, seasonal weather, field characteristics,
and disease history. The crop managerial practices include choices
of crop rotation, timing and delivery system of irrigation, flexibility
of time and depth of planting, and choices of tillage practices.
A mouse is used as a pointing device. The Keyboard can be used,
but using the mouse simplifies navigating through the program
by "pointing and clicking." The variables that need
to be defined to build a crop managerial scenario are accessible
through menus, control buttons, command buttons, check boxes,
icons, and input boxes.
The inference engine is the program’s protocol for navigating
through the rules and data. The inference engine of MoreCrop
is programmed to support forward and backward chaining. Forward
chaining is an inference mechanism that uses data and information
to establish a conclusion. Backward chaining is an inference
mechanism that starts from a conclusion and searches for supporting
data and information. MoreCrop uses forward chaining to tell
which diseases are more likely to occur based on the selected
region, agronomic zone, crop managerial practices, cultivars,
prevailing weather, and disease history. Backward chaining provides
the reason for the disease outcome by "tracking" backward
through the managerial options and the status of variables that
support the disease outcome. Backward chaining organizes and
provides the "back-tracked" data as the rationale for
a disease outcome.
Three inference engines are fired in sequence to provide information
related to a specific crop managerial scenario. The first inference
engine (Predictor) provides a list of diseases that may occur
and highlights in bold type those diseases that are more likely
to occur based on the selected crop managerial practices. Information
related to disease control practices and the rationale for the
disease outcomes are dynamically linked to the list of diseases
so that they are available by clicking the mouse. The rationale
for the disease outcome, which is constructed by backward chaining,
lists the reasons why a specific disease may or may not occur.
The second inference engine (Controller) makes disease control
suggestions. The output of Predictor is used by Controller as
the initial input for disease control options or suggestions.
Controller considers the diseases that are most likely to occur
and evaluates the various disease control options. The disease
control options include a seed treatment, one or two foliar sprays,
tank-mixed sprays, tank-mixed compatibility and label restrictions,
timing of spray application, and benefits from spraying based
on potential yield. Controller determines the best disease control
option and suggests a specific disease managerial program for
a specific disease outcome. The suggested disease control program
is extracted from an array of 1,073,741,824 possible combinations
of 30 diseases (twenty nine diseases and an insect pest that
causes disease symptom). The rule for all possible combination
is R = 2 c; where R is the number of combinations, where 2 corresponds
to the possible outcome (presence or absence of the disease),
and c is the number of diseases considered.
The third inference engine (Custom Controller) provides flexibility
and independence in managing wheat diseases. Custom Controller
provides options for seed treatment, single or multiple foliar
sprays, tank mixes, and kind of fungicide. A graphical display
of crop stages allows the user to customize the timing of each
spray application by positioning a spray arrow at any plant growth
stage. Custom Controller evaluates the control program tailored
by the user, and provides the list of diseases that can be controlled
by the customized program. The rationale for disease control
or absence of disease control is also linked to the list of diseases
that will provide information on why the tailored disease control
program succeeded or failed. Custom Controller provides an unlimited
opportunity to change the managerial decisions and re-customize
the disease control program.
MoreCrop also contains a library of information on the agronomic
and disease resistance characteristics of cultivars, description
and distribution of stripe rust races, and graphical maps of
geographical regions and agronomic zones. High resolution images
of diseases are available in the library or are linked to the
disease outcome. Warnings, caution statements and reminders appear
as pop-out dialog boxes for added information. MoreCrop can predict
diseases based on various parameters, reconstruct past managerial
decisions to replicate previous disease conditions, provide specific
disease control suggestions, and simulate crop managerial scenarios.
USES OF MoreCrop
MoreCrop is as a decision support system for wheat growers,
extension agents, consultants and other professionals involved
in wheat production. The program contains up-to-date information
related to wheat cultivars and their characteristics, agronomic
zones, fungicide technical information, crop managerial options
and other subject matter relevant to wheat production in the
PNW. MoreCrop is a powerful teaching system. It can be used as
an educational tool for managing wheat diseases. It can analyze
a predefined crop managerial scenario, test a customized disease
control program, serve as a training and reference tool to solve
real-time problems, and serve as prototype in developing a total
crop managerial program for wheat.
SYSTEM REQUIREMENTS
MoreCrop v2.0 requires a PC with Pentium microprocessor or
equivalent, at least 16 Mb of ROM, video card and monitor capable
of displaying true color, a hard disk with at least 18 Mb of
free disk space to store MoreCrop files, and Microsoft Windows
95 or the later version.
RELEASE DATE
MoreCrop v2.0 should be available for use in the spring of
1999 from USDA-ARS and WSU. |