This document discusses forecasting of pests and diseases in crops based on weather parameters. It explains that weather influences many crop pests and diseases, and predicting outbreaks using weather data can help minimize crop losses. It describes how different weather variables like temperature, moisture, leaf wetness duration, and light can impact the growth of pathogens and insects. Developing crop weather calendars that provide weekly weather trends and advisories on planting/harvesting times and pest/disease risks can help farmers better plan agricultural activities.

1. FORECASTING OF PEST AND DISEASES
BASED ON WEATHER PARAMETERS
By : Anurag Satpathi
ID - 54227
M.Sc. Ist Year
Dept. of Agrometeorology

2. INTRODUCTION
 Weather is related to many pests/insects and
diseases, which are bad for the development of
healthy crops.
 We can fight to prevent the destruction of our food
supply by learning more about the conditions that
bring them about.
 If we are able to predict disease or pest outbreaks by
using the weather, then we can prevent or decrease
high losses to a minimum.

3. INTRODUCTION
 DISEASES/PATHOGEN & PESTS
 Bacteria
 Fungi
 Viruses
 Insects
 HOST PLANTS
 ENVIRONMENT + WEATHER

4. THE INFLUENCE OF ENVIRONMENT AND
DISEASE ON THE HOST
FUNGI LOW Ta RAIN
SHADE TREES
PERENNIALS
TURF GRASS
LEAF SPOT DISEASE
FUNGI LOW Temp RAIN
ROOT PROBLEMS
FUNGI LOW Ta RAIN
DROUGHT-
STRESSED
PLANTS
CANKER DISEASES
FUNGI
DRY
CONDITIONS COLD Ta or
INTENSE
SUNLIGHT

5. WEATHER VARIABLES
 Temperature (Temp.)
 Moisture and Relative humidity (RH)
 Leaf wetness duration (LWD)
 Light
 Wind
 Other factors

6. TEMPERATURE
 Temperature influenced the epidemic development of number
of diseases.
 There is an optimum temperature for growth of any organism
and the cardinals (Maximum and minimum), outside which it
survives but cannot grow.
 Extremes of heat and cold not only check growth but, may
partially eradicate the pathogen/pest.
 Thus solar heat treatments of seeds is employed in number of
crops to control seed borne diseases like in case of loose smut
of wheat.
 For soil borne diseases the solar heat has been successfully
used to eradicate pathogen through soil solarization.

7. MOISTURE AND RELATIVE HUMIDITY
 Moisture and humidity is of importance for fungal diseases in
plants. Further disease is more affected by microclimatic
conditions is plant canopy than by the macroclimate ones
measured at meteorological stations.
 The fungal infestations are highly influenced by wet periods
particularly by creating surface wetness of plants. However,
some rusts and powdery mildew sporulate at low RH.
 For example : Fungal diseases of helianthus (charcol rot, leaf
blight) require prolonged moist period for infection are favoured
by prolonged drizzle (Mayee, 1991). While heavy and short rains
are effective for the outbreak of groundnut rust(Mayee, 1987).

9. LEAF WETNESS DURATION (LWD)
 According to Weiss et. al. (1989), the term leaf wetness
duration encompasses all forms of liquid water on leaf surface
whether caused by dew, precipitation or irrigation.
 Duration of LWD is important in the development of important
plant diseases including onion and carrot leaf blights, tomato
early blight, potato late blight, apples scab etc.
 The LWD for infection by several pathogens varies from 0.5
hours to more than 100 hours (Huber and Gillespie, 1992). For
example Phytopthera infestans requires a minimum LWD of 13
hours.

10. LIGHT
 There is little evidence that effects of light are direct on
epidemic development once pathogen is present in the canopy.
 For example: Rust of groundnut is generally enhanced on leaves
if 12 hours pre-darkness is provided (Munde and Mayee, 1980).
 Light effects are difficult to attribute to light alone. But then
there are several examples of the effect of light on sporulation,
spore germination and penetration (Manners, 1993).

11. WIND
 The principle effect of wind on plant epidemics is in spore
liberation and disposal.
 Nagarajan (1987) clearly stated that the urediniospores of black
rust of wheat arrive with rain, cause infection and is
subsequently spread by ground level wind currents.
 In case of groundnut rust, it has been observed that the
formation of infection takes place around the source of
inoculums, which is stretching towards the wind direction.

12. OTHER FACTORS
 Numerous environmental factors other than those stated above
affect the development of diseases and spread of insects.
 Temperature at night alone may be determining factor for
epidemic of rice blast (Padmanabhan, 1983).
 Another factor is shade. It can influence the microclimate and
thus may indirectly affect the growth of diseases such as blast
of rice, powdery mildew of peas and barley etc.
 Nagarajan (1983) observed that daily cumulative cloud cover
between November and april can be used as an index to find
out if would be a brown rust or yellow rust or no rust year.

13. Pre-requisites for developing a Forecast System
• The crop must be a cash crop (economic yield)
• The insect must have potential to cause damage(yield losses)
• The Insect pest should not be regular (uncertainty)
• Effective and economic control known (options to growers)
• Reliable means of communication with farmers
• Farmer should be adaptive and have purchase power

15. Crop Weather Calendars for improved
Agromet Advisory Services in India
 Proper planning for agricultural operations requires relevant and
reliable information in timely manner.
 Information on crop, its stages and the week by week weather
during the crop season is essential for proper management of
agriculture.
 Thus, farm operations planned in conjunction with weather
information are very likely to reduce the costs of inputs and
various field operations.

16. Cont..
 Crop weather calendar is a comprehensive guide for
farmers. It is a tool that provides information on
average weather of every week, planting, sowing and
harvesting periods of locally adapted crops in a specific
agro-ecological zone.
 Further, stage-wise pest disease infestation information can also
be added.
 It also provides information on the sowing rates of seed and
planting material and the main agricultural practices.

17. Crop weather calendar of Rice - Bhubaneswar

19. Uses of Crop Weather Calendars
 Crop weather calendars are excellent examples of the type of
compiled information that can assist forecasters in framing
weather warnings and forecasts directed at farmers.
 The All India Coordinated Research Projecton
Agrometeorology has developed 26 district level crop weather
calendars (CWC) for important crops viz., rice, wheat,
groundnut, soybean, maize, mustard, rabi sorghum, cotton and
chick pea in 22 states.

20. Cont…
 With proper guidance as services provided by agricultural
meteorologists, these calendars will also be of much interest to
the agricultural professionals and to the various government
departments concerned with Agriculture and Food Production,
as well as educationally to the general public.
 Most importantly, it will be a worthy tool for preparation of
crop contingency plans and identifying the growth stage specific
thresholds for designing weather based crop insurance products.

21. REFERENCE
 Huber L. and Gillepie, T.J. (2015) Modeling leaf wetness
duration of phytopathology
 Mayee, C.D. 1987 Rust disease of groundnut in Maharashtra.
 Mayee, C.D. 1991 Important diseases of sunflower and their
management in india.
 Kumar A., Weather induced insects, pests, diseases occurrence
and their management.