Presentation on theme: "AGROMET INFORMATION FOR PESTS AND DISEASE CONTROL By Linda De Wet."— Presentation transcript:
AGROMET INFORMATION FOR PESTS AND DISEASE CONTROL By Linda De Wet
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.
THE INFLUENCE OF ENVIRONMENT AND DISEASE ON THE HOST BACTERIAWINDRAIN APPLES CRABAPPLES PEARS SHOOTS TURN BLACK FUNGILOW TaRAIN SHADE TREES PERENNIALS TURF GRASS LEAF SPOT DISEASE FUNGILOW TaRAIN ROOT PROBLEMS
FUNGILOW TaRAIN DROUGHT- STRESSED PLANTS CANKER DISEASES FUNGI DRY CONDITIONS COLD Ta or INTENSE SUNLIGHT
WEATHER VARIABLES Temperature (Ta) Relative humidity (RH) Rainfall MODELS DEGREE DAYS / THERMAL TIME
EXAMPLES OF DISEASES CROPS Stem and Leaf Diseases – Fungal ALTERNARIA BLACK SPOT, Alternaria brassicae and A. raphani Symptoms Black spots Survival and Spread Soil Crop residue Seed Weed hosts RH > 80% Wind dispersal of spores Control Crop rotation High germination (over 90%).
CROPS Stem and Leaf Diseases – Fungal WHITE RUST, Albugo candida Symptoms White creamy yellow pustules develop - lower leaf surface and pods Infected flowers develop a "staghead" Survival and Spread Crop refuse Seed Rain Cool Ta at flowering Control Resistant varieties Three year crop rotation Control volunteer Canola and weeds
CROPS Stem and Leaf Diseases – Fungal BLACKLEG, Leptosphaeria maculans Symptoms White to gray spots on cotyledons and leaves Flowers blighted Few black fruiting bodies form. Survival and Spread Seed-borne Initial spread - airborne spores Secondary spread - splash-dispersed spores Ta 21 °C Stem canker development - 24 °C day Ta Night temperatures 16 °C. Control Plow down infected crop residue 4- year crop rotation Resistant varieties
CROPS Stem and Leaf Diseases – Fungal DOWNY MILDEW, Peronospora parasitica Symptoms Leaf spots initially angular, translucent, light green Stems of flower clusters become swollen Frequently associated with white rust Survival and Spread Spores Windborne Long periods of dew, damp and cool weather and low light intensity Control Destroy crop refuse Crop rotation
CROPS Stem and Leaf Diseases – Fungal YELLOW LEAF SPOT, Pyrenophora tritici-repentis Symptoms Small yellow-brown oval spots Leaves yellow and die Surivival and Spread Use leaf wetness meter - duration of wet leaf Rain and RH stays >90% “Smith simplified criteria”: 17h00 + rain + Ta >10 C ORrain in night + Ta >10 C at 08h00 Control Crop rotation Foliar fungicides may not be economical in many situations
SUNFLOWERS Stem and Leaf Diseases – Fungal PHOMOPSIS STEM CANKER, Phomopsis (Diaporthe) helianthi Symptoms Infection of lower leaves Light brown stem lesion Less chlorosis than inVerticillium Survival and Spread Overwinters in sunflower or Crop refuse High Ta and high RH disease Control Discing Crop rotation
ALTERNARIA LEAF AND STEM SPOT, Alternaria zinniae and Alternaria helianthi Symptoms Circular to angular spots – leaves Dark circular spots on back of head Seedling blight Survival and Spread Crop residue Airborne spores Wet weather + warm temperatures. Control Crop rotation SUNFLOWERS Stem and Leaf Diseases – Fungal
SEPTORIA LEAF SPOT, Septoria helianthi Symptoms Watersoaked spots - leaves dead areas Survival and Spread Crop refuse Water-splashed spores Rainy weather or center pivot-irrigation Control Crop rotation Bury crop refuse
SUNFLOWERS Head Diseases – Fungal RHIZOPUS HEAD ROT, Rhizopus spp. Symptoms Soft, mushy brown rot Shredding Head droops or falls off Survival and Spread Warm moist weather Birds or hail Control Unknown Reduce bird and insect damage to heads
SUNFLOWERS Head Diseases – Fungal BOTRYTIS HEAD ROT, Botrytis cinerea Symptoms Soft brown rot Wet weather - brown tissues develop velvety gray-brown surface Survival and Spread cool, wet conditions Control Unknown Not severe disease
FRUIT Fungal infection of leaves APPLE SCAB, Venturia inaequalis Symptoms Apples and leaves infected Survival and Spread Release of spores during rain Infected only if leaves stay wet Prediction uses “Mills” periods unbroken period of 20 hours + Ta 14 C + leaves wet Visible damage 3 weeks later Control Resistant varieties
EXAMPLES OF PESTS THE OLIVE FLY Bactrocera (Dacus) Oleae Symptoms Visual inspection of fruit number of times eggs laid number of larvae number of flies hatched Stings cause holes and a moon shaped blemish on olive Survival and Spread Ta > 40 o C for > several hours + low RH (< 35%) inhibits Water stress impedes Lack of fruit or cold weather impedes Control Timing of the first control measure of the year is crucial Lure and kill traps last 5 - 6 months Sprays last only days or weeks
WEATHER AND CLIMATE EFFECT ON PESTS Weather and climate can: compete with insects and their production can be beneficial (pollinate, protect) aid as a vector (e.g. mosquito). Management of crop / stock + insect populations NB Identify population processes How must activities of insects be managed? What is the susceptibility of hosts to insect attack? What is the effect of global warming? This information can be utilised by decision-makers.
1) Development Rate and Phenology Primary factor is TEMPERATURE (Ta) Degree days Warm areas - high Ta + water stress conditions Temperate areas - Ta starts slowly in spring, progresses rapidly and slowing again in autumn Can predict phenology from climate (Ta) and to do this one must consider: daily variations spatial differences insects with own Ta regulation Development of mites, earwigs, moths, worms, mosquitoes, butterflies, blowflies, dung beetles, bollworms and armyworms weather parameters and weather parameters development WEATHER AND CLIMATE EFFECT ON PESTS
2) Survival, Fitness and Population Size Mortality or death Extreme weather events Fitness of insects, means enough food which is influenced by: indirect effect of weather and microclimate. Use models, statistics and indexes for combination, transformation and integration of weather elements (mainly daily Ta, rain) Optimal conditions exist for specific insects Heavy rain high mortality rates Hot, dry conditions high mortality rates Ta and rain influences ticks, aphids, grasshoppers, fruit flies, wasps and vegetable bugs WEATHER AND CLIMATE EFFECT ON PESTS
3) Distribution of insects Insects have thresholds Tmx or Tmn + moisture stress distribution Distribution of insects - spatial over land, time or seasons because of different spatial occupations 4) Activity Weather affects vigour in insects e.g. flight is influenced by winds Sequence of events and conditions activity Radar - locust flight patterns WEATHER AND CLIMATE EFFECT ON PESTS
5) Migration Pests - vectors of insect-borne pathogens Locusts - Ta at dusk > 20 C + rain flight Moths – Change in season + Ta migrate Migration stops with Ta Winds migration Ta profile: with height convergence wind direction + wind speed 6) Continuity and Establishment of Infestation Crop rotation Frost - kills aphids (plant lice) Cold and drought kill insects - natural enemies Beneficial insects - bees and wasps WEATHER AND CLIMATE EFFECT ON PESTS
7) Outbreak Initiation Rain or drought Outbreak availability of food for insects 8) Host Susceptibility Damage incurred condition of crops Crops - wind-blown, rain-drenched, water- stressed, are more vulnerable Sheep – rain and mist increase in nematodes (round-, wire-worms) WEATHER AND CLIMATE EFFECT ON PESTS
9) Management Activities Bad weather disrupts normal management Farmers or growers - surveys + access to sprays Planting dates can be changed Efficiency of sprays depend on weather: RH, wind, stability and rain Management - daily farm management + long term decisions Short term decisions-use daily weather forecasts temperature rainfall Long term decisions-use weather in past week / month deviations from normal weather pattern interactions between weather elements GIS, satellite, models + decision support systems WEATHER AND CLIMATE EFFECT ON PESTS
INTEGRATED PEST MANAGEMENT (IPM) What is IPM? IPM is an approach to solving pest problems by applying our knowledge about pests to prevent them from damaging crops, harming animals, infesting buildings or otherwise interfering with our livelihood or enjoyment of life. IPM means responding to pest problems with the most effective, least- risk option IPM applied ONLY when unacceptable levels Impact on environment must be limited Applications of pesticides - always last resort in an IPM program
IPM Soil Preparation Suitable site Test soil Rotate crops Create raised beds Sufficient organic matter. Planting Tolerant varieties Planting time Row spacing diseases and insects prevention Forecasting Pest outbreaks Treatments timed prevent crop damage + saving sprays
Pest Trapping Traps to identify possible outbreak Monitoring Inspection of fields to determine damaging levels of pests Thresholds Before treating, growers wait until pest populations reach a scientifically determined level that could cause economic damage. Before threshold is reached, cost of yield + quality loss < than cost for control Cultural Controls Turn under crop residues Sterilize greenhouse tools Harvest early IPM
Biological Controls Conserve the many beneficial natural enemies Chemical Controls Select best pesticide Calibrate sprayers Good weather conditions Recordkeeping Pest traps, weather and treatments IPM
Who can use IPM? Farmers Buildings and grounds maintenance personnel Professional pest control operators Home dwellers What are pesticide risks? Humans exposed to toxic concentrations According to the WHO, > 3 million people are severely sickened and 220,000 die from pesticides each year worldwide In the U.S. alone, 110,000 people are poisoned by pesticides annually These are "acute" poisonings Long-term effects include cancer, birth defects and other disorders. IPM
Birds - 60 million to 70 million killed each year in US Fish and other wildlife Wild bees and honey bees - essential for pollination of many crops, but many are lost to pesticide exposure > one-third of calls to animal poison centers pets exposed Pests can also become resistant to pesticides control costs + crop losses + pest damage Many natural enemies of pests killed by pesticides Pesticides are powerful medicines for pest problems It’s not smart, effective or affordable to take medicines when you‘re not sick Eating right and staying fit is a great, low risk medicine for your health Using IPM to prevent pest problems is the best solution for a healthy environment for everyone IPM
CONCLUSIONS We are all aware that there is a definite increase in the appearance of disease and the frequency with which it occurs. Many diseases are weather-related and so we as Agrometeorologists can play an increasingly important role in the prediction of diseases. Development of models as early warning systems can assist in prevention of unnecessary application of sprays and fungicides and so increase the profits of those involved in the production of the food resources necessary for our survival and well- being.
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