L1 Pest control

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L1 Pest control

• Anna Drew

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Pest control

• Whether or not a pest depends on numbers present
• Fungi
• Insects
• Virus
• viral infected plant material has to be burnt
• great loss of money
• not as common

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Fungi (Eumycetes)

• Hard to control
• Mutate easily compared to insects
• Thallophyte members
• (not differentiated into root, stem and leaves)
• Either parasitic living on living animal/plant
• Or saprophytic living on dead or decaying
  organic matter
• Devoid of chlorophyll
• Plant body made of filaments or hyphae mycelium
• Characterised by
• Spore production
• Spore character
• Type mycelium
• Type of colony produced

? importance of characters gradually reduced
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Examples

• Phycomycetes
• Eg Phytophora infestans potato blight
• Ascomycetes
• Eg Venturia inaquelis apple scab
• Basidomycetes
• Eg Puccinia sp. rusts (cereals)
• Visual effects give common names

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Type of disease

• Depends what it affects
• Root
• wilt, damp (rot)
• eg Fusarium sp -gt soybean
• Leaves
• smut or spot
• eg Septoria sp -gt celery
• Stems
• cankers -gt soybean
• eg Rectria galligens
• Fruits
• scabs or rot diseases
• eg Gleosporium perennans -gt apple

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Celery spot
Soybean root rot stem canker
Ripe spot (Bulls-eye rot)
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Control

• Control depends on
• Lifecycle
• Knowing conditions for its success
• May need more than one host
• 12 depend on climatic conditions
• ie avoid humidity by pruning to open it out a bit
• 34 depend on susceptibility of plant
• eg fungi and resistance

1. Pre-penetration (leaf surface)
2. Penetration
4. Release dispersal
3. Post invasion
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Insects

• Arthropoda (segmented body, jointed limbs)
• Arachnida (mites)
• 8 legs
• 2 segments (head and thorax fused)
• (no wings)
• Hexapoda (insects proper)
• 6 legs
• 3 segments (head, thorax, abdomen)

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Lifecycles differ
does most damage
? control stages
Arachnida
Hexapoda
eggs (resistant)
egg
?
?
?
larvae
?
larva
?
?
?
nymph
pupa (resistant)
?
?
adult
?
?
adult
Mites life cycle is dependent on temperature
higher the temperature the shorter the lifecycle
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Points of control

• Also the reasons they are hard to control (areas
  to hit)
• Exoskeleton contact poisons
• absorbed through the body wall
• must come into direct contact with the insect to
  kill
• Alimentary canal stomach poisons
• ingested and kill by action on
• or absorption into digestive system
• Respiratory system fumigents
• Enter tracheal system in the form of a gas

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Exoskeleton
Hypocuticle ?
Diagrammatic section through the arthropod
integument
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• Epicuticle
• cement, wax or polyphenol
• aids in reducing evaporative water loss
• Exocuticle endocuticle procuticle
• Exocuticle
• chitin polymerised amino sugar and phenol
• makes it hard and impermeable
• Larval stage cuticle very soft
• Nymphoidal stage may be shedding, vulnerable
• Adult stage good protection but segmented for
  articulation and chemicals can be absorbed

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• Alimentary canal
• Main absorption is in the midgut
• Rest of the canal is covered with chitin lining
• Respiratory system
• Simple system of internal trachea
• Air enters on either side by spiracles
• Take up the fumigant (unless it causes spiracles
  to close)
• Not good for humans (in confined spaces)

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• Nervous system
• Paired ganglia to each segment
• Connected to head
• Main way drugs eventually act

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Methods of control

• Fungi
• 1. Natural control -gt plant breeding to produce
  resistant
• - fungi can change more quickly
• 2. Biochemical control all ? plant resistance
• - may cause thicker cuticle production
• - or change in metabolism eg ? sugar levels
• - or keep stomata closed
• 3. Chemical control
• (a) contact on the surface
• aimed at the spore or in wax layer
• (b) systemic take up via root/leaves and
  transport in plant
• problem is biochemistry of plant/fungi similar
• must be non-phytotoxic
• Contact always before infestation, systemic not
  always necessary

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• Insects
• Natural control
• Inside greenhouses control climate
• Outside change habitat eg drainage
• Legal control
• On moving live plant material between countries
• Biological control
• Investigate natural predators that can be
  introduced
• Contact method kill all so natural predator has
  nothing to eat or a lower stage in the food chain
  runs life
• Chemical control
• Contact collects on exoskeleton
• Systemic useful for aphids that suck sap

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Plant cuticle

• Important in formulation for contact pesticides
• will it run off or cover whole plant?
• governed by water repellancy
• 2 factors
• surface roughess
• depressed stomata
• composition of wax
• straight chains of alkane, hydroxy alcohols
  keto acids
• will alter water repellancy

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Pesticide classification

• According to type organism against which they are
  effective
• Insecticides
• Molluscicides
• Fungicides
• Acaricides
• Herbicides
• Rodenticides
• Nematocides