L1 Pest control Anna Drew

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

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

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

Type of disease Depends what it affects: Root »wilt, damp (rot) »eg Fusarium sp -> soybean Leaves »smut or spot »eg Septoria sp -> celery Stems »cankers -> soybean »[eg Rectria galligens] Fruits »scabs or rot diseases »eg Gleosporium perennans -> apple

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

Control Control depends on Lifecycle Knowing conditions for its success May need more than one host 1+2 depend on climatic conditions »ie avoid humidity by pruning to open it out a bit 3+4 depend on susceptibility of plant »eg fungi and resistance 1. Pre-penetration (leaf surface) 2. Penetration 3. Post invasion 4. Release & dispersal

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)

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

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

Exoskeleton Diagrammatic section through the arthropod integument Hypocuticle →

–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

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)

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

Methods of control Fungi 1. Natural control -> 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

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

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

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