Chemical control of insects

Meaning of insect control All measures which kill or repel insects interfering with their feeding,respiration,reproduction or dispersal

Types of insect control- A. natural control measure B. Artificial or applied method- Chemical control Biological control Physical control

Chemical Control Using pesticides or insecticides (chemicals).

Chemical Control Contact Poisons Affect the insect’s nervous system and must come into contact with insect to be effective.

Chemical Control Stomach Poisons Are sprayed on plant surfaces or are taken into the plant through absorption. Insect must eat or suck the poison to get it into the stomach for this method to be effective.

Chemical Control Fumigants Poisonous gases released into an enclosed place so that insects breathe the gases.

Agriculture Pesticide Applications Boom sprayer Aerial Enclosed cab Backpack wand Air blast sprayer

Pesticide Chemical Families -grouping based on similarities- Similar chemically (similar structure) Attacks pests in a similar way (toxicity) Common treatment + antidote Pyrethroid PY Organophosphate OP Carbamate C Organochlorine OC Chlorophenoxy Paraquat Diquat

Types of insecticide- Normal use: If ingested: High doses: Pyrethroids: are irritants to the eyes, skin and respiratory tract. The symptoms last from 1-2 hours. Systemic toxicity from inhalation or dermal absorption is low. Normal use: Paresthesias (cyno pyrethroids) Shortness of breath (wheezing) Mucous membrane irritation (throat nose) Skin itching If ingested: Loss of consciousness/coma Seizures (cyno-pyrethroids) High doses: Vomiting Diarrhea Excessive saliva Muscle fasciculation Ataxia Irritability: to sound ~ touch Cyno-pyrethroids: fenverlate, flucythrinate, fluvalinate cypermethrine, deltapermethrin,

Organochlorines: 10 - 480 lipophylic The nerves stimulating glands are not affected so you will NOT see: excessive salivation excessive sweating excessive eye tearing (or over-stimulation of small muscles like) twitching eyelids CNS Effects Muscle Weakness Dizziness Headache Numbness Nausea/vomiting LOC Seizures Tremors Ataxia Anxiety/restlessness Confusion

Paraquat dryness, cracks Paraquat is very toxic to the skin and mucous membranes. Particles are too large to get deep into the lungs*, but once in the blood it collects in the lungs. If ingested high case fatality rate. Skin: dryness, cracks erythema blistering ulcerations Nails: discoloration splitting nails loss of nails Respiratory tract: cough nosebleeds sore throat Eyes: conjunctivitis ulceration, scarring, blindness Ingestion: lung fibrosis (stiff lungs) multi-system organ failure, specifically respiratory failure kidney failure

DEET DIETHYLTOLUAMIDE Few toxic cases - given the widespread use Toxic if ingested Children: toxic encephalopathy w/ heavy use on large surface area on kids (+ ETOH - isopropyl or ethyl) Dermal problems: tingling, irritation, desquamination, contact dermatitis, exacerbate pre-existing skin dz Kids: use 5-6.5% formulations

Boric Acid Ants, Cockroaches in Residences “broiled lobster appearance”

Fluorides Transformed in stomach to corrosive hydrofluoric acid:  thirst, nausea-vomiting, diarrhea, abdominal pain Fluoride ion reduces extra-cellular fluid concentrations of Ca+ and Mg  hypocalcemic tetany Cardiac arrythmias- shock  2ndary to fluid/electrolyte imbalances, hypokalemia and the fluoride itself CNS  H.A. muscle weakness, stupor, seizures and coma

Disadvantage of using chemical control method

Biomagnification

Bioaccumulation & Biomagnification

One other problem from over using Chemical Sprays: RESISTANCE! Zero Damage Concept (Where no damage was acceptable) Failed Resulted in Spray, spray, and spray with loss in control Problems Wasted money when not economic Resulted in Resistance!!

Resistance Occurs when there is an ability of a pest to tolerate a pesticide that once controlled it. Can be managed through integrated pest management.

The DDT Case Study 1938; dichloro-diphenyltrichloroethane (DDT) Extremely toxic to insects, but seemed nontoxic to humans and other mammals. Cheap. Broad-spectrum and persistent Effective for disease prevention (typhus fever, malaria) Expanded agricultural production Paul Muller awarded Nobel prize in 1948

Other Problems with Dependence on Chemical Management Increasing levels of chemical output Chemicals persist in environment Non-target impact Public concern

Solution-Integrated Pest Management Regulatory (Quarantines) Cultural (Planting dates, harvest dates etc..) Biological (Lady beetles, lacewings) Resistance (WSS resistant winter wheat) Gene Manipulation Mechanical Control (Fly swatter or burning) Chemical

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