Richard Wall - pest control

Question 1

what is used to control endo/ectoparasites?

Answer 1

Endo: 
Anthelmintics
Endocides
Ecto: 
Insecticides, Acaricides, ectocides

Question 2

describe environmental preparations

Answer 2

space sprays, insecticides must be approved for this use.

atomised insecticide hits flying insects directly.

Question 3

what method of pest/parasite control has less environmental effects than environmental preparations?

Answer 3

1. Topical formulations
   Dips, sprays, pour-on, spot-on, powders, collars, ear tags
   in some african countries, the only way of maintinaing animal husbandary is to dip animals in insecticide.
2. Systemic formulations: go inside the animal.
   injectable, oral. eg, feed through. for fly control in poultry houses.

Question 4

problems with insecticide use

Answer 4

1. environmental contamination - toxicity to other orgs.
2. maximising effective application - must have ch activity exactly where pests are. usually only 10% reaches the pest.
3. bioaccumulation - depends on amount in environment and diet, rate ofexcretion, storage and metabolism. if Lipophillic will bioaccumulate as stored in fat.
4. biomagnification - increases in conc up food chain. eg uk birds of prey affected by biomagnification of DDT = thinning egg shells.
5. resistance - ch run out. low dose over longer period = higher selection for resistance.
6. resurgence - may kill beneficial non target orgs. may allow other specied to increase in abundance and become problem. original pest may return and be more severe because it natural enemies have been removed.

Question 5

examples of natural insecticides?

Answer 5

soot, dusts, ashes, soap, tar, kerosene, camphour, urine, pepper, sulphur. - many of these act as desiccants, making enviro too dry for insects.
Toxic plant extracts (Pyrethrum, rotenone, nicotine, Azadirachtin)
Oils (Refined petroleum oils
Botanical essential oils)

Question 6

how are synthetic neurotoxins made andgenerally how do they work?

Answer 6

• made from extracting compounds in natural insecticides and made very concentrated.
• work by Inhibition or excitation of ion channels in the synapses of the CNS or at neuromuscular junctions

Question 7

in the 1940s, which synthetic neurotoxins were popular?

Answer 7

Organochlorines & cyclodienes, eg DDT, gamma BHC, lindane, Dieldrin and aldrin.

Question 8

why was DDT so popular?

Answer 8

Dichloro Diphenyl Trichloroethane
first synthesised in 1873 then rediscovered by Muller 1939.
awarded nobel prize for prediction of rapid eradication of malaria.
low mammalian toxicity
long period of residual activity, more potent a lower temps.

Question 9

which synthetic neurotoxins were popular in 1950, 70, 80 and 90s?

Answer 9

1950s - Organophosphates (Diaxinon, dichlorvos, malathion) lower residual activity. also used to gas troops in trenches.
1970s - Pyrethroids (pyrethrum, pyrethrins, pyrethroids -1000x more potent than pyrethrum) v v short half life. surrounded in inert casing.
1980s - macrocyclic lactones, Actinomycetes. some natural and some synthetic. eg avermectin.
1990s - Neonicotinoids.
lower vertebrate toxicity but impacts on bees, some breakdown products toxic.
imidacloprid currently most widely used insecticide worldwide.

Question 10

what typesof insect growth regulators used in 1990s?

Answer 10

JH and JH analouges,
Methoprene, Pyriproxyphen.

Chitin synthesis inhibitors - BPUs,

others: cryomazine

Question 11

a terrible case of accidental toxicity

Answer 11

Cusco, 24 peruvian children died due to contamination of school dinner with insecticide after mistaken for milk powder.

Question 12

what is Dippers flu?

Answer 12

Organophosphate poisoning

reported by farmers in south west uk, from compulsory dipping of sheep 20 years ago.

Question 13

example of a pollutant that has comtaminated the marianas trench

Answer 13

POPS - Persistant Organic pollutants - PCB polychlorinated biphenyl

leaks from ndustrial accidents and discharges, leakage from landfills, or incomplete incineration. Not naturally degraded and persist in environment for decades. lipophillic so readily bioaccumulates in orgs, enter deep sea food chain.
PCB levels 50x higher in mariana than in crabs from contaminated paddy fields near the most pollluted river in china.

Question 14

what is needed for effective pest control?

Answer 14

detailed knowledge of pest ecology, appropriate management techniques and detailed knowledge of cost benefits of control.

Question 15

when is the best time to take action against pests?

Answer 15

when you meet the threshold of level of pest you can deal with.
if no threshold, action is unsustainable and inefficient.
a nominal threshold is not ideal but better than nothing.
Economic threshold is ideal

Question 16

what is the economic injury level?

Answer 16

level of pest density where damage exceeds cost of control. would be making losses if controlled before EIL.
shows that eradication of the pest is not always essential.
should start treatment just before reaching this threshold, as there is a time lag between treatment applied and effect on pop.

Question 17

eg of EIL

Answer 17

Economic injury level of stable flies on cattle in US is 50 flies.

Question 18

what alternative ways are there for management of pests and parasites?

Answer 18

1. natural resistance - environmentally/genetically derived resistance.

Question 19

example of genetically resistant livestock

Answer 19

N’Dama breed of cattle, a trypanotolerant breed found mainly in West Africa. relatively small so farmers reluctant to rear them.

Question 20

example of genetically resistant livestock

Answer 20

EasyCare sheep
common in uk
sheds wool in summer, doesnt need shearing, good meat and lambing ratios. combines best characteristics of selfshedding Wiltshire Horn with the robust Welsh Mountain sheep.

Question 21

benefits of alternatives to conventional pesticides

Answer 21

• Effective against target pest or parasite
• Safe to use
• Environmentally benign
• Cost-effective
• Long residual activity
• Long shelf-life
• Fit with existing practices

Question 22

3 types of biocontrol

Answer 22

use predators, patogens or parasitoids.
parasitoid wasps successful for controlling parasite flies in poultry houses, lay eggs in manure and larvae eat parasite flies.

Question 23

how can fungi be used for biological control?

Answer 23

entomopathogenic - in insects. eg Metarhizium anisopliae & Beauveria bassiana.
spore on insect cuticle germinates and germ tube grows over surface looking for soft spot to puncture,
fungi destroys tissues, takes all of the toxins and causes nutritional deficiency.

Question 24

advantages and problems of fungi biological control

Answer 24

advantages - host specific strains, inexpensive, may be self sustaining and self spreading. can be used in conjunction with insecticides.
problems: slow, wont eradicate a pest but suppress populations.

Question 25

how has fungi been used to control locust populations?

Answer 25

formulate fungus in oil, spray on hopper bands.

also used for control of adult african malaria mosquitoes. dip cloths in solution and hang over windows.

Question 26

what is sheep scab

Answer 26

Psoroptic mange
caused by microscopic mite feeding at sheep skin surface. sheep itch and rub themselves to death.
control using organophosphate diazinon and macrocyclic lactone injections.

Question 27

control of sheep scab using fungi. 3 problems of it.

Answer 27

use Metarhizium anisopilae.
dip sheep in conidial solution
after 5 days, found mite dead, and 10 days hyphae spread across scab. pathogenicity is reduced at higher temperatures.

problems: 1. Difficult to penetrate to the skin of a fully fleeced sheep. 2. It may not eradicate – only reduce abundance. 3. Effects may be unpredictable – high temperature

Question 28

investigation of fungi used to control cattle lice

Answer 28

cattle lice - Bovicola bovis
fungi - Metarhizium anisopliae
small chambers glues onto back of cow with lice in,
added diff concs of either silicone oil or Tween80 to control lice.
at higher conc most lice were infected.
perhaps back rubbers in enclosures could be developed for cows to apply conidia if they are itchy.could push population to below economic threshold.

Question 29

how should fungal control methods be used responsibly?

Answer 29

in an integrated ectoparasite management programme. must carefully consider parasite/host system.

Question 30

how do plant secondary metabolites/ essential oils, act as pesticides?

Answer 30

deterring insect herbivores and by attracting predators and parasites of herbivores.
mode ofaction may be mechanical - blocking trachea, or pharmalogical - acetylcholinesterase. inhibition.

Question 31

what are plant secondary metabolites/essential oils?

Answer 31

> 90% terpenes and terpenoids

aromatic hydrocarbons, low molecular weight, volatile chemical mixtures.

Question 32

benefits of essential oils

Answer 32

Generally low mammalian toxicities

Good public perception

Environmentally benign (easy disposal)

Some may also act as insect repellents

Question 33

how has cinnamic acid been experimented with for use as pesticide?

Answer 33

dip mites in oil, at higher concs get close to 100% mortality. (Wall and bates 2011) experimented by dipping cloths in oil and measured toxicity by number of mites walking over.
applied to sheep scab at 5% conc. must massage into sheep which to a lot of work for farmers. alpaca farmers are willing. made products: Aplaca scab dab using cinnamon oil.

Question 34

what are donkey chewing lice and how are they controlled?

Answer 34

Bovicola ocellatus - chewing lice on donkeys, obligate parasite and is a seasonal problem. large burdens cause heavy irritation and secondary infection.
use pyrethroids: cheap, easy application. however, drug location limited, resistance, environmental contamination.
however, peppermint and tea tree oil were good, most effective on adult lice.