S2 L4 Molluscicides, rodenticicides, fungicides

Anna Drew

http://curriculum.toxicology.wikispaces.net/2.1.16+Pharmacognosy

• relatively minor pests in agriculture• disease in developing countries bring

other challenges

• schistosomiasis (bilharzia)• South America, Africa, Far East• intestinal and bladder damage • parasitic blood fluke

– Schistosoma haemotobium, S.mansoni, S.japonicum

• part of its life-cycle in the fresh water snails– eg Biomphalaria glabrata– Bulinus, Biomphalaria, Oncolmelania

Mollusc control

http://www.wellcome.ac.uk/en/labnotes5/animation_popups/schisto.html

• Over 1000 plant species tested for molluscicidal activity 1980-1995

• Wide range showed promise» Leguminosae» Araliaceae» Compositae» Liliaceae

• Features» available in sufficient quantity» capable of easy propogation in region required» water soluble active constitiuents» easily extracted» high toxicity for molluscs; low for humans

• Phytolacca dodecandra• endod berry of this Ethiopian plant• triterpinoid saponins eg lemmatoxin

– composed of oleanolic acid– with branched sugar side chains at C-3

• cultivation outside natural habitat disappointing– does not kill snail egg masses

• Swartzia madagascariensis• Leguminosae tree found throughout Africa• pods contains similar saponins

• Swartzia simplex• South American species• leaves contain glycosides of oleanolic acid

– gypsogenin, gypsogenic acid

• Tetrapleura tetraptera• Leguminosae, Nigeria• Saponins

• Euphorbia conspicua latex

• Spirostanol saponins• Balanites aegyptica (Zygophyllaceae)• Potent• Balanitin 1-, 2-, 3-

• Tannins• Leguminosae

– eg Acacia sp

• Napthoquinones• Diospyros usambarensis, Malawi• juglone and plumbagin type• in bark (problem)

• Isobutylamines• Asteraceae, Rutaceae, Piperaceae

• Steroidal glycoalkaloids• Solanum mammosum

• Anthraquinones• Morinda lucida (Rubiaceae)

• Unsaturated anacardic acids• of cashew shells (Anacardium occidentale)• very active but treated water -> dermatitis

• Sesquiterpenes• Ambrosia maritima, Senegal

• Isoflavonoids• Milletia thoningii, W.African legume

• Saponins• Chenopodium quinoa

• Niclosamide

– used for flatworms in vet. medicine

– has been tested in waterways

– toxic to fish– expensive

• Trifenmorph

– also used for fascioliasis

• lifecycle includes snail

– toxic to fish

• Metaldehyde

– cyclic oligomer of acetaldehyde

– slugs, snails

• Metal salts– iron III phosphate– aluminium sulphate

(alum)

• Acetylcholinesterase inhibitors– contact

• Diatomaceous earth

Rodenticides

• Red squill• Urginea maritima (Liliaceae)• Constituents:

– cardioactive glycosides– glucosides – scilliroside, scillirubroside

• Action: convulsions, respiratory failure

• Strychnine

• Strychnos nux vomica (Loganiaceae)• Constituent: = alkaloid• Action: muscle contractions, death by asphyxia• Use: extermination of moles

– toxic to others – not poison of choice

• Coumarins• Naturally found in many plants

– eg woodruff Galium odoratum (Rubacieae)

• -> synthetic derivatives» Warfarin » Difenacoum » Bromadiolone » Chlorophacinone » Diphacinone » Flocoumafen » Pindone » Valone » Coumatetralyl

• eg Brodifacoum ‘superwarfarin’» long action; elimination half-life 20-130 days

• Action: “thin the blood”– inhibit vitamin K epoxide reductase– enzyme that recycles oxidated vitamin K to its reduced form after it has

participated in the carboxylation of several blood coagulation proteins, mainly prothrombin and factor VII

– ↓ blood coagulation– animal dies from internal bleeding– dehydration early on so animal seeks water

• Use: rat baits, also for rabbits and possums

Fungicides• Use: eg mildews

• Neem• Garlic (onion, chive)• Peppermint oil• Cinnamon powder• Apple cider vinegar• Tea• Couch grass• Elder leaf• Cyperus rotundus

• Sodium bicarbonate• Potassium bicarbonate• Diatomaceous earth• Bleaches / peroxide

• Inorganic salts

– Copper

• Bordeaux mixture CuSO4/lime

• Chestnut mixture CuSO4/NaCO3 – alkali varies

• Use: fruit and vines

• Action: – Cu2+ absorbed by spore drawing water in so it bursts

– alkali helps CuSO4 to stick to leaf surface

– (adhesion can also be improved with cotton seed oil)

– Sulphur

• as a dust or wettable powder, with lime• for copper-shy plants

– Mercury

• Seed dressing for monocots, certain turf diseases

• Organic mercurials– wheat bunt Tillia caries

• Dithiocarbamates • Thiram

– wettable powder as insoluble– seed dressings, Botrytis sp (soft fruit)– low mammalian toxicity

• Trichloromethylthiocompounds• Captan

– apple scab Venturia inequalis

• Quinones• Diclone, Chloranil

– light sensitive– seed dressings for Brassica legumes

• Nitro compounds• Dinocap, Dinitroorthocresol

– apple, pear– highly phytotoxic

• Chloronitrobenzenes• Quintozene, Technazine

– dry rot – Fusidarium on potato – pretreat before winter storage– Quintozene – good soil fungicide for Rhizoctonia solani

• Systemics:

– Organophosphorous compounds• Triamphos

– powdery mildew on roses

• Kitzin– Japan paddy rice pest Pyricularia oryzae

– Salicylanilide analogs• had been used in greenhouses for many years against tomato

disease Clodosporium fulvan• had to modify structure to make it systemic for rusts and smuts• -> Carboxin, Oxycarboxin, Benomyl

– Phosphorylated pyrimidines• Diazenon

– Phenols• Chlorineb

– good root protectors