Natural products for pest control

Background

The products described in this chapter are the most important ones among those authorized in the EU Regulation on Organic Farming. However, their use in organic farming must be considered a last and obliged alternative. Priority must always be given to correct agricultural and soil fertilization practices.

There are many substances and products available for plant protection. In this text, however, we will refer only to those authorized by the EU Regulation. The substances are divided in two groups: those against fungal and bacterial diseases and those suitable for the control of insects and mites. This distinction, however, is not so clear-cut due to the secondary effects of some products.

Pictures of the pests and their natural enemies can be found in the websites of companies selling natural enemies.

Objectives

Provide basic knowledge on the principal natural pest control products used in the Mediterranean region against cryptogamic diseases and pests.

Supply useful information on the proper execution of treatments, including time, dosages and combination of formulas.

 

Products against insects and mites

AZADIRACHTIN      (Extract from Azadirachta indica – Neem tree)

General information

Azadirachtin is extracted from the asiatic tree Azadirachta indica, or “ Neem tree”, and is one of the many active compounds known as limonoids, produced by this tree. Other limonoids of the Neem tree are azadirachtin, salannin, nimbin and nimbidin, found in all parts of the tree, but with a higher concentration in the kernel (0,1-1% of azadirachtin).

In Asia and Africa, parts of this tree are widely used to prepare pharmaceuticals, food, cosmetics, and pesticides.

Use

Azadirachtin is used as an insecticide. It acts through ingestion and operates as an antagonist of the ecdysone hormone, impeding the insect to molt. It is not active on eggs and adults and, on certain insects operates as an antifeedant.

Range of activity

Azadirachtin has a wide range of activity, including Homoptera, Lepidoptera, Diptera, Coleoptera and others, mites included. It also has a demonstrated effect against fungi and bacteria.

Range of application

Used in horticulture, fruit trees, nursery and ornamental plants.

Toxicity

Practically non-toxic to vertebrates.

The Neem oil (fo) can be phytotoxic at high doses.

Dose and compatibility

Largely depends on the formulas, approximately 25-50 g/ha of Azadirachtin.

It can be used in combination with Pyrethrins, virus, Bt, soft soaps.

 

PLANT OILS     (Mint oil, pine oil, caraway oil)

General information

Plant oils are a mixture of natural substances derived from various parts of plants such as flowers, seeds and fruits. They mostly contain oleic and linoleic acids. Traditionally, plant and mineral oils were used as fungicides and as pesticide carriers, improving distribution and duration.

Use and effects

Plant oils are used as insecticides, provoking asphyxia in the insects and their eggs.  They also act as repellents.

Range of action

Active against aphids, Coccidae, Diaspididae   and mites.

Field of application

Viticulture, fruit trees, horticulture.

Toxicity

Low toxicity to mammals. Plant oils are not specific and may cause loss of antagonist insects at high dosage.

Dose and compatibility

Depends on the preparation.

Usually use 200-300 ml/hl as additive, 1-3 g/hl as insecticide.

Plant oils can be mixed with most organic farming preparations.

 

PYRETHRINS      (Extract from Chrysanthemum cinerariaefolium)

General information

Pyrethrins are natural insecticides derived from plants of the genus Crysanthemum, cultivated mainly in Kenya, Tanzania and Tasmania. Flowers are collected after flowering, then dried and milled. The active compounds are a mixture of 6 molecules known as Pyrethrins, which are photosensitive and rapidly oxidized, if exposed to air and light. To increase their stability, some formulas contain substances which act as stabilisers (i.e. PPBO piperonilbutoxyd).

Use

Pyrethrins operate as contact insecticides. They attack the nervous system, paralysing the insects in a few seconds (knockdown effect). Depending on the dose that has been used, death can follow. Some insects eventually metabolise the Pyrethrins and recover. Because of this,  Pyrethrins can be activated with PPBO, which inhibits detoxification of the active compound, improving the efficiency of the treatment.

Range of action

Pyrethrins are effective against a wide range of insects (Homoptera, Lepidoptera, Diptera Coleoptera, etc.), and relatively active against mites.

Field of application

Horticulture, ornamental plants, and for the conservation of foodstuffs.

Toxicity

Low toxicity to mammals, but highly toxic to fish, reptiles and amphibians. Pyrethrins are non-selective  insecticides and, therefore, they can  be harmful to bees and to other beneficial insects. They are not phytotoxic.

Dose and compatibility

Usually 70-100 ml/hl.

 

QUASSIA      (Extract from Quassia amara)

General information

It is a natural insecticide derived from the Quassia amara tree, indigenous to Suriname, and from Picrasma excelsa (Jamaican Quassia). The active compounds are quassin and neoquassin. Quassia is used as a repellent for dogs and cats. It is also a medicinal plant.

 Use

Quassia operates on the nervous system, both through contact and ingestion. Its activity is relatively weak, due to its limited persistence. On locusts it has a phagodeterrent effect.

Range of action

Active against aphids and sawflies.

Field of application

Horticulture, fruit trees, viticulture, silviculture, ornamental plants.

Toxicity

Low toxicity

 

ROTENONE      (Extract from Derris spp., Lonchocarpus spp. and Tephrosia spp.)

General information

Rotenone is an alkaloid, first  isolated in 1895. It is extracted from the roots of some tropical plants of the Leguminosae family: Derris elliptica, Derris spp., Lonchocarpus utilis, Tephrosia spp. Rotenone rapidly decomposes upon exposure to light and air. Its persistence is therefore limited to 2-3 days in summer and 5-6 in spring.

Use

The active compound is more toxic through inhalation than ingestion. The degree of powder  fineness is very important to determine the level of toxicity. Rotenone can be stabilised with phosphoric acid and acts through contact and ingestion, inhibiting the mitochondrial electron transport.

Range of action

Rotenone has a wide range of activities: aphids, thrips, Lepidoptera, Diptera, Coleoptera, etc It is also relatively active against mites.

Field of application

Horticulture, fruit trees, ornamental plants, mosquitoes and flies. It is also used in veterinary medicine against Hypoderma flies.

Toxicity

Rotenone has low toxicity to mammals, while it is extremely toxic to fish. It is a non selective insecticide and is not harmful to bees.

Dose and compatibility

Generally 100 g/ha of active compound in horticulture. The waiting periods is 10 days. Rotenone is not compatible with alkaline substances.

 

GRANULOSIS VIRUS      (CpGV)

General information

This virus was first isolated in Mexico in a Cydia pomonella larva. CpGV is used against the Cydia pomonella of apples and seems to be effective also against some other Lepidoptera.

Use

CpGV operates through ingestion. For this reason it has to be applied on larvae of Cydia at the right time. Ultraviolet rays can inactivate the virus, therefore it is recommended to spray the compound around dusk or early morning.

Range of action

This virus is specific for 6 species of Tortricidae,  the most important being Cydia pomonella.

Field of application

Apple, pear and walnut trees.

Toxicity

Strictly specific compound, harmless to other insects. It is not phytotoxic.

Dose and compatibility

Must not be mixed with other alkaline-sensitive substances.

 

BACILLUS THURINGIENSIS

General information

In organic farming, Bacillus thuringiensis is the most widely used bacterial preparation. The bacterium occurs naturally in the soil and its insecticide properties are known since the 1960s. There are many varieties of Bt and it is used in many fields. During sporulation, the bacterium produces toxins (the most important is the delta-endotoxin) which represent the active compound of the formula. Pro-toxins are activated in the insect’s intestine and become lethal., The preparation is selective and harmless to vertebrates which have an acid reaction in the intestine.

Use

Bt is active only through ingestion. For this reason, it  is sprayed on harmful insects during the larva stage, when they are feeding on the surface and they are exposed.. Once the toxin is released in the intestine, the entire digestive tract is paralysed and the insect is unable to feed. Death occurs in a matter of hours or three days at most.

Range of action

The different varieties of Bt are specific to certain families or species of insects:

Bacillus thuringiensis var kurstaki is active against many species of Lepidoptera;

Bacillus t. var tenebrionis is active against some species of Coleoptera (e.g. potato beetle);

Bacillus t. var israelensis is active against mosquitoes;

Field of application

Horticulture, viticulture, fruit and olive trees, ornamental plants, silviculture.

Toxicity

Non toxic to vertebrates. It is highly specific and not dangerous to other insects. It is not phytotoxic.

Dose and compatibility

Highly depends on the formulas, generally from 0,5 to 2 kg/ha of the commercial preparations. It must not be mixed with alkaline fertilisers or crop protectants.

 

FATTY ACID POTASSIUM SALT      (Soft soap)

General information

This product, also known as potassium soft soap (or Marseille soap) is obtained by mixing vegetal oils with alkaline substances such as soda and potassium hydroxide. Aside from being widely used as a detergent, this product is also used in agriculture as an insecticide.

One of its important properties  is that it’s completely biodegradable (it is metabolised by bacteria in the soil).

Use

Potassium salt is used as an insecticide, additive for other crop protectants and also against fungi and weeds. Mixed with other insecticides such as rotenone and Pyrethrins, it improves the adherence and persistence of the solution. Soft soap acts as a direct contact insecticide, damaging the insects’ cuticle with soft tegument; it is also used for washing away honeydew and the waxy excreta of certain aphids.

Range of action

Soft soap is used against phytophagous insects, with soft exoskeletons, such as aphids, thrips and aleurodids. It is also active against mites.

Field of application

Apple, pear, peach, grapevine, aromatic herbs, vegetables and ornamental plants.

Toxicity

No toxicity is known to vertebrates and pollinator insects.

Dose and compatibility

Dosage of soft soap mixed with other insecticides is around 300 g/hl, used alone: 1000 g/hl. This product should not be used in hard water.

 

LIME SULPHUR      (CALCIUM POLYSULPHIDE)

General information

Calcium polysulphide is used as an  insecticide and fungicide. Barium polysulphate is also used in agriculture, but it is forbidden in organic cultivations. The active compound is sulphur in different forms.

Use

As an  insecticide it acts through direct contact, due to the causticity of the preparation. It is also efficient in partially melting cochineal shields.  A secondary action of this insecticide is asphyxia.

Polysulphide is also active as a fungicide because of the presence of sulphur. 

Range of action

Insects: Diaspididae (Quadraspidiotus perniciosus, Diaspis pentagona and D. leperii). Active also against the eggs of mites.

Crop protection: against oidium, peach blister canker and other diseases.

Field of application

Citrus, peach, apple, pear, apricot, cherry, grapevine and olive tree.

Toxicity

The substance is irritating if it is inhaled and if it comes to direct contact with eyes and skin. Polysulphides are also toxic to some predatory mites.  Due to their alkalinity, they can be phytotoxic, inducing burns in the vegetative organs. For this reason they are preferably used during winter.

Dose and compatibility

For winter treatments the following dosage is suggested: drupaceous 16 – 17 kg/hl; apple & pears 20-22 kg/hl. Calcium polysulphide is highly corrosive to the gear used for spraying. Thus, it should be thoroughly washed after using.

 

MINERAL OILS      (White, paraffin, petroleum oils)

General information

Mineral oils have been used since the end of nineteenth century. They are derived from the fractional distillation of petrol at high temperatures, hydrogenation and final extraction with solvents. Extraction conditions highly influence the composition and agronomic impact of mineral oils.

Use

Mineral oils act essentially through asphyxia, suffocating the insects and their eggs.  They are also active as repellents for feeding or egg deposition.

Range of action

Mineral oils are active through direct contact mostly against small insects, such as Diaspididae, Coccidae , aphids, psylla and mites. They can be active against oidium and weeds (due to their phytotoxicity).

Field of application

Fruit trees, horticulture, ornamental plants and nursery.

Toxicity

Very low to mammals, they can cause problems to other insects when sprayed.

Dose and compatibility

1-3 kg/hl as insecticide, and 200-300 ml/hl as additive. Waiting period 15-20 days.

Not compatible with sulphur.

 

SUBSTANCES USED IN TRAPS

PHEROMONES

General information

Pheromones are compounds produced by insects, and used for chemical communication among individuals of the same species. They affect behaviours such as aggregation, sexual interaction and alarm calls. They can be artificially produced in the laboratory and serve different purposes in agriculture, such as monitoring and pest control, being used as attractants in traps together with insecticides.

Use

Monitoring: pheromones are added in traps to attract and investigate the presence of insects in the field (suitable for lepidoptera).

Mass trapping: the objective is to avoid mating, capturing the males of a specific species in a trap which has been baited with an approved insecticide (only some pyrethroids for organic agriculture): Suitable for Lepidoptera and Diptera, like olive fly. 

Sexual confusion: the objective is to avoid mating, spraying large quantities of pheromones in order to confuse the males of a specific species.

 

DIAMMONIUM PHOSPHATE

This fertilizer is used as a bait for mass trapping of fruit and olive flies. Adult flies are attracted by the ammonium odor

 

METALDEHYDE

General information

Metaldehyde is used in agriculture against molluscs. It operates on the nervous system, after ingestion.

Use

The product has to be placed around the field which requires protection from snails and slugs.

Field of application

Horticulture and flowers, in the open field or in glasshouses.

Toxicity

Metaldehyde is toxic to humans and mammals. It is not toxic to fish and pollinator insects if distributed in pellets. It is harmless to plants.

Dose and compatibility

5-15 kg/ha.

 

HYDROLYSED PROTEINS

General information

Hydrolysed proteins are used as attractants only in combination with insecticides. They are used to control olive and Mediterranean flies, during the adult phase, when they need proteins for their diet.

Use

Used as an attractant compound. The insects are killed by the pesticide mixed with proteins.  In organic agriculture is allowed only if it is used in traps with bio-pesticides and certain pyrethroids

Range of action

Bactrocera oleae, Ceratitis capitata, Ragholetis cerasi.

Field of application

Used in olive, citrus and cherry tree.

Toxicity

H.P. do not have an impact on the environment. Possible drawbacks are related to the type of insecticide with which they are combined.

Dose and compatibility

Solution at 1%.

 

PYRETHROIDS  (only deltamethrin or lambda-cyhalothrin)

General information

These are a group of synthetic pesticides, similar to the natural pesticide Pyrethrins. These molecules are stable to light (Pyrethrins are not) and soluble in organic solvents. For this reason, they are much more persistent than their natural relatives.

Use

Pyrethroids operate through contact and ingestion, killing the insect in a few minutes

Their use in organic agriculture is permitted only in traps against olive and Mediterranean flies (Batrocera oleae and Ceratitis capitata).

Range of action

A wide range of insects are sensitive to Pyrethroids such as Coleoptera, Lepidoptera, Diptera, locusts, grasshoppers and ticks.

Field of application

Fruit and olive trees.

Toxicity

Relatively low to mammals, but high to fish and pollinators.

Dose and compatibility

Usually the product is already inside the trap.

 

Products against cryptogamic diseases

COPPER

General information

Copper-based products are widely used for their fungicide and bactericide properties. A wide range of copper-based formulas are used in agriculture: copper sulphate, hydroxide, oxychloride and cuprous oxide. The active compound of these formulas is copper ion (Cu++).

Copper is active through direct contact, inducing denaturation of enzymes and proteins of the cell membrane. It also inhibits spore germination.

Use

The persistence and efficiency of the treatment depends on the solubility and adhesiveness of the used product. On adhesiveness, the most widely used formulas are classified as follows: sulphate > hydroxide > oxychloride > carbonate. In order to increase adherence, bentonite can be added to the copper product.

As regards solubility, the different products are classified in the following manner: oxychloride and carbonate > hydroxide > sulphate.

Range of action

Copper is effective against a wide range of fungal diseases such as: peronospora, peach blister and other fungal diseases. It is relatively active also against bacteriosis. Copper can be phytotoxic if distributed in the wrong climate conditions (cold <10°C and wet), on sensitive varieties (peach and other stone fruits) and during the wrong vegetative phase of the plant (young leaves and branches). For example, it is not recommended to spray copper during flowering. 

Field of application

Viticulture, fruit trees, olive, beet root, horticulture, flowers.

Toxicity

Copper products are not dangerous to warm blood animals, while they are toxic to fish and other animals. Copper is not easily degradable and tends also to accumulate in water deposits.

For this reason, the use of  copper in organic farming needs to be reduced, in spite of being very important.

Dose and compatibility

The doses vary considerably depending on the different formulas. The waiting period is 20 days. It is not recommendable to mix copper products with sulphur, lime sulphur, mineral oils, and Bacillus thuringiensis.

Until 31/12/2005 the limit of copper use set by the EU Regulation 2092/91, is 8 kg/ha per year. From 2006 onwards, the limit will be set to 6 kg/ha per year.

 

POTASSIUM PERMANGANATE

General information

Potassium permanganate is a violet salt with fungicide properties. This energetic oxidant compound is soluble in water and used also as a disinfectant.

The active compound is potassium permanganate (KMnO4).

Use

Potassium permanganate operates through contact, oxidizing all organic materials. Its effect is rapid but its persistence is weak. It is used as a fungicide, bactericide and against molluscs.

Range of action

It is used for the protection of plants against oidium, fusarium (Cucurbitacae family), peronospora, verticillium (Solanaceae family) and Phomopsis cane and leaf spot of grapevine.

 Field of application

Horticulture, viticulture, fruit trees.

Toxicity

The concentrated product is caustic. No information on its selectivity is available. It is highly phytotoxic and it is not advisable to spray green vegetation with more than 300 g/hl.

Dose and compatibility

Winter treatments (fruits and grapevine): 1-2 kg/hl;

Grapevine Phomopsis cane and leaf spot 750 g/hl at sprouting;

oidium: 100-300 g/hl;

fusarium: 500 g/hl (soil treatment).

Potassium permanganate should not be mixed with organic substances (rotenone, Bt, etc), because of its corrosiveness.

 

SULPHUR

General information

Sulphur is widely used as a fungicide because of its limited environmental impact, its low cost and its polyvalence. Sulphur is a compound extracted in quarries, or obtained from the separation of sulphur hydrogenate from natural gas during the purification process.

Use

Sulphur is a fungicide with a secondary action against mites.  Because of its liposolubility, it can penetrate inside the fungal cells, dehydrating them.

Sulphur can be used in different preparations, classified in two different types:

Powder Sulphur:

Raw sulphur: low percentage of sulphur, high adherence;

Ground and ventilated sulphur (diameter 10-200 m);

Refined and sublimated sulphur (diameter 5-25 m), very fine and active;

Activated sulphur;

Copper sulphur: ground and mixed with copper salts.

Wettable Sulphur:

Common wettable sulphur;

Sulphur with bentonite,

Micronized sulphur (diameter 3-5 m);

Colloidal sulphur (diameter 2-6 m) very active, but also phytotoxic;

 

Range of action

Sulphur is active against oidium in almost all crops, fusarium, sclerotinia, grapevine excoriosis, rust, alternaria  and other fungal diseases. 

Field of application

Grapevine, stone fruits, apple and pear, olive, hazelnut, citrus, horticulture, potatoes, cereals, flowers.

Toxicity

Sulphur is not toxic to mammals, while it is toxic to certain insects (such as Hymenoptera). It is irritant for the eyes, therefore, caution should be exercised  when spraying. In organic farming sulphur should be used without Selenium.

Phytotoxicity: very fine sulphur products can be harmful to plants at high temperature. Powder sulphur is less phytotoxic.

Dose and compatibility

Dosage depends on the type of sulphur. Indicatively, for powder sulphur: in 25 (sublimated)-40 (raw) g/hl; for wetable sulphur: colloidal S. 100-200 g/hl, micronized S. 200-500 g/hl.

Sulphur is not compatible with mineral oils and crop protectants with alkaline reaction.

 

LECITHIN     

General information

The term lecithin generally designs a group of phospholipids. These compounds are extracted principally from soyabean, but also from sunflower, rapeseed, and eggs.

Lecithin is widely used in the food processing industry as an emulsifier, stabiliser and antioxidant.

Use and effects

Lecithin is a fungicide that operates through direct contact. Its activity seems to be related to the inhibition of spore germination.

Range of action

Oidium

Field of application

Cucumber, apple tree, ornamental plants

Toxicity

Not toxic to humans, insects or plants.

Dose and compatibility

Depends on the formulation.

Lecithin can be mixed with the majority of products used in organic agriculture.

 

Photos

 

Photo 1: Coccinetlidae- natural enemies for pest control