Field Cultivation

Insecticidal Plants

ANNONA – Soursop (Annona muricata) , Custard apple (Annona reticulata) , Sweetsop (Annona squamosa).

Fam. Ammonaceae

General

More than 90 species of small tree and shrubs are known in the Annonaceae family. They occur mostly in Tropical america, but some are found also in Asia and Africa. Soursop and custard apple are widely distributed in Central America and the Carribbean, while the sweetsop is commenest in India and Southeast Asia. They do not require special conditions of soil or water, but thrive best in places where ther is a clear division between the rainy and the dry season, and generally prefer dry sites in wich to grow.

The effective ingredients are in the unripe fruit, and in the seeds , leaves and roots. The oil content of the seeds amounts to 42-45 %.

Effective range

Contat – and stomac poison

Insecticidal , larvicidal , repellent , antifeedant.

Target Insects

Aphids                               -  general

Brown rice plant hopper  - Nilaparvata lugens

Diamondback Moth          - Plutella xylostella

Chrysanthemum aphid     - Macrosiphoniella sanborni

Grasshopper                    -  general

Green bugs                       -  general

Green rice leaf hopper              -  nephotettix virescens

Potato aphid                     -  Macrosiphum euphorbiae

Red pumpkin beetle         -  Aulacophora foveicollis

Whitebacked rice plante hopper – sogatella furcifera

Annona has not proved effective against the

Saw-toothed grain beetle         Oryzephilus surinamensis

Trouver une photo de Sweetop (annona squamosa)

Observations

The toxic effect of Annona sets in slowly , 2-3 days should be allowed.

Laboratory trials have shown that by extracting annona seeds with ether or petroleum ether, the toxicity can be increased 50-100 times. But since laboratory methods are impractical in the field, other locally availabe and cheap solvents could be tried, like petrol or kerosene.

When pulverising the seeds of A. squamosa , care should be taken to ensure that the powder does not come in contact with the eyes as this causes great pain.

The custard apple is the most effective of annonas against insects.

Methods of Use

Relatively little information exists on the preparation and use of annona. Wide-ranging laboratory trials have demonstrated its higly effective insecticidal values. Experimentally-inclined farmers could contribute much needed information about widely distributed plant.

         A 10 % concentration of seed oil produces a 90 % death rate of the bug Urnetius echinus within 72 hours. A 5-7 % concentration is still effective, but low concentration of 1 – 3 % produce no results.

         Pulverised seeds are used in China and the Philippines against Lecanium in West Africa. The writers gives no details regarding quantities.

         An extract of the leaves with ether proves higly successful against the red pumpkinn beetle (Aulacophora foveicollis). A diluted solution achieves a 91 % rate .

CHILIPEPPERS – Capsicum frutescens

Fam. Solanaceae

General

Chillies are widely distributed in the tropics and subtropics and originate in South America where they were early cultivated. They were introduced to the rest of the world by the Spaniards and the Portuguese. The ripe fruit has insecticidal properties and the effective substances are highest in the skin and in the seeds ;

Effective Range

Stomac poison

Insecticidal repellent , antifeedant , fumigant , viroid.

Trouver une photo de chili  (Capsicum frutescens)

Target Organisms

Ants                                                          - general

Aphids                                                               - general

Caterpillars                                                        - general

Colorado beetle                                       - Leptinotarsa decemlineata

Imported cabbage worm                                  - Pieris rapae

Rice Weevil                                                       - Sitophilus

Warehouse pests                                             -  general

Cucumber mosaic virus                                    - Pieris rapae

Cucumber ringspot virus                                  - Pieris rapae

Tobacco etch                                                    - Pieris rapae

Tobacco mosaic virus                                      - Pieris rapae

Tobacco mosaic virus                                      - Pieris rapae

Methods of Use

From kenya good results are reported o n the control of aphids in home vegetable gardens.

Hot chillippers are finely ground, stirred in water and allowed to stand overnight. After filtering through a cloth the solution is sprayed onto the plants , or if no syringe is available sprinkled with a whisk of twigs or grass.

A similar method is reported from Papua New Guinea where chilipepper is used as repellent

Finally ground chillies are covered with water and soap either as flakes or liquid. The mixture is well stirred and sprayed over affected plants.

Chilli spray preparation are also well knonw in the philippines :

100 g chillies, water, soap solution :

The chillies are finely pulvrised in a mortar, vigourosly shaken with 1 litre of water and filtered through a cloth. One part of ths concentrate is diluted with five parts of soapy water before spraying. It is effective against aphids and many other vegetable pests.

Too strong a concentrate causes burning of the leaves, so the right strengh should be found by testing.

Care should be taken because the solution irritates the skin.

Virus inhibition

MCKEEN reports that the young leaves of cowpea were rubbed with virus-infected sap expressed from chilli leaves the colour change was markedly reduced. Mostly there was even none. (The change of colour is regarded as an indicator of a virus infrection). When the experiment was repeated wuth the sap from virus-infected tobacco leaves the cowpea leaves underwent a strong colour change,  but when the tobacco sap was mixed with 5 % of chilli sap the number of leaves which changed colour was reduces by 95 %.

The efectivness of the virus inhibition depends on the host plant. It is probable that members of the same plant familly do not  work infallibly on one another virus inhibitors. Further tests showed that the virus-inhibiting ingredients is present in all parts og the chilli plant. However, extracts from the leaves and flowers showed the highest concentration and the roots are lowest.

In practise, it is important that chilli sap should be applied as a preventive measure before the virus infection affects the plant. Once the virus has taken hold it cannot be effectively controlled.

This is information is all derived from scientific sources. The writer has no results taken from practice in the field.

DERRIS – Deris elliptica , D. malaccensis , D. uliginosa

Family Leguminoseae

General

Derris is a small shrub originating in the tropical rainforests of the Malay Archipeligo. It grows in lowland areas and does not thrive at higher altitudes. It is the roots which contain the active substances, mainly rotenone. Grown in the shade D. malaccensis requires a period of 1 1/2 – 2 years for it to produce a worthwhile content of rotenone , but when grown i nfull sunlight needs only nine months for the roots to develop sufficiently.

Deris elliptica developped after 26 months the maximum amount of rotenone. Derris can propagated vegetavitely from 50 cm long cuttings when rooting follows after six weeks. The crop is harvested by exposing the shallow roots and cutting off those with a diameter of 2- 6 cm since these have the highest rotenone content. Derris thrives on many soils but particularly on loams and clays

Effective Range

Contact – and stomac poison

Insecticidal and repellent.

Trouver une photo de Derris ( D. elliptica )

Target Organisms

Adzuki bean beetle                        - Callosobruchus chinensis

Army worms                                   - Spodoptera litura

American bollworm                        - Heliothis armigera

Diamondback moth                        - Plutella xylostella

Fruit flies                                - Dacus spp.

Mediterranean fruit fly           - Ceratitis capitata

Melon aphid                                    - Aphis gossypii

- Crocidolomia binotalis

- Margaronia indica

- Crysodeixes chalsites

Derris is also effective against the fungus Pyricularia oryzae.

Remarks

                   Derry is most effective against larvae in the young stages. Caterpillars, aphids and beetles are very vulnerable, but it is not effective against cockroaches.

                  

                   Derris is affected  by sunlight , oxygen and temperature. After a week in strong sunlight deris dust is no longer effective. In the shade it retains its properties for a fortnight.

                   Handling derris dust can also cause skin rashes and should therefore be avoided. If derris dust or spray is inhaled over a period it can give rise to a numb feeling in the lips and tongue and throat.

                   Derris is harmless to bees , but toxic to fish.

Methods of Use

Sprays

                   Freshly cut roots from 2 – 6 cm diameter are washed and cut into 5 cm lengths. With a stone or pestle they are pounded together with soap and little water. Soap facilitates the solubility of the rotenone. When the roots are completely shredded into fibres the liquid is filtered off through a fine cloth. The resulting solution is diluted off through a fine cloth. The resulting solution is diluted to the apporved strength and used at once.

The following quantities are recommended :

                            1 part soap : 4 parts roots : 225 parts water

                   when finely powdered derris dust is obtainable the following proportions should be used for an extract :

                            100 litres water : 500 g neutral soap : 1 kg derris

                   A preparation which is highly effective agaisnt apple pahids can be made by stirring 2.5 kg derrisdust into 400 litres of soap solution.

Powder preparation

                   In trials pulverised derris roots containing about 5 % rotenone were dilluted with talc in the proportions of 1 : 5 . 1 : 10 and 1 : 20. These preparations were dusted at the rate of 30 kg/ha over cabbage plants which were infested with the larvae of the imported cabbage worm and Cabbage loopers. Three applications were given over a period of two weeks. The dilution of 1 : 5 produced the least feeding damage.

                   In another trial the following mixture was dusted over cabbages just as they were beginning to head :

                            30 % pyrethrum (1.16 % pyrethrin).

                            20 % derris dust (4% rotenone).

                            50 % alumina as carrying agent.

Two applications were given at an interval of 7 days. A week later the plants were examined with the following results :

On 50 plants a total of only 4 caterpillars were discovered.

App. 40 numbers of flea beetles were killed and many plants had 50 – 100 dead flea beetles on the outer leaves.

The date rate among aphids was unstatifactorily low ;

Thrips, which inhabit the underside of the outer leaves were not reduced.

GARLIC – Allium sativum

Fam. Liliaceae

General

Garlic is a cosmopolitan plant which grows in temperate zones as well as in the tropics and subtropics. It probably aroginated in Central Asia whence spread to the Mediterranean, around whose shores it still finds its greatest use in the kitchen.

It is much cultivated  and easy to grow in field, garden or backyard. For use as an insecticide it should not be grown with mineral fertilizers since it has been established that heavy doses of fertilizers reduce the concetration of effective substances.

Effecitve Range

Insectidical , repellent , antifeedant, bactericidal , fungicidal , nematocidal and effective against ticks.

Trouver une photo de Allium sativum

Target Organisms

Aphids                                                               - general

Army worms                                                      - Spodoptera litura

Colorado Beetle                                      - Leptinotarsa decemlineata

False coding moth                                            - Cryptophlebia leucotreta

Kharpa beetle                                                    - Trogoderma granarium

Mexican bean beetle                                        - Epilachna varivestis

Inported cabbage worm                                   - Pierris rapae

Wire worms                                                       - general

Garlic has also been found to be effective against fungus such as mildew and beanrust.

Remarks

                   Some gardeners in Germany have long made garlic solution in water to use against pest. According tothem it should be applied immediatly after the preparation so that the volatile oil do not escape into the atmosphere before to exerttheir effects on plants (ILLMANN, pers.comm.)

                   Laboratory trials indicated that an extract of garlic reduced feeding by older larvae less than by younger larvae.

Methods of Use

100 g garlic cloves, 0.5 litres of water , 10 gm soap , 2 tea spoons mineral oil.

Steep the finely  grated garlic for 24 hours inthe mineral oil. Dissolve the soap in the water , mix the infusion of garlic and mineral oil, stir well together and filter through a fine cloth. Before use this solution is dluted with 20 parts of water. It is effective against the most commom pests , but different strengths should be experimented with regarding specific insects.

Steep 3 finely grounded garlic bulbs for 2 days in liquid parafin and then stir well with a large spoonful of soap flakes and 10 litre of water. This preparation is effective against wide range of insect pest.

The following preaparation is successful against caterpillars in fruit trees :

2 finely grated garlic bulbs and two spoon chillipeppers are stirred into 4 litres of hot water in which a nut sized piece of soap has been dissolved.