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

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.