Little inforamtion is available on the effect of commercial neem products on viruses. AH-MED(1988) reports that 'Wellgro' a product of ILTD is used by farmers to control TMV in the West Godavari district. The effectiveness of the treatement seemed to be as good as spraying neem leaf extracts, but no detailed data or quantities were given. Other commercial products are used in the control of vector as vector repellents, like 'RD-Repelin' which is a mixture of extracts of neem(A.Indica), karamja(Pongamia Pinnata), castor (Ricinus Communis), Mahua (Madhuca Indica) and sesame(Sesamum Indicum). In addition to a repellent effect against the pea aphid. Acyrthosiphon Pisum, which did not prevent virus transmission, a delayed symptom expression for zucchini yellow mosaic virus(ZYMV) was observed in 81% of the test plants. The mixture of ingrediants does not, however allows us to contribute this finding to a particular plant extract. No influence on virus replication by 'RD-Repelin' was found, because the ELISA-readings of untreated and treated plants did not differ significantly.
ADDING NEEM TO SOIL
The use of neem cake as an amendment to agricultural soils is a well known practice in India, mainly to exploit the fertilizer properites of this material but also in combination with synthetic chemicals for plant protection. The influence on viruses has not been studied yet in details. Some experiments with neem cake(NC), neem seed kernels(NSK) and dried neem leaves(NL), in the field and under greenhouse conditions yielded very different results, depending on the virus and host plant used. In field experiments, when neem was added to 1% of the upper 10cm layer none of the neem products used was able to prevent infection of zucchini with watermelon mosaic virus. In a second experiment under much higher infection pressure, the results in the neem plots were much better than in the control, and a delay in symptoms expression was significant for NSK powder and to some extent for NL powder. In a greenhouse experiment with artificial inoculation, in which the zucchi plants were planted in prickout pans with soil containing 1% neem, the inhibition was low but marked: only 80% of the zucchini plants treated with NS, 85% with NC and 82% with NL, but 100% of the control plants became infected, as determined by symptom expression.
When hups were used as test plants with the same method, a reduction of the ELISA reading for hop mosaic and hop latent catlaviruses was obtained in the plots treated with crushed NSK and NL, but the differences from the control were not significant. Another system used for testing this type of application was Prunus Necrotic ringspot virusand cucumber planted in 10cm pots of five plants each. In this artificial system the use of neem did not prevent virus infection after artificial inoculation, but there was a reduction in the number of plants successfully inoculated and with increasing amounts of neem added(0.5%, 1%, 2,5%) there was a significant reduction in symptom expression. This corelated with the average vales for the ELISA-readings. The efficacy increased from Soxlet extracted NC to NC to NSK, but 5% NSK induced also phytotoxic reactions, measurable as reduced growth and fresh weight.
ADDING NEEM TO SOIL
The use of neem cake as an amendment to agricultural soils is a well known practice in India, mainly to exploit the fertilizer properites of this material but also in combination with synthetic chemicals for plant protection. The influence on viruses has not been studied yet in details. Some experiments with neem cake(NC), neem seed kernels(NSK) and dried neem leaves(NL), in the field and under greenhouse conditions yielded very different results, depending on the virus and host plant used. In field experiments, when neem was added to 1% of the upper 10cm layer none of the neem products used was able to prevent infection of zucchini with watermelon mosaic virus. In a second experiment under much higher infection pressure, the results in the neem plots were much better than in the control, and a delay in symptoms expression was significant for NSK powder and to some extent for NL powder. In a greenhouse experiment with artificial inoculation, in which the zucchi plants were planted in prickout pans with soil containing 1% neem, the inhibition was low but marked: only 80% of the zucchini plants treated with NS, 85% with NC and 82% with NL, but 100% of the control plants became infected, as determined by symptom expression.
When hups were used as test plants with the same method, a reduction of the ELISA reading for hop mosaic and hop latent catlaviruses was obtained in the plots treated with crushed NSK and NL, but the differences from the control were not significant. Another system used for testing this type of application was Prunus Necrotic ringspot virusand cucumber planted in 10cm pots of five plants each. In this artificial system the use of neem did not prevent virus infection after artificial inoculation, but there was a reduction in the number of plants successfully inoculated and with increasing amounts of neem added(0.5%, 1%, 2,5%) there was a significant reduction in symptom expression. This corelated with the average vales for the ELISA-readings. The efficacy increased from Soxlet extracted NC to NC to NSK, but 5% NSK induced also phytotoxic reactions, measurable as reduced growth and fresh weight.
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