Organic farming found to eliminate plant parasites longer than conventional chemical pesticides

Organic farming practices may help mitigate the proliferation of plant-parasitic nematodes (PPN), a study published in the journal Agriculture, Ecosystems & Environment revealed. According to the scientists, a combination of agriculture intensification and poor agronomic practices led to increased incidence of PPN and other soil pathogens in East Africa. This then resulted in reduced crop productivity in smallholder farms.

A team of researchers carried out two field trials — one in farmer fields and one on-station — in order to assess the efficacy of organic farming against PPN and other soil pathogens. The field trials involved maize that was intercropped with beans and in rotation with beans as a sole crop.

The scientists also examined three farming methods during the study. Organic farming method involved compost, Tithonia diversifolia, and neem cake, while conventional farming used fertilizer and various nematicide. The experts also assessed farmer practice that received manure, Tithonia diversifolia, and wood ash. Likewise, a farm with no input application served as the study’s control farm.

The findings revealed that twelve genera of PPN were recovered from soil and root samples from the trials after three years of continuous cultivation.

However, the scientists observed that the incidence rates of PPN — such as Pratylenchus and Meloidogyne — were significantly lower in the organic system than the conventional, farmer practices, and control trials.

According to the experts, organic farming showed efficacy in curbing the genera of PPN below the control for up to four months, compared with only two months observed in conventional farming and farmer practice. The research team concluded that organic farming might help suppress PPN at a farmer level. The scientists noted that policy development and extension services could consider organic farming as an alternative treatment for soil-borne nematodes in smallholder farms.

However, the experts stressed that the findings warrant further research on other crops, location, and the duration needed to establish the practice’s efficacy in suppressing PPN. (Related: Organic food isn’t just better for you – it tastes better too.)

Analysis backs organic farming’s efficacy as nematode killer

2011 review published in The Journal of Nematology showed that the use of organic soil amendments might help trump nematode proliferation in various crops. The researchers cited various studies that examined the nematicidal properties of the neem plant. Data from 33 clinical trials examined showed that neem extracts, oil cakes, or whole plant materials showed powerful properties against nematode survival. Likewise, the experts observed that combining neem with other organic amendments enhanced each other’s nematicidal properties.

The research team also found that decomposition products from cruciferous plants were harmful to nematodes and other plant pathogens. Furthermore, the experts observed that castor and velvet bean plants showed potential as nematode killers. Marigold, Crotalaria spp. and sunn hemp was also touted to eliminate nematodes effectively. According to the researchers, the tannins and phenolic compounds released by the plants appeared to be highly toxic to nematodes.

“Organic amendments have been widely used for management of plant-parasitic nematodes. Relatively rapid declines in nematode population levels may occur when decomposing materials release toxic compounds, while longer-term effects might include increases in nematode antagonists… While amendments may improve plant growth and stimulate soil food webs, additional study and testing are needed before they could be used reliably for management of plant-parasitic nematodes under Florida conditions,” the researchers concluded.

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