Researcher highlights ways to control root-knot nematodes in carrot crops

One of the recurring issues registered at Embrapa Hortaliças' Citizen Assistance Service (SAC) has been from carrot producers who report root deformation problems and seek guidance on the causes and possible solutions. The presence of nematodes, microorganisms that inhabit the soil, mainly those of the genus Meloidogyne, or root-knot nematode, has generally been the diagnosis used to identify the problem. Root-knot nematode species especially affect the appearance of the root - the marketable part of the carrot, which represents losses in the market value of the vegetable.

To identify the presence of these microorganisms - visible only with the use of a microscope -, simply observe the forking of the roots, together with the presence of galls (hence the name “knot nematode”), as explained by researcher Jadir Pinheiro, when pointing out other symptoms that occur from the infestation. “After a cycle that varies between 20 and 45 days, the nematode penetrates the root when germination begins, subsequently forming forked roots with 'galls', which interfere with nutrient absorption.”

With the confirmation of the presence of nematodes, the producer will have to live with the problem, given the impossibility of eradicating them, but the good news is that there are ways of controlling them, through management techniques. The first of these techniques would be the use of organic matter to prepare the area for cultivation:

“The organic matter - consisting of cattle and poultry manure and ground grass - in the soil stimulates the development of natural microorganisms such as fungi and bacteria that will help control nematodes”, points out Pinheiro. Another tip from the researcher concerns crop rotation to prevent the multiplication and spread of nematodes.

“When the plant that replaces carrot cultivation is not a host – such as some cultivars of corn and millet and certain species of sunn hemp -, that is, it does not facilitate the survival of these natural microorganisms, the nematode does not survive due to lack of food”, notes Pinheiro, for those who choose the variety of carrot to be cultivated would be another measure to be considered, as there are cultivars available on the market that present resistance and tolerance to root-knot nematodes.

“By using management measures, the producer can maintain the nematode population at a controlled level and, thus, count on satisfactory production, in quantity and quality”, he summarizes.