The name nematode is derived from the Greek, nemato, which literally translates to “thread-like.” These thread-like multicellular invertebrates (animals without a backbone) are so unique that they have their own phylum group called Nematoda. They are the most numerous multicellular organisms in the world.
Populations of other soil-borne organisms pale in comparison. Ecologist Peter Warshall observed that the top few centimeters of soil covering a square meter of land could harbor a total combined population of 200,000 ants, mites, pot worms, slugs, earthworms, springtails, and beetles. In that same soil sample, you would find 12 million nematodes. Temperate grassland can hold as many as 9 million nematodes per cubic meter of soil, and more than 25% are plant parasites which makes agriculture vulnerable.
The citrus nematode (Tylenchulus semipenetrans) is ubiquitous across California citrus groves and considered a serious issue impacting the citrus industry. The citrus nematode causes a slow but chronic debilitation of the tree. Over time trees are stunted, they show a loss of yields and degradation of the fruit, and finally there is the death of the entire tree. Meanwhile, stone fruit trees are damaged by root-knot nematode (Meloidogyne spp.) and ring nematode (Criconemella spp.).
Most plant-parasitic nematodes, however, have many hosts — they are seldom plant-specific. The sheath nematode (Hemicycliophora arenaria) went unnoticed as an endemic pest of native desert plants in the Coachella Valley for many years. The devastating potential of this species came to the surface only when valley agriculturists began to convert that virgin ground to crop land.
The aboveground symptoms of disease caused by nematodes can be difficult to detect and may be often confused with symptoms of nutrient deficiency: plants do not thrive, they are paler than normal, and they may wilt in the heat of the day. But interestingly, nematodes are good bioindicators of soil health or condition. The population size and mix of nematodes depends on several factors, including the condition of soil, the climate, the season and the crop being grown. Analysis of the diversity and complexity of nematode communities in the soil is a valuable tool for assessing overall soil health.
Although on average a typical nematode life cycle may be only 30 days at summer temperatures, their reproduction is extremely fast.This means that even if nematode counts are low at the beginning of the growing season, populations can rapidly increase and become harmful to the crop in a relatively short period of time. The sheath nematode’s short life cycle, spanning about 16 days, was found to be partly responsible for the explosive infestation of the crops planted in the central valley. On tomatoes, for example, 150 females produced a population of 1.5 million in just 3 months. This case illustrates the characteristic course of parasitic associations that has occurred with introduced or non-native crops.
Nematodes have been adapting and developing their associations for over 600 million years, and commercial agriculture is, in comparison, but a few seconds old. When a commercially grown crops are placed into the environment, the parasitic nematodes, hardened over the ages through selective pressures, are capable of multiplying to epidemic proportions on the “soft” new host.
Limitations on the use of chemical pesticides such as Telone have brought increasing interest in studies on alternative methods of nematode control. Andaman Ag offers a number of tried and tested solutions to mitigate nematode damage, stimulate root and plant growth and improve soil conditions. Please call, text, or email for more information.
