Slow decline symptoms and citrus nematode populations vary, like spreading decline, according to the natural environment. There are many factors that contribute to the overall disease complex of either nematode, but one factor stands above all others, the soil environment, so let us examine its role in the disease syndrome. Also, infected trees had approximately one-half as many functional feeder roots as noninfected trees. Because, burrowing nematodes attacking citrus are found mainly at soil depths below 20 inches. It is in such an environment that burrowing nematode reproductive potential and activity are the highest.
Organic matter favors soil fungi and other organisms.
In deep sands which are virtually free of organic matter, development of other organisms is reduced, giving the nematode free rein to move about and infect roots. Burrowing nematodes, in this relatively sterile environment, reproduce and increase to great numbers. Invasion by other organisms creates an unfavorable environment for nematode activity and the nematode migrates, seeking once again more suitable feeding sites free of competitive organisms. Conversely, the citrus nematode invasion and reproduction is slower in sandy, coarse-textured soils than in other soil types. Soil organic materials greatly influence the rate of nematode infection and subsequent reproduction.