PLANT NEMATODES THE GROWER
 SHOULD KNOW
 DR. G. STEINER1

 For some decades nematologists have emphasized the presence of
Enormous numbers of nematodes in our crop lands and have singled out
many species which are plant parasites or plant pathogens and therefore
Pf significance to plant growth and crop production. But only during
recent years has an increasing realization of the economic significance
pf plant nematodes as pests of crops, and as limiting factors in crop
production been developed by growers and research workers. That this
plisregard of nematodes as a factor in soil response has had its serious
consequences in research, particularly in soil science, may be illustrated
y the fact that various extensive fertilizer tests made in Florida have
had to be repeated because of their insidious damage. It is obvious that
jest crops having diseased and parasitized root systems will not respond
in the same manner as would those with normal and healthy roots. The
loil scientist should therefore be aware of the modifying effect nema-
todes may have on the results of his studies with fertilizers, cover crops,
race elements, etc.
 For years the opinion was prevalent that there was just one signifi-
rant nemic plant pest, the root-knot nematode, and it was spoken of as
"the nematode." Although root-knot nematodes are recognized the world
pver as the worst and most perplexing agricultural pests they are cer-
tainly not the only significant ones. There are many other important
plant nematodes such as the meadow nematodes (a group of forms
elonging to the genus Pratylenchus Filipjev); the spiral nematodes
(Genus Helicotylenchus Steiner); the kidney-shaped nematode (Genus
flotylenclulus Linford); the lance nematodes (Genus Hoploaimus v.
sDaday); the puncturing nematodes (Genus Dolichodorus Cobb); the
stylet nematodes (Genus Tylenchorhynchus Cobb); the ring nematodes
I(Subfamily Criconematinae Chitwood); the pin nematodes (Genus
Paratylenchus Micoletzky); the seed gall nematodes (Genus Anguina
Scopoli), to which belongs, e.g., the wheat nematode (A. tritici [Stein-
'buch] Filipjev); the bulb and stem nematodes (Genus Ditylenchus Fil-
ipjev), which represent a group of different species including, e.g., the
Rice nematode (Ditylenchus angustus [Butler] Filipjev) and the potato
rot nematode (Ditylenchus destructor Thorne); the sugar-beet nema-
Itode (Heterodera schachtii Schmidt); the golden nematode of potatoes
(H. rostochiensis Wollenweber); the citrus nematode (Genus Tylenchu-
Ilus Cobb); the bud and leaf nematodes (certain species of Aphelen-
choides Fischer) such as the fern nematode (A. olesistus Ritzema Bos),
the cocopalm nematode (A. cocophilus Cobb), the strawberry nema-

 1 Recently retired Head Nematologist, Agricultural Research Service, U. S. Dept.
 of Agriculture.