First report of the sting nematode Belonolaimus longicaudatus on Soybean in Delaware

Authors: Handoo, Zafar; Skantar, Andrea; MULROONEY, ROBERT - University Of Delaware

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2009
Publication Date: 1/31/2010
Citation: Handoo, Z.A., Skantar, A.M., Mulrooney, R. 2010. First report of the sting nematode Belonolaimus longicaudatus on soybean in Delaware. Plant Disease. 94(1):133.

Interpretive Summary: Plant-parasitic nematodes are microscopic worms that attack plant roots and cause an estimated ten billion dollars of crop loss each year in the United States and 100 billion dollars globally. One problem facing growers is that the nematodes in their counties and states are often unknown. Sting nematodes are an important group of nematodes damaging the roots of many kinds of plants in the United States, including soybeans in the Southeast. This brief report describes how a team of ARS and University of Delaware scientists identified a type of a sting nematode in two soybean fields in very sandy soil in southern Sussex County, Delaware. This discovery is significant because this is the first report of this nematode in Delaware. Therefore, this report will serve as a useful guide to researchers and diagnosticians identifying economically important sting nematode species, especially in soybean-growing areas in Delaware.

Technical Abstract: In August 2005, several large irregular areas of severely chlorotic, stunted and dead soybean plants were observed in two fields of soybean (Glycine max) 5 miles apart, in very sandy soil (94% sand, 2% silt, 4% clay) in southwestern Sussex county, Delaware. The grower also had observed stunted corn the previous year in the same areas and thought the fields had a fertility problem. The morphology of adults and molecular analyses of the juveniles isolated from soil samples established the identity of the species as the sting nematode Belonolaimus longicaudatus Rau, 1958. Morphological characters used for identification included female body, stylet and tail length, shape of head, stylet knobs, tail and tail terminus, number of lines in the lateral field and vulva percentage in relation to body length. The male characters critical for identification were the following: body, stylet, spicule and gubernaculum length; shape of head and stylet knobs; and number of lines in the lateral field. Molecular diagnosis as B. longicaudatus was confirmed by sequencing of two ribosomal DNA markers from three juveniles. Sequence of the internal transcribed spacer region ITS1&2 (GQ896549) from this population was 99% identical to Florida isolate BlCi6 (DQ672368) and the 28S large ribosomal subunit D2-D3 expansion region (GQ896548) was 99% identical to Florida isolate BlCi4 (DQ672344). A high degree of similarity (>98%) was also shared by several other B. longicaudatus sequences. This detection represents a new state record in Delaware for B. longicaudatus within the United States. Since this detection in 2005, there have been no new reports of other observations of sting nematode or spread from these two fields tilled by the same farm operator in Delaware.