Utilizing management zones for Rotylenchulus reniformis in cotton: Effects on nematode levels, crop damage, and Pasteuria sp.

•Nematode management zones in fields based on soil texture and elevation are useful.•Soil texture and elevation influenced Rotylenchulus reniformis population levels.•Treatment effects on R. reniformis were the same in all management zones.•Pasteuria sp. endospores per nematode was lower where sand content was greatest.•Pasteuria sp. endospore attachment was reduced by 1,3-dichloropropene + aldicarb.

Nematode management zones (MZs) based on soil electrical conductivity (EC, a proxy for soil texture) have not been published for Rotylenchulus reniformis. We tested 1) whether R. reniformis levels and the amount of damage caused to cotton differed among MZs, 2) if the relative effectiveness of nematicides differed among MZs, and 3) whether the prevalence of Pasteuria sp. on R. reniformis differed among MZs and nematicide treatments. A field was divided into three MZs where MZ3 had sandier soil than MZ1 or MZ2, which were the same, and MZ2 had higher elevation than MZ1 or MZ3, which were the same. Levels of R. reniformis near planting in plots not receiving nematicide averaged 1342 (per 150 cm3 soil) in 2008, 610 in 2009, and 869 in 2010. Both soil texture and elevation influenced R. reniformis population levels with greater reproduction in finer-textured soil and reduced R. reniformis levels at higher elevation. Treatment effects on R. reniformis levels were the same in all MZs (no MZ × treatment interactions). The effects of texture and elevation on yield were similar to the effects on nematode levels. We observed endospores of Pasteuria sp., a bacterial parasite of nematodes, on R. reniformis at the field site used for this study. Pasteuria sp. generally had greater spore attachment to juvenile R. reniformis than to adults with no differences among MZs in percentage of nematodes with endospores, but the number of spores per nematode was lower in MZ3, which had the greatest sand content. The percentage of R. reniformis with endospores and the number of attached endospores were reduced by 1,3-dichloropropene + aldicarb. We documented that R. reniformis levels are affected by modest differences in soil texture and elevation, but levels of R. reniformis were above the action threshold in all MZs, therefore a uniform rate of nematicide would have been recommended and there would have been no cost savings from utilizing MZs in this field.