Jennifer Dudak1 and Reagan Noland2
1. Graduate Research Assistant, Texas A&M University
2. Assistant Professor & Extension Agronomist, Texas A&M AgriLife Extension Service, San Angelo, TX
As the threat of reniform nematodes increases on cotton yields in Texas, so does the need for tools to contend with this pest. A two-part study was initiated to identify the most effective management tools among cotton genetics and nematicides. This is a brief summary of findings from the first year (2019) at three locations across the state with known reniform nematode infestations, Damon, Wall, and College Station.
The cotton genetics study consisted of 6 or 7 varieties (site dependent) with a varying range of nematode resistance (Table 1). A nematicide [fluopyram and prothioconazole (13.6 oz A-1 in-furrow)] was applied as a split-plot treatment, compared to untreated. Growing conditions were well represented due to the spread of the locations. Management at Wall and Damon were left to the cooperator’s digression, while the College Station location was managed based on Texas A&M Cotton Extension’s routine practices. Cotton growth measurements and yield were recorded, and a composite soil sample of each plot was taken post-harvest to determine nematode populations.
Table 1 Cotton varieties tested at each site, and associated nematode resistance
At all three locations, lint yield was influenced by variety, with PHYEXP W3FE among the top at all three sites (Figure 1). DP18R628 was also among the top at Damon and College Station. The application of fluopyram and prothioconazole increased “height a” in Damon and yield at Wall, but did not have an effect at the other locations. Variety did not influence nematode populations at any location.
Figure 1. Lint yield from Damon (top), College Station (middle), and Wall, Texas (bottom). *Non-resistant check
The second study compared three different nematicides, alone and in all applicable combinations, and an untreated check (Table 2), applied to two varieties. Aldicarb 15G was applied in-furrow at planting with insecticide boxes (5 lb A-1), fluopyram and prothioconazole combination (Propulse) was also applied in-furrow at planting (13.6 oz A-1) and oxamyl (Vydate C-LV) was foliar broadcasted (17 oz A-1) at 30 and 45 DAP. The same measurements were collected as the cotton genetics study.
Table 2. Nematicide treatments and costs used for economic analyses.
The addition of nematicide treatments did not affect yield and showed no partial net return at all three locations. At College Station, the combinations of Aldicarb 15G + Oxamyl and Fluopyram and Prothioconazole + Oxamyl reduced final reniform nematode concentrations within the susceptible variety, compared to other nematicides and the untreated check (although this did not translate to differences in yield). Nematicides did not affect reniform nematode populations at Damon or Wall.
In summary, PHYEXP yielded consistently among the top at all locations, while DP18R628 was among the top at Damon and College Station. The application of nematicides increased plant height at one location for one timing, but did not show an effect on yield and nematode populations, nor offset the cost of the chemical. This indicates that genetic resistance is likely a better option for reniform nematode control in cotton. The experimental lines tested in this research are not commercially available varieties, but these sources of genetic resistance will be integrated in future varieties.