An estimated 70 percent of Georgia’s cotton fields are infested with at least one species of potentially damaging plant-parasitic nematodes. In a statewide survey of cotton fields (nearly 1800 samples were collected) approximately 69 percent of the fields were infested with root-knot nematodes and 5 percent were infested with reniform nematodes. An effective tactic to manage either of these plant parasitic nematodes in cotton production is to plant resistant varieties. Cotton producers in Georgia have the opportunity to plant a number of different varieties that have resistance to the southern root-knot nematode, Meloidogyne incognita. As of 2022, growers now have the opportunity to plant cotton varieties with resistance to both M. incognita and Rotylenchus reniformis, the reniform nematode.
The objective of this study was to assess the performance of cotton varieties with resistance to plant-parasitic nematodes as compared to nematode-susceptible varieties planted with and without nematicides. The treatments included four nematode-resistant varieties (DPL 2141, DG 3644, PHY 443, and PHY 411) and various at plant treatments with a nematode susceptible cotton variety (DPL 1646). This plot was planted on May 19, 2022. Vydate was applied to 7-leaf cotton on June 20, 2022. The plots were six rows wide and averaged 870 feet long. Each treatment was replicated four times. The seven treatments are listed below.
| Treatment | Variety | At Plant Treatment |
| 1 | DPL 1646 | 5 lb Aglogic |
| 2 | DPL 1646 + Vydate 17oz (7 Leaf) | 5 lb Aglogic |
| 3 | DPL 1646 | 3.5 lb Aglogic |
| 4 | PHY 443 | 3.5 lb Aglogic |
| 5 | PHY 411 | 3.5 lb Aglogic |
| 6 | DPL 2141 | 3.5 lb Aglogic |
| 7 | DG 3644 | 3.5 lb Aglogic |
The chart below shows the end-of-season root-knot nematode counts from all the treatments. No significant differences among the treatments were noted, but several numerical differences need to be pointed out. The end-of-year threshold for RNK is 100 RNK per 100 cc of soil. All the DPL 1646 treatments had nematode levels above that threshold. All the nematode-resistant varieties were well below end-of-year thresholds.
Lint yields from the plot are reported below. No significant differences among treatments. Lint yields ranged from 1038 to 1268 lb per acre. The highest yielding treatment in this study was DPL 2141, and the lowest yielding treatment was PHY 443. Numerical differences were noticed among the DPL 1646 treatments. A yield increase of 168 lbs was noted when the rate of Aglogic was increased from 3.5 to 5 lbs per acre.
The research could not have been possible without the help and support from Heath Cross – Colquitt County Young Farmer Advisor, Demott Farms, Farmers Gin, Bayer Crop Science, Aglogic, Phytogen and Corteva.