Effect of seed treatment with the biological agent Pasteuria thornei on the control of Pratylenchus zeae in Maize

This study had two objectives: 1-evaluate the efficacy of Pasteuria thornei as seed treatment for Pratylenchus zeae control in maize; 2-measure the effects of P. thornei on preventing the yield losses caused by P. zeae. Four P. thornei doses (5 × 106, 1 × 107, 1.5 × 107, and 2 × 107 endospores/seed) were tested in two efficacy experiments, along the traditional treatment with abamectin (0.5 mg/seed) and the combination of P. thornei and abamectin (1 × 107 endospores + 0.5 mg). The treatments in two subsequent yield experiments were: one P. thornei dose (2 × 107 endospores/seed), abamectin, the combination of P. thornei and abamectin, and P. zeae -free control. Experimental plots consisted of 9L pots filled with soil infested with 9,000–11,000 specimens of P. zeae. Agronomic variables, including grain weight, were measured, as well as nematode population density. The highest concentration of P. thornei reduced nematode populations by 47–54%. Synergistic effects between P. thornei and abacmetin in nematode control was not observed. Results of the yield experiments showed that P. thornei control was similar to what was observed in the efficacy study. Abamectin reduced the yield losses caused by P. zeae, the same was true for treatments containing P.thornei in a single yield experiment. Therefore, P. thornei shows potential not only for reducing P. zeae populations densities but can also mitigate yield losses caused by this phytonematode. This work is the first to demonstrate the effectiveness of P. thornei as a biological control agent for P.zeae management.