Control of Globodera pallida Using Brassica juncea Seed Meal Extract and the Trap Crop Solanum sisymbriifolium

Abstract

Globodera pallida, the pale cyst nematode, is a regulated potato pest which is economically detrimental. Restrictions on use of the soil fumigant methyl bromide, and lack of resistant russet type varieties for US markets have led to investigations of alternative strategies to control this pest. The efficacy of Brassica juncea seed meal extract (SME) (0, 0.14, 0.28, 0.56, 1.12, and 2.24 t/ha) was studied, either alone or in combination with the trap crop Solanum sisymbriifolium under greenhouse and field conditions. The impact of the application of SME pre- or post-planting of S. sisymbriifolium was also determined. Solanum sisymbriifolium only induced hatch of G. pallida and significantly fewer (up to 57 and 55% in pre- and post-plant experiments, respectively) encysted eggs remained at termination of the experiment compared to the untreated control. However, when SME was applied pre-plant, the encysted eggs remained unchanged which may indicate that SME inhibited egg hatch in the presence of S. sisymbriifolium. When applied individually, S. sisymbriifolium in all experiments, or SME at all rates tested in greenhouse and 0.56 t/ha or higher rates of SME in the field significantly reduced the viability, hatch, and reproduction of G. pallida. Combined treatment with S. sisymbriifolium and SME at lower rates, 0.14 t/ha for pre-plant or 0.56 t/ha or less for the greenhouse post-plant experiment further reduced G. pallida egg hatch than each strategy alone. In the field, a combination of S. sisymbriifolium and SME at 1.12 t/ha or less reduced G. pallida more effectively than SME alone. SME alone applied at higher rates of 0.56 and 1.12 t/ha in pre-plant greenhouse trials, whether combined with S. sisymbriifolium, eliminated G. pallida reproduction. Under field conditions, SME applied at a rate of 1.12 t/ha highly reduced G. pallida reproduction compared to the untreated control by 97% and 61% in 2019 and 2020, respectively. Furthermore, reproduction of G. pallida was eliminated when SME was combined with S. sisymbriifolium. Our results indicated that a combination of SME and S. sisymbriifolium reduces the amount of SME needed to control G. pallida and further decreases the potential reserve of the viable population remaining after individual treatment with each strategy.