|Klose, Susanne - UC, DAVIS|
|Ajwa, Husein - UC, DAVIS|
|Fennimore, Steve - UC, DAVIS|
|Browne, G - UC, DAVIS|
|Subbarao, Krishna - UC, DAVIS|
Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 28, 2006
Publication Date: May 7, 2006
Citation: Klose, S., Ajwa, H.A., Fennimore, S.A., Martin, F.N., Browne, G., Subbarao, K.V. 2006. Dose response of weed seeds and soil-borne fungi pathogens to 1,3-d and chloropicrin. Crop Protection. 26(2007):535-542 DOI:10.1016/j.cropro.2006.05.004 Interpretive Summary: The objective of this study was to evaluate the concentrations of the fumigants 1,3-dichloropropene and chloropicrin applied together that are needed to control soilborne pests such as weeds and several soilborne plant pathogens. The tests were conducted in controlled laboratory experiments to determine the effect of specific doses under controlled conditions. Some weed seeds were more sensitive than others to the fumigants with Portulaca oleracea the most sensitive with M. parviflora and E. cicutarium insensitive. Differences in the sensitivity of fungal soilborne pathogens to the fumigants also was observed with Pythium ultimum the most and Verticillium dahliae the least sensitive.
Technical Abstract: InLine (a combination of 1,3-dichloropropene (1,3-D) and chloropicrin) has potential to replace methyl bromide as a preplant soil fumigant. The efficacy of InLine to control five weed seeds (i.e., Polygonum arenastrum, Stellaria media, Portulaca oleracea, Malva parviflora and Erodium cicutarium) and four soil-borne fungal pathogens (i.e., Verticillium dahliae, Fusarium oxysporum, Pythium ultimum and Phytophthora cactorum) was evaluated in a laboratory dose-response study after 24 h of exposure to different fumigant concentrations in a sandy loam at 20 degrees C in microcosms. InLine was applied to the microcosms to achieve final concentrations of 0, 50, 125, 250, 375, 500, 625, 1250, 2500, 3750, 5000, 6100 and 12200 µM. These doses correspond to InLine concentrations in the soil ranging from 0 to 10620 µmol kg-1 [dry wt.]. Logistic dose-response models were used to estimate the effective dose to reduce weed seed and pathogen viability by 50 (LD50) or 90 (LD90) percent. Among the weeds, the seed of P. oleracea was the most sensitive to soil fumigation with InLine (LD50 = 352 µmol kg-1, LD90 = 583 µmol kg-1), followed by S. media and P. arenastrum with LD90 values of 780 and 1636 µmol kg-1 soil, respectively. The seeds of M. parviflora and E. cicutarium were not sensitive to fumigation up to the highest InLine dose of 10620 µmol kg-1 soil. Among the pathogens, P. ultimum (LD50 = 30 µmol kg-1 soil, LD90 = 46 µmol kg-1 soil) was the most sensitive and V. dahliae (LD50 = 625 µmol kg-1 soil, LD90 = 2735 µmol kg-1 soil) was the least sensitive to InLine fumigation. Phytophthora cactorum and F. oxysporum exhibited intermediate susceptibility to this soil treatment (LD50 equal to/less than 397 µmol kg-1 soil, LD90 equal to/less than 1113 µmol kg-1 soil). In this sandy loam soil, InLine at a concentration of 1636 µmol kg-1 (or 196 mg kg-1) controlled 90 percent survival of P. oleracea, S. media, P. arenastrum seeds and all fungi pathogens tested except for V. dahliae at 20 degrees C after 24 h exposure. This concentration corresponds to a potential InLine field application rate of 383 kg ha-1 or 342 lb A-1 (15 cm soil depth, 1.3 g cm-3 bulk density).