Toxicity of Tioxazafen to Meloidogyne incognita and Rotylenchulus reniformis

Abstract

Tioxazafen is a seed-applied nematicide used in row crops. Currently, there are no data on nematode toxicity, nematode recovery, or effects of low concentrations of tioxazafen on nematode infection of a host root for Meloidogyne incognita or Rotylenchulus reniformis. Nematode toxicity and recovery experiments were conducted in water solutions of tioxazafen, while root infection assays were conducted on tomato. Nematode paralysis was observed after 24 hr of exposure at 27.0 µg/ml tioxazafen for both the nematode species. Based on an assay of nematode motility, 24-hr EC50 values of 57.69 µg/ml and 59.64 µg/ml tioxazafen were calculated for M. incognita and R. reniformis, respectively. Tioxazafen rates of 2.7 µg/ml and 27.0 µg/ml reduced the nematode hatch after 3 d of exposure for both the nematode species. There was no recovery in nematode motility after the 24-hr exposure of M. incognita and R. reniformis to their corresponding 48-hr EC50 values of 47.15 µg/ml and 47.25 µg/ml tioxazafen, respectively. Mortality of M. incognita continued to increase after 24 hr exposure, whereas R. reniformis mortality remain unchanged after nematodes were rinsed and removed for 48 hr from the tioxazafen solution. A 24-hr exposure to low concentrations of 0.38 to 47.15 µg/ml for M. incognita and 47.25 µg/ml for R. reniformis reduced the infectivity of each nematode species on tomato roots. The toxicity of tioxazafen was similar between nematode species; however, a greater rate of tioxazafen was needed to suppress R. reniformis infection of tomato than for M. incognita.

Morphology Root-Knot Nematode Meloidogyna incognita on Cucumber Plant in Southern Iraq

“…In order to prepare permanent slides and study nematodes, the following steps were conducted: M.incognita egg sacs were isolated directly from the infected plant parts and from the females that were thumb-printed. Eggs were extracted according to [11] method. The eggs were placed in a 100 ml flask in an incubator (Binder) at a temperature of 25 ° C for 4 days, after which the eggs hatched to the second larval stage, which was drawn using the method [12].…”

Attraction of second‐stage juveniles of Meloidogyne species to fluopyram

“…Neither of these two fungicides showed attraction of M. javanica J2 on agar plates. Moreover, these two fungicides have been reported to have no nematicidal activity on M. incognita 6 . These results raised the possibility that the high number of Meloidogyne J2 near the fluopyram deposited on the agar plate might be caused by random encounters of the J2 with the nematicide and their consequent death near the nematicide, rather than by active movement of the J2 toward fluopyram.…”

“…Examples are fluensulfone and fluopyram, whose modes of action differ from that of the formerly used acetylcholine esterase‐inhibiting organophosphates and carbamates. Fluopyram, a succinate dehydrogenase inhibitor (SDHI), 4,5 was developed as a fungicide, and its nematicidal activity was discovered later on 6 . The mode of action of fluensulfone is still unknown, but differs from that of the old nematicides 7,8 .…”

Pacific shoot‐gall disease control in annual bluegrass putting greens using a new formulation of abamectin

“…Fluopyram's long half‐life reported as 180 to 360 d (New York State Department of Environmental Conservation, 2017), provided a nearly impassable barrier for the nematodes. Although abamectin is UV‐sensitive and its half‐life in sunlight was reported for up to 21 h, in the soil and presumably in the grass‐shaded target zone, it may last 20 to 47 d (Faske & Starr, 2006; Gannon et al., 2017). When the infected grass died during the weeks and months following the applications, and the shoot‐galls decomposed, A. pacificae nematodes migrating out of the gall cavity were likely to become again exposed to the remaining nematicides.…”