Studies on the Rhizoctoia Large patch of Zosia turfgrass (IV)

Influence of spraying of several harbicides on outbreak of this disease

Abstract

1. Because of the spraying of some herbicides on the Zoysia turfgrass, it is supposed that the turfgrass becomes susceptible to the outbreak of Rhizoctonia large patch.
Therefore, this experiment was carried out to find out the relationship between the outbreak of this disease and the spraying several different herbicides.
2. To see whether the outbreak of this disease happens more frequently under the in fluence of the spraying of several preemergent herbicicides, the herbicides were sprayed on the turfgrass respectively prior to the occurrence in spring. And ofter that, the pathogen was inoculated to the plots by the artificial method.
As the result of this, in the first half of the occurrence, the degree of infection of plots with CAT 0.3g (/200/m²), SAP 2cc, Siduron 2g and TCTP 3g became higher than the nontreated plot, while the plots of Butamifos 2g, Propysamide 0.6 g and Orthobencarb 1.5cc showed the same rate of infection as the nontreated plot.
In the latter half of the occurrence, the leision, which had already occurred, spreaded on all plots, at the same degree as on the nontreated plot.
3. Since it was supposed that the disease would occur naturally on all plots after the next season, the same herdicides were sprayed on the same plots respectively prior to the occurrence in autumn.
In the first half of the occurrence, the leision appeared more largely on the plots of CAT, SAP, siduron and TCTP than the nontreated one, as was the case last spring. In the latter half of the occurrence, however, the leision of all plots spread at the same rate.
The same experiment was performed again in the next spring. This time, throughout the occurrence, the outbreak of the disease on all the plots appeared at the same degree as the non-treated plot.
Incidentally, the disease appeared to a larger extent on the outer edge of the plots of CAT, SAP, siduron, and TCTP than other plots. And the plots of CAT, SAP, Siduron and TCTP have deep caused by poor drainage.
In consegnent, it can be said that throughout the entire period of the occurrence the turfgrass does not become Susceptible to the outbreak, of Rhizoctnia large patch as the result of the spraying of herdicides.
4. This conclusion can be supported dy a similar test conducted at another place. In this case, the same degree of infection was witnessed on the plots of CAT, Orthoben carb and Butamifos as on the non-treated one.
It was also tested whether the leision, which had already occurred, would spread further as the result of the spraying of the abovementioned seven harbicides. No specific differences were witnessed in this test between the plots with herbicidal treatments and the non-treated plot.
5. To see the effect of some post-emergent harbicides on the further spread of the disease, the herdicides were sprayed in spring and autumn on the already occurred leision.
The plots of MCPP 1.5cc (/200cc/m²) and Asulam 1.5 cc showed the same degree of infection respectively as shown in the nontreated plot, although the phytotoxity of both herbicides appeared clearly throughout this test.
Therefore, it is supposed that the effect of post-emergent herbicides on the spread of the disease is rather minimal.
On the other hand, the spread of the leision to which DSMA 0.5 g was sprayed, was clearly inhibited. Therefore, it is supposed that DSMA has a contsolling effect on this disease.