In recent years, a new disease has occurred on golf greens of bentgrass (Agrostis palustris Huds.) during summer season. The typical symptom is a round-shaped patch with characteristic white color. In this study, two isolates of the causal pathogen were subjected to the tests of pathogenicity, cultural behaviors and identification.
(1) Inoculation tests on sods (adult plants) and seedlings of creeping bentgrass in the pots revealed that both isolates were pathogenic at the temperature range of 15 to 30°C; and the degree of the damage was severe at 25 and 30°C.
(2) Behaviors of mycelial growth of both isolates were compared on 5 cultural agar media. Mycelial growth was abundunt on PDA, corn meal and oat meal agar media. Sclerotia formation was abundunt on PDA, while no sclerotia formation was observed on Czapek agar medium.
(3) Mycelial growth on PDA was evident in the range of 10 to 35°C and was maximum at 25 and 30°C. There was no significant differences between the isolates and the pathogen of a brown patch pathogen. Both isolates formed salmon coloured irregular sclerotia, in contrast the brown patch pathogens formed regular round shaped brown sclerotia. The hyphal anastomosis of the isolates was observed with R. oryzae and R. zeae, but not with the 15 representative isolates of other anastmosis groups of R.solani. Based on these results, two isolates were identified as Rhizoctonia oryzae Ryker et Gooch.
(4) Inhibition of mycelial growth was observed on PDA agar plates containig 13 fungicides. Chemicals most effective (ED₅₀<0.lppm) were diclomezine, flutolanil, mepronil, tolclofos-methyl, polyoxin D, propiconazole and TPN (ED₅₀<0.1ppm) for both isolates. Benomyl and pencycuron were less effective (ED₅₀>10ppm) .

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Generally, turfgrass infesting scarabaeid grubs are very difficult to control. In this paper, a simple and exact experimental method was conducted to select effective chemicals for control of them.
The results obtained were as follows.
1. On the relationship between thickness of soil layer and the effect of insecticides against 3rd-instar larvae of cupreous chafer, a extreme decline in mortality was observed in every plots of each insecticide applied to the soil layer more than 5cm. Daiazinon 5G, however, showed high mortality compared with fenthion 5 G and isofenphos 5G in 10cm plots because of its high vapor pressure.
2. By combined application insecticides and Aqua-GRO, a penetration adjuvant, insecticidal action was improved in 10cm plots. Especially, diazinon 5G, isofenphos 5G, chlorpyriphos 40EC and fenitrothion 50EC showed high level of mortarity, respectively. Besides, on residual activities in soils treated for 2 weeks, lower 5 cm soils from combined application plots showed high level of motalities, but, those from nonAqua-GRO-treated plots did not. According to these results, it seems that Aqua-GRO improved the penetration of insecticides into the soil.
3. On the effect of Aqua-GRO to the water retention, the soil with Aqua-GRO mainta fined more water than non-treated soil, and the upward movement of soil moisture owing to the vaporization was suppressed to a certain extent for 2 days after the treatment. It seems that the effect of the penetration adjuvant like this is important for the penetration of insecticides into the soil.
4. It seems that combination of insecticides and penetration adjuvants is very effective on utilization of existing insecticides and control of soil insects.

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Susceptibilities of three cool-season turfgrasses, kentucky bluegrass (cv., Hunts Ville), tall fescue (cv., Falcon) and perennial ryegrass (cv., Kentucky-31), to ten soil applied type herbicides sprayed at pre-seeding, pre-emergence, post-emergence (1L stage) and after cutting were evaluated by pot tests in greenhouse, and ED10 values, which indicate dosages of the herbicides for 10% reduction of plant heigh, were obtained. In addition, susceptibilities of Poa annua L. to the herbicides applied at pre-emergence were determined, and ED90 values which indicate the dosages of the herbicides for reducing the dry weight of the above-ground parts of the weeds by 90% were obtained in a simiar manner. Relative selectivity of these herbicides towards the turfgrasses and Poa annua L. were then discussed in terms of ED10 /ED90. The results obtained were summarized as follows.
Selective phytotoxicity of each herbicide was shown in Figs.1 to 10. Bensulide were highly selective to all the turfgrasses even at the 1L stage, and the others showed higher selectivities to perennial ryegrass rather than to kentucky bluegrass. In general, selectivity of the herbicides increased with developing growth stage of the turfgrasses, and the highest selectivities were observed when applied after cutting.
Accordingly, it was suggested that bensulide can be used safely for the control of Poa annua L. in the three cool-season turfgrasses, and that acephenone and benfluralin can also be used safely in tall fescue and perennial ryegrass, when the turfgrasses have grown up to the 1 L stage before spray.

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In order to prove the usefulness of NSK-850 as a turf herbicide, pre-emergence herbicidal activity of the chemical and its influence on the growth of turfgrasses were examined by pot tests in green house. The results obtained were summarized as follows.
1. Pre-emergence herbicidal activity
(1) Herbicidal spectrum of NSK-850 by preemergence treatment.
NSK-850 effectively controlled annual grassy weeds such as Poa annua, Setaria viridis and Digitaria cilialis. at a dosage of less than 3 g a.i./a. Broadleaved weeds including Bidens pilosa, Ipomoea indica, Capsella bursa-pastris were rather tolerant to the herbicidal and were not controlled even at a dosage of 100 g a.i./a (Table 3) .
(2) Effects of soil water content on the preemergence herbicidal activity of NSK-850.
An excellent control of Setaria viridis was obtained at the highest soil water content (39.3%, W/W) (Fig. 1) .
(3) Effects of spray volume on the preemergence herbicidal activity of NSK-850.
In general, spray volume greatly affected the efficiency of the applied herbicide, and an optimum spray volume for the control of Digitaria ciliaris and Setaria viridis was 10 1/a (Fig.2) .
2. Influence of NSK-850 and simazine on the growth of turfgrasses.
(1) Treatment after cutting off the shoots of turfgrasses.
NSK-850 did not affected the growth of both Zoysia japonica and Zoysia matrella but showed a slight phytotoxicity on Agrostis palustris.
(2) Treatment after top dressing.
When Utsunomiya upland soil (diluvial loam soil) was used for top dressing, the growth of Zoysia matrella was inhibited by simazine but not by NSK-850. Both of the herbicides, however, inhibited the growth of the turfgrasses when Kinugawa coast soil (alluvial sandy loam) was used for top dressing.
(3) Root treatment
When the herbicides were applied to the roots of the turfgrasses, among them Agrostis palustris showed the highest susceptibility to NSK-850 and simazine.
In conclusion, it was suggested that NSK-850 is an useful preemergence herbicide for the control of annual grassy weeds in Zoysia japonica and Zoysia matrella, but it should not be applied directly to the roots

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