Plant Growth‐Regulating Effects of Systemic Fungicides Applied to Kentucky Bluegrass¹

Abstract

Systemic fungicides applied to Kentucky bluegrass (Poa pratensis L.) turf often cause visible alterations in plant morphology. Compounds derived from 5‐pyrimidinemethanol and 1,2,4‐triazole may induce changes in color, growth rate, and density of the stand while also providing outstanding disease control. Because plant growth and stress responses contribute to the severity of many turfgrass diseases, nontarget plant growth regulating effects could influence the disease control activity of systemic fungicides. Studies were conducted to determine the effects of several systemic fungicides on Kentucky bluegrass morphology and physiology. Fungicides were compared, when possible, to growth‐regulating compounds with similar chemical and/or biological properties. Commercially available or experimental formulations were applied as soil drenches to greenhouse‐grown seedlings and as foliar sprays to field‐grown sod of ‘Merion’ and ‘Fylking’ Kentucky bluegrass. Application rates of the fungicides were as recommended for controlling Fusarium blight. Growth regulators were applied at rates comparable to the fungicides or at rates previously reported to have an effect on plant growth. Oven‐dry root weights, shoot densities (tillers plus nonemerged rhizomes), and leaf growth rates were measured. The chlorophyll content of young leaves was determined by extraction with dimethylsulfoxide. Chlorophyll retention of excised, mature leaves was measured following dark incubation. Total nonstructural carbohydrate (TNC) content in mature foliage was determined using the anthrone method. When applied to greenhouse‐grown seedlings, pyrimidinemethanol and triazole derivative fungicides reduced leaf growth rates, shoot densities, and root weights of one or both cultivars. Pyrimidinemethanols increased the chlorophyll content of Fylking and increased TNC contents of both cultivars. Triazoles also increased TNC levels while increasing chlorophyll retention of excised leaves. Chlorophyll retention was also enhanced by cytokinin analogs, including a benzimidazole fungicide. Results obtained from field experiments were inconsistent although similar growth‐regulating effects were observed following certain treatments. Our results show that the systemic fungicides studied have nontarget plant growth‐regulating activity on Kentucky bluegrass. These effects could influence the severity of stress related diseases such as Fusarium blight.

Alterations in carbohydrate metabolism and enhancement in tuber production in white yam (Dioscorea rotundata Poir.) under triadimefon and hexaconazole applications

“…TDM treatment, uniconazole and ectaconazole increased the total non-structural carbohydrates in potato (Kane and Smiley 1983). Paclobutrazol increased the starch and sorbitol concentration in apple (Wieland and Wample 1985).…”

The effect of certain exogenous growth regulators on quality of grafted grapevine rootlings

“…Applications of FM exhibited a slight tendency for a reduction in shoot length and weight, but there were no significant differences compared to control. Certain chemicals normally used as fungicides can exhibit growth-regulating attributes (Kane and Smiley 1983), FM being one among them (Unruh and Brecke 1999). GA exhibited the opposite effect on shoot length to that of PB and CM, however that effect (relative to control) was not significant.…”

Investigation of Fungicides Inhibitory Effect of on Summer Patch Disease, Caused by Magnaporthiopsis poae, in Kentucky bluegrass

“…Triazole계 농약의 경우 병원균 억제효과가 높지만 생장 조절제 역할을 하며 잎을 검게 변화시킨다 (Buchenauer and Grossman, 1977;Kane and Smiley, 1983;Reicher and Throssell, 1997). 식물체에서 중요한 지베렐린 생합성을 억 제하여 왜화시키며 특히 온도가 높을 때는 약해를 발생시 킨다고 알려져 있어 (Bigelow et al, 1995;Buchenauer and Grossman, 1977;Kane and Smiley, 1983) 사용에 주의가 필 요하다.…”

“…식물체에서 중요한 지베렐린 생합성을 억 제하여 왜화시키며 특히 온도가 높을 때는 약해를 발생시 킨다고 알려져 있어 (Bigelow et al, 1995;Buchenauer and Grossman, 1977;Kane and Smiley, 1983) 사용에 주의가 필 요하다.…”