Effect of cultural practices on turfgrass diseases

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EFFECT OF CULTURAL PRACTICES ON TURFGRASS DISEASES

Retman S.V.,

Doctor of agricultural sciences, professor, Institute ofplant protection of National academy of agrarian sciences of Ukraine, Kyiv, Ukraine

Nychyporuk O.M.,

Researcher, Institute of Water Problems and Land Reclamation of National academy of agrarian sciences of Ukraine, Kyiv, Ukraine

Shevchuk, O.V.

PhD, senior researcher, Institute ofplant protection of National academy of agrarian sciences of Ukraine, Kyiv, Ukraine

Abstract

The article presents the results of the effect of different culture practices on severity of the main turfgrass diseases. It was proved that application of nitrogen fertilizer contributes to an increase in powdery mildew, septoria leaf blotch and yellow rust infection. The severity of powdery mildew increased most of all. Such measures as mowing, aeration and verticutting contribute to the reduction of severity of all diseases. The greatest effect was achieved with the integrated application of spring aeration, scarification and autumn verticutting.

Key words: turfgrass; disease management; cultural practices; powdery mildew; septoria leaf blotch; yellow rust

Turfgrass is an integral part of the man-made environment and becomes increasingly important. It is widely cultivated for its many functional and recreational uses. This culture is primarily concerned with its utilitarian and aesthetic qualities. While these are determined, in part, by the inherent potentials of the individual species and cultivars, they are influenced by the interaction of many factors, including soil water, fertilization, mowing frequency [13].

Mowing is a fundamental practice unique to turfgrass culture. It is the means by which the uniformity of the turf surface is attained. As it is a defoliation process, it affects the physiological, developmental and growth responses of the turfgrass [4, 5, 13].

The fertilization program is an inherent part of turfgrass management. Nutrients like nitrogen, phosphorus, and potassium are a key ingredient for turfgrass growth. Few soils possess enough natural fertility to maintain healthy, functional landscapes through the entire growing season. Nitrogen is the nutrient that most frequently controls growth. It is not only a dominant factor in controlling shoot growth, but also the balance between root and shoot growth [3, 12]. Nitrogen is also required in the largest quantity of all the macro nutrients. Severity of disease in turfgrass can also be modified by N levels [11].

Lawns are subjected to thatch accumulation, this procees being caused by excesive accumulation of roots, dried shoots and clippings. A thatch layer thicker than 1.5 cm may have a negative impact on water and nutrients infiltration into the soil, also it can increase the development of fungal diseases. Removing thatch can lead to a lower necessity of a wide range of inputs like expensive fertilizers, pesticides, irrigation, overseeding and extend the life of lawns [13].

Aerification is a common cultural practice used to improve soil physical properties and rooting of newly laid sod and existing turf. This can be accomplished by using solid tines or hollow tines. Aerification is postestablishment cultural practice used to enhance water infiltration as well as increase gas exchange within the rootzone by disrupting the soil layer. Repeated aerification has been shown to alleviate soil layering and the problems associated with soil layering [6-9].

Scarification is best combined with other operations, like top dressing, overseeding and applying fertiliser. Scarification is carried out to remove organic matter from around the base of the grass plants and tidy up any straggly lateral growth [10, 13].

Verticutting is an important turf management tool to reduce thatch. It can be used to control graining, remove thatch, prepare for seeding, cultivate the soil or disperse core materials following aerification [10, 13].

Cultural practices influence the phytosanitary situation in crops, changing the conditions of existence of both harmful and useful species. However, it is necessary to clearly realize that these changes and shifts in the mutual relations of species in agrocenoses can go in different directions. It is very important to know the response of turfgrass to different cultural regimes and plan the management strategy.

Aim of investigations: To evaluate effect of cultural practices on severity of the main turfgrass diseases.

Methods of investigation

The experiments were established in 2015-2017 in the Polissya region of Ukraine (Zhytomyr region, garden center “Artvil”). For experiments “Universal” mixture (Lolium perenne L. cv. `Gator' - 25%, Festuca rubra L. cv. `Gerald' - 55%, Poa pratensis L. cv. `Sobra' - 20%) was used. Experimental plot area was 50 m² with four replicates.

We studied the effect of such culture practices: nutrition, mowing, aeration, verticutting and scarification. Experiments were performed in two blocks. Nutrition and mowing were investigated in a two-factor split-plot experiment. Factor A - nitrogen application with different dosage (N15, N30, N50, N75). The control variant for the factor A was the non-fertilized treatment Factor B - the mowing frequency with two graduations: 7 days and 14 days.

In the second experimental block effect of aeration, verticutting and scarification was studied with following graduations: spring aeration, spring verticutting and complex use of spring aeration, scarification and autumn verticutting. The experimental design was a randomized complete block. All plots were fertilized monthly with N50 high nitrogen dosage and mowed every 14 days.

Plots were visually assessed before every mowing and 14 days after the last mowing. Disease complex and diseases severity were determined [1, 2]. Visual turf quality were rated by area of projective coverage. Generally, the effects nitrogen and mowing increased with time, with larger differences at the end of the experiment than at the beginning. For this reason, only the data for the final assessment are given.

Repeated-measures analysis of variance was used to determine which treatment main effects were significant (P < 0.05). Fisher's protected Least Significant Difference (a = 0.05) was used to separate treatment means.

Results. As a result of phytopathological analysis of samples, it was found that the most common diseases during the research period were powdery mildew (Erysiphe graminis DC.), septoria leaf blotch (Septoria spp.) and yellow rust (Puccinia striiformis Westend).

The most spread disease in all years was powdery mildew. Its severity varied from 2.6 to 36.4% depending on the cultural practices applied. Severity of septoria leaf blotch was significantly lower - 7.8-19.4%. Yellow rust also was less spread than powdery mildew and at the end of vegetation is severity varied from 8.3 to 18.4%.

The results showed that nutrition with nitrogen fertilizers contributed to the development of powdery mildew (table 1). This is especially noticeable on variants were dosage of N50 and N75 was used with less frequent mowing (once per 14 days). The statistical analysis of the data showed that both of the investigated factors had a significant impact on powdery mildew severity.

As for septoria leaf blotch, nitrogen had a less noticeable effect on the progress of the disease. Its severity increased from 7.8% at control plot to 19.4% at plots where the maximal dosage of nitrogen was applied. But this difference was significant only for N50 and N75 dosage in all timings and N30 with twice a month fertilization.

Yellow rust appeared on field later than other diseases. Despite this it developed quite rapidly and at the end of the vegetation its severity in control reached 8.315.2%. Nitrogen application, even with a lower dosage, led to an increase in disease infection. The highest disease severity was noticed on plots were N75 was used.

Table 1 Effect of fertilization and mowing on severity of turfgass diseases