turf talk
Disease Control Options with the
SDHI Class of Fungicides Winter
Jesse Benelli and Brandon Horvath, Ph.D., The University of Tennessee
is fast approaching, and now is a great time to reevaluate your disease control options for the upcoming season. Tennessee is in the heart of the transition zone, and disease activity from a wide array of pathogens is common on both warm- and cool-season grasses. SDHI (succinate dehydrogenase inhibitor) fungicides have been used in the turf industry since the 1980s. These fungicides interfere with the electron transport chain within fungal cells, which in turn prevents energy production needed for fungal growth. This relatively new class of fungicides may be a valuable addition to your fungicide lineup for the upcoming season. Currently, the only two SDHI fungicides registered for turfgrass use are flutolanil and boscalid. Penthiopyrad is a new SDHI fungicide and is soon to be released. All three fungicides have a similar mode of action, but disease control associated with these compounds is uniquely different.
Flutolanil Flutolanil (Prostar), from Bayer Environomental Science, was the first SDHI
fungicide labeled for use in turfgrass. This fungicide has become an industry standard against basidiomycete diseases (fairy ring and Rhizoctonia) in both warmand cool-season grasses in Tennessee. One of the more challenging and costly diseases to manage in Tennessee is large patch of zoyziagrass. Research conducted at our Knoxville location has shown excellent results when flutolanil is integrated within a large patch program in both Z. matrella and Z. japonica zoysiagrass (Table 1 and Photo 1). Application timing is crucial when managing this disease preventively. It is best to initiate your large patch program when soil temperatures reach 70ยบF to 74ยบF in the fall and then reapply 28 days later. A spring application may be necessary to achieve complete control of this disease. In cool-season grass, flutolanil is an excellent alternative control option for
brown patch, when rotating with strobilurin fungicides. Turfgrass diseases such as dollar spot, anthracnose, Pythium blight, and spring dead spot, however, are not effectively controlled by this fungicide.
Boscalid In 2004, BASF launched boscalid (Emerald) as the second SDHI fungicide labeled for disease control in turfgrass. This fungicide, much like flutolanil, controls a very specific set of diseases. Despite a similar mode of action and target site within fungal cells, these two fungicides offer no overlap in disease control. Boscalid is primarily used for dollar spot control on creeping bentgrass putting greens. This fungicide prevents dollar spot development up to 28 days when the high rate (0.18 oz./M) is applied preventively. In Tennessee, applications of boscalid should be made in late spring and early fall when the dollar spot pathogen is most active. Boscalid is also sold in a pre-mixture product called Honor. Honor includes
Table 1.
Percent large patch Treatment and rate per 1,000 ft2
Application timing
Untreated check
26
Z. japonica
Z. matrella
April 11
April 25
May 16
April 11
April 25
May 15
11.5%
29.3%
58.8%
12.0%
13.0%
21.3%
8.8%
1.8%
3.8%
6.5%
3.3%
7.5%
Prostar 70WG, 2.2 oz.
Fall
Triton FLO, 0.75 fl. oz.
Spring
Prostar 70WG, 2.2 oz.
Fall
Triton FLO, 0.75 fl. oz.
Fall (28 days after Prostar) & Spring
0.8%
1.8%
2.8%
2.3%
3.0%
3.0%
Prostar 70WG, 2.2 oz.
Fall & Spring
3.3%
1.8%
8.3%
6.5%
4.8%
9.5%
TENNESSEE TURFGRASS December/January 2012 Email TTA at: tnturfgrassassn@aol.com