The Year Combos Came To Town

November 7, 2005 - 12:08

If there weren’t many fungicides and bactericides introduced this year, there were certainly a lot of new uses.

One of the problems with predicting events is that they rarely occur on time — if at all. Last year, I described three new fungicides (BAS500-pyraclostrobin, cyazofamid and Fenstar-fenamidone) that were in line for ornamentals registration, and indeed, they are all still in line. Not one of them made it to the ornamentals market this year. There was a variety of reasons why, but at least the EPA cannot be blamed for all of the delays.

This year, I want to revisit one of these three products and alert you to some new fungicides as well. One of the ways to avoid overanticipation in the future is to only talk about the products the companies themselves are talking about — but this assumes they are better at guessing than anyone else.

 

Insignia (BAS500) Update

Insignia (BAS500) is the newest strobilurin fungicide being brought to the ornamental market by BASF Corporation. Insignia is 20-percent pyraclostrobin and is being investigated as a stand-alone product as well as in combination with other active ingredients at various ratios for different crops. The active ingredient is currently registered on vegetables, fruits and turf but not ornamentals.

Experimentally, Insignia has provided excellent control of Alternaria, Cercospora and Spaceloma (scab) leaf spots and Phytophthora aerial blight. It resulted in very good to excellent control of both downy and powdery mildews, Rhizoctonia stem rot, Myrothecium crown rot and Sclerotinia blight. For Cylindrocladium cutting rot, black spot on rose and Fusarium wilt, Insignia gave very good control but only some control of Anthracnose (like Colletotrichum, Glomerella and Gloeosporium). Trials showed that Insignia gave variable control of rust, Botrytis blight and Pythium root rot (none to very good).

Insignia is expected to be registered as a drench for Rhizoctonia and Phytophthora root diseases. As it currently stands, the label suggests addition of other products for best control of Fusarium and Pythium root rot. A bulb dip will be included as well as foliar applications for most leaf spots. Higher rates than those for most leaf spots are expected for the best control of Sclerotinia, Botrytis and Anthracnose. Finally, a few plants are listed as sensitive to Insignia including some grapes, Euonymus vegetus, impatiens and petunias in flower. Our trials have shown that the rates for Insignia on the proposed label are appropriate.

 

Fungicide Combos

So many companies have brought combinations of active ingredients to us for testing that this year should officially be labeled as the year of the fungicide combo. I have listed some of the companies in Figure 1, below, that are investigating new active ingredients, combinations, formulations or new uses.

Concert. This is the first year we have worked with Concert (38.5-percent chlorothalonil and 2.9-percent propiconazole). Syngenta Professional Products is bringing this combination to the turf industry first, with plans to register the product later for ornamentals. We have completed only a few trials to date, including one on powdery mildew of crape myrtle Á (Concert was the best product in this trial) and one on Cercospora leaf spot (see Figure 2, right). We treated the myrtle before inoculating them and again afterwards for a total of four applications on a 14-day interval. This leaf spot was relatively slow in developing, thus the length of the trial. In this case, the chlorothalonil (Daconil Ultrex, Syngenta Professional Products) portion of Concert was most responsible for the excellent control achieved, since the propiconazole (Banner MAXX, Syngenta Professional Products) did allow a few leaf spots to develop. Similarly, the other sterol inhibitor (Eagle, Dow AgroSciences) had a few spots, whereas each of the strobilurins tested (Compass O, OHP; Insignia, BASF Corporation; and Heritage, Syngenta Professional Products) were 100-percent effective in preventing this Cercospora leaf spot on myrtle.

Hurricane WP. Syngenta Professional Products is also launching Hurricane WP. The product will initially be labeled as a drench with intent to add foliar applications. Most of the work on Hurricane occurred in 1999 and 2000. This product was called Broadside at that time and is a combination of 32-percent fludioxinil (Medallion 50WP, Syngenta Professional Products) and 15.5-percent mefenoxam (Subdue MAXX, Syngenta Professional Products). One trial showed no control of Fusarium wilt on cyclamen at 1.5 oz. per 100 gal., although some control was seen with Medallion at 2 oz. per 100 gal. in the same trial. In contrast, both Medallion (1 oz.) and Hurricane (1.5 oz.) gave very good control of Cylindrocladium cutting rot on azalea. Very good to excellent control was seen when Hurricane was used at 1.5 oz. per 100 gal. for Rhizoctonia aerial blight on Boston fern or Rhizoctonia damping-off on impatiens (sprench — not drench!). The most important part of this is the ability to legally use the product for downy mildew, Botrytis, Alternaria and other foliar diseases. The foliar application will likely be accompanied by a 48-hour REI.

Hurricane will not control mefenoxam-resistant Pythium spp. any better than Subdue MAXX alone, so you might consider adding Heritage if resistance is a concern. Our trials with Heritage on Pythium root rot on geranium and pansy have shown very good control when used at labeled rates as drenches. Rotating Hurricane with a combination of a phosphonate for Pythium and Phytophthora and thiophanate methyl for Rhizoctonia and Fusarium is recommended. I think rotating Hurricane and Heritage would be an effective strategy. I will be testing a tank mix of the two this next year since simplicity is often the best approach.

Palladium. Palladium (Syngenta Professional Products) is a combination of 37.5-percent cyprodonil and 25-percent fludioxinil (Medallion 50WP). It will be registered as a foliar spray for control of Rhizoctonia, Botrytis, Erysiphe (powdery mildew), Alternaria and Phomopsis. Both cyprodonil and fludioxinil are effective on Botrytis and will provide built-in resistance management of this serious pathogen. Cyprodonil can be expected to aid in the control of Botrytis, Sclerotinia, powdery mildew and Alternaria. I think the most important addition is the ability to control powdery mildew since this greatly expands the benefit of the combination.

We tested this combination several years ago under a different trade name, but most recently we looked at it for control of both Rhizoctonia stem rot on impatiens and Alternaria leaf spot on zinnia. The Rhizoctonia trial was performed by applying the fungicides to the impatiens once in a sprench about two days before inoculating with Rhizoctonia solani. Figure 3, left, shows the response two weeks after inoculation. The rates tested were somewhat high, 4-24 oz. per 100 gal. Medallion gives excellent control of this disease when used at 0.5-1 oz. per 100 gal. and is 50-percent active ingredient (ai), which would be 0.25-0.5 oz. ai per 100 gal. Thus 4 oz. of Palladium should contain 1 oz. ai of fludioxinil. For some reason we saw a little Rhizoctonia stem rot even at 2 oz. per 100 gal. of Medallion. It was interesting that even the 24-oz. rate used a single time as a sprench was safe on these impatiens. Of course, Medallion is not registered for either impatiens or geraniums due to phytotoxicity concerns. Our trials have repeatedly shown that the negative effects are the result of drenching.

Palladium provided excellent control of Alternaria leaf spot on zinnia when used at all four of the rates tested without any signs of phytotoxicity. The products were each sprayed onto the zinnias to drip on a 14-day interval for a total of three applications. These results were better than those obtained with Medallion alone and probably due to the inclusion of the cyprodonil ingredient. This new combination should prove very helpful for ornamental growers.

 

Conclusions

I would have loved to talk about all of the work we have been doing on new products. Next year, I am hoping many more products will be close to release, and we continue to add to our fungicide arsenal in ornamental product. Remember to read the labels carefully on these new products when you actually start to use them. Preliminary labels are often modified during the final stages of approval at EPA, and the details I list here may not be included on the final label.

About The Author

A.R. Chase is pathologist and president of Chase Research Gardens, the industry’s premier independent chemical testing company. She can be reached by phone at (530) 620-1624 or E-mail at archase@chaseresearch.net.

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