Specific Fungicides

Fungicides

Jay W. Pscheidt, Extension Plant Pathologist

Abound (azoxystrobin)

Abound (azoxystrobin) is registered for hazelnuts and is a FRAC group 11 fungicide. This material has translaminar properties meaning that it moves into the plant tissue but does not move with the transpiration stream. Abound is best used as a protectant material at 10 day intervals. Greenhouse trials have shown that this product does not have after infection activity.

Rates should be kept high at 12 fl oz/A as stated on the label. We obtained 96% control during the spring of 1998 using Abound at 15.4 fl oz/100 gal water. However, control has averaged only 62% when rates were dropped to 3 fl oz/100 gal water.

See also the prepackaged mixes QuiltXcel and QuadrisTop below.

 

Aproach (picoxystrobin)

Aproach (picoxystrobin) was registered for use on hazelnuts early in 2019. Eastern filbert blight control has been variable with 100% control in low pressure years but only 77% control in high pressure years. One trial indicated better control with the addition of a surfactant. Group 11 fungicides are typically absorbed by plant tissue over a few days with more uptake when used with spreader-stickers. Overall, when used at the labeled rates along with a surfactant the average control was 91% out of 13 trials. All were significantly better than the non-treated control.

 

Bravo (chlorothalonil) and generics such as Echo

Bravo (chlorothalonil) is an excellent, broad-spectrum fungicide registered on a wide variety of crops. It is one of the longest residual fungicides on the market today. Another useful characteristic is redistribution during rain events. A small but important portion of each application redistributes to other possibly unprotected parts of the plant during rainstorms. After approximately two weeks, depending on weather events, much of the material is washed off and reapplication is necessary for continued protection. Soil microorganisms quickly decompose any material washed onto the ground. Some people develop an allergic skin rash upon repeated exposure to this chemical.

Bravo was one of the first fungicides we found to be highly effective against EFB. I can still remember walking through a trial in 1989 that everyone thought was a failure. Many fungicides had been applied to several replicate trees but primarily during the dormant season.

A lot of disease developed in the trees, which is why no one thought much of it. I walked to each replicate without knowing where each treatment was located and picked out the best looking tree. In 6 out of 8 replicates I picked out the Bravo treatment. It turned out that one of the spray applications was close to bud break. By the spring of 1990 we had an emergency exemption for use of Bravo on hazelnuts and a full special local needs registration (SLN or 24 C) in 1996.

There have been close to 50 field trials during the 1990's that included Bravo but each with a specific and often different objective.

Objectives have included different numbers of applications, rates, timings and application methods. When all of this information was combined, both good and bad results, the average level of control was only 65%. If we only consider the labeled rate then the average level of control is 83% (30 trials). To understand why Bravo is considered a good product we must evaluate the data more closely.

For example, if we consider only trials evaluating various numbers of applications at labeled rates we get a different picture. A single application at bud break resulted in an average of 51% control but only 7 out of 11 trials resulted in control that that was significantly better than no application at all. If another application was applied two weeks after the bud break spray then the average control is 59%. With a total of 3, 4, and 5 applications (all starting at bud break and 2 weeks apart) then the average level of control jumped to 77, 90 and 85%, respectively. In addition, all of these later trials were significantly better than no applications at all. The data suggest that a total of 4 applications is essential.

Rate trials with Bravo 720 have shown that as the rate was reduced the level of control was reduced. The number of significant trials also drops such that Bravo's performance against EFB becomes similar to that observed for the copper hydroxides.

A negative aspect of Bravo applications to hazelnuts is the chance of increased summer sunburn. Spring applications of Bravo have resulted in a noticeable increase in sunburned leaves during August. Although this does not affect yields it may increase the number of leaves on the ground during harvest. The affect was only observed on slow growing, non-vigorous trees. The manufacturer suspected an interaction with other pesticides, which we have not been able to duplicate. Nevertheless, the label recommends that no other pesticides, especially oils, be tank mixed with Bravo and that Bravo applications not occur within one week of a application of oil-based products.

Because of the volume of data and its effectiveness against EFB, Bravo will be the standard by which we will compare most other fungicides. There are other formulations of chlorothalonil (such as Echo and Equus) which provide a similar level of efficacy. Home labels such as Bnoide Fung-onil or Hi-Yield Vegetable, Flower, Fruit and Ornamental fungicide can also be found.

Cabrio (pyraclostrobin)

Cabrio (pyraclostrobin) has a label for EFB and has also been tested under the code name BAS 500. Cabrio, like Abound and Flint, is a strobilurin (group 11 fungicide) and has translaminar properties meaning that it moves into the plant tissue but does not move with the transpiration stream. Cabrio is best used as a protectant similar to the way Bravo is used. We observed 91% control in 10 trials when it was used in this way.

In one greenhouse trial, Cabrio was shown to have significant activity when applied 2 days after spores of EFB were applied to young hazelnut seedlings. This activity, however, was gone after 3 days.

See also the prepackaged mixes Merivon and Pristine below.

 

Cevya (mefentrifluconazole)

Like many fungicides in FRAC group 3, Cevya has excellent activity against EFB. This material was developed to help combat pathogens that had developed resistant to other FRAC 3 fungicides. After a few years of testing at 3 to 5 fl oz per 100 gal water, it has averaged 96% control. We suspect that it will have similar activity and properties to other materials in this FRAC group.

Copper Hydroxides

Use of copper as a fungicide has a long history starting with the use of Bordeaux mixtures during the 1880's. Further developments of copper-based fungicides were aimed at improving the handling and safeness to plants over copper sulfate and lime mixtures while trying to maintain its retention properties. The closest result was the development of copper hydroxide.

Several formulations have been evaluated for efficacy against EFB. Interest in these materials occurred early since they were already registered on hazelnuts for control of bacterial blight. Control has varied from 53% to 89% over the years. In general, trials with copper hydroxide products have been inconsistent unlike those with Bravo. In some years, applications of these materials even at highest labeled rates have not provided significant control of EFB over using no fungicide at all. This is why Bravo has been favored over copper hydroxide products for management of EFB.

There have been 6 trials where both Bravo and copper hydroxide were in the same test, applied at the same timings, in the same location, during the same year. In these tests, the average level of control obtained for the copper hydroxide materials was 72% compared to an average of 79% for Bravo 720. So, in those years where copper hydroxide works against EFB it works about as well as Bravo.

In all of the tests with copper hydroxide it was used with the addition of supreme oil, as recommended on the label. Oil alone was evaluated (0.25%) but was not found to be effective against EFB. Some labels of copper hydroxide still carry the old and outdated recommendation to use dormant applications for the control of EFB. Only spring applications when shoots are actively growing will be effective against EFB.

 

Elite (tebuconazole) and generics

Elite (tebuconazole) is in the DMI family of fungicides (FRAC group 3) and has both locally systemic and kickback activity. This product was the next generation from Bayleton, Bayer's first DMI product.

Use of Elite alone in 13 different research trials has resulted in an average of 84% control of EFB. When compared head to head with Bravo the average control was 84% for Elite and 90% for Bravo. Higher rates are more effective. An average of 87% control was gotten at the 4 oz/100 gal water rate compared with 78% control at 2 oz/100 gal water. When used in a combined program using Bravo first at bud break followed by multiple applications of Elite, there was an average of 97% control.

Elite can be used right at bud break. Some DMI fungicides, like Rubigan, need a little more green tissue exposed after bud break to be effective. Other fungicides, like Elite or Tilt, are effective when starting applications at bud break. The flowable formulation of tebuconazole, Folicure, does not seem to be equally effective with an average control of 72% and only significant in 2 out of 3 trials.

An emergency exemption (section 18) for use of Elite on hazelnuts for the control of EFB was issued by EPA for the 2000 and 2001 growing seasons. The emergency use expired on May 30th, 2001 and was denied for 2002.

The generic Tebucon is registered for use on hazelnut. The combination material Unicorn has both tebuconazole and sulfur. Sulfur alone has had variable results averaging 44% control but only significant in 1 out of 3 trials. Unicorn averaged 76% control in 3 trials. It might be useful on the second application to also catch big bud mite crawlers.

 

Flint (trifloxystrobin)

The registration of Flint for use on nut crops during the summer of 2002 was a pleasant surprise. Flint is a strobilurin or FRAC group 11 fungicide and has translaminar properties meaning that it moves into the plant tissue but does not move with the transpiration stream. Flint is best used as a protectant similar to the way Bravo is used. We observed 87% control in 7 trials when it was used in this way. The average dropped in 2003-04 when it did not preform as well as other chemicals such as Bravo.

In one greenhouse trial, Flint was shown to have significant activity when applied 2 days after spores of EFB were applied to young hazelnut seedlings. This activity, however, was gone after 3 days. This is very exciting as other members of the strobilurin group (Abound and Sovran) did not have any kickback activity.

A flowable formulation called Gem was introduced to the marketplace in 2006 but, technically, it is no longer registered for use on hazelnuts.

A few combination products that contain trifloxystrobin are registered for control. The products include Stratego (propiconazole plus trifloxystrobin) and Luna products. Stratego has both a FRAC group 3 and 11 fungicide and does very well against EFB. Luna Sensation also contains trifloxystrobin but in addition contains fluopyram (FRAC group 7). Fluopyram did not do well and was not significantly different from trees that did not get treated with any fungicide. Based on this result we are not recommending the use of Luna Sensation or any of the Luna products.

 

Merivon (pyraclostrobin plus fluxapyroxad)

Merivon has a label for EFB and contains both Cabrio (pyraclostrobin, FRAC group 11) and Xemium (fluxapyroxad, FRAC group 7). Cabrio works very well alone against EFB. Xemium (also known as Sercadis) averaged 83% control in two trials. Unlike other combination fungicides (such as Pristine or Luna products) we do recommend the use of Merivon for EFB. Use of Merivon at 3.25 to 4 fl oz per 100 gal water resulted in an average of 93% control in 4 trials.

 

Miravis Duo (pydiflumetofen plus difenconazole)

Miravis Duo has the group 7 fungicide pydiflumetofen plus the group 3 fungicide difenconazole. All the group 3 fungicides have good to excellent activity against EFB. Miravis Duo averaged 96% control in 5 trials spanning both high and low disease pressure years. Testing of pydiflumetofen alone averaged 88% control in 2 trials, however, both trials occurred during very low disease pressure years. A combination, called Miravis Prime, contains pydiflumetofen and a group 12 fungicide called fludioxonil. Miravis Prime averaged only 53% control in 2 trials during normal disease pressure years. This is similar to another combination product containing fludioxonil, Switch, which resulted in 59% control in 2 trials. So, we think there is some activity with pydiflumetofen but not enough to use it alone.

 

Pristine (pyraclostrobin plus boscalid)

Pristine has a label for EFB and contains Cabrio (pyraclostrobin, FRAC group 11) and Endura (boscalid, FRAC group 7). Cabrio works very well alone against EFB but Endura does not. Endura had an average of 13% control and was not significantly different from trees that did not get treated with any fungicide. Based on this result we are not recommending the use of Pristine even though we have observed 93% control in 2 trials.

 

Tilt (propaconazole) and similar generics

The active ingredient propaconazole was originally sold by a wide variety of trade names depending on the market and location of the sales. Orbit was the name used for the tree fruit and nut markets. Tilt was traditionally for agronomic crops such as grass seed. Generic names include Bumper and Propi-Max.

The average level of control when using the product Banner was 91% (7 trials) while 10 trials with Orbit have resulted in 82% control. Two trials looked at only 3 applications for the season which resulted in 74% control. Greenhouse trials have show that Orbit has a 2-3 day kickback activity against EFB and is greater when used at higher rates.

An attempt to get a section 18 in 1999 was not successful but was granted in 2003, 2004, 2005 and 2006. A regular section 3 registration was obtained in 2007.

Application of Tilt will result in what is called plant growth regulation (PGR) effects. The young developing shoots produce smaller, greener leaves and shorter internodes. This picture shows normal shoots on the right and shoots treated with Tilt on the left. Shoots seem to grow out of the effect 2 weeks after the last application. From 1994 to 1996, we sprayed the same young Ennis trees with various amounts of Orbit (2 to 16 oz/A) to see if there were any adverse effects on yield. The PGR effects were seen each year and the average leaf area was reduced at 4 or more oz/A. However, trees sprayed for 3 consecutive years with 10 oz Orbit/A or 2 years with 16 oz Orbit/A did not result in a significant difference in fresh nut weight, fresh kernel weight or dried kernel weight when compared with trees that had never been sprayed.

Research during 2002-03 and 2003-04 has shown that whether Orbit is used for a total of 4 applications or once at bud break or once 6 weeks after bud break, the average shoot length at the end of the season is the same as on trees that had not been sprayed with any fungicide at all.

In 1995, a few mature Barcelona trees were sprayed in commercial orchards to see how growers might react to this PGR effect. Grower comments included, "If the whole orchard were sprayed with Orbit you would never notice the difference or think anything was wrong." and "Does not represent a significant problem."

A few combination products that contain propiconazole are registered and recommended for control. The products include QuiltXcel (propiconazole plus azoxystrobin) and Stratego (propiconazole plus trifloxystrobin).

 

Procure (triflumizole) and generics

Procure (triflumizole) received an emergency section 18 registration in 2001 and 2002 and regular section 3 registration late spring 2006 for use against EFB. Trials have tested Procure from 1.5 to 6 oz/100 gal water for an average of 78% control (17 trials).

Procure has the same mode of action (group 3) as Tilt, Elite or Rubigan. We expect it to have similar curative or kickback properties, as do the other materials in this group. In one greenhouse trial, Procure was shown to have significant activity when applied 2 to 3 days after spores of EFB were applied to young hazelnut seedlings.

Procure has not shown a plant growth regulation (PGR) effect on hazelnuts even though it is in the same chemical class as Tilt. Leaves on Procure treated trees appear to have the same size and color as nontreated trees.

 

QuadrisTop (azoxystrobin plus difenconazole)

Another mix of two effective products against EFB - Abound (azoxystrobin, FRAC group 11) and difenconazole (FRAC group 3). Both FRAC groups have worked well against EFB. Testing of rates from 7 to 14 fl oz/100 gal water averaged 91% control in 5 trials. The only problem with using combination materials is that you must switch to a different chemistry after 2 applications. The only other chemistries to alternate with would be materials that contain chlorothalonil (such as Bravo), Ziram or copper-based materials.

 

Quash (metconazole)

Quash (active ingredient metconazole) is registered for use against EFB. It is in the same chemical group as Tilt, Procure and Rubigan (all FRAC group 3 materials). Tests for the last 4 years have found this material effective only at the 4 oz rate. However, better control (91% in 2 trials) was found when a surfactant was used. We used the surfactant Regulaid but suspect any surfactant will help boost efficacy of this material. This product can only be used in two sequential sprays before you must switch to a different product in a different chemical group.

 

QuiltXcel (propiconazole plus azoxystrobin)

QuiltXcel is a prepackaged mix of Tilt (propiconazole, FRAC group 3) and Abound (azoxystrobin, FRAC group 11). This material was tested at 14 fl oz/100 gal water in 6 trials resulting in an average control of 91%. The label rate allows use of 14 to 21 fl oz/A. As with any product that contains propiconazole you will see a growth regulation effect of smaller deeper green leaves. Hazelnuts begin to grow normally 2 weeks after the last application.

 

Stratego (propiconazole plus trifloxystrobin)

Another prepackaged mix of two effective products against EFB - Tilt (propiconazole, FRAC group 3) and Gem (trifloxystrobin, FRAC group 11). Both products have worked well against EFB. This material was tested at 5 fl oz/100 gal water in 3 trials resulting in an average control of only 79% but when tested at 7 fl oz/100 gal water it resulted in 93% control. The label rate allows use of 12 to 15.4 fl oz/A so use the higher rate for better control.

As with any product that contains propiconazole you will see a growth regulation effect of smaller deeper green leaves. Hazelnuts begin to grow normally 2 weeks after the last application. If you use combination materials, you must switch to a different chemistry after 2 applications. The only other chemistries to alternate with would be materials that contain chlorothalonil (such as Bravo), Ziram or copper-based materials.

Tesaris (fluxapyroxad)

This FRAC 7 fungicide is the only one in this group with good activity against this fungus. It averaged 81% control out of 2 trials using it alone. Use rate is 3.4 to 5.7 fl oz/A and it is ok to add a surfactant. We have been able to use it in the past but only as a combination product called Merivon. Merivon has this same FRAC 7 fungicide and a FRAC 11 fungicide (Cabrio).

TopGuard (flutriafol)(also Rhyme)

TopGuard (flutriafol, FRAC group 3) is one of the most systemic materials of all of FRAC group 3 products. It can move so well with the transpiration stream that it can accumulate at the leaf margins. When combined with a surfactant this systemic activity can work too well and result in some phytotoxicity at the leaf margin. Although registered at a rate of 7 to 14 fl oz/A, it is recommended to use the higher rate for best performance. Rhyme is more concentrate with a use rate of 3.5 to 7 fl oz/A.

 

Ziram

Ziram was registered for use on hazelnuts on December 12, 2017. Growers must have the supplemental label on hand as well as the label from the product container before use. This material has been very effective on eastern filbert blight. Use this contact only material much like you would any of the chlorothalonil products such as Bravo or Echo. It does not have systemic activity and must be reapplied after significant shoot growth. As always, use at bud break and then every two weeks for two months for best control of EFB.

Testing has shown good efficacy but many of them were done during low disease pressure years. Rates at 3 lb/100 gal water resulted in an average of 95% control in 6 trials. Rates at 4 to 6 lb/100 gallons water have been 100% effective in 6 trials. Use of surfactants is recommended for improved handling if not efficacy. Tank mixes with other fungicides is allowed. Application by air is NOT allowed.