Last week, when I was supposed to be writing this newsletter, Mike and I played hooky for a couple of days. We visited some wild west ghost towns and California State Parks. One of the things we saw at Bodie State Park was a notification that the Governor of California is considering closing the state parks to save money. The notice clearly stated that this would result in a loss of revenue of $350 million annually which far exceeded the savings. It really does not make much sense does it?

That got me thinking about the cost of diagnoses. We are naturally asked how much our diagnosis fee is but nobody ever asks what it is worth. If you only consider the immediate cost of the diagnosis, you are missing the boat. You must remem-ber that the cost of guessing incorrectly includes the cost of applying the fungicide and achieving no control. It also can include phytotoxicity which increases dump. It includes the cost of holding the crop on the bench longer than optimal which includes, water, additional fertilizer and certainly labor to water and sometimes dump plants that do not reach salable quality. Finally, include the cost of losing a customer due to failure to meet a delivery date or a quality standard.

Next time you are reluctant to send a sample in remember that it is the only way to make sure your control strategy is on tar-get and worth doing at all. Our turn-around time is usually one week from sample receipt which will also save you money since you will not have to wait too long. We can always sug-gest a stop-gap application of a product which can be fine-tuned once the full diagnosis is completed. It would be great if as individual growers and nurs-erymen, we make smarter deci-sions than some of our politicians!

Timely Diagnoses Save Money!

CHASECHASE NEWSNEWS Chase Horticultural Research, Inc. Volume 8—Issue 7 (July)

WOODY ORNAMENTAL FOCUS ( Tower herbicide for pre-emergent weed control in roses, Phyto-toxicity of aqueous ozone in nursery crops)

2

PERENNIAL PLANTS PAGE 3

RESEARCH UPDATES (Gerber daisy powdery mil-dew trials, Can fungicides act as a miticides?, Py-thium and Phytophthora spread by insects)

4

STROBILURINS FOR PYTHIUM ROOT ROT CONTROL ON GERANIUMS, DOES DELIVERY

METHOD AFFECT FUNGICIDE EFFIACY ON AL-TERNARIA LEAF SPOT ON IMPATIENS?

5

MORE RESEARCH HIGHLIGHTS (Daylily Rust Eradication, Preventing Rose Powdery Mildew)

6

CONTENTS

Mike at Bodie State Park in California (above) and Virginia City, Nevada (below)

An old-time lab in Bodie, California (below). Ours is more up-to-date!

WOODY ORNAMENTAL FOCUS Page 2 Chase News

TOWER HERBICIDE FOR PRE-EMEGENT WEED CONTROL IN ROSES—Gary Osteen and I have started working on herbicides in the past six months. The first trials were conducted in central Cali-

fornia in rose produc-tion fields. We did one trial in bud-ded roses ( s e c o n d year) and one in plug p r o d u c e d roses. The treatments i n c l u d e d : untreated, Tower (32

oz/acre) and Tower and Pendulum (32 and 64 oz/A, respectively). Products were applied in late March and we did evaluations about 2 months later. We report here the results for the budded rose trial. The grower accidentally weeded the trial before we could stop him but we were able to count weeds later. The spurge were counted separately while other weeds (flax-leaf fleabane, sow thistle and common groundsel) were lumped. Numbers in the same column followed by a different letter shows statistically significant differ-ences.

These data clearly show best results when Pendulum is added to the Tower since this broadens the activity range dramatically.

Speaking of herbicides—Did you know that herbicides can carryover in hay, manure, compost and grass clippings? Herbicides in the pyridine carboxylic acid group including aminopyralid, clopyralid, picloam and triclopyr have each been shown to carryover in these materials and cause damage in garden plants like tomato, potato, lettuce, spinach, dahlias and roses. Symptoms include twisted, cupped and elongated leaves. North Carolina State University has published a couple of articles on the subject. Contact me for more information.

PHYTOTOXICITY OF AQUEOUS OZONE IN NURSERY CROPS—Graham et al. (University of Guelph, Ontario, Canada) published on safety to Salix, Weigela, Spirea, Hydrangea and Physocar-pus. Ozone was applied using different rates in overhead irrigation for six weeks. The authors found that all rates tested (based on labels for pathogen and biofilm control) were safe on these crops. For a complete report see: HortScience 44(3):774-780 (2009).

Pythium root rot and P h y l l o s t i c t a (=Phoma) dieback on Cotoneaster. It is hard to tell which came first since both fungi can act as secondary invaders after the plant is stressed. Control must include both pathogens at this point and since one pathogen is soil-borne and the other foliar, two meth-ods must be used (drench and spray).

Pythium root rot on cuttings often results in tip burn and mar-ginal necrosis. Be sure to check roots before de-ciding this is a foliar disease. I have seen many samples in the past few weeks.

When I was down in the central valley of California checking the herbicide trials, Gary showed me an impressive outbreak of rust on almonds (see be-low). The weather was so favorable for rust, the grower decided to spray the orchard with a fungi-cide.

Treatment # spurge per 20 feet of bed

# other weeds per 20 feet of bed

Untreated 6.5 c 3.7 a

Tower 2.5 b 2.8 a

Tower and Pendulum

0 a 0.8 a

A week or so ago, I did some consulting in a few Pacific Norwest nurseries and thought you might be interested in seeing some of the current problems on perennials. These problems are consistent on perennials regardless of the part of the country you might inhabit. The only I have found is that some parts of the country have a dis-ease, like downy mildew, year-round. Others might only have a downy mildew outbreak during the late winter or early spring.

Some of the problems I saw are pretty common like root rot on As-tilbe (top, left), calla lily (middle, left) and oriental lily (below).

The Astilbe developed root rot due to water-logging in a low spot in the production field. Calla lilies are attacked by Pythium root rot late in their production cycle. Fi-nally, the Oriental lily developed Pythium root rot more rapidly along the edge of the bed where

they were exposed to the af-ternoon heat and roots were damaged.

Pythium root rot can be con-trolled with Subdue MAXX, Terrazole (or Truban), Seg-way or FenStop. It is best to alternate monthly drenches to avoid resistance to any of these fungicides. Each of those listed has a different MOA (mode of action) and any two would make good rotation partners in gen-eral. If you use a single product or single MOA group, your chances of Pythium developing resistance are much greater.

This has happened throughout the country where growers have relied on Subdue MAXX alone. If you are not getting good re-sults with this fungicide on Py-thium root rot, the pathogen can be checked by some labs (including ours) for possible Subdue MAXX resistance.

Root diseases are best treated with drenches and not sprays. Our work on phosphonates like Aliette shows excellent results on downy mildew and Phy-tophthora almost always but significant control only about 50% of the time on a Pythium diseases. Monthly preventative drenches on sensitive crops can be very helpful

Page 3 Chase News PERENNIAL PLANTS PAGE

We have seen quite an array of crown rots on perennials during the past month in nursery visits and our diag-nostic lab. The Vinca minor (above) shows typical Phyllosticta (Phoma) die-back. Don’t forget this fungus can also cause leaf spots. Optimal control of this disease in our trials has been accomplished with Spectro 90WDG sprenches on a 14-21 day interval.

The Sedum to the right was diagnosed with Fusarium crown rot. This disease is very hard to control but our trials have shown some positive results with Insignia or Pageant (has boscalid in addition to pyraclostrobin found in Ins-ginia). Crown rot diseases are best treated with sprenches.

Pythium root rot on Oriental Lily

Pythium root rot on Calla Lily

Fusarium crown rot on Sedum

Phyllosticta dieback on Vinca minor

Pythium root rot on Astilbe

CONTROLLING POWDERY MILDEW ON GERBER DAISY—One of the most com-mon powdery mildew diseases is found on Gerber daisy. I found a number of reports from all over the US on different approaches to controlling this dis-ease. Dr. Mary Hausbeck and S. L. Glaspie (Michigan State University) reported a trial with a granular azoxystrobin in Plant Disease Management Reports (3:OT008). The products tested included two formulations of azoxystrobin granular at three rates compared to Heritage (4 oz/100 gal), Eagle (8 oz/100 gal), Compass (2 oz/100 gal) and Terraguard (16 oz/100 gal). The azoxystrobin granular was ap-plied by soil incorporation alone to test the systemic ability to control a foliar disease. Eagle and Terra-guard completely prevented disease development. Heritage and Compass did not perform very well in this trial, nor did the azoxystrobin granular products. The pathogen was identified as Podosphaera xanthii.

In a second trial, the same researchers (PMN 3:OT009) tested some experimental products (Palladium, SP2059) compared to Heritage (0.4, 0.9 and 1.8 oz/100 gal) and Eagle (12 oz/100 gal) ap-plied on a 2 week interval. Initial results showed significant control with all products and rates tested. By the end of the trial, best results were seen with Palladium (6 oz/100 gal) or Eagle. Palladium is not currently registered for use on ornamentals.

EVALUATIONS OF BIOPESTICDES FOR GERBER DAISY POWDERY MIL-DEW—Moyer and Peres reported on work con-ducted at the University of Florida in the Proceedings of the Floirida State Horticultural Society 121:389-394 (2008). They tested calcium silicate, potassium silicate, Actigard (not currently labeled for ornamen-tals), K-phite (phosphonate), Milstop, Tricon (boron and orange oil), Cease (=Rhapsody) and AgSil (potassium silicate). Results suggested that neither potassium or calcium silicate were effective. Acti-

gard, AgSil, Cease and Milstop did suppress mil-dew compared to un-sprayed controls but were not as effective as Heritage alternated with Eagle. The most effec-tive biofungicides were K-phite, Milstop and Tri-con. The authors sug-gest rotating between a biofungicide and a more traditional fungicide.

RESEARCH UPDATES Chase News Page 4

CAN FUNGICIDES ACT AS A MITI-CIDE?-Dr. Ray Cloyd (Entomologist at Kansas State University) recently reported on some work to control two-spotted spider mites. Ray decided to evaluate some miticides and fungicides that acted on the pest’s mitochondrial electron transport system. The products included Shuttle, Ovation, Akari, San-mite and Judo for the miticides ad and Heritage, Cygnus and Compass O for the fungicides. The an-swer is that none of the fungicides included con-trolled the spider mites at all. So, pest control is not simply a matter of MOA since their targets differ so greatly (fungi vs. mites). For a more complete arti-cle see—Greenhouse Grower June 2009—pages 40-41.

PYTHIUM AND PHYTOPHTHORA SPREAD BY INSECTS—Researchers at the University of California at Riverside have been work-ing for a number of years on pathogen spread via insects. Their most recent work was published in Plant Disease 93:720-726 on the ability of spores of Pythium and Phytophthora to be ingested and pass viably through the digestive tracks of some insects. Phytophthora capsici and Phy. nicotianae sporangia and hyphal swellings of Pythium splendens, Py. Syl-vaticum and Py. ultimum did not remain viable after being ingested by adult shore flies. Similar tests on fungus gnat and shore fly larvae did show that some propagules were viable after being ingested. Hyder et al. also showed that snails could feed on oospores and chlamydospores of Phytophthora ramorum and defecate viable propagules.

HERBICIDES IN IRRIGATION WATER— Gettys and Haller (University of Florida) reported on the effect of four herbicides in irrigation water on some bedding plant species. Plants included wax begonia, annual vinca, melampodium and common impatiens. Plants were irrigated with water contain-ing herbicides that might be found in irrigation water treated to control weeds like hydrilla, water hyacinth and watermilfoil. Damage was notable on melampo-dium especially but differed by plant and herbicide tested. Their tests indicate that low levels of expo-sure might be acceptable for some plants and herbi-cides but in other cases, the top quality and size of the bedding plant with as little as four irrigations with water amended with herbicides in 10 days could result in significant damage. See HortTechnology 2009 19(3)546-552 for a complete report.

These reports all show that researchers are con-stantly on the look out for the unusual and trying to answer questions in our horticultural industry.

Page 5 Chase News STROBILURINS FOR PYTHIUM ROOT ROT ON GERANIUM

We performed a trial recently on Pythium root rot on geranium with a few strobilurin fungicides compared to Subdue MAXX. The Pythium irregulare isolate we employed has been shown to be resistant to mefenoxam so we do not expect to see much (if any) benefit with Subdue MAXX.

Geranium plugs (Pelargonium x hortorum ‘Multibloom Pink’) were planted in 3.5 inch pots containing Fafard Mix 2. Pots were top-dressed with 3-4 month Osmocote Plus 15-9-12. Plants were treated with fungicide drenches (about 1 pint/square foot) once before inoculation and then three more times on a 14 day interval. The fungicides included Subdue MAXX (1 oz/100 gal), Heri-tage (0.9 oz/100 gal), Insignia (10 oz/100 gal) and Disarm O (2 or 4 oz/100 gal). All except Subdue MAXX are strobilurins. At the end of the trial, we rated the height, top grade and percent of healthy appearing roots.

Subdue MAXX gave some control of this re-sistant Pythium but not as good as any of the strobilurins. The best control was seen with Insignia and Disarm O, although Heri-tage was very good too. The differences in active ingredient and rate of use may explain some of the difference in results. It is clear from this test, that strobilurins are very effective for control of Pythium root rot on geranium.

We started working with Whitmire Micro-Gen over 12 years ago with evaluations of total release fungicides. A couple of years ago we saw some of this work finalized with the registration of FungaFlor TR. A few

months ago, we started looking at some other fungicides delivered in a total release form. The first trial, we ran with rust showed no control with the TR products in that trial. We then conducted one on Botrytis and saw very good con-trol of this pathogen on Geranium and stock (Matthiola) with triticonazole (wet spray or TR) that was comparable to the standard Decree.

We are now are reporting one conducted on Impa-tiens Wallerana (common impatiens) ’Super Elfin XP Red’ for control of Alternaria leaf spot. The plants were treated once before inoculating with spores of Alternaria alternata and then once more one week later. Treatments are shown in the table.

All of the products, whether they were traditional wet sprays or the same active ingredient delivered as a total release application, were equally effective in con-trolling Alternaria leaf spot on impatiens. Hopefully, we will see more fungicides developed using this no wa-ter delivery technique. Any time we can reduce water in a fungicide application while maintaining efficacy it will further reduce disease development.

64

37

4953

5861 60

0

10

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30

40

50

60

70

Noninoc Inoc SMAXX-1 Heritage-0.9 Insignia-10 Disarm O-2 Disarm O-4

% good roots

Effect of strobilurins fungicides on severity of Pythium root rot on Geranium

DOES DELIVERY METHOD AFFECT FUNGICIDE EFFIACY ON ALTERNARIA

LEAF SPOT ON IMPATIENS?

Treatment Rate/100 gal Number of spots

Water noninoculated —— 0 a

Water inoculated —— 7.2 b

Pageant 12 oz 0.5 a

Cygnus 6.4 oz 0 a

Kresoxim methyl TR Adjusted to match Cygnus wet spray

0 a

Trinity 12 oz 0.2 a

Triticonazole TR Adjusted to match Trinity wet spray

0.4 a

MORE RESEARCH HIGHLIGHTS Page 6 Chase News

PREVENTING ROSE POWDERY MILDEW— Sometimes we work for months before conditions are right for disease development. This was the case with a rose powdery mildew trial we started in early May and could not finish until the end of June. We sprayed these plants a total of six times. All fungicides were amended with Latron B 1956 at the rate of 4 oz/100 gal). The products and rates are listed in the table to the left (rates are in oz/100 gal following the product name). The experimental product was used at 2, 3 or 4 oz per 100 gal.

Disease pressure was low in this trial but statistically significant (and equal) control with all products and rates did occur. The best control was seen with Banner MAXX at 8 oz/100 gal which was 100% effective. We did see some phytotoxicity with the Hoist used at 6 oz/100 gal as expressed by slight reduction in size. The PGR effects of cer-tain fungicides in the sterol inhibitor class are well-known and sometimes important. Our previous trials on rose powdery mildew

have shown similar results for control and safety.

Contact Us: www.chasehorticulturalresearch.com

or archase@chaseresearch.net.

DAYLILY RUST ERADICATION—We had some unusual weather in the past six weeks that resulted in some really active rust infections. We saw rose rust (Phragmidium) locally, myrtle rust (Puccinia psidii) in San Diego County and daylily rust (Puccinia hemero-callidis) in Sacramento. We collected some 1-gallon daylilies (Earth Fire) and started an eradication trial on an experimental product. The fungicide standards we included were Heritage and Pageant. We did add Capsil at 4 oz/100 gal to every spray since we had a very active and severe infection when we started the trial. Plants were sprayed three times on a weekly interval and were rated for rust severity one w e e k a f t e r

each spray. Rust was rated on the following scale: 1 = none, 2 = slight rust activity, 3 = moderate, 4 = severe.

The best initial results were seen with Heritage showing nearly all rust activity stopped by a single spray. However, the other two products (Pageant and experimental) were just as effec-tive after the second and third sprays. Under severe rust pressure it is clear that multiple sprays are needed. None of the products caused any adverse effect on these daylilies. Remember that both Heritage and Pageant have strobilurin chemistry and thus the same MOA (mode of action). Be sure to rotate to a different chemical group (MOA) such as a sterol inhibitor (like Banner MAXX, Hoist or Strike) to avoid development of resistance to fungicides.

2.3

1.3

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2.1

2.7

1.7 1.6

2

2.4

1.3 1.2

1.6

0

0.5

1

1.5

2

2.5

3

water Heritage Pageant Exp. 1

Severity of rust on daylily after one (light blue), two (medium blue) and three (dark blue) sprays. Rust was rated on the

following scale; 1(none), 2 (slight), 3 (moderate), 4 (severe).