EXECUTIVE SUMMARY

Integrating Control of Botrytis, Powdery Mildew, and Downy Mildew in Flower Crops

Mary Hausbeck (Michigan State Univ.), Margery Daughtrey (Cornell Univ.), and Larry Barnes Crexas A&M Univ.)

Growers must face increased regulation and adopt environmentally~sound practices which may increase production costs and decrease profits. In addition to these challenges, growers of flower crops must manage a host of potentially devastating diseases including powdery mildew ~M), downy mildew ~M) and Botrytis. Still considered a new disease in the U.S., little is known about PM on poinsettia. The fungus is currently referred to as Oidium sp. since information necessary to classify it further is lacking. Information and scanning electron microscope pictures from our study may further efforts to classify the PM fungus and therefore increase our knowledge regarding host range and origin. A PM management program emphasizing early disease detection via scouting, removal of infected leaves, and appropriate fungicide selection and timing is now available which benefits growers involved in the finishing and postharvest phases of poinsettia production. Studies indicate that high (30 C) temperature eradicative treatments might be helpful in situations where propagators are interested in treating rooted cuttings prior to shipment to insure the poinsettia cuttings are free of PM. Propagators using Terraguard or Systhane on stock plants can anticipate an extended period ofprotection (~55 days) for those cuttings removed from the stock plant soon after fungicide application.

Research has been expanded to include foliar disease management strategies for gerbera, delphinium, snapdragon, and rose. Several new fungicides were investigated for their usefulness in a PM management programi for roses. New fungicides are needed because the PM fungus has likely developed resistance to fungicides currently relied upon. Research studies will help to identify new fungicides that offer promise for commercial development and use. Similar studies are underway for PM on gerbera. There is little information regarding DM on floriculture crops even though this disease continues to negatively impact certain sectors of the floriculture industry. Floriculture crops are also constantly threatened by Botrytis blight. While much is known about the general biology of Botrytis, this fungus continues to cause significant losses at all stages of production. Since the environmental requirements for thc fungi that cause PM, DM, and Botrytis are different, the individual thresholds must be integrated into a comprehensive disease managemert strategy.

Integrating Control of Botrytis, Powdery Mildew, and Downy Mildew in Flower Crops

Submitted by: Mary Hausbeck Michigan State University), Margery Daughtrey (Cornell University), and Larry Barnes (Texas A&M University)

DESCRIPTION AND OBJECTIVES

Powdery mildew ~M), downy mildew ~M), and Botrytis are arriong the most economically important foliar diseases affecting flower crops. The primary foliar disease ofpoinsettia has traditionally been leaf stem, and bract blight caused by Bofiytis cinere~ However, another foliar fungal disease called powdery mildew (Oidium sp.) continues to be a problem for poinsettia growers, especially those in the northern U.S. and Canada. Downy mildew caused by the fungus Pe~onospota antirThini is a devastating~disease on cultivated snapdragons especially in seedlings-raised in humid conditions. Rose growers must manage Botrytis, PM, and DM. Powdery mildew management on delphinium and gerbera continue to offer significant challenges to growers.

The first observation of PM on poinsettias in the United States is reported to have occurred in Pennsylvania and the Pacific Northwest in 1990. Growers in Mexico reported PM on poinsettia during 1988 and 1989 and growers in Puerto Rico have also observed PM. In April 1992, growers from the Midwest, South, and East Coast reported PM (Daughtrey and Hall, 1992; Daughtrey and Macksel, 1994). PM occurrences continue to be reported in the U.S. and Canada (M. Ilausbeck and M. Daughtrey, personal observations). Since PM is a relatively new disease on poinsettia, the specific causal agent is unidentified. PM species are host specific and the PM that occurs on poinsettia has not been transferred to other crops (Daughtrey and Hall, 1992). In general, the occurrence, distribution, and severity of a PM infection are affected primarily by temperature, relative humidity (RH), light, and wind. Conidia germinate on the leaf surface and produce germ tubes, followed by the production of haustoria which penetrate the host’s epidermis.

Botrytis frequently causes storage blights of cut flowers, including gerbera and roses. When cut roses are stored under high humidity, petal spotting caused by B. cinerea may progress rapidly and blight the entire flower head. Gerbera flower blight can be a li?~ilting factor in production, with symptoms often occurring during storage or transport and shipment, when temperature fluctuations result in high humidity and condensation on flowers (Salinas and Verhoeft, 1995). Free moisture and temperature are of primary importance for B. cinerea conidial germination and subsequent infection, although conidia can be very tolerant of drying (Good and Zathureczky, 1967). When free moisture is present, conidia of D. cinerea germinate within 60 minutes of inoculation at the optimum temperature of 20 C. Four hours after inoculation, 40% of the conidia have germinated and by 6 hours, 77% of the conidia have germinated (Hausbeck, unpublished data). Botrytis conidia! “showers” are typically associated with grower activity (Hausbeck and Pennypacker, 199 1). The occurrence of conidial “showers” during and immediately after harvesting is important in disease management.

In order to protect plants, fungicides that are effective against B. cinerea are used repeatedly. Continuous use of systemic fungicides has resulted in the selection ofresistance in greenhouse B. cinerea populations ~oorman and Lease, 1992). Environmental modification in a commercial greenhouse has been a successful control tool to reduce B. cinerea inoculum and blight. Environmental modification could be used in conjunction with a disease prediction system to reduce sole dependency on fungicides (11ausbeck, 1993).

Downy mildew of snapdragon caused by Peronospota an!irrhini results in plant stunting and foliar chlorosis. Although downy mildew is primarily a seedling disease, the fungus may also infect the growing points of established plants CNelson and Strider, 1985). There is little information regarding the influence of environment and sta~ bes of the P. antirrhini infection cycle. In general, sporulation ofPeronospora spp. requires high humidity or dew and temperatures of 4-7 (022-25 C(arwood, 1943). The following objectives are proposed:

1. Conduct fungicide trials using registered and experimental fungicides and biocontrol agents in both the greenhouse and the field to:
   a.) Control PM in gerbera, delphinium, rose, and poinsettia stock plants and cuttings;
   b.) Control Botrytis in postharvest roses; and
   c.) Control DM in snapdragon.
2. Work with IRA and counterparts across the U.S. to support additional registrations for needed fungicides on flower crops, including (0ut not limited to) poinsettia, gerbera, delphinium, snapdragon, and rose.
3. Survey and meet with snapdragon plug producers to explore options for cultural management ofDM and initiate a trial to compare susceptibility of snapdragon cultivars to DM.
4. Research the environmental and cultural factors affecting disease development (epidemiology) and delayed symptom expression (latency) of Botrytis, DM, and PM on gerbera, delphinium, snapdragon, poinsettia, and rose. Investigate the erncacy of heat treatments in eliminating active and latent infections.
5. Initiate research regarding the source of downy mildew epidemics in snapdragon, including seed, plugs, crop residue, soil, and nearby plantings.
6. Evaluate applicability of molecular tools for disease detection in flower crops.
7. Develop grower recommendations for integrated control of Botrytis (rose, poinsettia), PM gerbera, delphinium, poinsettia) and DM (snapdragon).

PROGRESS TO DATE AND FUTURE ANTICIPATED BENEFITS

Observations of the PM fungus 3nd the time required to infect Oinsettia. A scanning electron microscope(SEM) was used to determine that PM conidia began to germinate within 2 hours of landing on a poinsettia leaf at 20 C (85% RH). Con idial germination peaked at 76% within 36 hours after inoctilation. Within 24 and 48 hours after inoculation, 32.5 and 51.0%, respectively, ofgerminated conidia had the structures (appressorium and haustorium) necessary to infect the plant leaf. Using SEM, unique morphological features of the powdery mildew fungus were observed including an arced basal cell and thin ridges on the subterminal cells of some conidiophores(Celio and Hausbeck, 1998). Benefit to the Industry: Still considered a new disease in the U.S., little is known about PM on poinsettia. Our studies indicate that infection occurs within 24 hours of a PM conidium landing on the poinsettia leaf. The fungus is currently referred to as Oldium sp. since the information necessary to classify it further is lacking. Inforrnation and pictures from our study may further the progress in accurately classifying the PM fungus and therefore increase our knowledge regarding host range and origin.

Influence of temnerature on the PM funaus and disease develonment on poinsettia. Maximum germination of conidia was 72,61, and 42% at 25,20, and 15 C, respectively, when RH was 85%. Appressorium formation was not significantly affected by temperature or RH with >89% of the germinated conidia forming appressoria. Shriveling of conidia was least (6%) at 25 C and 95% RH; greatest (39%) at 20 C and 35% RH (Hausbeck and Kalishek, 1994). Con idial germination was reduced, and development of secondary germ tubes and haustoria was severely limited when incubation temperatures were 30 C (Ceho and Hausbeck, 1998). Atmospheric conidial concentrations were highest in research greenhouses between 1000 and 1700 hours and were associated with increases in temperature and reduction in relative humidity. Results indicate that conidia are not readily produced at high temperatures (>30 C) (Shaw and Hausbeck, 1995). Benefit to the Industry: Temperature manipulation may be a useful tool in managing PM on poinsettia. Iligh temperature eradicative treatments might be feasible when vegetative growth is desired such as during stock plant production or following rooting of cuttings. In may be advantageous for rooted cuttings to be exposed to a high eradicative treatment since the plant size is small, requiring treatment of a much smaller area than if treating larger stock plants. While these treatments would not be helpful in a situation where reinoculation is possible, it may be helpful in situations where propagators are interested in treating rooted cuttings prior to shipment to insure the poinsettia cuttings are free of powdery mildew. Though it is unlikely that heat treatments can be used alone, there may be the potential to incorporate temperature manipulation with scouting and fungicide applications to further reduce growers’ powdery mildew management costs.

Develonment of~ PM scoutin~ pro~r~m for noinsettias. A weekly scouting program was implemented among poinsettia stock plants in a commercial greenhouse that had just been discovered to have poinsettias infected with PM. Two properly timed fungicide applications were made. Within 6 weeks of the initial scouting date, PM could not be detected and did not reappear (Hausbeck eta!., 1994). Benefit to Industry: Fungicides need not be applied preventatively but can be initiated once PM is detected. Weekly scouting is encouraged.

Develonment of~ PM snriy nro~r’.m for finishin~ ~rid nosthirve~t nh,ses of noinsettia nroduction. Several studies were conducted to determine which fungicides protect bracts in the finishing or postharvest production phase.

1. To evaluate the length ₉f time fungicides can provide protection against PM, plants were maintained for 56 days beyond the last fungicide application in a greenhouse full of severely infected poinsettias. No PM colonies were active 42 days after higher rates of Terraguard SOW (16.04.04.0 oz or 16.0-8.0-8.0 oz/l00 gal, a total of3 sprays) were applied following disease detection (Hausbeck, 1995).
2. Several fungicides limited the incidence of PM to <5 leaves per plant and included the high (4.0 oz’100 gal) rate of Strike 2SDF, the low (4.0 oz’100 gal) and high (8.0 ozl100 gal) rates of Pipron 84.8LC applied weekly, Rubigan EC, and the low (4.0 oz’100 gal) and high (8.0 oz(100 gal) rates of Terraguard SOW ~ausbeck and Kusnier, 1996, Unpublished data; Hausbeck et a!., 1997).
3. On leaves, all treatments gave significant control of PM compared to the untreated control. Weekly sprays with cKsPunge + Latron or Latron alone gave significant control on foliage, but were ineffective on bracts. On bracts, the best control (no colonies) was seen in Tenraguard treatments. A strobilurin fungicide, BAS 490 was also tested at 2 week intervals and provided control of PM on bracts that was statistically similar to Tenaguard, although a few scattered colonies were visible. Weekly treatments with the experimental fungicides WAC-72 and WAC-73 was also cffcctive at controlling disease on bracts although leaf and bract tip burn was observed. An experimental biocontrol was also tested and provided bract control significantly better than the untreated control but not as good as Terraguard (Daughtrey and Macksel, 1997). Benefit to Industry: Effective fungicides have been identified that have systemic properties and offer supeflor control of PM (Ilausbeck et al~, 1997; Daughtrey eta!., 1997). Timely applications of products tested in our studies have been the key for many growers in turning around a PM epidemic and ensuring that PM colonies do not reappear after plants leave the greenhouse.

Development of 3 PM snrav nro~ram for the stock nlant 2nd euttin~ T)h2ses of noinsettia t)roduction. Studies were initiated to determine whether an application of a systemic fungicide to a stock plant could provide protection to the cuttings that would subsequently be removed from that plan~ Stock plants were given a single treatment with Terraguard or Systhane eight days before cuttings were taken. After the cuttings were removed from the stock plant, they were inoculated with powdery mildew conidia and maintained in an environment conducive to disease development. The Terraguard treatment suppressed PM development for approximately 29 days. The Systhane spray controlled PM infection for 55 days. In another study, when cuttings were removed two months following fungicide application they becarne as diseased by PM as cuttings from stock plants receiving no fungicide sprays (Unpublished data; Byrne and Hausbeck, 1998). Benefit to Industry: Propagators using Terraguard or Systhane on stock plants can anticipate an extended period of protection for those cuttings removed from the stock plant soon after fungicide application. As a result, fungicide applications to cuttings could be delayed from one to two months depending on the fungicide used. This strategy would save unnecessary fungicide expense. Decreasing fungicide use is important so that the PM fungus does not become resistant to our most effective systemic fungicides.

Screen poinsetti.~ cultivars for resist.~nce to PM. Cultivars with red bracts (Freedom Red, Red Sails, V-14 Glory, Supjibi Red) had significantly more bracts infected (>91.2%) than the cultivars with pink (\’-14 Pink, Hot Pink) (85%), white (Topwhite, V-14 White, V-17 Angelika White) (53-96%), or variegated bracts (Jingle Bells 3, Pink Peppermint, V-17 Angelika Marble).(53-79%) (Ceho and Ilausbeck, 1994; Ceho and Hausbeck, 1997). Benefit to

Industry: Poinsettias are susceptible to PM regardless of bract color. Since cultivars with red bracts are particularly susceptible to PM, additional attention should be paid to red-bracted poinsettias when scouting. While cultivars with white bracts are less susceptible to PM, it is worth noting that detection of PM in a commercial setting may be delayed due to low visibility of PM on white bracts.

Evaluation of trcatmcnts for control of ppwderv mildew on miniature roses.

1. A monopotassium phosphate product (cKsPunge) with and without spreader-sticker was compared to Terraguard SOW. Treatments of Latron, eKsPunge + Latron, and Terraguard at 7-day intervals provided significant reduction of disease, but the level of control was acceptable only with the Terraguard treatment. Terraguard at a 7-day interval was superior to the other
2. An experimental fungicide (WAC-72) was compared to Cleary’s 3336 50WP and Pipron + Latron B1956. At the final rating, the most effective treatments were Pipron (804 + Latron B-1956 and the combination of these two materials with Cleary’s 3336 (16 oz) (Daughtrey and Macksel, 1997). A Pipron label expansion in 1997 allows application to all ornamentals, notjust roses.
3. A new fungicide (Recover FL) was compared with Pipron LC, Strike 25WP, and Terraguard SOW. All fungicides significantly limited PM on foliage and flowers compared with the untreated control. Pipron LC, Strike 25WP, and the high (300 ppm) rate of Recover FL were especially effective in limiting the number of flowers infected (<0.3%) (unpublished data; Hausbeck et al., 1997).
4. The experimental fungicide BAS 490 + Latron B-1956 was compared with Strike + Latron B-I 956. Both fungicides significantly limited PM on flowers and foliage in comparison to the untreated control. There was no significant difference between type of fungicide used or length oftreatment interval (7 vs. 14 days) (unpublished data; Ilausbeck et al., 1997).
5. Clearys 3336 WP, Pipron LC, and combinations of these two fungicides with Clearspray T/O were tested for their ability to control PM. All fungicides significantly limited PM on foliage compared with the untreated control. Cleary’s 3336 WP + Pipron LC + Clearspray T/0, Cleary’s 3336 WP, and Cleary’s 3336 WP + Clearspray T/O significantly limited the number of flowers with PM compared with the untreated control (unpublished data; Ilausbeck et al., 1997). Benefit to Industry: Several new fungicides were investigated for their usefulness in a PM management program for roses. New fungicides are needed for the industry because the PM fungus has likely developed resistance to currently relied upon fungicides. Research studies will help to identify new fungicides that offer promise for commercial development and use and provide data necessary for label expansions and registrations.

Evalution of treatmcnts for control of nowdery mildew on ~crbcra. Eight fungicides and IS treatments are currently being investigated for their ability to control PM on gerbera. Chemicals include Medallion (2 oz applied at 7- or 14.day intervals) , Strike (I vs. 2 oz applied at 30-day intervals), Triact (0.5% applied at 7-or 14-day intervals), soluble silicate (500 or 1000 ppm applied every 7 days), Terraguard (4 or 8 oz applied as needed), Sys~hane (4 oz applied at 14- or 2 F-day intervals), and a systemic acquired resistance product (applied at 7-, 14-, or 21-day intervals). Bcncfit to Industry: Several novel fungicides are included for comparison to systemic fungicides and may provide new tools for PM management.

Meet with snapdragon nlu~ t’roducers and screen snapdra~on cultivars for resistance to DM. Researchers visited with floriculture plug producers and cut flower growers to assess current cultural management strategies. Snapdragon plugs of nine different common bedding plant snapdragon cultivars were exposed to DM to determine differences in susceptibility. Chemical control studies have also been initiated. Disease had not yet developed at the time of this reporting. These trials will be continued through the spring months of 1998. Benefit to Industry: A better understanding of DM and an evaluation of whether cultivars differ in their susceptibility to this disease will be crucial in development of an effective management program.

MATERIALS AND METHODS

1. Conduct fungicide trials using registered and experimental fungicides, biorationals, and biocontrol agents within both greenhouse and field to:
   a.) Control PM in gerbera, delphinium, rose, and poinsettia stock plants and cuttings,
   b.) Control Botrytis in posth,arvest roses, and c.) Control DM in snapdragon.
   Research Proposed:
   a.) Studies Investigating the ability of fungicides applied to healthy poinsettia stock plants to protect harvested cuttings from subsequent exposure to PM will be repeated (see progress-to-date).
   b.) Efficacy of fungicides applied to poinsettia stock plants exposed to PM to provide curative effects to cuttings throughout propagation will be tested. Stock plants growing in a greenhouse with poinsettias with sporulating PM colonies will be treated with fungicides at 7-, 14-, or 30-day intervals or unsprayed. Cuttings will be removed weekly and propagated in a PM-free environment. Disease incidence and severity will be recorded to assess fungicide program erncacy.
   c.) Replicated, controlled fungicide trials targeting downy mildew on snapdragons are planned for grower commercial Sites.
2. Work with IRA and counterparts across the U.S. to support additional registrations for needed fungicides on flower crops, including but not limited to gerbera, delphinium, snapdragon, and rose. Based on the results of the fungicide efficacy trials, requests for additional registrations will be submitted to the appropriate industry representatives and/or IRA orncials. Dr. Hausbeck’s laboratory is equipped and has experienced personnel to conduct trials according to Good Laboratory Practice necessary to comply with IRA requirements.
3. Compare susceptibility or snapdragon cultivars to downy mildew. A trial to compare susceptibility of several commercially significant snapdragon cultivars to DNI will be conducted on site with grower cooperators who have yearly disease outbreaks.
4. Research the environmental and cultural factors 2rfecting disease development (epidemiology) and delayed symptom expression (latency) of Botrytis, DM, and PM on gerbera, snapdragon, poinsettia, and rose. Investigate the efficacy of heat treatments in eliminating active and latent infections.Research Prooosed: PM sporulation on poinsettia will be investigated using inoculated plants maintained under optimum condit~ions for con idial germination and infection. Following the incubation period, plants will be moved to a (15-25 C) growth chamber at 60-90% RH. The time to colony appearance will be noted and leaf discs removed, fixed, and the newly-formed conidia counted. To investigate the ability of the fungus to remain latent in host tissue, poinsettias will be inoculated and incubated in a growth chamber under a regime favorable for germination and infection (as determined by previous experiments). Following incubation, cuttings will be removed and maintained in a growth chamber under conditions that are unfavorable for colony development for 1, 4, and 8 days. Plants will then be returned to the environmental conditions that are known (0ased on previous studies) to prompt PM development. The time to colony formation will be noted. Histological studies will be pursued.

   To investigate the efficacy of heat treatments in eliminating active and latent PM infections on poinsettia, cuttings will be inoculated and incubated under conditions favorable for germination and infection. Cuttings will then be exposed to temperatures of 28,30,32,34, or4O C for 2,7, or 12 hours. Following the exposure, cuttings will be placed under environmental conditions favorable for PM. Note: Similar studies of environmental conditions necessary for PM development on gerbera will be pursued.

5. Initiate research regarding the source of DM epidemics in snapdragon, including seed, plugs, crop residue, soil, and nearby plantings. There is no definitive research regarding sources of inoculum for DM epidemics among floriculture crops. Based on completion of the above objectives, methodologies to investigate this area will be developed and pursued in the third year of this proiec.
6. Evaluate applicability or molecular tools for disease detection in flower crops. Many tools are now available that allow researchers to accurately detect and identify fungal pathogens. One commonly used technique involves PCR fingerprinting. This objective will be pursued in the third year of this project once the previously described objectives are completed.
8. Develop grower recommendations for integrated control or Botrytis (rose, poinsettia), PM (gerbera, delphinium, poinsettia) and DM (snapdragon). These strategies will be based on information from research studies and will include scouting tips, rates and application intervals of efficacious fungicides, and incorporation of resistance management. The information will be made available to the floral industry via a fold-out color fact sheets developed, and formatted for inclusion in a three-ring binder.

LITERATURE CITED*

Ceho, GI. and M.K. Hausbeck. 1998. Conidial germination, infection structure formation, and early colony development of powdery mildew on poinsettia. Phytopathology (in press).

Daughtrey, M. and Macksel, M. 1997. Evaluation of treatments for control of powdery mildew on poinsettia. Long Island Horticultural Research Laboratory Annual Report p.17.

Daughtrey, M. and Macksel, M. 1997. Control of powdery mildew on miniature roses with monopotassium phosphate. Long Island Horticultural Research Laboratory Annual Report p.19.

Daughtrey, M. and Macksel, M. 1997. Control of powdery mildew on miniature roses with the experimental fungicide WAC-72. Long Island Horticultural Research Laboratory Annual Report p.19.

Daughtrey, M., Hausbeck, M., and Barnes, L. 1997. Managing powdery mildew on poinsettias. Greenhouse Product News 7(9):26-29.

Daughtrey, M., Barnes, L., and Hausbeck, M. 1998 (1n Press). Powdery mildew prevention: 6 myths to dispel for better poinsettia crops. GMPro, March, 1998.

Hausbeck, M., Da~ghtrey, M., and Barnes, L. 1997. Doing it right: controlling powdery mildew on poinsettias. AFE Research Upda~e. Grower Talks 61(9)68-74.

*Only literature not cited in previous proposals listed as suggesfed by the proposal guidelines.

BUDGET

Greenhouse Supplies: lncludes growing media, containers, fertilizer ($1,500/researcher)

Undergraduate hourly assistance ($2,500/researcher)

Growth and Dew Chamber Usage and Supplies ($SO/unit/month X 3 units)

Salaries:

4,500
7,500
1,800
* Graduate Student (Ph.D.) Stipend (1/2 time)
* Graduate Student (M.S.) Stipend (1/2 time)

AMOUNT REQUESTED FROM AFE

20,200
16.000
$50,000

Technical support
Chemical Industry Contribution ($12,000)

QUALIFICATIONS OF RESEARCHERS

Dr. Mary Hausbeck is an Assistant Professor and Extensi9n Plant Pathologist at Michigan State University. Her current responsibilities at MSU include greenhouse crops. She has completed studies on the crown and root rot of geraniums caused by Pyihium uhimum documenting etiology, symptomatology, flingicide efficacy, and cultivar resistance. She has als₉ provided information essential to the development of environmental manipulation of B. cinere~ In addition, she routinely screens fungicides for efficacy against foliar pathogens.

Ms. Margery Daughtrey is a Senior Extension Associate with the Department of Plant Pathology, Cornell University and conducts a research and extension program on diseases of ornamental plants. She has conducted numerous powdery mildew control trials on annuals, woody, and herbaceous perennials and greenhouse poinsettias, testing conventional fungicides as well as biological and biorational materials. Ms. Daughtrey has assisted in the development of the NY Greenhouse 1PM program, which has successfully developed and executed improved management strategies for tospoviruses.

Dr. Larry Barnes is an Associate Professor and Extension Plant Pathologist at Texas A & M University. Dr. Barnes received his B.S. degree in microbiology and his M.S. degree in plant physiology from Texas Tech University. He received his Ph.D. in plant pathology from Texas A & M University. Dr. Barnes is responsible for supervision and operation of the Texas Plant Disease Diagnostic Laboratory as well as plant pathology extension educational programs in greenhouse and nursery crops.

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