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| February 2009 |
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This month's articles Strategies for resistance management Downy mildew update Powdery mildew update Botrytis blight update Phytophthora root rot update Agricultural labor statistics for winter 2009 Floriculture AoE website updated MSU Annual Trials website New MSU Extension publication: Heating buildings and business operations with biomass fuel Insect activity increasing in greenhouses Breeder systems E-Verify: new Internet-based program to verify employment eligibility |
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| Strategies for resistance management February 26, 2009 --Pathogen resistance is a real threat to the most successful of disease management programs. In the laboratory, pathogen resistance can be seen on Petri plates when Botrytis or Phytophthora grows despite the addition of a fungicide. In the greenhouse, pathogen resistance can be seen when disease becomes uncontrollable despite the use of fungicides that have been previously proven to work. Another term for fungicide resistance is control failure. Control failure is the result of the fungicide no longer working and the resulting plant loss from disease. To avoid control failure and keep effective fungicide tools working, keep the following in mind:
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| Downy mildew update February 26, 2009 --Downy mildew is a water mold and related to the well-known Pythium and Phytophthora pests. Impatiens, rose, snapdragon, alyssum, pansy and salvia are susceptible to downy mildew and often suffer from the disease. Other crops such as cineraria, lisianthus, ranunculus, coleus and anemone may also become infected by a downy mildew pathogen although the disease problems are less frequent. Snapdragons, roses, impatiens and other crops susceptible to downy mildew each have a unique downy mildew pathogen. While the disease may look similar on the different crops, they are quite different. The downy mildew on snapdragons cannot blight roses, nor can the downy mildew on impatiens spread to coleus.
Downy mildew recommendations Don’t forget to look under the leaves. Downy mildew may be restricted within the plant without causing severe injury. For instance, leaf spots are called “local infections” and are considered mild symptoms because the downy mildew is limited within the plant. However, if downy mildew advances and invades the internal or vascular part of the plant, the disease becomes “systemic” and is more destructive. When the infection is systemic, it affects the internal mechanism of the plant and hampers its ability to grow. Plants become stunted and yellowed with distorted leaves. When young plants and seedlings are infected, they generally do not survive. Downy mildew produces purplish, gray fuzz on the underside of the leaves. This can go unnoticed because growers are not accustomed to turning over the leaves to look for plant problems. Other than an especially severe case of Botrytis, no other disease causes gray or purplish fuzz on the underside of the leaf. Look for the disease. Downy mildew is often explosive and early detection is critical. The downy mildew pathogen produces plenty of spores called sporangia that are spread via air currents to nearby healthy plants. Turn the leaves over to look for gray or purplish fuzz. Susceptible crops should be scouted weekly. Don’t forget to check the susceptible crops when you receive them and continue to check them once they’re potted especially if they’re in baskets that are hard to monitor. Keep the production area clean. If you had downy mildew last year, this pest may persist in soil and growing media and mats via a thick-walled spore. The downy mildew pest can also reside in compost or cull piles where volunteer plants are likely. Once these volunteer plants become infected, spore production ramps up and the disease is off and running. Downy mildew likes water. Limit this disease by venting, reducing the time that leaves are wet, and keeping relative humidity to a minimum. Water plants at a time of day that allows the foliage to dry quickly. Downy mildew is a water mold because it needs water to grow and develop. Any strategy that reduces water, leaf wetness, and relative humidity in a greenhouse will help limit downy mildew. Apply effective fungicides preventively. Fungicides should be used for plants prone to downy mildew when the weather is favorable for an outbreak but before disease develops. A protectant fungicide such as mancozeb acts as a barrier to the downy mildew pathogen but is not absorbed by the plant so the spray program must begin prior to a disease outbreak. At MSU, downy mildew studies with snapdragons and vegetable crops have shown that weekly sprays of mancozeb effectively limit downy mildew if applications are made early and repeated frequently. Mancozeb sprays can serve as a relatively low cost, effective foundation for downy mildew protection. Systemic fungicides can be added to the fungicide program as needed. Systemic fungicides can be especially helpful in managing downy mildew because these products are absorbed by the plant in a limited way and can fight the pathogen from the inside out. Systemic fungicides include mefenoxam (example: Subdue MAXX), which is labeled as a soil drench only. Mefenoxam 2 applied to the soil performed well in most of our downy mildew trials with snapdragon. Stature and Fenstop are also downy mildew fungicides. Cyazofamid is currently an unregistered product that provided exceptional control in two trials. Other products that appeared helpful but did not always perform as well as Stature include Compass, zoxamide + mancozeb (not registered), Echo, Aliette, and cymoxanil (not registered). Downy mildew has a tendency to change and become resistant to the systemic fungicides (Subdue MAXX is an example.). Since Subdue MAXX is especially at risk, it should only be used once in a production program and must be applied as a drench only. Using mancozeb is not likely to cause the pathogen to change and become resistant so using multiple applications of this fungicide is considered OK. Fungicides such as the strobilurins (Compass is an example.) and Aliette should be used only in rotation with other fungicides that have a different mode of action to ensure that they remain effective and reliable tools. Evaluation of fungicide sprays or drenches for control of downy mildew of coleusA 288-cell flat of coleus ‘Volcano’ seedlings were purchased from a commercial greenhouse and transplanted into four-inch plastic pots containing Baccto Professional Potting Mix on July10. Plants were fertilized weekly with 200 ppm of Peter’s water soluble fertilizer. Six replications per treatment with one plant per replication were arranged in a completely randomized design. Fungicides were applied either as a drench or until run-off using a hand-pumped compressed air sprayer and on July 21. A sporangium solution was prepared by placing sporulating leaf tissue into a solution and agitating to release spores. Plants were placed into plastic bags on July 23 and the conidial solution was sprayed onto the plants using a janitorial spray bottle, after which the bags were immediately closed. The plants were removed from the bags on July 29. On August 5, plants were placed into baskets covered in clear plastic for increased humidity. The number of leaves sporulating with downy mildew, the percent of the infected leaf tissue sporulating, and a disease severity rating (1-10) were noted on August 11. Disease pressure was severe in this trial with the untreated inoculated plants averaging 6.5 infected leaves. Adorn 4FL (4 fl oz) and Subdue MAXX EC were the only treatments that completely prevented infection from Peronospora sp. in this trial. Although not significant, a rate response trend was observed with the drench applications of Adorn 4FL. With each subsequent increase in the rate of Adorn, fewer infected leaves and a reduced leaf area with pathogen sporulation was observed. The application of the experimental product V-10116 as a drench or a spray was not effective in preventing infection and received ratings similar to the untreated control. Plants treated with Stature DM, the unregistered product Mandipropamid, and Heritage WDG, although statistically healthier than the untreated control, had obvious signs of infection from Peronospora sp., making the plants commercially unsaleable. No phytotoxicity was observed on any of the treated plants in this trial. |
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| Powdery mildew update February 26, 2009 --Powdery mildew is a common and difficult problem if not managed effectively. Powdery mildew can occur on all above-ground plant parts and results in white growth on the plant’s surface. When the fungus reproduces, the abundant conidia (spores) give a white, powdery or fluffy appearance. Severe infection can cause yellowing and withering of leaves and restrict plant growth. Powdery mildew can infect plants even when the relative humidity is low, but epidemics are prompted when relative humidity is high. Sometimes the powdery mildew progresses unnoticed until many plants are infected. Powdery mildew is well known for its ability to adapt and develop resistance to fungicides, and it is important to rotate among fungicides with different modes of action. Using as few sprays as possible also helps to delay the development of resistance. Usually, powdery mildew is best controlled when fungicides are begun prior to the appearance of the disease. With especially susceptible crops, it would likely be of benefit to begin a spray program prior to disease development and apply systemic fungicides (alternate products) effective against powdery mildew at two to three week intervals (depending on product used, crop susceptibility, and environment) to maintain a healthy crop. Control of powdery mildew on Gerbera daisy with experimental and fungicide applications Six week old gerbera seedlings were potted into six-inch plastic pots containing Baccto high porosity professional planting mix. Plants were maintained in a research greenhouse and fertilized three times weekly with a 250 ppm Peter’s 20-20-20 liquid feed. Six replicates per treatment were arranged in a completely randomized design. Plants were inoculated when moved into a greenhouse containing actively sporulating Podosphaera xanthii on mature gerbera plants. Fungicide treatments were applied with a hand-pressurized sprayer until drip point every two weeks on June 20; July 3 and 18; and August 6 and 20. SP2050 and SP2059 applications were made every seven days on June 18 and 25; July 2, 9, 16, 26 and 30; and August 3, 13, and 20. Disease pressure in this trial was significant with nearly 47 percent of leaf area colonized by Podosphaera xanthii of the untreated plants. All treatments significantly limited powdery mildew infection. Plants treated with Eagle and the new, unregistered fungicide Palladium (both rates) had significantly less leaf area infected compared to Heritage (both rates), SP2050/SP2059 and SP2059 treatments and the untreated control. Evaluation of Pageant and Eagle fungicides for controlling powdery mildew on verbena Verbena plugs were transplanted from 84-cell trays to four-inch plastic pots filled with a soilless media on April 2. Six one-plant replicates per treatment were arranged in a complete block design. Plants were fertilized twice weekly with 200 ppm Peter’s 20-20-20 liquid fertilizer, and were grown at 85ºF day temperature, 67ºF night temperature. Inoculation was accomplished by placing Podosphaera xanthii-infected plants within the treatment blocks. Treatments were applied to runoff with a hand pump compressed air sprayer on April 19 and May 4 and 18. The percentage of foliage showing infection from powdery mildew was estimated on May 7, 21and June 4.
Disease severity in this trial was moderate. Untreated plants had an average of 65 percent of their foliage infected with powdery mildew on the last rating date. Between May 7 and 21, unseasonably high temperatures resulted in a decrease in the amount of infection on the untreated plants. The new fungicide Pageant was effective in limiting infection from powdery mildew and had ratings similar to that of the commercial standard Eagle 20EW at all rating dates.
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| Botrytis blight update February 26, 2009 --Stem, leaf, and flower blights caused by the fungus, Botrytis cinerea, can limit all phases of ornamental production. Botrytis is well known for its ability to produce large masses of gray conidia that may be picked up and carried on air currents and transported to healthy plants where blight can become established. Monitoring the occurrence and build-up of this inoculum in the greenhouse can signal the need for implementing control measures. On bedding and stock plants, Botrytis typically becomes established and produces spores on aging lower leaves that are near the moist soil surface and under the plant canopy. In addition, Botrytis readily infects the broken or cut stem surface of stock plants and progresses downward, causing a dieback of the entire stem. Fungicides are often important in managing Botrytis and should be chosen carefully. Geraniums are good test plants because they seem to be a “magnet” for this disease. All fungicides are applied and allowed to dry prior to introducing Botrytis spores. Each time a test is conducted, fungicides that are considered especially effective are included for a comparison. Over the years of testing fungicides for Botrytis control, Decree, Chipco 26 GT, and fungicides containing chlorothalonil (Daconil and Echo) have been used as standards because they consistently provide effective control. Evaluation of fungicides for control of Botrytis blight of poinsettiaIn a research greenhouse on the campus of MSU, 60 poinsettias of uniform size were selected and placed in individual humidity chambers. Treatments were replicated six times in a completely randomized design with a single plant per replicate. Plants were watered as needed. Treatments were applied to runoff using a pressurized air sprayer on December 3 and 10. Botrytis cinerea cultures were grown on potato dextrose agar for four weeks. Plates were flooded with sterile distilled water and scraped with a sterile spatula to dislodge spores. Liquid from the plates was strained through cheesecloth, and diluted to 5 x 106 conidia/fl oz. Botrytis cinerea inoculum was applied to runoff after treatments had dried using a handheld mister on December 3 and 10. Infected leaves, sporulating leaves, disease severity and amount of residue were recorded on December 10 and 18.
Disease pressure was severe in this trial with the untreated plants receiving a rating of 8.3 (10=plant death) by the end of the trial. All treatments with the exception of Actinovate and Insignia significantly reduced infected leaves and disease severity by the final rating date. On December 18, plants treated with the experimental fungicide V-10135 had significantly fewer infected leaves and less overall disease severity than the untreated control and all other treatments except Decree 50WDG, Palladium 62.5WG (not yet registered), Endorse 11.3DF, and Chipco 26019 50WDG. Similar results were seen for number of leaves with pathogen sporulation. Spray residue was evaluated for all of the treatments. Of the products shown to be effective in this trial, those with the least residue included Palladium 62.5WG and Endorse 11.3DF. |
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Phytophthora root rot update Phytophthora is difficult to control because it produces several different spores that can cause disease. Thick-walled oospores survive between crops on plant containers, benches, floors, and in potting media or soil. Other spores include lemon-shaped sporangia, thick-walled chlamydospores, and swimming zoospores. Water is important for disease and under warm, wet conditions many spores develop on infected plants and lead to a rapid build-up of disease and spread in a short period of time. Once an epidemic has developed in a production site it is often difficult to determine how the Phytophthora was introduced, how it is spreading, and if it is surviving from year to year. Using genetic tools, research conducted at MSU showed that Phytophthora spread within the greenhouse can occur from sporangia that can travel through the air or zoospores that spread through the water. Recent research also shows how Phytophthora may spread among producers. For instance, snapdragon producers at two locations purchased plugs from the same supplier. The Phytophthora from the two locations was identical. While it is possible that the disease was introduced to the locations via infected plants, it is also possible that the Phytophthora was already established at these production sites. The Phytophthora recovered from snapdragons was identical to the Phytophthora collected from the same facility in a previous year indicating the potential for this pathogen to survive even with a fallow period and treatment with a fumigant (methyl bromide/chloropicrin). In another example, verbena propagated at one greenhouse via cuttings was sold to two other greenhouses for finishing. The finding that the Phytophthora from all three locations were genetically identical suggests that infected plants could have spread P. nicotianae from the propagator to the two growers. Controlling the spread of Phytophthora spp. within and among production facilities can be difficult and there are two major challenges. First, Phytophthora must be kept out of the production site. This is particularly difficult with floriculture crops because of the widespread distribution of pre-finished plants. Also, plants may not exhibit obvious symptoms until the infection is well established or the plant becomes stressed (e.g., over- or under-watering). Infected plants treated with fungicides may appear healthy until the fungicides wear off and Phytophthora increases. The second challenge is eradicating Phytophthora once it has been introduced. Removing visibly diseased plants will not prevent spore production and spread from plants showing few if any symptoms. Sanitation can limit disease and includes removing plant debris, disinfecting pots, and production surfaces. Routinely treating plants with fungicides including mefenoxam (Subdue MAXX) can be helpful. However, Phytophthora can develop resistance to these fungicides and new management strategies and tools are needed. Evaluation of registered and unregistered fungicides in managing Phytophthora root rot of poinsettiaCuttings of poinsettia ‘Freedom Red’ rooted in oasis cubes were transplanted into four-inch pots containing a soilless medium on June 19. Inoculum was prepared by growing an isolate of Phytophthora drechsleri on ¼-strength V8 agar for one week. Two 0.48-inch plugs of P. drechsleri were placed on each side of the oasis cube of each rooted cutting during transplanting into four-inch plastic pots on June 19. Six one-plant replicates per treatment were arranged in a completely randomized design. Immediately after transplanting, treatments were applied as a drench. Treatments were applied again on July 11 and 25. Plants were fertilized twice weekly with 200 ppm Peter’s 20-20-20 liquid fertilizer, and were grown at 85ºF day temperature, 67ºF night temperature. Plant health (1-5; 1=healthy, 2=chlorosis/stunting, 3=minor wilting, 4=severe wilting, 5=plant death), and death (%) were assessed on June 29, July 18, and August 1. Disease pressure was severe with 66.7 percent of the untreated inoculated plants dead with the remaining alive plants severely stunted. Adorn 4FL (both rates) and commercial standard Subdue MAXX were the only treatments that resulted in plants showing no symptoms from Phytophthora and received plant health ratings of 1.0 (1=healthy, 5=plant death). Alude significantly reduced infection compared to the untreated inoculated while ZeroTol had 100 percent plant death by the second rating date. A high and low rate of the unregistered fungicide Cyazofamid, Heritage, and Adorn were included in this trial with no significant differences between the rates for each treatment on the last rating date. Strobilurin products Heritage and Insignia were not effective in controlling infection and resulted in plant health and death (percentage) similar to that of the untreated inoculated. No phytotoxicity was observed on any of the treated plants in this trial.
Acknowledgement for resistance management and disease update articles This research was funded in part by a Cooperative Agreement #59-1907-5-553 with the Agricultural Research Service and the American Floral Endowment. |
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| Agricultural labor statistics for winter 2009 February 24, 2009 -- This past January, wage rates were generally above a year ago in most regions. That does, however, not include the wage rates in the Lake region (Michigan, Minnesota, and Wisconsin). The average wage rate for the country was $10.93 per hour during the reference week, up 12 cents from last January. This January, field workers received $9.96 per hour, up 29 cents for last January. Livestock workers earned $10.27 per hour, up 9 cents from a year ago. These wage rates includes supervisors and other workers, such as bookkeepers and pilots, but do not include the value of benefits. The average wage rate in the Lake region for all hired workers, including supervisors and other workers was $11.02; down by 70 cents from a year ago. Field workers earned $10.83; livestock workers earned $9.96 per hour. Compared to the week of January 6-12 last year, field worker wages are down by 10 cents, and livestock worker wages are down by 71 cents. The Lake region has lost its rank among the highest wage regions. In addition to analyzing wage rates by type of worker, NASS provides wage data by type of farm with slightly different results. These data combine field workers and livestock workers, but exclude other typically higher paid groups. The average hourly wage rates in 48 states, excluding Alaska and Hawaii, during this January were $10.08 overall, $10.67 for field crop farms, $9.68 for other crop farms, and $10.28 for livestock and poultry farms. All wages are up from a year ago, except for other crop farms where the wage rate was the same a year ago. Other crops include greenhouse and nursery crops, as well as vegetables and fruits. The hourly wage rates in the Lake region were $10.20 for all farms, $11.25 for field crop farms, $9.80 for other crop farms, and $10.16 for livestock and poultry farms. For the type of farm calculations, the country is grouped in only 10 regions, while there are 18 regional groups for the previous set of calculations. Among the 10 regions, the Lake region is also moving away from being a top wage rate region. To read Dr. Bitsch’s complete newsletter go to her website at http://www.msu.edu/user/bitsch. Under “News” click on “Agricultural Labor Issues in Michigan” for a list of available newsletters. For more details, the NASS release is available at http://www.nass.usda.gov/. On the right, under “NASS Publications,” “Title,” search for “Farm Labor.” |
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| Floriculture AoE website updated February 17, 2009 -- The Floriculture Area of Expertise (AoE) website is frequently updated so that growers in Michigan and beyond have access to the latest research-based production information and knowledge about upcoming programs. Most recently, floriculture production articles that have appeared in national trade magazines have been re-indexed and presented in a more user-friendly manner. Visit the Floriculture AoE Team website at: www.hrt.msu.edu/floraoe. To view recent published articles on various production topics, visit www.hrt.msu.edu/floraoe/productioninfo.htm This website also includes:
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| MSU Annual Trials website February 17, 2009 -- The following information was obtained from the Floriculture Area of Expertise Team web site and should be of interest to growers in Michigan. As you know the MSU Trial Gardens have been trialing new flower varieties for over 25 years on campus in the Horticulture Demonstration Gardens. This site has information that all greenhouse growers who sell plants in Michigan would find useful. To visit, go to: www.msutrials.ath.cx/ . Providing the best performing annuals to your customer is the most efficient way of increasing sales. If the end user is successful with their experience they will purchase again and again. Information on the site includes the following items:
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| New MSU Extension publication: Heating buildings and business operations with biomass fuel Thomas Dudek District Extension Horticulture and Marketing Educator February 17, 2009 -- This new MSU Extension publication written by Dr. C.H. Schilling at Saginaw Valley State University and Mark Seamon, Thomas Dudek and Stephen Harsh from Michigan State University, is a detailed 24-page publication written by experts in the field of biomass fuels as alternative heat sources. The publication outlines the pros and cons of biomass heating systems, economics involved, and the environmental and regulatory issues related to the use of biomass burners in Michigan. To obtain a copy of this publication either download the pdf at: www.web2.msue.msu.edu/bulletins/Bulletin/PDF/E3044.pdf or contact your local MSU Extension office and request a copy of bulletin E-3044. |
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| Insect activity increasing in greenhouses February 17, 2009 -- Are your sticky cards out in your greenhouse? Have you been scouting and checking susceptible plants for insects? Do your cuttings coming in look insect-free after inspecting them? If you can answer yes to all of these questions, your pest management is under control. However, I would like to remind you that we have been seeing the following in area greenhouses:
See Dr. Smitley’s article in the January 2009 Greenhouse CAT Alert articles titled “Greenhouse insect management” for control recommendations. |
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| Breeder systems February 10, 2009 -- What is a breeder system? Just what it sounds like. A breeder system enhances breeding/reproduction of the beneficial, predacious insect, Amblyseius cucumeris. Western flower thrips can be a problem in the production of annual and perennial plants in our spring crop. Historically, when light levels, temperatures and pollen pressure increases, thrips’activity explodes. I’ve seen numbers of thrips on a sticky card jump from under 10 to 100-plus in as short as three days. With that said, the concept of the breeder system is to start early with the presence of beneficials and build your predator population (Amblyseius cucumeris). Early in the system, you are not relying on the thrips as the food source for the beneficials. You are utilizing a food source that is not a pest in the greenhouse system. The breeder system is a mixture of bran mites, Amblyseius cucumeris in a base of bran that serves as food for the bran mites to maintain a population and provide a food source for the Amblyseius cucumeris. Thrips development from egg to adult can range from 20 days at 68ºF to 12 days at 86ºF. The female thrips utilize their ovipositor and put a slice into the plant tissue and lay an egg. The egg hatches within a few days and the larvae begin feeding. At the second instar, they fall to the ground or media in the greenhouse and pupate, emerge, and the feeding begins again. Amblyseius cucumeris are mobile and prefer to feed on first instar thrips. |
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| E-Verify: new Internet-based program to verify employment eligibility E-Verify is an Internet-based program allowing employers to verify new hires’ employment eligibility by accessing information in the Social Security Administration’s (SSA) database, as well as, the U.S. Citizenship and Immigration Services’ (USCIS) database. Basically, participating employers can compare information taken from a new hire’s I-9 form against the SSA and Department of Homeland Security (DHS) immigration databases. To participate, an employer must accept a Memorandum of Understanding (9 pages) and should consider the users’ manual describing the details of the E-Verify program (79 pages). An employer who participates in E-Verify is required to verify the employment eligibility of all new employees, independent of their citizenship status. However, participation in E-Verify does not provide a safe harbor from worksite enforcement. A notice of participation and an antidiscrimination notice must be posted clearly visible to prospective employees. According to Scharfen, Acting Director of USCIS, over 69,000 employers representing 269,000 worksites were signed up to use E-Verify by June 2008. According to DHS, more than 10 percent of all new hires were checked through the E-Verify program earlier this year. Several states do require or encourage the use of E-Verify under certain circumstances and one state is trying to limit its use. The E-Verify program was scheduled to sunset November 29, 2008. However, on July 31, 2008 the House of Representatives voted to reauthorize the voluntary E-Verify program for an additional five years. The Senate was not able to agree on a similar bill, but voted on September 27, 2008 to approve a continuing resolution extending the E-Verify program to March 6, 2009. President Bush signed this bill September 30, 2008. The extension opens up the possibility of a broader immigration debate or an increase in available visas, shortly after the election. On December 23, 2008 the U.S. Chamber of Commerce, in conjunction with other plaintiffs, filed suit against the Department of Homeland Security for making E-Verify compulsory for federal contractors. The Obama administration is currently reviewing this and other programs. To read Dr. Bitsch’s complete newsletter go to her website at http://www.msu.edu/user/bitsch. Under “News” click on “Agricultural Labor Issues in Michigan” for a list of available newsletters. Please remember that these newsletters serve educational purposes only and do not constitute legal advice. |
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