Great Lakes Fruit, Vegetable & Farm Market EXPO Michigan Greenhouse Growers EXPO. December 6-8, DeVos Place Convention Center, Grand Rapids, MI

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1 Great Lakes Fruit, Vegetable & Farm Market EXPO Michigan Greenhouse Growers EXPO December 6-8, 2011 DeVos Place Convention Center, Grand Rapids, MI Asparagus Where: Gallery Overlook (upper level) Room A & B Recertification credits: 2 (1B, COMM CORE, PRIV CORE) CCA Credits: SW(0.5) PM(1.0) CM(0.5) Moderator: Gene Kokx, Jr., MVC Board, Hart, MI 9:00 am Asparagus Disease Research and Update Mary Hausbeck, Plant Pathology Dept., MSU Leah Granke, Plant Pathology Dept., MSU Brian Cortright, Plant Pathology Dept., MSU 9:30 am Asparagus Irrigation Research Update Daniel Brainard, Horticulture Dept., MSU 10:00 am Asparagus Miner Ecology and Management Research Update Zsofia Szendrei, Entomology Dept., MSU 10:20 am Keeping the Grass Green: Postharvest Storage and Handling of Harvested Asparagus Randy Beaudry, Horticulture Dept., MSU 10:50 am Michigan Asparagus Advisory Board Update John Bakker, Michigan Asparagus Advisory Board and Michigan Carrot Industry Development Program, Dewitt, MI

2 Asparagus Disease Research Update Dr. M.K. Hausbeck ( ), Dr. L. L. Granke and B.D. Cortright Michigan State University, Department of Plant Pathology, East Lansing, MI Soilborne Diseases Fusarium spp. cause crown and root rot of asparagus and Phytophthora asparagi causes spear, crown, and root rot. Both of these pathogens may kill asparagus crowns in nursery and commercial fields. Since asparagus is a perennial crop, crown rot may progress unnoticed for years before crown death occurs. Extreme weather conditions of heavy rainfall and drought stress the plant and favor crown rot. Control of Fusarium and Phytophthora rot is challenging as the pathogens persist in the soil and cultural and chemical control options have been relatively ineffective. The treatment of crowns before planting and fumigation of crown nurseries and production fields may reduce the amount of disease in the crowns, which will extend the longevity and increase the productivity of the asparagus field. Crown Soak Trial. To determine the efficacy of fungicide soaks in controlling Fusarium spp. or Phytophthora asparagi, a replicated study was performed using 1-year old crowns recently harvested from a fumigated crown nursery. The crowns were sorted to a uniform size and soaked in various fungicide treatments for 10 minutes (Table 1). The crowns were then inoculated with either Fusarium spp. or Phytophthora asparagi spores to ensure infection. Each treatment was replicated 10 times and planted in a randomized order. The treated and inoculated crowns were planted in 5 gallon pots containing soil from an Oceana asparagus field.. The potted asparagus was grown during the summer outside on wooden pallets and watered excessively to promote disease. In the fall, crowns were removed from pots and were evaluated for crown weight gain, disease severity, fern height and overall health. Table 1. Crown soak study with 1-year old crowns comparing fungicide soaks for the control of Fusarium spp. or Phytophthora asparagi. Treatment Rate/ 100 gal Fusarium rating (0-10 scale) * Phytophthora rating (0-10 scale) * Fern height (inches) Untreated control Fusarium 4.0 b ** 28.1 Cannonball 50WP 0.5 oz 1.0 a 26.0 Topsin M 1.0 lb 1.0 a 30.4 Fontelis 1.0 pt 1.1 a 28.9 Untreated control Phytophthora 4.1 b 26.9 Presidio 4.0 fl oz 0.7 a 29.9 Ridomil Gold EC 1.0 fl oz 1.9 a 30.7 * Disease rating scale from 0-10, where 0=no disease, 1=trace of disease, 2=trace-5 lesions, 3=5-10 lesions, 4=10-15 lesions, 5=15-20 lesions with trace of rotted roots, 6=>20 lesions with slight root rot, 7=>20 lesions with moderate root rot, 8=>20 lesions with heavy root rot, 9=>20 lesions with all root rotted, 10=complete crown death. ** Column means with no letter or a letter in common are not significantly different, Fisher LSD (P=0.05).

3 The disease level was significant for both the Fusarium and Phytophthora portions of the study. The fungicide treatments targeting Fusarium infections (Cannonball, Topin M, and Fontelis) were effective in limiting the amount of lesions that developed on the roots. The Cannonball, Topsin M, and Fontelis soaks lowered the amount of infections but were not able to eliminate lesion development completely. The Topsin M soak had the largest amount of crown weight gain and the tallest fern for the treatments inoculated with Fusarium. The Presidio and Ridomil Gold EC soaks lowered the amount of Phytophthora lesions significantly when compared to the untreated control. Both of these fungicides resulted in taller fern than the untreated control that was inoculated with Phytophthora. Only Cannonball is registered for asparagus crown soaks at this time. Foliar Diseases The most common foliar fungal diseases of asparagus fern include rust (caused by Puccinia asparagi) and purple spot (caused by Stemphylium vesicarium). Symptoms of purple spot may be observed on both the spears and ferns. Infected spears may be rejected for the fresh market. Purple spot is favored by cool, wet weather. Ferns may be infected with purple spot and rust at the same time. Severe infections can stunt or kill young shoots and can defoliate plants. Defoliation caused by these pathogens results in decreased carbohydrate stores in the crown, which may limit yield in subsequent years. Damage is most severe when fern is attacked several years in a row. Plants stressed by foliar diseases may also become more susceptible to soilborne diseases. Some varieties of asparagus are less susceptible to rust or slow-rusting. The rust fungus produces several types of spores over the course of the growing season: basidiospores, aeciospores, urediospores, and teliospores. Basidiospores develop in the very early spring on asparagus debris from the previous growing season. Basidiospores infect spears, resulting in light orange, oval lesions. Bright orange aeciospores develop in these lesions on volunteer asparagus and young plants that are not harvested. The next stage of the rust life cycle that occurs is the repeating or uredial stage (mid- to late-summer). Urediospores are produced in great numbers and may resemble a reddish dust. A relatively small number of urediospores can reproduce rapidly to cause significant and damaging levels of disease. The final stage occurs in late summer with production of the black teliospores, which overwinter in plant debris. Interrupting the aeciospore stage in the early spring prevents development of the repeating urediospore stage and dramatically decreases the need for fungicide sprays later in the season. Using slow-rusting varieties, removing volunteer plants, scouting fields and applying fungicides early in the season before rust becomes established is a sound management practice. Current control of these foliar pathogens relies on preventative applications of fungicides that are registered for use on asparagus. Currently there isn t one chemical that can control both purple spot and rust with equal efficacy. Ongoing fungicide trials at MSU are being conducted to determine the best application strategy and rotation (Table 1). At the current time an alternating program of Bravo, Equus, or Echo (chlorothalonil chemistry) with Folicur (tebuconazole) has historically been the best for method for controlling both foliar pathogens. Relationships between weather and airborne urediospore concentrations. Airborne urediospore concentrations and weather conditions (leaf wetness, relative humidity, temperature, rainfall, solar irradiance, and wind speed) were monitored at an abandoned asparagus farm in 2002 and at commercial asparagus farms in 2002, 2003, and Airborne urediospores concentrations were positively associated with wind speed and solar irradiance and negatively associated with leaf wetness values and relative humidity. Rainfall did not appear to be associated with airborne spore concentrations. Hence, urediospores are more likely to be released to the air and move on wind currents during dry sunny days. Urediospores were detected earlier in the growing season at the abandoned farm than at the commercial site. Since disease and spore production may occur sooner on asparagus fern at abandoned farms,

4 abandoned farms may represent an important source of spores to initiate disease on fern at commercial farms. Table 1. List of currently registered and pipeline fungicides tested at MSU for the control of asparagus foliar disease. Chemical Active ingredient Company Registered on asparagus Manzate Pro Stik mancozeb DuPont Yes Bravo WeatherStik chlorothalonil Syngenta Yes Quadris azoxystrobin Syngenta Yes Folicur tebuconazole Bayer Yes Flint trifloxystrobin Bayer Yes Endura boscalid BASF No Inspire difenoconazole Syngenta No Fontelis penthiopyrad DuPont No Cabiro pyraclostrobin BASF No Quilt Xcel azoxystrobin/propiconazole Syngenta No Tilt propiconazole Syngenta No Inspire Super difenoconazole/cyprodinil Syngena No Luna Experience fluopyram/tebuconazole Bayer No Figure 1. A week at the abandoned farm 2002 showing trends in A, 4-hour total airborne urediospore concentrations and hours of leaf wetness B, 4-hour average ambient temperature and relative humidity, and C, 4-hour total rainfall and solar irradiance. Funding for this work was provided by Michigan Asparagus Research, Inc., USDA CSREES CAR , USDA NIFA PMAP , and USDA NIFA SCRI

5 Sub-Surface Drip and Overhead Irrigation Effects on Jersey Supreme and Guelph Millenium Daniel Brainard and Ben Byl, Department of Horticulture, Michigan State University A440A Plant and Soil Sciences Building, East Lansing, MI phone: ext 1417 SUMMARY. Irrigation may play an important role in improving the resilience of asparagus to pests and drought. Irrigation may also create opportunities for valuable complementary practices including high planting densities, cover-cropping and fertigation. A field trial was initiated in Hart, MI, with the longterm objective of evaluating the impact of irrigation system (none, overhead or sub-surface drip) and asparagus variety (Guelph Millenium or Jersey Supreme) on yield and profitability. Asparagus was planted in Hart, MI in 2010 with sub-surface drip-tubing placed below the crowns. In 2011, of irrigation per event were applied at approximately weekly intervals during dry periods in July and August. Sub-surface drip irrigation resulted in more efficient delivery of soil moisture to the asparagus rooting zone compared to overhead irrigation. For both varieties, irrigation reduced stem death, and increased canopy light interception compared to the unirrigated controls. For Jersey Supreme, irrigation also resulted in an increase in cladophyll dry weight. Reduced light penetration was associated with fewer weeds. No differences in the incidence of purple spot between irrigation treatments were detected. The effects of irrigation on asparagus yield and profitability will be assessed beginning in INTRODUCTION. Drought stress may be an important factor contributing to the decline in asparagus fern health and yield. Although asparagus is deep rooted and relatively drought tolerant, soil water content during fern growth is an important determinant of crop yields (Drost and Wilcox-Lee, 1997; Hartman 1981). Drought stress during fern growth can limit the capacity of plants to produce the soluble carbohydrates in roots necessary for high yields in subsequent seasons (Drost and Wilcox-Lee, 1997). Stressed plants may also be more susceptible to fungal diseases that increasingly plague the asparagus industry. Warmer temperatures and more variable rainfall patterns observed in MI in recent years make irrigation an increasingly important tool for reducing risks of yield loss in asparagus production. Irrigation may also create opportunities for valuable complementary practices including covercropping and fertigation. In irrigated systems, cover crops growing below the fern canopy may be established with reduced risk of competition for water with the asparagus crop. These living mulches may provide several important benefits including soil protection and weed suppression (Brainard et al. 2011). Chemical pesticides and fertilizers may be applied through drip-irrigation systems to improve the efficiency of delivery and reduce adverse environmental impacts of these products. Relatively little is known about the impact of alternative irrigation systems on commonly grown asparagus varieties under Michigan weather and soil conditions. A field experiment was initiated in 2010 to evaluate the long-term impact of irrigation system (none, sub-surface drip, or overhead) on fern growth, yield and profitability of both Guelph Millenium and Jersey Supreme asparagus varieties. Secondary objectives include assessment of impacts of irrigation system on the incidence of insect, disease, and weed pests. METHODS. A field experiment was initiated in 2010 in Hart, MI examining irrigation (none, overhead or subs-surface drip) effects on two varieties of asparagus (Guelph Millenium and Jersey Supreme). Crowns were planted at a density of approximately 16,600 crowns per acre in spring Sub-surface drip tubing was placed below the crowns at planting. In 2011, inch of irrigation was applied per

6 Light Pentration (%) Fern dry weight (g/m2) VWC (%) event at approximately weekly intervals during dry periods in July and August. Volumetric soil moisture content was monitored at multiple depths with a Diviner 2000 soil moisture probe throughout the summer. In addition, light interception by the developing fern was estimated by measuring photosynthetically active radiation (PAR) above and below the canopy. Asparagus fern was sampled on 10/4, dried, separated into cladophyll (leaf-like modified petioles) and stem tissue and weighed. A visual rating of purple spot severity and the number of mature marestail (Conyza canadensis) plants per plot were assessed in August. RESULTS Figure 1. Volumetric water content by depth, August 2011 None Overhead Drip Depth (cm) Figure 2. Asparagus fern dry weight, 10/4/11 Stem Cladophyll AB AB None Overhead Drip None Overhead Drip Jersey A a b ab b ab b B AB Millenium B Soil water content and distribution. Soil volumetric water content in irrigated treatments was significantly higher than in the un-irrigated control for much of August. Overhead irrigation resulted in higher soil moisture at the surface, but lower soil moisture at depth compared to sub-surface drip irrigation (Figure 1). Fern growth and dry weight. Jersey Supreme fern dry weight was greater than that of Guelph Millenium (Figure 2). Sub-surface drip irrigation increased cladophyll dry weight of Jersey Supreme. No statistically significant effect of irrigation on total fern dry weight was detected for either variety (Figure 2). However, irrigation resulted in reduced light penetration below the fern (Figure 3), indicating that fern leaf area was significantly increased under irrigation. Trends in both fern dry weight and light penetration suggest that Jersey Supreme fern growth may be more responsive to subsurface drip irrigation compared to overhead irrigation, and vice-versa for Guelph Millenium. Figure 3: Light penetration below fern, Aug.-Sept a Jersey Millenium 25 b b ab c c None Overhead Drip Irrigation

7 Dead stems (%) Irrigation effects on weeds, purple spot and stem death. We had anticipated that overhead irrigation might increase purple spot severity by increasing leaf wetness relative to sub-surface drip and nonirrigated treatments. However, no detectable effect of irrigation on purple spot was detected for either variety in 2011 (Table 1). We also hypothesized that overhead irrigation would promote weed growth by increasing moisture availability at the soil surface. However, no effect of irrigation on weeds was detected (Table 1). Interestingly, marestail density was higher in Guelph Millenium treatments relative to Jersey Supreme treatments (Table 1), presumably due to greater light penetration (Figure 3) under the smaller Millenium fern. The number of dead stems Figure 4: Dead stems as percentage of all stems increased during the month of August, with the Aug greatest increase occurring in the non-irrigated 24-Aug 14 treatments (Figure 4). By the end of August, A approximately 13% of stems in non-irrigated 12 controls had died, compared to approximately 10 7% in irrigated treatments (Figure 4). AB LITERATURE CITED a Brainard, DC, J Bakker, DC Noyes and N Myers. Rye living mulch effects on soil moisture and weeds in a None Overhead Drip asparagus. HortSci. (in Press). Irrigation System Drost, DT and D Wilcox-Lee Soil water deficits and asparagus. Scientia Horticulturae 70: Hartmann, HD The influence of irrigation on the development and yield of asparagus. Acta Hort. 119: 309. Wilson, DR, SM Sinton and HA Fraser-Kevern Irrigation responses of established asparagus Proceedings VIII International Symposium on Asparagus. ACKNOWLEDGEMENTS. Funding for this research was provided by MAES Project GREEEN the Michigan Asparagus Research, Inc and USDA/MDA Specialty Crop Block Grant (#791N ). We also thank Beau Shacklette and the Trickl Eez company for donating irrigation equipment and technical assistance to the project and Norm Myers, John Bakker, Corey Noyes, Timothy Vinke, Paul Banks, Dan Drost, Oomen Bros Farm, Malburg Farms and Oomen Farms for their valuable advice and assistance with the project. 8 6 a B

8 Asparagus Miner Integrated Pest Management Research Update Zsofia Szendrei and William R. Morrison Department of Entomology, Michigan State University, East Lansing, MI, For questions: Lab website: Research at Michigan State University s Vegetable Entomology Lab focuses on the integrated pest management of the asparagus miner (Ophiomyia simplex (Loew), Diptera: Agromyzidae). This insect is a putative vector for pathogenic species of Fusarium fungus, which is the causative agent for early decline syndrome in asparagus fields. ASPARAGUS MINER DEGREE DAY MODEL DEVELOPMENT We have been monitoring the abundance of asparagus miners througout the 2011 field season, by counting the adult flies weekly on yellow sticky cards placed at five commercial asparagus fields in the Hart area. At each trapping site, one trap was placed at ground level and another at canopy level. We started monitoring in early May, and stopped in early October. In three of the five farms, we placed weather stations, which provided site specific data for creating a degree day model. Degree day models can be used to predict the appearance of certain life stages in the field and target management practices more precisely. We observed a peak in adult activity in mid- to late-june corresponding to ca. 650 Growing Degree Days and a smaller peak in mid- August, around 1900 Growing Degree Days. Last year we observed a prollonged period of adult activity from mid-july to early-august, which in Degree Days corresponds approximatley to the second, smaller peak of adult activity in the 2011 growing season.

9 ASPARAGUS MINER MONITORING WITH BAITS We are exploring the chemical interaction of the asparagus miner with the asparagus. In particular, we are looking for plant volatiles involved in the attraction of the miner to plants. Plant volatiles can be used in management by incorporating them into baits on traps to improve monitoring or using them in the population management of adult miners. In the 2011 growing season, we tested 7 plant volatiles that were identified from asparagus plants or are known attractants for related insects. The different plant volatiles were attached to yellow sticky traps in the field and the number of adult miners was counted on the traps weekly. Yellow sticky traps baited with cis-3-hexen-1-ol caught about 6 times more adults than most of our other treatments, including the no-volatile control. Methyl salicylate baited traps caught the second highest number of adults on average, but this was not significantly different from any of the other treatments. ASPARAGUS MINER BIOLOGICAL CONTROL We are currently in the process of identifying naturally occurring arthropod parasitoid species of the asparagus miner pupae, as well as examining their abundance in commercial asparagus fields. About 12% of the asparagus miner pupae collected from 5 commercial asparagus fields were killed by parasitic wasps in the 2011 growing season. EVALUATION OF SYSTEMIC AND FOLIAR INSECTICIDES FOR CONTROL OF ASPARAGUS MINER IN ASPARAGUS In 2011, the MSU Vegetable Entomology Lab conducted an insecticide trial in an experimental asparagus field in Hart, MI. This is a two-year old field, with asparagus crowns planted and a drip irrigation system set up in In 2010, chemigation treatments were able to suppress asparagus miner damage, indicating that control of this pest could be attained through chemigation. Unlike in 2010, in 2011 the chemigation treatments did not result in suppression of asparagus miner damage. In 2011, the early season foliar application of Movento 240SC significantly reduced the number of damaged stems after three weeks, compared to all other treatments (see figure below). However, despite a second application

10 of Movento on 14 June (three weeks after the first application), subsequent sampling dates did not result in any significant differences between treatments. Asparagus miner numbers were quite high during this period, leading to heavy damage to all plots. The reason for the second application of Movento providing ineffective control is unclear, but one possibility is that this product is less successful at moving into the older, tougher fern, relative to the young fern earlier in the season. Stem tissue analyses showed that none, or only trace amounts, of the various drip treatments were incorporated into the plant tissue, which explains the lack of control in these treatments. Percent asparagus stems damaged by asparagus miners on 14 June Movento was applied on 24 May and the drip treatments on 25 May Bars with the same letter are not significantly different.