§      Height control strategies for mixed containers
§      Test now, don't pay later
§      Control of anthracnose (Colletotrichum gloeosporioides) on ornamental lupines with fungicides
§      Report on rust on daylilies: Control with fungicides and varietal susceptibility

In the past few years, production of flowering plants in large containers and hanging baskets has been increasing, while sales of flats have done just that -- relatively flat.  With the increase in larger container use, we're seeing more and more combinations of different species in the same container.  One of the new challenges that has emerged is to only control plant growth of some crops, but not others, in a mixed planting.  Here are a few strategies to consider.

First, make an attempt to combine plants that have similar vigor.  For example, avoid planting Supertunia with Alyssum.  In time, the Alyssum gets drowned out by the more aggressive Supertunia.  If you decide to combine vigorous plants with slower-growing varieties, then try using different sizes of plant material.  For example, use small plants (or plugs) for the aggressive species, and larger plant material for the slower growing varieties.  This can at least give the larger, less-vigorous plants a head start.

Second, try to combine plants that have similar growth responses to the environment.  For example, mix plants that grow best at cooler temperatures together, and those that do better at warm temperatures together.  What will happen if you plant an Osteospermum (cool-season) with a New Guinea impatiens (warm season)?  At cooler temperatures, the Osteospermum will thrive and the impatiens will stall; at high temperatures, the opposite will occur.  Also combine plants that have similar sun or shade requirements, as well as water and fertility demands.

Finally, another option is to apply growth retardants just to the vigorous plants prior to transplanting.  All growth retardants are effective as sprays, while Bonzi, Sumagic, and A-Rest are useful as drenches or liner dips or soaks.  Below are some guidelines for the various application techniques.  Here, a good time to make PGR applications is one or two days prior to transplanting into the larger container.

PGR spray considerations

§      Rate (ppm): determine proper rates based on published guidelines, past experience, and the chemical product labels.
§      Volume (2 to 3 quarts per 100 ft²): be consistent and ensure you get uniform coverage.
§      Water plants the day before application so that plants are turgid.
§      Avoid watering within 6 hours following B-Nine, Cycocel, and A-Rest applications. For Bonzi and Sumagic, you only need to wait a minimum of 30 minutes.

PGR drench considerations

§      Rate (ppm): determine proper rates based on published guidelines, past experience, and the chemical product labels.
§      Volume (ounces per pot, depends on pot size): apply a uniform volume of drench solution to each container (for example, 2 ounces per 4" pot).
§      Water plants the day before application so that the root mass is moist but not wet.

Liner dip/soak considerations

§      Rate (ppm) determine proper rates based on published guidelines, past experience, and the chemical product labels.
§      Duration of dip (10 to 15 seconds): be consistent.
§      Water plants the day before application so that the root mass is moist but not wet.

For the most aggressive species, particularly some of the vegetatively propagated annuals, consider using Sumagic or Bonzi.  These chemicals are more potent and thus have a longer residual (carry-over) effect than some of the other PGRs.

Remember, the rates (ppm) that you use as a drench or liner dip application will be much lower than what you might use for a spray application.  Be careful not to use too high of a rate -- you do want the plants to grow out eventually!  As with all chemical applications, always read the product labels first, and then conduct your own trials, on a small scale first, to determine proper rates.

Test now, don't pay later

Dean Krauskopf
Integrated Crop Management Agent, Southeast Michigan

Testing water quality and for the presence of combustion by-products and fungus gnats before planting the crop will lead to better quality, faster crop times and more profit.

Sample your water three to four weeks before the first crop, even if you are on a municipal source.  Water quality from wells and ponds reflects the amount of rain the previous year while water from municipal sources varies depending upon the wells they are using or if they have to change the amount of bicarbonate or chlorine they add due to changes in the river or reservoir.  Contact the laboratory for a container and instructions on how to take the sample.  The two most common mistakes are not letting the water run long enough before taking the sample so you're testing the water from the well rather than what is in the pipes and allowing air bubbles in the sample bottle (air bubbles increase the bicarbonate levels). It would be good idea to take another sample past the injector just to see how well it's calibrated.  The lab should report soluble salts, pH, bicarbonate (alkalinity), the macro nutrients (N, P, K, Ca, Mg and S), the micronutrients (B, Cu, Mn, Fe, Zn, Mo) and sodium (Na) and chloride (Cl).

Five weeks before you will be opening houses, plant some tomato seeds and grow them in an area that isn't contaminated by ethylene or other combustion by-products.   Tomatoes are very sensitive to ethylene but can lose that sensitivity if they are grown in an atmosphere where ethylene is present at low levels.   A day or two after you've started up the heaters put a couple of well-watered tomato plants in the greenhouse in the evening.  Check the plants early the next morning.  If they look wilted and the soil is still moist you are seeing epinasty, a symptom of the presence of ethylene or ethylene-like air pollution.

Media manufacturers have made many changes recently to reduce the possibility of fungus gnat infestation, but you still need to check.  Place media samples taken from several bags into 6-inch pots, water them well and place them where the temperature is between 65° and 70° day and night.  You can put a clear plastic bag over each pot (use a rubber band to make a tight seal around the top of the pot) and look for adult gnats after ten days or so, or bury some potato wedges or strips just under the surface of the media and look for larvae (easy to see their black head capsule against the white potato) after 48 to 72 hours.  Pull samples every time a new batch of media is delivered. 

Lupines (Lupinus spp.) are popularly grown as perennial ornamentals in North America. Russell hybrids (Lupinus spp. 'Russell Hybrid') have brilliant flowering racemes and are among the most popular ornamental lupines grown in the United States. Anthracnose was observed from about 1997 in Russell hybrid lupines in several nurseries in Michigan. Anthracnose of lupine is seed-borne and occurs in most regions where forage lupines are grown. Seedlings are very vulnerable and show wilting, leaf and stem necrosis leading to death. More mature plants, after exposure to inoculum produced from initial disease loci, exhibit stem bending, leaf spots and in severe cases, the crowns rot and foliage is generally discolored (red to yellow). Isolation from affected tissues consistently yields a Colletotrichum sp., which has now been identified as Colletotrichum gloeosporioides. Growers in Michigan have noted that fungicides registered for use on lupines were not effective for control of anthracnose especially when the disease occurred early in the season. Fungicides are normally most effective when applied to plant tissues prior to pathogen challenge.  

The results from two experiments are reported here. The mortality and rate of decline of immature lupine seedlings affected by anthracnose and the efficacy of fungicides against anthracnose during the early plant establishment in ornamental lupines grown from seed were determined. All trials were carried out in temperature-controlled environment chambers, 106 ft³ volume at 650F at Michigan State University.  The rate of decline of seedlings was determined by planting one lupine seed into each well of ten replicate 50-well plastic trays filled with potting compost. Seedling trays were placed on plastic trays and watered every 4 days from below to ensure adequate soil moisture. Seedling death that occurred between planting was determined by counting the number of emerged plants ten days after planting. An anthracnose index was calculated; indices of 0 - 25 = 0 - 2%; 26 - 50 = 3 - 10%; 50 - 75 = 11 - 50% and > 75 = 51 - 100% foliar anthracnose symptoms. Lupine foliar anthracnose was evaluated 10, 15, 20 and 25 days after planting. The average index for each evaluation was expressed as a function of time after planting and a rate of index development on immature lupine foliage was calculated. The rate of mortality due to seed-borne anthracnose was estimated by subtracting the number of plants in anthracnose category 4 from the number that emerged ten days after planting at each date.

Efficacy of fungicides against early symptoms of seed-borne foliar anthracnose was evaluated.  Seeds were planted for three replicated runs of the experiment on 19 Jun, 31 Jul and 15 Aug 2001 in peat mix in a 50-seedling tray-bed. When plants were about 3 to 5" tall with 2 palmate leaves fully expanded they were inoculated with a spore suspension of Colletotrichum gloeosporioides about 20 days after planting. Foliar fungicide applications were applied once 24 hours after inoculation with a backpack mounted R&D spray boom delivering 40 gal/A (40 p.s.i.) and using one XR11003VS nozzles per tray.  The anthracnose index described above was calculated. A single evaluation was made 35 days after planting, 15 days after inoculation. 

Results

Mortality and rate of decline of immature lupine seedlings affected by anthracnose.

On average 86.8 + 0.84% of seeds planted emerged. Anthracnose symptoms appeared after about 15 days and 25 days after planting, many plants were severely affected (Figure 1). There was a significant decrease in the number of plants with less than 50% foliar tissue unaffected by anthracnose 25 days after planting in comparison with 10, 15 and 20 days after planting.  The rate of mortality was given by the second order quadric equation (r² = 0.66).

Figure 1. Effect of time on average number of plants in 50-well seedling trays with greater than 50% foliage unaffected by anthracnose. Bars with the same color are not significantly different at P = 0.05 (Tukey Multiple Comparison). The bars represent the least square error of the mean and the line is a hand drawn estimate of the best fir quadratic equation P = 27.8 + 2.45x - 0.09x² (where P = plant decline and x = time).

The anthracnose index increased with time (Figure 2). The rate of increase was linear with the equation; A = 3.07t - 24.8 (where A = anthracnose index and t = time).

Figure 2. Effect of time on anthracnose development in lupine seedlings, average index of surviving plants in 50-well seedling trays. The regression line A = 3.07t - 24.8 (where A = anthracnose index and t = time) is indicated with 95% confidence interval (r² for the relation was 0.89).

Evaluation of foliar fungicide treatments for seedling lupine anthracnose control

Anthracnose developed quickly from seed-borne infection but the supplementary inoculation enhanced the rate of anthracnose development. The untreated non-inoculated control had an index of 20.2, which was significantly lower than the all other treatments (Table 1). The inoculated control reached an index of 100 in untreated controls 15 days after inoculation. Several treatments had significantly lower indices than the untreated control however, Banner Maxx 3.6EC 0.25 pt/A, Manzate 75DF 2.0 lb/A, Kocide 4.5FL 2.67 pt/A and Medallion 5SC 0.42 pt/A did not significantly lower indices than the untreated inoculated control. Terraguard 50WP 0.5 lb/A had a significantly lower index than the untreated non-inoculated control but had an index of 80.1, which was greater than 50% average defoliation. Cleary's 3336 50WP 0.75 lb/A and Heritage 2SC 0.8 pt/A had significantly lower indices than treatments listed previously and had indices in the range 60 - 65, which could only be considered partial control. The most effective products with indices between 40 and 50 were Fluazinam 5SC 0.42 pt /A, (experimental product from Syngenta),  Cygnus 50WP 0.4 lb/A and  Daconil WS 6SC 1.5 pt/A.

Seed-borne C. gloeosporioides clearly causes significant reduction in establishment and survival of seedlings of ornamental lupines. Within 25 days the number of plants that could potentially survive declined significantly. Fungicide intervention is essential at an early stage in seedling development. The most effective treatments were fluazinam, Cygnus and Daconil.

Table 1. Efficacy of foliar fungcides and plant defense system stimulators against seed-borne anthracnose of lupines.

¹ An anthracnose index was calculated by counting the number of plants  from each sample of 50 plants falling onto class 0 = no visible symptoms; 1 = 1 - 2% of plant tissue with lesions; 2 = 3 - 10% of plant tissue with lesions; 3 = 11 - 50% of plant tissue with lesions; 4 = 51 - 100% of plant tissue defoliation. The number of plants in each class is multiplied by the class number and summed. The sum is multiplied by a constant to express as a percentage. Indices of 0 - 25 cover the range 0 - 2%; 26 - 50 cover the range 3 - 10%; 50 - 75 cover the range 11 - 50% and > 75 cover the range 51 - 100% foliar symptoms

² Values followed by the same letter are not significantly different at P = 0.05 (Tukey Multiple Comparison).

Report on rust on daylilies: Control with fungicides and varietal susceptibility

William Kirk, Rob Schafer, Diane Brown-Rytlewski and Devan Berry.
Western Michigan Greenhouse Association, Metro Detroit Flower Growers Association.

Daylily rust was not reported or confirmed in Michigan in 2002. Favorable conditions for rust development did occur, warm temperature and humid environment, but overwintering conditions in Michigan were such that no inoculum survived. Our trials indicated that infection did not occur at temperatures below 50°F and this was confirmed in spore germination trials conducted by Dr. James Buck (University of Georgia). In addition, the primary host (Patrinia spp.) is not widely grown and those planted at the MSU trial did not become infected.  A variety trial and a fungicide trial were planted in October 2002 at MSU Muck Farm; about 90 cvs were planted and a 25 treatment fungicide trial (cv. Stella d'Oro). No rust developed at the trial, despite an attempted inoculation in late August. Leaf streak (Aureobasidium microstictum) developed in both trials and the susceptibility of varieties and efficacy of fungicides against leaf streak were evaluated.

A sample of the best controls (total treatments = 24) is shown in Table 2. Leaf streak developed throughout the season, and by late August, plants in untreated plots had 25 to 50% of foliage affected (Table 2).  On August 5, Heritage 50WDG 0.5 lb, Daconil 82.5WDG 1.5 lb, Terraguard 50WP 0.25 lb, Cygnus 50WDG 0.125 lb, Myconate 100WP 0.11 lb, Headsup 100WDG 0.25 lb, Messenger 5WP 0.42 lb, Contrast 70WP 0.19 lb alternated with Headline 2WP 0.2 lb, Cleary's 3336 50WP 4 lb and Systhane 40WP 0.143 lb programs had significantly less leaf streak affected foliage than the untreated control. All other programs were not significantly different from the untreated control. By August 27, only Daconil 82.5WDG 1.5 lb, Headline 2WP 0.2 lb, Terraguard 50WP 0.25 lb, Cygnus 50WDG 0.125 lb, Headsup 100WDG 0.25 lb, Cleary's 3336 50WP 4 lb and Systhane 40WP 0.143 lb had significantly less leaf streak affected foliage than the untreated control. All other programs were not significantly different from the untreated control. The decrease in the number of fungicide programs with significant efficacy against leaf streak may be due to two factors; lack of efficacy against the pathogen and the potential damage that application of fungicides and biological control products can cause to the cuticle of the foliage, which may allow the infection propagules of the pathogen access to the foliage.

Variety trial: Cultivars ranged in percentage establishment from 0 (Cranberry Baby) to 100%. There was no correlation between ploidy level or dormancy type and plant establishment. Leaf streak ranged from 0.3 (Banana candy) to 2.7 (Double Firecracker) again there was no correlation between ploidy level or dormancy type and susceptibility to leaf streak.

Table 2. Efficacy of foliar fungicide applications for control of leaf streak in daylily cv. Stella d'Oro.

¹ Fungicides and biological control agents were applied in 25 gal water/A at 40 p.s.i..

² Leaf streak was evaluated with a scale from 0 to 5; where 0 = no symptoms; 1 = less than 5%; 2 = 5 - 10%; 3 = 10 - 20%; 4 = 20 - 50%; 5 = 50 - 100% of the foliage affected.

³ Application dates A = 26 Jun; B= 10 Jul; C= 24 Jul; D= 7 Aug.

⁴ Values within a column followed by the same letter are not significantly different at P = 0.05 (Tukey Multiple Comparison).