What Is Asparagus Rust: Tips On Treating Rust In Asparagus Plants
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By: Mary H. Dyer, Credentialed Garden Writer
Asparagus rust disease is a common but extremely destructive plant disease that has affected asparagus crops around the world. Read on to learn more about asparagus rust control and treatment in your garden.
What is Asparagus Rust?
Asparagus rust is a fungal disease that attacks the bushy green tops of asparagus plants. If the disease is allowed to continue, the roots and crown of the plant are affected and the plant is severely weakened. As a result, asparagus spears are smaller and fewer in number.
Plants that are severely affected may die during hot and dry summer weather. Additionally, asparagus rust disease stresses plants, making them more susceptible to other plant diseases such as fusarium rot.
Asparagus rust spores live on plant residue during the winter and germinate in early spring. The disease is spread by wind and rain and spreads quickly during wet or foggy weather or damp, dewy mornings. Rusty orange spores on the feathery stem tops are the first sign of the disease and are evident during the summer.
Asparagus Rust Control
Treating rust in asparagus involves some preventative measures. Here are some tips that will help with that as well as for managing plants once rust disease develops.
Cut back affected stems and tops. Clean up severely infected asparagus beds. Burn the debris or dispose of it safely away from the garden. Also, destroy any wild or volunteer asparagus plants that grow in the area, including plants found along fences or roadsides.
When harvesting asparagus, use a sharp knife to cut spears below the surface of the soil. This may help prevent asparagus rust disease from developing on the stubs.
After harvest, spray remaining stems and foliage with a fungicide spray or dust containing active ingredients such as mancozeb, myclobutanil, chlorothalonil, or tebuconazole, repeating every seven to ten days, or according to label directions. Keep in mind that some fungicides are best used as preventatives.
Water asparagus plants carefully, avoiding both over and under watering.
Plant asparagus in an area where prevailing winds provide good air circulation around the plants. Avoid crowding. Also, plant new asparagus in a location away from areas where infected plants grew.
Prevent asparagus rust by planting rust-resistant asparagus varieties such as ‘Martha Washington’ and ‘Jersey Giant.’ Ask your local Cooperative Extension Agent for more specific information about asparagus rust control and about types of rust-resistant asparagus cultivars that perform well in your area.
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How to Deal with Plant Rust (Fungus) in Your GardenSteph Coelho
Steph is a certified Square Food Gardening Instructor who has been gardening for more than 10 years in Canada where the winters are long and cold, and the summers are unpredictable. She is a volunteer for her community's Incredible Edible project. In the past she created an educational gardening space for seniors and taught classes at a local community center where she created her own curriculum and activities. She participated in several local municipal garden days where she set up a booth to educate citizens about the joy of gardening.
When you spot something that doesn’t look quite right on your plants, it can be devastating. What the heck is that weird coloring? Is that plant rust?! What do I do.
Noticing something awry on your previously pristine plant is stressful. Treating the problem takes time and effort and requires a bit of know-how on your end.
So how do you deal with rust on your plants? Is it possible to successfully restore plants to their original condition? Read on to find out more about this all too common disease.
The pathogens are ubiquitous and appear to be present in most field soils where it can survive indefinitely. The disease is spread by movement of infested soil and by contamination of seed. Infection occurs at any point below the ground and once inside the plant, the fungi invade the water conducting tissue. Fusarium populations in infested fields have been shown to decline to a base level after five years however, the low levels persist for long periods. Adverse environmental factors such as poor drainage and poor cultural practices that increase plant stress predispose plants to disease.
Common asparagus beetle adults live through the winter in sheltered places such as under loose tree bark or in the hollow stems of old asparagus plants. Adults appear in gardens just as the asparagus spears are coming out of the soil in spring.
The beetles lay many dark brown, oval-shaped eggs in rows on the spears, ferns or flower buds of asparagus plants.
- The eggs hatch within a week.
- The larvae move to the ferns to start feeding.
- They feed for about two weeks and then fall to the ground to transform into pupae in the soil.
- About a week later, adults emerge to start another generation, feeding on the ferns for the rest of the growing season.
The spotted asparagus beetle has a similar life cycle but usually appears in gardens later than the common asparagus beetle in mid-May. It is gone by late July.
They lay greenish eggs on the ferns. The orange larvae feed on the berries of the asparagus.
Known as "the food of kings,” asparagus can be an interesting addition to your family’s kitchen or market garden.
Asparagus, known as the “food of kings,” is one of the first crops to emerge from the spring garden.
Asparagus is indeed a delicacy, much loved by consumers. Known as “the food of kings,” asparagus was grown by Romans and shipped to nobility in distant lands. Louis XIV of France had asparagus grown in greenhouses. In Russia and Poland, thick green stalks of asparagus grow wild, and horses and cattle graze on them. Asparagus is a wonderful gift from nature, and an excellent addition to the diversified farm.
Asparagus shoots are the first vegetable to pop out of the ground in spring, and for a month or two, the fields need to be harvested frequently to pick the newly emerging shoots as soon as they appear. The annual cultivation cycle includes a busy spring harvest, then a summer and fall foliage-growing period during which the plant shoots grow tall and bushy and store energy in the buried crowns. In the winter, some farmers clear the dead growth, while others let the brush provide winter-cold protection.
Growers must wait a year or two after planting for the asparagus to mature before they begin full-scale harvesting. Once established, an asparagus bed is often described as a “lifetime planting,” lasting 12 to 20-plus years. Asparagus farming requires a lot of room, and growers will need to plant large areas in order to produce a sizable crop. As with all crops, there are female and male plants. Female asparagus plants expend more of energy producing seed, so they produce 20- to 30-percent fewer spears than males, though their spears are larger.
Asparagus generally doesn’t do well in regions with long hot summers and mild winters. For centuries, farmers in all of Europe and the Mediterranean region have grown asparagus, while Michigan, New Jersey and the West Coast states have been the traditional American asparagus-growing regions. Now, new varieties and irrigation techniques are stretching the geographical borders—even Hawaiian farmers grow asparagus for the local market.
A well-tended planting yields a lot of asparagus, approximately 25 pounds per one 100-foot row. If you take your asparagus-growing larger scale, 1 acre can produce between 2 and 8 tons of salable asparagus per year. A best-case scenario includes two harvests per day yielding 1,000 pounds.
Planting New Beds
Asparagus are deep-rooted plants, so selecting a site with good drainage is crucial. A low to medium pH is preferable, and good sun exposure in early spring is a must. Asparagus also doesn’t tolerate salt well, which is something coastal and sodic-land farmers should keep in mind.
New asparagus plants start growing early in the season, so ideally, the beds for new plantings should be prepared the previous fall. Plant seedlings 1 foot apart, and space rows 2 to 4 feet apart. Many gardeners believe thicker spears are obtained by spacing the plantings further apart and that the colder your climate, the deeper you should plant.
The underground bodies of the asparagus plants are called crowns. The crown size increases as the asparagus ages, so the bed will eventually become completely filled with crowns and the width of the bed will start to enlarge.
New growers usually plant 1- or 2-year-old crowns into their fields. Obtaining new plants by planting seed is another popular method, but asparagus is not usually direct seeded, rather grown in nursery beds and moved into the fields the following year. Plants grown from seed are thought to be less likely to have disease problems. Rootstocks for new plantings can be expensive, and installing any sort of field irrigation is not cheap. Growers should expect to spend several thousand dollars per acre to establish new fields
The most notable problems with asparagus plants are rust and fusarium fungal diseases. There’s no thoroughly effective treatment for infected beds, so it’s no surprise that prevention is the best tool against these problems. Buying disease-free stock and planting in sunny, well-drained areas helps most farmers avoid fungus problems. The old-fashioned technique of salting beds was started to help control fusarium. Rust is best controlled by burning the fields in winter to reduce the overwintering capacity of the disease. Studies also indicate that introducing domesticated fungal mycorrhizae into field soils might help reduce crop plants’ susceptibility to fusarium by out-competing the disease-causing fungus varieties.
The black-and-white and green-spotted asparagus beetles are asparagus’ most common insect enemies, and most asparagus growers will see some level of these insects during the year. The beetles feed on young shoots in the spring, causing damaged and unsaleable spears, and in the summer, they feed on the foliage, which reduces the vigor of the plants and decreases next season’s crop yields. After the shoots have been harvested, it might not seem like much of a problem to have a few beetles chewing on the abundant leaves, but maintaining fern health is critical to the following years’ production. Like its cousins—daffodils and lilies—asparagus needs to have a long leafy period in the annual cycle to recharge itself and remain healthy.
The best organic way to control beetles is to remove or burn the dried fronds once they turn brown. This will at least eliminate the sites where the beetles overwinter. Historically, chickens, ducks and geese have been allowed to wander in asparagus fields during summer to eat insects and sprouting weeds.
Weed control, especially of perennial weeds, is a major concern for asparagus farmers—new plantings should not be installed until the fields are completely weeded. Canada thistle and quackgrass are particularly dangerous perennial weeds that could require extensive cultivation, treatment and asparagus replanting to remove the problem. Annual weeds are abundant in most all asparagus beds, and they are mostly controlled through cultivation that kills the weeds after they sprout.
Mulching Asparagus Beds
Mulching asparagus plantings is a time-consuming and expensive task, but it can be the backbone of an organic cultivation system. Mulching beds during the summer growth period helps to conserve moisture, minimize weed growth and encourage healthy microorganism activity in the soil. Covering the beds with mulches during the winter months helps nourish the spring crop and promote earlier shoot emergence. The preferred material for mulching is a mixed base of assorted organic debris, such as leaf collections and residual crop wastes. Apply the organic mulches generously, up to 1 foot thick. Some growers use black plastic mulch with perforations that allow summer foliage to poke through.
The dates for spring harvest vary from one location to another. From the mountains, to the coast, to the hot interiors, the advent of warmer temperatures fluctuates and so does the asparagus harvest. The harvest period for American farms usually lasts 60 to 90 days, somewhere between January and May.
Farmers need to pick all the spears that emerge during the harvest season, otherwise the developing leaf stalks retard the growth of other new shoots. Spring plants often grow so quickly that a spear that sprouts up one day becomes too tall the next. When an asparagus grower speaks of tilling the crop under, he’s not destroying the field but rather knocking the emerged sprouts off. The crowns under the ground are untouched and produce a new batch of shoots within a few days.
One experienced picker can usually harvest almost 1 acre per hour. While tractor-pulled seats for harvesters increase worker comfort, they don’t speed the work significantly. Small farmers can enlist the help of friends and family to make the harvesting process more enjoyable.
Asparagus spears, like fresh-cut flowers, are very perishable and their ends should be plunged in cold water immediately after harvest. Even after harvest, the shoots are still growing, so if you’re packaging in boxes, allow space at the top for the spears to elongate. One post-harvest problem is that asparagus stacked sideways can grow away from the pull of gravity and produce bent spears that are less desirable for market.
Harvested asparagus can be kept for moderately lengthy periods—weeks, even months—at very cool, nearly freezing, temperatures.
Planting new asparagus fields is expensive, and it can take experienced growers several years just to break even. Still, many mixed-crop farmers report that asparagus is their most profitable crop, so enterprising small growers can certainly find plenty of opportunity in the industry.
While in the U.S., we’re accustomed to green asparagus, white asparagus has been the preferred product of modern Europe and could attract attention to your stand at the farmers’ market. White asparagus is cultivated by heaping extra soil over the beds and then harvesting the shoots in early morning before the exposure to sunlight triggers the production of green chlorophyll. Systems that use black fabric covers have made obtaining white asparagus easier, as well. Purple asparagus varieties, from exotic French violets to the sturdy dark Italian types, are also an exciting farmers’ market find.
Wild asparagus varieties, often called sparrowgrass, get top dollar among gourmet chefs, according to the few farmers who have acquired seed and planted domestic fields of the wild types. Wild asparagus varieties produce stalks that are smaller in diameter and more twisted but have a robust flavor that has been popular on rural tables for centuries.
Small-scale farmers have long found profitability by using their asparagus crops to create a value-added product, such as asparagus soups, sauces and stews. Native Americans had a history of drying asparagus for later use, and in China, asparagus is commonly candied. An enterprising farmer could try employing these preservation methods, too.
For pricing, the old cooperative extension rule for new, small and fresh asparagus growers is to measure the local population within a 25-mile radius, and then figure that the market will support about an acre of asparagus for 10,000 people in the area. Find out who else is growing asparagus near you, and make your market calculations accordingly.
About the Author: Rick Gush is an American small farmer living in Italy.
This article was excerpted from the February/March 2003 issue of Hobby Farms.