Asparagus Pest and Disease Problems luv2garden.com

Asparagus Beetles

Asparagus beetle adults are a blue/black beetle with a red underside and yellow spots. The larvae are a soft, green /Yellow grub. Both feed on asparagus spears by chewing the tips and spear surfaces which leads to scarring and staining of the spears.

Eggs are laid on developing spears with the eggs being small, elongated and black - sticking out lengthwise from the side of asparagus spears.

Early control of beetles is important to reduce feeding damage later. The first defense once there presence has been detected is Pyrethrin

Malathion Spray, will provide an effective chemical control in the event of severe chronic infestation .
Effective Predator insects are Lady Bugs and Lace wings

Fusarium Root and Crown Rot [Image]

The major disease problem of asparagus is caused by two species of fungi which causes decay of storage roots, stems and crowns. This fungus is present in all agricultural soils and infects corn, grasses, and related plants as well as asparagus.

The fungus colonizes old roots and crowns, invading directly through root tips or through wounds Asparagus plants which are under stress are more susceptible to this infection than those which are growing vigorously.

Affected spears may shrivel and rot in spring before or after emergence Infected crowns have hollow, rotted feeder and storage roots . When crown and stem tissue is sliced open, a reddish-brown discoloration is visible. Symptoms on fern includes stunting, yellow to brown discoloration of one or more stalks per crown, and fewer stalks per crown . Affected crowns decline in vigor and die.

Cercospora leaf spot is caused by a fungus , it affects all foliar parts of the plant but not the roots. Infection usually first occurs on young leaves in the margins. Lesions are small and round with a tan to back center and an indefinite yellow halo. Many spots on one leaf can cause withering and death. Infection of the leaf stalks results in pale centered, elliptical tan lesions. Disease development is favored under warm and humid weather. [ Bonide Remedy Fungicide ]

Cercospora Asparagi / Needle blight may become a problem when asparagus foliage remains wet for long periods. Plant with wide spacing and in a location with good air circulation to help prevent needle blight development. [ Bonide Remedy Fungicide ]

Asparagus Rust

"Asparagus spears are usually harvested before extensive rust symptoms appear. Symptoms are first noticeable on the growing shoots in early summer as light green, oval lesions, followed by tan blister spots and black, protruding blisters later in the season.

There are three distinct stages of rust disease. In the first stage, occurring from April to July, lesions develop. These oval lesions are raised, light green in color, and 10-20 mm in length . The lesions are sometimes inconspicuous and decrease in number from the base of the shoots upward. The lesions turn cream-orange in color and become sunken in the center as they mature. During summer months, the second stage of rust disease begins as reddish-brown, blister-like pustules develop on the asparagus shoots . When the pustules mature, they release large numbers of rust-colored spores that cause new infections throughout the summer. Reddish, rust-colored, powdery spores are seen when rubbed against light-colored clothing. Later in the season the third stage replaces rust-colored spores with black, over-wintering spores. In some lesions, both reddish-brown and black spores appear together. Plants affected by rust are more susceptible to Fusarium crown and root rot.

Spores overwinter on host plant residue, germinate in early spring, and produce new infections on growing asparagus spears. The light green, oval lesions are surrounded by a concentric ring pattern. In young plantings, before stalks are harvested, lesions develop yellow spore-bearing structures in concentric rings. " Plant Pathology University of Minnesota

See Also : Diseases of Asparagus : Ontario Ministry of Agriculture

Grey Mold- Also known as Botrytis rot (Botrytis cinerea).

The fungus that causes gray mold invades the plant and flower bracts that have been damaged by slugs ,frost, insects, or other factors. Infected plants turn brown on the outside. On the inner surface is the characteristic gray growth . The fungus survives on decaying organic matter. Botrytis rot is most common during rainy weather. Plant in well-drained areas. Remove infected plant parts and protect plant buds from damage caused by invertebrates. When storing chokes, remove infected chokes immediately.

Any fungicides registered for grey mold control must be applied before infection takes place, they won't cure an existing infestation. If you've had problems with gray mold in the past apply fungicide before the infestation gets to the plant.

Avoid injuring the foliage. Damaged foliage from Fertilizer-burn or frost- is much more susceptible to grey mold infection.
Avoid densely spaced seedlings growing levels by selecting a container that allows adequate spacing for seedling development. Containers can also be placed at a wider spacing to allow better air circulation during periods when seedlings are especially vulnerable.

Follow a strict sanitation policy that includes removal and destruction of all plant debris, prompt removal of infected seedlings, and sterilization of containers ,growing area and surfaces between plants.
Avoid excessive moisture, and allow for proper aeration to reduce the presence of moisture for more time than is actually necessary.

Powdery Mildew "appears as a dusty white to gray coating over leaf surfaces or other plant parts . In most cases this fungal growth can be partially removed by rubbing the leaves. It might be identified incorrectly as dust that has accumulated on the leaves. Powdery mildew, however, will begin as discrete, usually circular, powdery white spots. As these spots expand they will coalesce, producing a continuous matt of mildew (similar to dirt or dust). A plant pathologist using a microscope can determine whether a fungus is present anytime the whitish patches are present." [Cornell University Powdery Mildew] There are a number of products which can be utilized to control and eradicate Powdery Mildew [Fungicides for the treatment of Powdery Mildew] .