Resources - Pests

Disease Control

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Table of Contents:

1. Introduction
2. Disease Symptoms
3. Fungal Morphology and Disease Spread
4. Disease Control

1. Introduction

Although bacterial disease on sugar beet is common, most of the bacteria cause little damage. The exception to the rule is the destructive bacteria Erwinia carotovora subspecies betavasculorum, the causal agent of bacterial vascular necrosis and rot. The disease is most prevalent and destructive in the warmer parts of California, Washington, Idaho and Texas.

2. Disease Symptoms

Root symptoms can vary from a dry to soft rot (see Image #1), and root vascular tissue turns black and necrotic. When a infected beet is cut open to expose the diseased vascular tissue, the area surrounding the necrotic tissue turns pink to reddish (see Image #2). Above-ground symptoms are not always observed. When they appear, they include black streaks running along the petioles, white froth in the center of the crowns (see Image #3) and foliar wilt if the root is severely effected (see Image #4). Click image for full page view.

Image #1 Image #2

Image #3     Image #4

3. Fungal Morphology and Disease Spread

The causal agent of the disease is a bacteria named Erwinia carotovora subspecies betavasculorum. The bacteria is single celled, rod-shaped and gram-negative. Isolated colonies of the bacteria are white with a yellow to orange center and undulating to coralloid margins, resembling a fried egg (see Image #5).

Image #5 (click image for full page view)

The primary host is the sugar beet. It can overwinter on unharvested beets, and can be detected in soil up to two months after harvest. It has also been isolated on weeds. It is thought that the disease is spread by infected soil deposited in plant crowns by farm machinery, splashing water and insects. Injury to the crown, petioles, crowns is necessary for infection.

4. Disease Control

The most effective way to control Erwinia is by using resistant seed varieties. Cultivation practices that produce injury to the beets should not be used. The optimal distance to plant stands is spacing beets 6-8 inches apart, which should reduce losses in susceptible cultivars. Other factors can decrease disease levels are judicious nitrogen fertilization, early planting.

More information:

 

First Report and Virulence Evaluation of Erwinia carotovora subsp. betavasculorum on Sugarbeet in Montana