Diseases & Pests

Sugarbeets attract a number of diseases and pests. Generally, farmers have fewer problems with disease and pests when adequate crop rotation is applied.

The most common diseases and pests are:

Beet Nematode

In managing nematode always read and follow instructions that the manufacturer has printed on the pesticide label. Use only pesticides registered for nematode control. Follow all safety precautions when using nematicides.

There are two species of nematode of great concern to sugarbeet growers: sugarbeet cyst nematode and false root-knot nematode. Both can cause serious economic loss. Control methods can effectively check infestations so that beets can be successfully grown.

The sugarbeet nematode is a microscopic eel-shaped animal that punctures the plant cells and sucks out the fluid. This puncture wound can leave the sugarbeet open to fungal or bacterial invasion. No chemical treatment will completely eliminate nematodes; however, chemicals will effectively check infestations so that sugarbeets can be successfully and profitably grown.

Control methods include: crop rotation, chemical treatments and keeping tare dirt out of fields.

Sugarbeets should be planted in fields on a three-year or longer rotation. Plant the crop as early as possible each year when in a cyst nematode infested field. Control weeds in preceding crops. Be selective when using herbicides in preceding crops to minimize herbicide carryover.

As part of your management practices, have a nematode sample taken with your soil samples. Be aware that nematodes are spread by man. Infected soil should be cleaned from harvest equipment between fields. Do not return tare dirt to your fields.

Cercospora

This disease can have a devastating effect upon the sugarbeet crop in many areas. Symptoms start out s tiny, dark-red pinholes on leaves which rapidly lead to total defoliation if left untreated. This disease causes reduced tonnage, lower sucrose content and high impurities in the beets if left untreated after detection. Warm day and night time temperatures, linked with relative humidity of 90% or more, are ideal conditions for this disease. Use of resistant varieties is the primary method to keep disease in check. Foliar application of fungicides is also an important means of inhibiting progress of leaf spot.

Since there is concern about development of resistance by fungi to systemic fungicides. All growers are urged to alternate the type of spray for each application. Early detection and spraying, especially on non-resistant beet varieties is very important to good control of this potentially devastating disease.

Rhizomania

Rhizomania is one of the most destructive viruses ever identified on sugarbeets with losses as high as 100% in infected, susceptible fields. This disease was first found in the early 1950's in Europe and can now be found throughout Europe and Japan.

Most recently, its presence has affected more than 200,000 acres of sugarbeet fields in California with several infected fields identified in Idaho, Nebraska and Wyoming. Symptoms include stunting of the root with a large number of small lateral roots growing out of the main tap root giving the beet a heavy bearded look. The root may be small with dark veins or totally rotted off. Leaves will be light in color and extend upright  from an abnormal large crown. Also, laves may wilt and become flabby or show yellowing through the veins. The fungus responsible for carrying this virus is Polymyxa betae and is present in most soils throughout the United States. The virus can be spread by wind, equipment and tail water from furrow irrigation and is persistent in soil  Rotation of non-host crops is ineffective as a control measure. The current strategy of control is to avoid planting in fields were the disease is present. Soil fumigation and planting of moderately resistant varieties are currently being tested. Eventually a resistant variety will have to be bred to economically grow sugarbeets in fields affected by this virus.

Virus Yellows

Beet Western Yellow Virus is the most widely distributed and abundant virus affecting sugarbeets in the world. Initial symptoms appear as yellowing on tops of older mature leaves. As the virus infection develops, yellowing increases throughout the whole plant but veins remain green in color while leaves become thick and brittle. The virus is transmitted to sugarbeets by a least eight species of aphid. Degree of damage depends upon virulence, persistence of the virus strain and susceptibility of the variety. Because continuous crops of sugarbeets are not grown in the western area, this virus has a difficult time regenerating and living on susceptible hosts from year-to-year. Therefore sugarbeets are relatively safe from this virus with only occasional isolated outbreaks occurring.

Fusarium Yellows, Rhizoctonia Root and Crown Rot

Symptoms of Fusarium Yellows include yellowing of older leaves between large veins early in the growing season which spreads to younger leaves, eventually causing many leaves to die and lay in a clump around the crown of the beet. The vascular system will show distinct dark rings through the entire length of the root.

Symptoms of Rhizoctonia include chlorosis of leaves and sudden wilting with many leaves turning black and dying around the crown area. Either the crown, or the root, or both will turn partially or totally dark brown to black and appear rotten at the infected sites.

Control of both Fusarium and Rhizoctonia has been most successful through longer crop rotations with corn or small grains. There are resistant varieties available for both diseases, but these varieties normally will not produce as high sugar yields as non-resistant varieties. Deep ditching out will increase the activity of Rhizoctonia and make it worse.

Powdery Mildew

This disease can first be seen as a powdery film or mold starting on the underside of leaves. Usually the disease will first appear after July 15th in Nebraska and Colorado, but is rarely seed before August 15th in Montana and Wyoming. Temperatures and humidity greatly affect how harmful this disease is to the beet crop. Conditions favorable for disease are temperatures between 60F and 85F with a relative humidity of 30% or greater. Early detection of the disease in mid-summer may warrant at least one spray application of a sulfur product. If the disease does not appear until September, spraying will probably not be needed.

If the disease is to be controlled, it is important to:

1. Detect and treat it early.
2. Get as good a leaver cover as possible with sulfur dust or spray.
3. Spray a timely second application if needed.
4. Follow labels and directions to apply the correct amount.

Curly Top

This virus affects the sugarbeets growing region on northern Wyoming and southern Montana. First symptoms of this virus included rolled-up leaves that are twisted and swelled veins on the underside of the leaf. The intensity of infection is directly related to the state of growth at the time of infection, the susceptibility of the sugarbeet, virulence of virus and stress of the crop. This disease is only transmitted by the sugarbeet leafhopper which is able to over-winter on numerous winter annual host weeds such as the mustards. During the spring, as these weeds begin to dry, the spring hatched beet leafhoppers will more to more succulent vegetation on irrigated ground carrying  the virus with them. If sugarbeets are infected in the seedling state, they may become severely stunted or even die. If infection occurs later, plants may be stunted and not reach full growth potential.

Roots show a darkening of the vascular tissue with may lateral roots appearing, giving the beet a bearded look. The best practices to minimize infection are:

1. Use curly top resistant varieties.
2. Plant early.
3. Establish a uniform stand.
4. Close canopy early.
5. Use recommended systemic insecticides at planting.
6. Spray for the leafhopper when it appears.