Tuesday, September 29, 2015

Shepherd’s purse (Capsella bursa-pastoris)

Picture of weeds
Shepherd’s purse (Capsella bursa-pastoris) infestation
(Photo L. Beck NMSU)
Featured Diagnosis: Shepherd’s purse (Capsella bursa-pastoris) is a weed that has become well-established throughout the state of New Mexico. Though this weed is generally considered to be a winter annual, its’ ability to tolerate a wide range of temperatures often allows for germination and growth at multiple points throughout the year. Germination generally occurs in the late summer, early autumn, and even in the early spring depending on temperatures and moisture. It can be found in multiple cropping systems including nursery, agronomic and vegetable crops, landscape, horticulture, and roadsides.

The plant initially grows as a basal rosette with leaves that closely resemble those of dandelion as the plant matures. One way to distinguish shepherd’s purse rosette leaves from dandelion is to look at the teeth points on the outer edges (margins) of the leaves. The margin teeth of dandelion tend to point downwards towards the center of the rosette while shepherd’s purse teeth tend to be more rounded when young, and become larger and more deeply toothed (pointed straight) as they mature. 

Additionally the leaves of the shepherd’s purse tend to be smooth to lightly hairy on the top and hairy on the bottom. As the plant matures it forms erect, slender stems that hold the small white flowers and unique fruit pods anywhere from 3 to 18 inches up in the air. The fruit (or seed pods) generally appear from April to September, though temperatures often allow for seed production throughout the year. Fruits are easily identifiable as a triangle-heart-shaped, 2-chambered (separated by a dividing line down the middle), flattened pods that hold numerous seed per chamber. Each plant can produce thousands of dull reddish to yellowish seed capable of surviving for multiple years in the soil.

The fruit can taste peppery and is sometimes added to salad greens as a spice; however, foliage and seeds contain digestive irritants which can cause stomach problems when consumed in higher quantities. Management options like repeated cultivation to prevent seeds from maturing, and manually removing plants (including the shallow taproot) before they produce viable seed, can help maintain small populations in gardens and landscapes. While the rosette foliage might be confused with other members of the mustard family, the flat, heart-shaped pods easily distinguish shepherd’s purse from its’ mustard relatives.

Picture of a shepherd's purse plant with lobbed leaves
Shepherd’s purse (Capsella bursa-pastoris) rosette stage.
(Photo: L. Beck NMSU)
Picture of shepherd's purse plant with a seed stalk
Shepherd’s purse (Capsella bursa-pastoris) pressed
specimen. (Photo L. Beck NMSU)

Picture of heart shaped fruit of shepherd's purse plant
Shepherd’s purse (Capsella bursa-pastoris)
fruit (Photo L. Beck NMSU)
Flower stalk of shepherd's purse plant
Shepherd’s purse (Capsella bursa-pastoris)
inflorescence. (Photo L. Beck NMSU)

Friday, September 4, 2015

Curly Top Virus Strikes Again

Curly Top Virus Strikes Again

Image of a tomato plant with curled leaves
Tomato infected with Beet Curly Top Virus
Characteristic symptoms include curled, thickened (stiff) foliage
with purple coloration on the underside of the leaves.
(Photo: N. Goldberg, NMSU - PDC)
Curly top virus (CTV), or beet curly top virus (BCTV) as it is more formally known, is widespread throughout arid and semi-arid regions of the world. The virus is common in the western United States from Mexico to Canada and in the eastern Mediterranean Basin. The virus has a wide host range, causing disease in over 300 species in 44 plant families. The virus appears to be restricted to broad-leafed plants, as no monocotyledonous plants have been identified as hosts for this virus. The most commonly infected hosts include sugar beets (for which the disease was first named), tomatoes, peppers, beans, potatoes, spinach, cucurbits, cabbage, alfalfa, and many ornamentals. The virus also survives in many weeds, such as Russian thistle (tumbleweed) and mustard.

Symptoms vary depending on the host; however, this disease also produces some general symptoms. Other factors that relate to the type and severity of symptom development include virus strain and host physiology. The virus exists in many different strains, which vary in the severity of symptoms produced particularly in relation to the host. Severity of disease is also dependent on the age of the plant when infected. For example, when young plants are infected they will often die shortly after infection. When plants are infected after the seedling stage, the plants survive but are yellow and stunted. Infected leaves of some hosts, particularly tomatoes and peppers, become thickened and crisp or stiff, and roll upward as the petioles curve downward. The leaves turn yellow with purplish veins. Leaves of other hosts such as beets become very twisted and curly. In most cases, yield is reduced, and the fruit that is produced ripens prematurely. The immature, dull and wrinkled fruit is a good diagnostic symptom for tomatoes infected with CTV. If plants are infected after they have begun to set fruit, it is not uncommon to see infected and healthy fruit on the same stem.

Image of three yellow and stunted chile pepper plants in a field
Beet Curly Top Virus on chile peppers (Photo: N. Goldberg, NMSU - PDC)

Image of a yellow and stunted pumpkin plant in the field
Pumpkin infected with Beet Curly Top Virus
(Photo: N. Goldberg, NMSU - PDC)

Image of two bean plants; the yellow one on the left is infected with a virus, the green one on the right is healthy
Beet Curly Top Virus infected bean next to a healthy bean plant
(Photo: J. French, NMSU - PDC)

Image of spinach plants in the field. The yellow stunted plants are infected with virus
Beet Curly Top Virus on spinach (Photo: N. Goldberg, NMSU - PDC)

Thursday, September 3, 2015

Plant Clinic Coming to the Farmington Growers' Market

Advertising flyer announcing the Farmington Plant Clinic

A composite photo with pictures of people at the plant clinic in Portales, NM in 2015
Scenes from the Portales Plant Clinic on August 31, 2015

A composite picture showing people at the plant clinic in Clovis, NM in 2015
Scenes from the Clovis Plant Clinic on September 1, 2015