INSPECTION MANUAL

Program History 

U.S. farm lands produce more than 3 billion bushels of wheat, oats, barley, and rye from about 100

million acres each year. These four small-grain crops are all potential hosts to the organism causing

black stem rust (BSR). Under suitable conditions (e.g., susceptible host plant varieties, virulent races of

the pathogen, suitable environmental conditions) BSR may be responsible for losses in the United

States of as much as 37 million bushels of grain a year. Without resistant crop varieties and effective

barberry control programs, losses could grow to 10–30 times present losses. Although chemical control

of BSR through the application of fungicides is possible, treatment of a low-value crop such as wheat is

rarely initiated due to the relatively high cost. 

Breeding varieties of small grains for resistance to BSR began in the United States around 1900

meeting with rapid success from crosses with wheat varieties from Russia and Turkey. By 1938,

farmers were planting resistant wheat varieties in the areas of the United States where BSR had been

most destructive and continued to develop new resistant crop varieties. The difficulty with this approach

is that while an individual crop variety may be resistant to several races of BSR, there are more than

200 existing races of BSR. The presence of BSR-susceptible barberry bushes providing the

opportunity for new hybrid races of BSR to develop complicates the problem further. The use of

resistant crops alone would never provide farmers with adequate protection from BSR. With the

increasing demand for U.S. wheat, an alternative method of defense against a catastrophe the

magnitude of the BSR epidemic of 1916 was needed. 

The eradication in northern grain-growing regions of susceptible barberry bushes was this alternative

method. Eradication would delay the onset of the annual rust infestations and slow the development of

new BSR races. Farmers could now safely use resistant varieties for longer periods. In addition,

breeders would have additional time to develop new resistant varieties. 

An early attempt at barberry eradication in New England in 1726 had failed because scientists of those

times did not understand the exact nature of the relationship between barberry and BSR until 1865. In

1918, the U.S. Department of Agriculture (USDA) initiated a barberry eradication program in

cooperation with 13 north-central States (Colorado, Illinois, Indiana, Iowa, Michigan, Minnesota,

Montana, Nebraska, North Dakota, Ohio, South Dakota, Wisconsin, and Wyoming). In 1935, four

additional states (Missouri, Pennsylvania, Virginia, and West Virginia) joined the program, followed by

Washington State in 1944. This time, the program resulted in the destruction of several hundred million

susceptible barberry and mahonia bushes in over 700,000 square miles. 
Although barberry eradication is a cooperative project with State personnel, USDA has always played

a leading role. USDA established Quarantine 38 (7 CFR Part 301.38), the black stem rust (BSR)

quarantine with the following goals: To prevent the importation of susceptible Berberis and Mahonia

varieties into the United States. 

< To prevent the importation of susceptible Berberis and Mahonia varieties into the

United States 

< To regulate the interstate movement of susceptible Berberis and Mahonia varieties.

< To prevent the reintroduction of susceptible Berberis and Mahonia into eradication

areas. 

< To eradicate susceptible Berberis and Mahonia varieties from the United States.

USDA supported the eradication program by providing funding for it and performing the following

crucial program activities— nursery inspections 

< surveys 

< destruction of susceptible plants 

< certification of resistant plants 

USDA’s funding for the barberry eradication program ended in 1980. Although several States

continued some barberry eradication activities, the extensive eradication program also ended in 1980.

When USDA’s Animal and Plant Health Inspection Service, Plant Protection and Quarantine

(APHIS-PPQ) proposed ending the black stem rust quarantine in 1981, 17 States and the Crop

Quality Council requested that PPQ retain the BSR quarantine. PPQ agreed in the absence of a more

satisfactory solution. In 1985, PPQ and the regional plant boards reevaluated the needs of the BSR

program, and PPQ decided to retain the quarantine with the following significant changes: Movement of

rust susceptible nursery stock in the genera Berberis, Mahonia, and Mahoberberis into or through a

protected area (i.e., former eradication areas that continued to conduct nursery inspections to maintain

their “susceptible-free status”) would be prohibited. 

< Movement of rust resistant nursery stock into or through protected areas would be

regulated. 

< Restrictions for growing or shipping susceptible or resistant varieties between

unregulated states would be lifted. 
States must also enforce restrictions on the intrastate movement of regulated articles equivalent to those

in the BSR quarantine for interstate movement. Other State responsibilities are:

< Employing inspectors with the responsibility for issuing and canceling certificates and

compliance agreements 

< Training inspectors 

< Maintaining and enforce an inspection program 

• Inspect every plant nursery within the State at least once a year 

• Ensures that the nurseries are free of plants susceptible to BSR 

< Enforcing the quarantine 

• Issuance of certificates and limited permits 

• Conducting periodic surveys to maintain the protected area free of

rust-susceptible barberry plants 
Biology 

The fungus Puccinia graminis causes the disease black stem rust. Although plant pathologists take pains

to distinguish between the symptoms and the causative organism, in common use, BSR can refer to

both. This pathogen has a wide host range among species in the grass family, including wheat, oats, rye,

barley, and timothy, as well as several other wild and cultivated grasses. BSR fungus can attack any

aboveground part of wheat or other grasses, resulting in smaller, fewer, and lower quality kernels from

reductions in root and foliage development. Because BSR is a heteroecious (“two houses”) rust, it also

has alternate hosts in a different plant family. In this case, the alternate hosts are various species and

hybrids of Berberis and Mahonia (of the barberry family). Although damage to the alternate hosts is

minor and mostly cosmetic, the economic significance of the disease to the grain crop varieties it infects

is extensive. 

BSR can exist in all areas where host crops are grown, but the disease is usually most damaging in

moderately moist and northern areas. In the United States, this corresponds to the spring wheat areas

of the upper Mississippi Valley and the areas to the north. The amount of damage depends upon the

age of the plant at the time infection. Since northern farmers plant their grain crops relatively late in the

spring, infection in this area occurs when the plants are young and causes extensive damage. The

symptoms on wheat appear as long, narrow blisters, parallel to the axis of leaves, stems, and sheaths.

As the blisters mature, the covering ruptures, revealing powdery masses of brick-red spores (“red rust”

urediospores). The urediospores can splash or blow to other susceptible wheat or other small grain

plants where additional infections occur. Several generations of urediospores can be produced in a

single growing season; it is these repeating infections that cause the most damage to crops. 

Urediospores do not survive the winter in northern areas. Late in the season, the lesions that had earlier

produced urediospores become dark to black. The second spore type, the teliospores, form in the

lesion and overwinter on stems and straw of wheat or other grass family hosts. The teliospores

germinate in the spring producing basidiospores that can infect any susceptible barberry plants in the

immediate vicinity. It is in the basidiospore stage in the life cycle of the rust that sexual recombination

occurs, providing the opportunity for developing new races of BSR. Later in the spring, aeciospores

form on the leaves of infected barberry plants. Aeciospores complete the life cycle of BSR by being

blown by wind and to wheat or other susceptible grass family hosts and germinating. The life cycle then

begins again. 

In southern areas where the weather conditions are mild, BSR does not depend on having to complete

its entire life cycle in a single growing season. In these areas the fungus can live from year to year by

overwintering in the uredial stage on susceptible grains and grasses. It is possible for infestations to

develop early in these areas. If these urediospores blow north in large numbers, epidemics of BSR may

occur where susceptible grain hosts are present. In the south, the typical infestation involves the more

gradual development of urediospores, while in the north, infection areas occurs later in the season.

Eradication of susceptible barberry plants from northern grain-growing areas can reduce the negative

impact by BSR for a number of reasons— Early season infections are rare; therefore, destructive
epidemics are also extremely rare. 

< The opportunity for the development of new BSR races in barberry is reduced

significantly. 

< BSR races and resistant varieties of grain maintain their stability for longer periods.

< Breeders have more time to develop new varieties of resistant wheat and barberry. 

< Farmers can enjoy the benefits of planting resistant varieties with high yield potentials

for longer periods. 
Compliance Agreements 

Compliance agreements may be executed with nurseries and/or shippers to facilitate the movement of

regulated articles into or through protected areas in accordance with the requirements stated in Section

301.38–6 of the BSR regulations. Written compliance agreements may authorize the issuance of either

limited permits (for the movement of regulated articles through protected areas) or certificates (for the

movement of regulated articles into or through protected areas).

Limited Permits 

Limited permits may be issued, either individually or under compliance agreement, for regulated articles

not eligible for certification when the applicant can meet the following conditions: The destination(s) to

which the regulated articles are to be moved must be specified on the limited permit. 

< The destination(s) to which the regulated articles are to be moved must be outside of a

protected area. 

< The regulated article(s) to be moved must be placed in a closed, sealed container that

prevents the unauthorized removal of the regulated article, and the container must

remain sealed until the regulated article(s) reaches the final destination stated on the

limited permit. 

< At the final destination, the sealed container must be opened only in the presence of an

inspector or with the authorization of an inspector obtained expressly for that shipment. 

These conditions can be met in a variety of ways. It will be up to the inspector issuing the limited permit

or drawing up the compliance agreement to insure that the agreements section of the compliance

agreement contains language sufficient to insure that the four conditions stated above are met. 

Certificates 
Certificates may be issued, either individually or under compliance agreement, for regulated articles that

are eligible for movement into or through protected areas, when the applicant can meet the following

conditions: 

< Plants of the genus Berberis must show at least 2 years’ growth, and must be identified

as being rust resistant by belonging to a species and/or variety listed in Section

301.38–2[b]. 

< Plant parts capable of propagation (seeds, fruits, etc.) of the genus Berberis must be

identified as being rust resistant by coming from plants belonging to species and/or

varieties listed in Section 301.38–2[b]. 

< Plants, seedlings, and plant parts capable of propagation (seeds, fruits, etc.) of the

genera Mahoberberis and Mahonia must be identified as being rust resistant by

belonging to a species and/or variety listed in Section 301.38–2[c]. 

< Seed of any of the genera listed above can only be issued a certificate when it can be

determined that the property at which the seed is produced contains only rust resistant

species and/or varieties of these genera (Section 301.38–2[a] and [b]). In addition,

visual inspections must have been conducted to confirm that all Berberis,

Mahoberberis, and Mahonia plants within one-half mile of the property at which the

seed is produced are rust resistant. 

If the identity of plants can be determined by tags or labels attached to the individual plants or pots, the

certificate may be a stamp affixed to an appropriate shipping document. If the individual plants are not

labeled as to species and/or variety, each plant (or pot) must have affixed a sticky-back certificate or

other evidence that the plant meets the APHIS requirements for certification as stated above. 
General Aids to Identification 

Inspectors must be able to distinguish between susceptible and resistant species of barberry. This is

necessary to insure that plants are correctly labeled, that plants are true to type, and in order to identify

unlabeled plants. In many cases, recognizing a few simple characteristics will enable the inspector to

identify rust-susceptible barberry species. The rust-susceptible species most likely to be encountered is

the common European barberry, Berberis vulgaris. Other rust-susceptible species that may be

encountered will frequently have characteristics similar to those that distinguish the common barberry.

Five types of characteristics will be most helpful in distinguishing rust-susceptible from rust-resistant

barberry varieties. A guide to how these characteristics may be used is shown in the table below: 

RUST SUSCEPTIBLE RUST RESISTANT

LEAVES saw tooth edge smooth edge

BARK grey reddish brown

BERRIES in bunches singly or in twos

SPINES groups of three single

STEMS straight angled at nodes

When all of the characteristics commonly associated with a susceptible or resistant species occur

together, a correct identification can be almost always made. Barberry plants found to have

sawtooth-edged leaves, grey outer bark, berries occurring in bunches, spines in groups of three, and

straight stems will usually belong to a rust-susceptible species. Barberry plants found to have

smooth-edged leaves, brown to reddish-brown bark, berries single or in twos, single spines, and

strongly angled stems will usually belong to rust-resistant species. 

Unfortunately, many of the plants encountered in the field will not be as easily identified. In some cases

the characteristics may be indistinct leaves may be “sort of rough” on the edge, or stems may change

color, depending on age. In other cases, the plant may have some characteristics associated with

rust-susceptible species and other characteristics associated with rust-resistant species. This may be

due to the fact that the plant is not one of the “typical” species, or that the plant belongs to a hybrid

variety resulting from a cross between susceptible and resistant species. 

When plants having characteristics that are not as well defined as those listed above, and/or have a

mixture of types of characteristics are encountered, further effort will be required to identify the

particular species or variety to which the plant belongs. To aid in making this identification, two

additional types of identification systems are provided. The first is taken from an earlier barberry survey

manual and requires matching of characteristics of the unknown plant with those contained in a series of

pictures with descriptions of a number of more common berberis and mahonia species. 
The second identification system involves the use of a key developed by Agriculture Canada.

Identification using this system involves following the key and making choices depending on the

characteristics that are present in the unknown plant. This is a more conventional, and often more

accurate, method but does require that the identifier understand a number of terms that are used by

taxonomists to describe plant characteristics. 

Some people will find that one or the other of these two identification systems will work best for them.

Many people will find that being able to use both systems will be most effective. Regardless of which

identification system is used, there will be occasions in which the unknown plant does not fit any of the

descriptions that are provided. This may be due to a poor specimen, inexperience on the part of the

identifier, or to the fact that the plant in question is not included in either of the keys. If this is the case,

contact David Long in St. Paul, MN to submit a specimen of the plant for testing of its resistance to

black stem rust.