Biology Reference
In-Depth Information
rapidly converted to wheat farms by 1900 (Meinig 1968) and were surrounded by
forests (Daubenmire 1970) in which barberry could also reside.
Execution of this later campaign profited from lessons learned in the 1920 and
1930s. Admirable emphasis was placed on inspecting every land parcel, whether in
private or public ownership (Busdicker 1945). As a result, adequate attention was
placed on detecting isolated plants as well as obvious populations near buildings. Only
after a once infested site was found to harbor no barberry plants for three consecutive
years was it declared barberry-free (D.S. Jackson, pers. comm.). Here as in the Great
Plains, the public was engaged in the effort, and all this work was underpinned by
exceptionally detailed recordkeeping and hand-drawn maps of the surveyed areas
(Whitman County Barberry Eradication Program, 1943-1978) (Fig. 3.2).
Herbicides that had been developed since 1940 were widely used, so plant exca-
vation or application of rock salt or kerosene to destroy barberry was minimal
(Whitman County Barberry Eradication Program, 1943-1978, D.S. Jackson, pers.
comm.). Inspection across the uneven terrain was simply accomplished through the
determination of the field workers. The Ponderosa pine-dominated forests that bor-
der much of the region's agricultural fields often support almost impenetrable under-
stories of tall shrubs (e.g.
Physocarpus malvaceus
) on steep slopes (Daubenmire and
Daubenmire 1968). Under these circumstances, barberry could be easily overlooked.
Consequently, team members walked parallel transects in sight of each other, sweep-
ing back and forth across these sites (D.S. Jackson and J.W. Burns, pers. comm.).
Only the smallest barberry seedlings would have escaped such close order drill!
Whitman County (5,592 km
2
) is typical of this western US wheat-growing area
in which the Eradication Program operated from ca. 1944 until 1978. Approximately
36% of the county's area supports cereal agriculture (wheat, oats, barley) (National
Agricultural Statistics Service 2002). Using the current occurrence of barberry as a
proxy for the region, we investigated the effectiveness of the eradication campaign
in the mid-twentieth century. With the original survey records and the enthusiastic
cooperation of long-retired personnel from the Eradication Program (D.S. Jackson
and J.W. Burns), a resurvey was conducted in 2002-2003. The resurvey concen-
trated on the approximately 100 sites that had not been officially released from fur-
ther inspection when the Program ended in 1978, i.e., sites most likely to still
harbor barberry. Each site was surveyed by walking along transects that were 10 m
apart; any barberry plants were recorded by GPS (Foster 2003).
The results obtained in 2002-2003 are striking. A grand total of just nine bar-
berry plants on six properties were found in Whitman County, compared with at
least 49,313 plants that were removed during the 33 years of the Program's opera-
tion. All these remaining plants were adults (1-3 m tall), and on the basis of ring
counts, all were at least 25-years old. Some were probably seedlings that were still
too small for detection by the Program's end in 1978; others likely germinated post-
1978 (Foster 2003). Given that all the detected plants are adults, we of course
searched thoroughly in their vicinities for seedlings; none were found. We have no
explanation for this quite fortuitous lack of barberry recruitment.
Neither in the Great Plains nor in Whitman County, WA was eradication sensu
stricto achieved; some plants escaped detection. But the low to nil incidence of stem
