Mar 13, 2017

Crop Protection WCRC Croprotection-NorthAmerica WCRC1
Abstract                                                                         Back to Table of contents

A boll weevil (Anthonomus grandis [Boheman]) eradication program was begun in September 1978 as an approximately 6,000 ha upland cotton (Gossypium hirsutum L.) trial in the northeast counties of North Carolina (NC) and the southeast corner of Virginia (VA), the northeastern-most cotton growing area of the US and was subsequently expanded in 1983 to include the remainder of NC and all of South Carolina (SC) (48,900 ha total).  Primarily due to the elimination of the boll weevil, foliar insecticide use in NC has dropped from a mean of 10.2 applications ha-1 of primarily organophosphate insecticides employed at rates varying from 0.56 to 3.4 kg a.i. ha-1 for the five year period preceding 1978, compared with the post-eradication (1979-1993) mean use of 2.6 applications of mostly pyrethroids at rates varying from 0.02 to 0.067 kg a.i. ha-1.  Planted cotton acreage in NC has increased from an all-time low of 18,200 ha in 1978 to a high of 188,000 ha in 1991.  Employing a linear yield model based upon 20 years of data from 19 NC counties, a yield increase of 77 kg ha-1 resulted from eradication, in addition to a 71% drop in total insect control costs (compared with a 39% drop outside the eradication area) and a greater return on investment to land which was converted from less profitable crops such as corn and soybean to cotton because of reduced costs achieved by the eradication.  Despite the finding of occasional, passively-transported boll weevils into the "weevil free" area (two weevils were found in 1993, one in 1992 and none in 1991 in approximately 200,000 total Grandlure®-baited traps) and an elevation in the pest status of the European corn borer (Ostrinia nubilalis [Hübner]) and the green stink bug (Acrosternum hilare [Say]) in the weevil-free area, the subsequent elimination of these transported localized weevils and the greater ease of managing the bollworm/tobacco budworm complex Helicoverpa zea (Boddie) and Heliothis virescens (F.), respectively, and other pests, such as the cotton aphid, Aphis gossypii Glover, has allowed the development and deployment of an inexpensive, biocontrol-oriented, threshold-based, pest-specific system of managing cotton insects unique to the Southwest and the mid-South.


Fifteen years of post-eradication research, survey information and grower experience in NC suggest that the benefits of eliminating the boll weevil from the cotton ecosystem and the present ease of tobacco budworm and cotton bollworm control far greatly outweigh the negative impact of species which have been elevated in status following eradication, such as the European corn borer and the green stink bug.  Without the disruptive treatments once required to control boll weevils, NC's cotton producers can now manage cotton insects relying largely upon:-

  • a minimal 2.75 foliar applications per year for all insects (except the at-planting treatment)

  • naturally occurring predators and parasites for early season aphid and tobacco budworm control

  • avoidance of late "cutout" to shorten the late season protection window by avoidance of organophate insecticides

  • pathogenic fungi to reduce or eliminate aphids in opening cotton.

If the Boll Weevil Eradication Program continues to expand, the relative contributions of boll weevil eradication in other cotton production regions will likely vary and await quantification.  However, the dynamics of insect-related changes in the various regional cotton agroecosystems induced by the elimination of the boll weevil and its requirement of organophosphate insecticides for control in many situations likely will be positive and place a greater premium on beneficial arthropods and less reliance upon insecticides.

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