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Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 1/4/2006 Publication Date: 6/1/2006 Citation: Tillman, P.G. 2006. Sorghum as a trap crop for Nezara viridula L. (Heteroptera: Pentatomidae) in cotton in the southern United States. Environmental Entomology. 35(3):771-783. Interpretive Summary: The southern green stink bug (SGSB) may disperse from alternate host plants, especially corn and peanuts, into cotton. Because trap crops may intercept dispersing stink bugs, the ability of sorghum to trap SGSB adults in cotton was investigated for three years. The 2002 and 2003 small plot experiments demonstrated that SGSB adults strongly preferred sorghum to cotton. Overall, percent parasitism of SGSB adults by the red-legged fly was higher in sorghum than in cotton. In 2003, the number of SGSB adults was lower in cotton fields with sorghum trap crops than in cotton fields without this trap crop. Furthermore, economic threshold for N. viridula was not reached along the boundary of the corn-cotton farmscape in any cotton field with sorghum plots. In contrast, economic threshold was reached in 61.5% of the control cotton fields. In 2004, each cotton field was partitioned into four sides and three interior block locations. Side A occurred along the interface of the peanut-cotton farmscape. In control cotton fields, the number of SGSB adults was much higher in Side A than in any other field location, strongly indicating that SGSB adults dispersed from peanuts into these cotton fields. Overall in 2004, control cotton fields were treated with insecticides for control of SGSB 1.4 times while cotton fields with sorghum trap crops were treated for control of this stink bug only 0.2 times. These results demonstrate that sorghum can serve as a trap crop for SGSB adults in cotton fields. Technical Abstract: The southern green stink bug, Nezara viridula (L.), may disperse from alternate host plants, especially corn and peanuts, into cotton. Trap crops may be useful to intercept dispersing stink bugs. Therefore, the ability of sorghum to trap N. viridula adults in cotton was investigated for three years. The 2002 experiment was designed to compare the ability of small plots of sorghum and cotton to trap N. viridula along the interface, or common boundary, of a corn and cotton field. In the 2003 experiment, cotton fields with sorghum and cotton plots planted along the interface of a corn-cotton farmscape were compared with cotton fields without these interface plots. In both experiments, N. viridula adults strongly preferred sorghum to cotton, and marking studies revealed that most N. viridula adults that dispersed into sorghum remained in sorghum instead of moving into cotton. Overall, percent parasitism of N. viridula adults by Trichopoda pennipes (F.) was higher in sorghum trap crop plots than in interface cotton control plots. In 2003, density of N. viridula adults was lower in cotton fields adjoining sorghum trap crop plots than in control cotton fields. Furthermore, economic threshold for N. viridula was not reached along the interface of the corn-cotton farmscape in any cotton field with sorghum plots. In contrast, economic threshold was reached in 61.5% of the control cotton fields. In the third season, a full-scale field experiment was conducted to determine the effectiveness of sorghum, planted in a strip along the length of the interface of a peanut-cotton farmscape, as a trap crop in cotton. Before the test, each cotton field was partitioned into eight side-edge and three interior block locations. Each field had four sides with side A occurring along the interface of the field. Edge 1 was 0-3.66 m from the outside edge of the field, and edge 2 was 3.66-7.31 m from the outside edge of the field. In control cotton fields, density of N. viridula adults was much higher in the interface side in edge 1 than in any other side-edge location, strongly indicating that N. viridula adults dispersed from peanuts into these cotton fields. Control cotton fields had higher numbers of N. viridula adults in the interface side in edge 1 compared to cotton fields with sorghum trap crops. Overall in 2004, control cotton fields were treated with insecticides for control of N. viridula 1.4 times while cotton fields with sorghum trap crops were treated for control of this stink bug only 0.2 times. These results demonstrate that sorghum can serve as a trap crop for N. viridula adults in cotton fields. |
