Impact of field margin vegetation management of tarnished plant bug, Lygus lineolaris (Palisot de Beauvois) infestations in cotton, Gossypium hirstum (L.)
1Northeast Research Station, LSU AgCenter, St. Joseph, LA, USA
2Macon Ridge Research Station, LSU AgCenter, Winnsboro, LA, USA
3North Mississippi Research and Extension Center, Mississippi State University, Verona, MS, USA (Current Address)
Correspondence: dcook@ext.msstate.edu
A large-scale field study evaluated the effects of native winter-spring host plant management on tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), infestations in cotton, Gossypium hirsutum (L.), in Tensas Parish, LA during 2004, 2005, and 2006. The treatments consisted of a herbicide-sprayed and a non-sprayed area on commercial farms located near Newellton and Waterproof, LA during each year. During 2004, both areas were ca. 611 ha. During 2005, the herbicide-treated area was ca. 1317 ha and the non-treated area was ca. 2094 ha. During 2006 the herbicide-treated area was 2094 ha and the non-treated area was 1317 ha. Each area (treated and non-treated) was divided into four quadrants. During January, 100 sample locations were established at each site (25 sites per quadrant). These locations were sampled with a 38.1 cm diameter sweep net at least bi-weekly during the period, February to June to estimate densities of tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), adults and nymphs. During late February to early March, a herbicide combination (2, 4-D, mecoprop, and dicamba [Strike 3, Agriliance, LLC, St. Paul, MN]) was applied to the field margins in the herbicide-treated areas to destroy all broadleaf plants. These herbicide applications were made ca. three to five weeks prior to the associated fields being planted to cotton. Within the herbicide-treated and non-treated areas on each farm, cotton fields were randomly selected within each quadrant were sampled with a sweep net at least bi-weekly and the numbers of tarnished plant bug adults and nymphs were recorded from May until August. Tarnished plant bug numbers on native vegetation were similar at each site prior to herbicide application in all years. Following herbicide applications to field margins, numbers of tarnished plant bug adults and nymphs at the treated sites on native vegetation declined and remained low until the end of the sampling period during 2004 and 2005. During 2006, tarnished plant bug numbers were higher in the herbicide-treated areas compared to the non-treated area from early March until mid-April, after which tarnished plant bug numbers in the non-treated areas increased to levels above those in the herbicide treated area. During 2004, tarnished plant bugs were lower in cotton fields within the herbicide-treated areas compared to that in the non-treated areas during June and early July. During late July and early August, numbers of tarnished plant bug adults in cotton were similar between herbicide-treated and non-treated areas. Numbers of tarnished plant bug nymphs were greater than 2-fold higher in cotton fields at the non-treated site compared to fields in the herbicide-treated areas. During 2005, tarnished plant bug adults within the two sites were generally similar during mid-to-late June. Numbers of tarnished plant bug adults were ca. 2.6-fold higher in cotton fields in the non-treated areas compared to fields at the herbicide-treated areas during early July. During mid-to-late July, tarnished plant bug adults were higher in cotton fields within the herbicide-treated site compared to that in the non-treated areas. Densities of tarnished plant bug nymphs were 1.1-fold to 2.2-fold lower in cotton fields in the herbicide-treated areas compared to fields in the non-treated areas from mid June to late July. During 2006, tarnished plant bug adults and nymphs were higher in cotton fields in the herbicide-treated areas from late June until late July. Tarnished plant bug adults ranged from 1.2-fold to 1.9-fold higher in fields within the herbicide-treated areas compared to fields in the non-treated areas. Tarnished plant bug nymphs ranged from 1.0-fold to 2.8-fold higher in fields within the treated areas compared to fields in the non-treated areas. The sampling information for cotton fields within the two areas during 2006 were markedly different compared to the results collected during 2004 and 2005. The broad host range of tarnished plant bug includes many plants that occur along field margins and in non-crop area that may be adjacent to cotton fields. In the Mid-South, non-crop wooded areas and property enrolled in federal conservation programs occurred in close proximity to cotton fields. During all three years, these types of lands were present at both locations. Many of the available host plants that occurred in these non-crop areas could not be managed with the herbicide strategy evaluated in this study. During 2004, these types of lands that could not be treated with herbicides represented 8% of the total herbicide-treated area. During 2005, those lands that could not be treated represented ca. 7.5% of the total area within the herbicide-treated site. During 2006, those non-treatable lands represented 35% of the total herbicide-treated area. Results from this study indicate that managing winter-spring host plants of tarnished plant bug can impact early season tarnished plant bug populations and have implications for management of this pest in adjacent cotton fields. However, the amount of area representing those lands that cannot be treated with herbicides within the crop landscape should be considered before employing this management strategy. The distribution and size of these areas may greatly influence the results and value of this management strategy for tarnished plant bug management in cotton.
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