Relationships Among Differing Stink Bug Boll-Feeding Symptoms; and of Boll Damage to Lint Gin-Out and Quality Eric Blinka 1, John Van Duyn 1, Ames Herbert 2, Sean Malone 2, Phillip Roberts 3, J.R. Bradley 1, and Jack Bacheler 1 1 North Carolina State University, Raleigh & Plymouth 2 Virgina Tech, Suffolk 3 University of Georgia, Tifton 1 North Carolina State University, Raleigh & Plymouth 2 Virgina Tech, Suffolk 3 University of Georgia, Tifton

INTRODUCTION  Stink bug pest status in cotton continues to increase.  Additional information is needed on boll damage symptoms and aspects of lint yield / quality relating to stink bug feeding.  Current scouting techniques require boll dissection and examination of boll interior.

 Does an adequate correlation between external and internal stink bug damage exist to support damage monitoring via external boll inspection?  Can external symptom based boll examination improve in-field scouting for stink bug management?  What are the relative impacts of differing internal stink bug damage symptoms on yield factors and lint quality? RESEARCH QUESTIONS

MATERIALS AND METHODS  Bollgard ® and Bollgard II ® fields across northeastern NC were surveyed.  Eight sites were selected in 2006 and 9 in 2007 with high stink bug boll damage.  Each field test consisted of two cohorts: “Same Day Bolls” and “Black Seed Coat Bolls”.  Each cohort consisted of 100 quarter sized, first position bolls.

MATERIALS AND METHODS  Bolls were selected from the same node(s) within each field test.  Selected nodes varied between fields from 7 to 10, depending upon cotton maturity.  “Same Day Bolls” were removed from plants, examined for external damage (sunken lesions), & dissected to determine internal damage, on the initial day.

MATERIALS AND METHODS Table 1. Data Categories For “Same Day Boll” Collection. Figure 1. (a) External Lesion and (b) “Maybe” External Lesion. (a) (b) Boll Diameter (cm) # Obvious External Sunken Lesions # “Maybe" External Sunken Lesions # Internal Puncture Marks # Warts <2mm # Warts >2mm # Minor Stains # Major Stains # Locks Destroyed

MATERIALS AND METHODS Figure 2. (a) Internal Marks, (b) Internal Wart, (c) Lint Stains, & (d) Destroyed Locks. (a)(b) (c) (d)

MATERIALS AND METHODS  “Black Seed Coat Bolls” were selected when study was initiated, tagged, numbered, and examined while on the plant for external bug damage (sunken lesions).  Tagged boll remained intact on plants until reaching the black seed coat stage and were removed just prior to boll crack.

MATERIALS AND METHODS  To preserve initial bug damage, fields were spayed weekly with 6 oz / acre of Bidrin 8E + 2 oz / acre of Centric 40WG.  Prior to boll-crack, “Black Seed Coat Bolls” were collected and examined by lock.

MATERIALS AND METHODS Table 2. Data Categories for “Black Seed Coat Bolls”.  Both Same Day and Black Seed Coat data were subjected to Poc Corr and Proc GPlot in SAS ®. # Locks # Obvious External Sunken Lesions # "Maybe" External Sunken Lesions # Warts <2mm # Warts >2mm # Minor Stains # Major Stains # Locks Destroyed

MATERIALS AND METHODS CleanMinor DamageMajor Damage  “Black Seed Coat Bolls” locks were separated into damage categories, dried, and ginned to determine % lint gin-out. Table 3. Ginned Cotton Damage Categories.

 Ginned samples were sent to Cotton Inc. and subjected to the Advanced Fiber Information System (AFIS) and High Volume Instrument (HVI) lint quality analyses. MATERIALS AND METHODS

RESULTS AND DISCUSSION Table 4. Same Day Pearson Correlation Coefficients For Individual Categories, Categories Internal Marks Small Warts Large Warts Minor Stains Major Stains External Lesions "Maybe" External Lesions Total External Lesions

RESULTS AND DISCUSSION Table 5. Same Day Pearson Correlation Coefficients For Individual Categories, Categories Internal Marks Small Warts Large Warts Minor Stains Major Stains External Lesions "Maybe" External Lesions Total External Lesions

RESULTS AND DISCUSSION Table 6. Same Day Pearson Correlation Coefficients for Combined Categories, Categories WartsStainsTotal Damage External Lesions "Maybe" External Lesions Total External Lesions

RESULTS AND DISCUSSION Table 7. Same Day Pearson Correlation Coefficients for Combined Categories, Categories WartsStainsTotal Damage External Lesions "Maybe" External Lesions Total External Lesions

RESULTS AND DISCUSSION Table 8. Same Day Pearson Correlation Coefficients for Combined Categories (R 2 values), Categories WartsStainsTotal Damage External Lesions "Maybe" External Lesions Total External Lesions

RESULTS AND DISCUSSION Table 9. Same Day Pearson Correlation Coefficients for Combined Categories (R 2 values), Categories WartsStainsTotal Damage External Lesions "Maybe" External Lesions Total External Lesions

RESULTS AND DISCUSSION Figure 3. Predictability of Internal Damage Based on Total External Lesions from “Same Day Bolls”, 2006.

RESULTS AND DISCUSSION Figure 4. Predictability of Internal Damage Based on Total External Lesions from “Same Day Bolls”, 2007.

RESULTS AND DISCUSSION AFIS % LintL(w) [in] L(w) CV [%] UQL(w) [in] SFC(w) [%] No Damage ’ a Minor Damage ’ a Major Damage ’ b No Damage ’ a Minor Damage ’ a Major Damage ’ b Table 10. Lint gin-out and Advanced Fiber Information System values for boll damage categories, 2006 & Significant at P<0.05

RESULTS AND DISCUSSION HVI MICUHMUISTRELO No Damage ’ Minor Damage ’ Major Damage ’ No Damage ’ Minor Damage ’ Major Damage ’ Table 11. High Volume Instrument Values for Boll Damage Categories, 2006 and 2007.

 Moderately strong Pearson Correlation Coefficients of in 2006 to in 2007 were found between total external lesions and total internal damages for the same day cohort.  The strength of this correlation increased sharply as external marks increased.  R 2 values decreased from 0.44 to 0.25 between total external lesions and total internal damages for the same day cohort and may reflect variation between training of those judging external lesions. CONCLUSIONS

 Moderately strong Pearson Correlation Coefficient of in 2006 to in 2007 were found between total external lesions and total internal damages for the same day cohort.  The strength of this correlation increased sharply as external marks increased (variability decreases).  R 2 values decreased from 0.44 to 0.25 between total external lesions and total internal damages for the same day cohort and may reflect variation between training of those judging external lesions. CONCLUSIONS

 Moderately strong Pearson Correlation Coefficient of in 2006 to in 2007 were found between total external lesions and total internal damages for the same day cohort.  The strength of this correlation increased sharply as external marks increased (variability decreases).  R 2 values decreased from 0.44 to 0.25 between total external lesions and total internal damages for the same day cohort and may reflect variation between training of those judging external lesions. CONCLUSIONS

 Percent lint gin-out was significantly reduced for our “major damage” category but not with “minor damage”.  Based on AFIS and HVI results, lint quality declined based upon the type of bug damage, especially the quality related to fiber length. CONCLUSIONS

 Percent lint gin-out was significantly reduced for our “major damage” category but not with “minor damage”.  Based on AFIS and HVI results, lint quality declined based upon the type of bug damage, especially as related to fiber length. CONCLUSIONS

 Yes, there is a meaningful correlation between external bug induced symptoms with internal damage, lint yield, and quality.  Based upon the moderate, positive correlations, and increasing strength of relationship as external punctures increase, a new scouting technique will be available for investigation. CONCLUSIONS

 Yes, there is a meaningful correlation between external bug induced symptoms with internal damage, lint yield, and quality.  Based upon the moderate, positive correlations, and increasing strength of relationship as external punctures increase, a new scouting technique will be available for investigation. CONCLUSIONS

 Cotton Incorporated  Virginia State Cotton Support Committee  Northeastern North Carolina Producers  North Carolina State and Virginia Tech. Technicians and Summer Workers ACKNOWLEDGEMENTS

QUESTIONS?