Obj. 1A Hybrid Susceptibility to SCA: Do thresholds differ with S and R hybrids

Transcription

1 Obj. 1A Hybrid Susceptibility to SCA: Do thresholds differ with S and R hybrids Sorghum Sugarcane Aphid Research Exchange Meeting Dallas, TX January 3 4, 217 Name Affiliation Trial Location David Kerns Texas A&M AgriLife Ext. Winnsboro, LA Nick Seiter University of Arkansas Monticello, AR Alana Jacobson Auburn Headland, AL Michael Brewer John Gordy Texas A&M AgriLife Res./Ext Corpus Christi, TX * Rosenberg, TX * Gainesville, TX * * Additional data partly financed by Texas Grain Sorghum Board

2 Introduction Commercial hybrids vary in response to aphids and aphid abundance varies 1. Are R hybrids susceptible to sugarcane aphid within range of aphid pressure experienced in the U.S. (do they experience loss)? 2. Do we need to adjust thresholds for S and R hybrids?

3 Current thresholds Vegetative: EILs: 5-2 aphids/leaf for S hybrids ET: aphids/leaf for S (4 hybrids, 5 states, dryland/irrig) Vegetative: 2 to 3% of plants infested with established colonies and honeydew present

4 Materials & Methods Aphid pressure by V5 to V9 Sivanto (4 oz/ac) and Transform (1 oz/ac) 5, 125, 3 sca/leaf, UTC Hybrids: common S and multiple R (> 3) 4 reps, small plots, factorial (> 48 plots) Measurements Weekly aphid cts on 2 top/bottom leaves Count < 3, 1s > 3, 1s >5 Max. aphid/leaf, Cum. Aphid-day/leaf Leaf injury weekly, stand counts, days to 5% flower Yield (lb/acre)

5 Location Hybrid Maturity Water Presumed susceptibility Winnsboro LA Monticello, AR Headland, AL Corpus Christi, Rosenberg Gainesville REV9782 DKS DKS P8 (P) DKS P17 DKS P8 (P) DKS P17 DKS 37-7 DKS 48-7 DKS DKS 37-7 DKS SP 7715 BH 41 Hybrids Med/Full Early Late/Med Early Med/Full Early Late/Med Full Early Med/Full Early Late/Med Full Early Med Early Late/Med Early Full Full Med/Full irrigated Highly Tolerant (?) Susceptible Highly Tolerant (R) Irrigated Irrigated dryland, good moisture Susceptible Susceptible Highly Tolerant (?) Highly Tolerant (R) Susceptible Susceptible Highly Tolerant (?) Highly Tolerant (R) Highly Tolerant (R) Susceptible Highly Tolerant (R) Susceptible Highly Tolerant (R) Highly Tolerant (R)

6 Yield (lb/ac) Arkansas: Yield -- Max aphid (highest aphid pressure) AR Hybrid ET Factorial Summary - Yield=MAX by hybrid Hybrid=P83P17 83P17 P =.13 Inter = 4629 AR Hybrid ET Factorial Summary - Yield=Max by hybrid Hybrid=P84P8 84P8 (S) P =.1 slope= Inter = 453 R 2 =.54 1 AR Hybrid ET Factorial Summary - Yield=MAX by hybrid Hybrid=DK377 DKS377 P =.77 Inter = AR Hybrid ET Factorial Summary - Yield=Max by hybrid Hybrid=DK3888 DKS3888 (S) P =.4 slope= Inter = 364 R 2 = Max aphids/leaf

7 Arkansas: Yield Cum. aphid-days (modest improvement) 83P17 P =.3 Slope= Inter = 4857 R 2 =.48 84P8 (S) P =.1 Slope= --.4 Inter = 4411 R 2 =.75 8 DKS 377 P =.76 Slope= -flat Inter = 4242 DKS 3888 (S) P =.1 Slope= Inter = 3889 R 2 =.74 Cumulative aphid-days/leaf 8

8 Yield (lb/ac) Alabama: Yield -- Max aphid AL Hybrid ET Factorial Summary - Yield=Max by hybrid HYBrid=83P17 83P17 P =.36 Inter = AL Hybrid ET Factorial Summary - Yield= by hybrid HYBrid=84P8 84P8 (S) P =.5 slope= -13. Inter = 8648 R 2 = AL Hybrid ET Factorial Summary - Yield=Max by hybrid HYBrid=DKS_377 DKS 377 P =.95 Inter = AL Hybrid ET Factorial Summary - Yield=Max by hybrid HYBrid=DKS_ Max aphids/leaf DKS 3888 (S) P =.76 Inter =

9 Alabama: Yield Cumulative aphid-days 83P17 P =.5 Slope= -flat Inter = P8 (S) P =.5 Slope= Inter = 8813 R 2 = DKS 377 P =.87 Slope= -flat Inter = 7133 DKS 3888 (S) P =.89 Slope= -flat Inter = Cumulative aphid-days/leaf

10 Yield (lb/ac) Yield (lb/ac) Louisiana: Yield -- Max aphid 6 6 LA Hybrid ET Factorial Summary - Yield=Max by hybrid Hybrid=REV LA Hybrid ET Factorial Summary - Yield=MAX by hybrid Hybrid=DKS377 DKS377 P =.97 Inter = REV9782 P =.2 slope= Inter = 5268 R 2 =.64 4 LA Hybrid ET Factorial Summary - Yield=Max by hybrid Hybrid=DKS3888 DKS3888 (S) P =.8 slope= Inter = 4924 R 2 = Max aphids/leaf 3

11 Yield (lb/ac) Texas, N Central: Yield -- Max aphid (2 nd highest pressure) ield NTX Hybrid ET Factorial Summary - Yield= by hybrid Hybrid=SP7715 BH41 P =.5 slope= 33.7 Inter = 1674 R 2 =.25 NTX Hybrid ET Factorial Summary - Yield=MAX by hybrid Hybrid=SP7715 SP7715 P =.5 Inter = 1997 NTX Hybrid ET Factorial Summary - Yield=MAX by hybrid Hybrid=DKS5367 DKS5367 (S) P =.94 Inter = NTX Hybrid ET Factorial Summary - Yield=MAX by hybrid Hybrid=DKS487 DKS487 P =.84 Inter = 2638 NTX Hybrid ET Factorial Summary - Yield=MAX by hybrid Hybrid=DKS377 DKS377 P =.78 Inter = 2167 NTX Hybrid ET Factorial Summary - Yield=MAX by hybrid Hybrid=DKS3888 DKS3888 (S) P =.53 Inter = Max aphids/leaf

12 Yield (lb/ac) Texas, Upper Gulf: Yield -- Max aphid UGC Hybrid ET Factorial Summary - Yield=Max by hybrid hybrid=bh41 BH41 P =.5 slope= 3.5 Inter = 2239 R 2 = UGC Hybrid ET Factorial Summary - Yield=MAX by hybrid hybrid=sp7715 SP7715 P =.1 Inter = UGC Hybrid ET Factorial Summary - Yield=MAX by hybrid hybrid=dks5367 DKS5367 (S) P =.18 Inter = UGC Hybrid ET Factorial Summary - Yield=MAX by hybrid hybrid=dks487 DKS487 P =.3 Inter = UGC Hybrid ET Factorial Summary - Yield=MAX by hybrid hybrid=dks Max aphids/leaf DKS377 P =.15 Inter = 27 UGC Hybrid ET Factorial Summary - Yield=MAX by hybrid hybrid=dks3888 DKS3888 (S) P =.43 Inter = 2741

13 Yield (lb/ac) Texas, Lower Gulf: Yield -- Max aphid LGC Early Hybrid ET Factorial Summary - Yield=MAX by hybrid hybrid=bh41 BH41 P =.5 Inter = LGC Early Hybrid ET Factorial Summary - Yield=MAX by hybrid hybrid=sp7715 SP7715 P =.68 Inter = LGC Early Hybrid ET Factorial Summary - Yield=MAX by hybrid hybrid=dks5367 DKS5367 (S) P =.31 Inter = LGC Early Hybrid ET Factorial Summary - Yield=MAX by hybrid hybrid=dks487 DKS487 P =.73 Inter = LGC Early Hybrid ET Factorial Summary - Yield=MAX by hybrid hybrid=dks Max aphids/leaf DKS377 P =.1 Inter = 1258 LGC Early Hybrid ET Factorial Summary - Yield=MAX by hybrid hybrid=dks3888 DKS3888 (S) P =.54 Inter =

14 Key Learnings Modest to high aphid pressure, good growing conditions Aphid pressure up to 3 aphids/leaf (BH41, SP7715) and 2 aphids/leaf (DKS487, DKS377) without loss. These hybrids kept aphids below 1 aphids/leaf at some locations. Aphid pressure did not exceed 1 aphids/leaf on 83P17, but was variable Aphids peaked at 4 aphids/leaf in another R hybrid (REV972) and experienced loss Aphids peaked as high as 5 aphids/leaf on S comparators (DKS5367, DKS3888), but was highly variable

15 Next Steps Compile and compare these data with other sources Compare Cum. and Max. Aphid days Incorporate other factors affecting aphid/ dynamics (water stress, temperature, rainfall, natural enemies) Repeat? Revise with larger strip plots?

16 Discussion: Thoughts on Adjusted Thresholds Hybrid Maturity Irrig: Y/N Max aphids/leaf Yield loss DKS 37-7 Early: Y/N 1-2 no none DKS (S) Early Late/ Med: Y/N Current ET Adjusted ET Test at >2 5 variable 5 5, Less risk in excellent conditions DKS 48-7 Med: N 1-2 no none Test at >2 BH 41 Med/Full: N 1-3 no none Test at >3 REV9782 Med/Full: Y 2-4 yes none 5 84P8 (S) Med/Full: Y yes P17 Full: Y 1-15 no none Test at >1 DKS 5367 (S) Full: N 5 variable 5 5, Less risk in excellent conditions SP 7715 Full: N 1-3 no none Test at >3 Repeat? Revise with larger strip plots?