Up dates on Banana BBTV management program

Transcription

1 Up dates on Banana BBTV management program Koon-Hui Wang Cerruti R 2 Hooks UH CTAHR PEPS UMD Dept. of Entomology

2 Current tactics recommended for mitigating BBTV 1) timely identify and destroy virus-infected plants, 2) apply insecticide on virus-infected plants prior to rouging, 3) replant with known virus-free plants (tissue culture), 4) control banana aphid populations.

3 Questions remained. 1) Where to scout for banana aphids? 2) How thorough should the insecticidal spray cover? 3) Is it necessary to control ants? 4) How long does imidacloprid residue last? 5) Did rouging technique with glyphosate suppress BBTV spread immediately? 6) Do current commercially available banana cultivars have different susceptibility to BBTV?

4 Distribution of banana throughout the banana mat Robson et al. (2006) suggested sampling suckers < 1.5 m (5 ft) tall because they are easily accessible & may contain higher aphid populations. However, the distribution of banana aphids throughout the entire banana mat (from the largest mother plant to the smallest sucker) has not been determined.

5 Objectives Verify whether some of the findings by Robson et al is relevant to the entire banana mat. Determine the population dynamics of the banana aphid throughout the banana mat. Determine distribution of aphids in the mother plant. Determine if ants can be used as an indicator of aphid presence.

6 Experimental protocol (aphid sampling) 25 survey sites (large to small banana planting)

7 Experimental protocol (aphid sampling) Arbitrarily choose mats/site Sample 3 plant ea mat: small (sucker 1) < 1.5 m (5 ) medium (sucker 2) > 1.5 < 2.5 m large (mother) > 2.5 m (8 ) Aphids found were classified into: (i) 0 (ii) < 10 (iii) > 10 < 100 (iv) >100 < 1000, or (v) >1000 per plant presence of cigar leaf ( ) ) & it s colonization by aphids.

8 Table 1. Comparison of mean relative aphids per meter of plant height and proportion of infested plants (+ SE) Plant Stages Relative aphid densities Infested plants(%) Sucker Sucker Mother Effect P-values Sucker 1 vs Sucker Sucker 1 vs Mother Sucker 2 vs Mother

9 Location of aphids in canopy of mother banana plant Stage of the mother plant Aphids on the peduncle, flower, fruit, or cigar leaf? Frequentness with which aphids were discovered > 2.5 m up the mother plant.

10 Table 2. Incidence of banana aphid in different areas of the mother banana plant. Location Sample no. No. positive Positive (%) Bunch Flower Peduncle

11 Occurrences of ants or aphids alone or ants + aphids on the same plant ANT APHID ANT + APHID

12 Table 3. Mean proportions of samples in which only ants or aphids or ants and aphids were discovered on the same plant. Plant stage Ants alone Aphids alone Ants + Aphids Sucker Sucker Mother Effect P-values S 1 vs S S 1 vs Mother S 2 vs Mother

13 Summary of findings Plants where cigar leaves were not infested with aphids but aphids were found on other plant parts showed that for sucker 1, sucker 2, and mother, this occurred 47.5, 50.7 and 50.7% of the time, respectively. The probability of observing ants on banana plants without aphids was 41, 49, and 63% for sucker 1, sucker 2 and the mother plant, respectively. Although ants can be found on banana plants in the absence of aphids, there is an increase likelihood of finding ants on banana plants with high aphid numbers for all plant stages.

14 1) Where to scout for banana aphids? Sampling suckers 5 ft provide better aphid detection than sampling larger plants. If cigar leaves are used for scouting, the infestation rate obtained will be 50% less than actual rate. 2) How thorough should the insecticidal spray cover? Only 7.6% plants sampled had aphids > 2.5 m (8.2 ft) from the base of the plant (usually found on the trunk). 2) Is it necessary to control ants? Ants are most likely found on mother plants. Ants will be present on banana plants in the absence of aphids. Thus, baits or other tactics should not be used to control ants for the purpose of managing banana aphids. Conclusion Hooks, Wang, Pradhan, Manandhar, Varsino, and Wright Journal of Economic Entomology (in press).

15 Questions remained. 1) Where to scout for banana aphids? 2) How thorough should the insecticidal spray cover? 3) Is it necessary to control ants? 4) How long does imidacloprid residue last? 5) Did rouging technique with glyphosate suppress BBTV spread immediately? 6) Do current commercially available banana cultivars have different susceptibility to BBTV?

16 Provado Residue Effects on BBTV Transmission by Aphids Treatments: Spray Provado at 8 fl oz/100 gal + Silwet at 16 oz./100gal, introduced 10 aphids+bbtv (acquired for 48 hours) per plant at 1. 1 day after spray (1 DAS) 2. 2 days after spray (2 DAS) 3. 6 days after spray (3 DAS) 4. Control (spray Silwet only) Repeat ed the spray on 15 April plants/trt were inoculated. Cage inoculated plants with Cage Introduce were removed on day 5, Superorganza First sprayed aphids+ fabric on BBTV nets aphids were 9 in capsules killed with Provado. for April, 5 days

17 Materials and Methods Repeated the spray on 15 April Introduce aphids+ BBTV in capsules Cage inoculated plants with Superorganza fabric nets for 5 days. 24 plants/trt were inoculated. Cage were removed on day 5, aphids were killed with Provado.

18 BBTV symptomatic plants only begin to show on Jan 14, 2011 No. BBTV Symptomatic plants DAS 3 DAS 6 DAS Control

19 Questions remained. 1) Where to scout for banana aphids? 2) How thorough should the insecticidal spray cover? 3) Is it necessary to control ants? 4) How long does imidacloprid residue last? 5) Did rouging technique with glyphosate suppress BBTV spread immediately? 6) Do current commercially available banana cultivars have different susceptibility to BBTV?

20 Susceptibility of banana cvs to BBTV BBTV + and BBTV -, 5 plants/plot, 4 replications Check for symptomatic plants

21 Susceptibility of 3 banana cvs to BBTV BBTV + and BBTV -, 5 plants/plot, 4 replications % plants % BBTV Symptomatic plants March 31, 2011 % plants showing symptom Apple Largo Saba AAB ABB BBB Largo Saba Compact Inoculated with BBTV-aphids on 9/24/09, 1/17/10, 5/1/10

22 Susceptibility of 3 banana cvs to BBTV BBTV + and BBTV -, 5 plants/plot, 4 replications % BBTV symptomatic plants a ab b Chinese Pisang Awak Saba AAA ABB BBB Chinese Pisang Awak

23 Acknowledgement PBARC Minor Crop Project University of Hawaii CTAHR Hatch project 960H and Smith-Lever Alton Arakaki Jan McGwen Virginia Easton-Smith Adam Radford Darryl Aquino Scot Nelson Jari Sugano 25 Banana Farms Mike Kawate Julie Laughlin James Ken Poamoho Farm Crew Roshan Manandhar Zoe Eisenpress Jane Tavares ADSC Paul Krushelnycky William Haines