Field experiments were conducted in Oahu, Hawaii, to investigate the effects of banana bunchy top virus (BBTV) infection on growth and morphology of banana (Musa acuminata). The time interval between aphid inoculation of BBTV and the initial appearance of disease symptoms (i.e. incubation period) was also determined. Plants infected with BBTV showed a significant reduction in petiole size (i.e. length and distance), plant canopy and height, leaf area, pseudostem diameter and chlorophyll content compared with control plants. Growth differences between virus-infected and control plants were not observed until 40-50 days after the plants were inoculated with viruliferous aphids. Other growth parameters such as petiole width and leaf production were not statistically different between infected and control plants. The incubation period of banana bunchy top disease or appearance of symptoms ranged from 25 to 85 days after aphid inoculation. However, PCR assays provided earlier detection of BBTV in banana plants compared with visual symptoms.

Field and laboratory experiments were carried out on the island of Oahu, HI, to compare the susceptibility of the two most commonly grown banana (Musa sp.) cultivars in the state ('Dwarf Brazilian' or Santa Catarina [locally known as dwarf apple] and 'Williams') to the aphid-borne Banana bunchy top virus (genus Babuvirus, family Nanoviridae, BBTV). Several morphological and physiological features of the two cultivars were monitored to determine whether the banana aphid, Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae), transmits BBTV to both cultivars at a similar rate; and whether after successful inoculation, does each cultivar respond similarly to viral infection. Results from the laboratory experiment showed that a similar percentage of both cultivars were infected with BBTV by aphid vectors (> 90% for both cultivars). However, field results showed a significantly lower percentage of dwarf apple (39%) infected with BBTV compared with Williams (79%). We also found that all physiological and morphological features measured (i.e., plant height, leaf area, canopy, chlorophyll level, and moisture content) for both cultivars were impacted similarly by BBTV. The incubation period, or the time between plant infection and initial appearance of disease symptoms, was similar for both cultivars. Results also showed that BBTV transmission efficiency was lower in the field than in the laboratory, despite that more aphids per plant were used for field than laboratory inoculation tests. The results highlight the potential use of less susceptible cultivars to help manage BBTV and the importance of screening banana varieties in the field to determine their response to vectors and associated diseases.

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