This study examined the effects of bunch trimming and leaf removal on rate of bunch filling, severity of the maturity bronzing fruit peel disorder, and other yield and quality paramaters. There were 4 levels of leaf removal (4, 7, 10, 13 leaves retained) and 4 levels of bunch trimming (male bud retained, male bud removed, male bud and 2 hands removed, male bud and 4 hands removed) imposed on banana bunches at flowering. The experiment was carried out at South Johnstone, North Queensland. The 320 plants in the trial produced a range of fruit-filling rates that were largely unrelated to the imposed treatments. With the exception of the duration of fruit filling and extra large fruit weight, leaf removal and bunch trimming acted independently on the attributes measured. Leaf removal reduced maturity bronzing and bunch trimming increased it. Increased bronzing was associated with increased finger length, possibly due to epidermal cells in the fruit peel elongating beyond their elastic limit. Bunch trimming reduced bunch weight and but did not improve the quantity of extra large fruit. Leaf removal reduced bunch weight when <10 leaves remained, due largely to a reduction in finger length throughout the bunch. Fruit greenlife was also reduced by leaf removal. Therefore, the reduction in maturity bronzing achieved by leaf removal is of no immediate benefit to growers. Removal of the male bud increased bunch weight due to an increase in finger length. Dry weight analysis indicated that the male bud represented a significant competing photosynthetic sink. For maximum yield of quality fruit, growers should remove the male bud, practice no bunch trimming, and ensure the retention of at least 9-10 leaves from flowering to harvest.

The timing of bunch covering during the development of bananas was examined to find the optimum for fruit quality and reduction of maturity bronzing. Bunch covers, either open or sealed, were applied at various stages of bunch development. The experiments were carried out at South Johnstone, North Queensland. Sealed covers increased the severity of maturity bronzing whenever they were applied. Sealed covers applied for the period either before or after finger diameter of the third hand had reached 2.7 cm increased maturity bronzing, but not by as much as when covers remained sealed throughout bunch filling. These data indicate that sealed covers increase maturity bronzing throughout fruit growth. Maturity bronzing was slightly less when open covers were applied as the last female bract lifted on the bunch (early), compared with a week or so later when the fingers had curled up. Bunch weight was not increased by the application of open covers, but the use of sealed covers increased bunch weight by up to 9%. This was due to increased finger length along the entire bunch. The application of covers (both open and sealed) at earlier than conventional times increased finger length at the proximal end of the bunch, the effect being greater the earlier covers were applied. Open covers reduced the time taken from bunch emergence to harvest by 5-11 days compared with no covering. Very early and early covering gave the largest reductions. Sealed bunch covers delayed harvest by up to 16 days compared with no covering. There was a non-significant reduction of 2-4 days in fruit greenlife, related to the delay in bunch filling caused by sealed covers. Sealed covers led to some fruit abnormalities, including severe spotting by Deightoniella sp., slightly s-shaped fruit, and dull fruit appearance. Early application of open bunch covers is recommended to reduce maturity bronzing. This treatment also increases finger length, and bunch filling time is reduced by about 1.5 weeks. This effect suggests sensitivity to the environment during and soon after bunch emergence.

Bananas cv. Williams were grown at a range of plant densities (1 157-2825 plants ha-1) in single and double rows in North Queensland for 3 crop cycles to determine the best spacing in double rows and to compare yield and plant characteristics of different planting systems. Yield increased with increasing density in each crop cycle (from 16 to 2 1 t/ 1000 plants over the range tested). The duration of the crop cycle was unaffected by density in the plant crop. In the ratoons, the length of the crop cycles increased with increasing density (from 9 to 12 months in ratoon 1 and from 10 to 12 months in ratoon 2). Thus productivity (t ha-1 year-1) averaged over the 3 crop cycles only increased by 10 t/ 1000 plants over the range tested. Single rows had taller following suckers than did double rows at harvest of the plant crop (average of 207 v. 177 cm). Together with the shorter pseudostem height at which single rows bunched, this led to more rapid cycling than at similar densities in double rows in ratoon 1 (9 v.11 months). In double rows, spacings of 1.5 m between the 2 rows of the double row and 1.5-1.8 m between plants in the row made for considerably easier selection of followers than did closer spacings.

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