and many of these insects have been observed each spring in the pawpaw orchards at KSU. Low pollinator activity is usually observed on cool cloudy spring days (unpublished). If cool and cloudy weather conditions coincide with the main bloom period, pawpaw fruit set may be low. Since the pawpaw flowers are strongly protogynous (Willson and Schemske, 1980), lack of pollen availability from other pawpaw genotypes could also limit pollination. Pawpaw growers report that placing carrion in buckets in pawpaw trees has resulted in improvements in fruit set (L. Sibley, personal communication), thus supporting the theory that pawpaw flowers may be pollinated by carrion flies. Fruit set has been high in the past in the KSU orchards; fruit set was 25% ± 10% in 1998 for 10 seedlings that were in their ninth year (eighth leaf) in the KSU pawpaw orchards. Many pawpaw genotypes are in close proximity at the KSU farm. Flies are usually abundant in the KSU orchards and a herd of cattle is maintained in a field less than 152.4 m (500 ft) from the pawpaw trees. Fruit set was not examined in the PRVT orchards. It has been suggested by some hobbyists that the variety Sunflower may be self-fruitful; however this has not been experimentally documented. Interestingly, ‘Sunflower’ did produce the greatest number of fruit per tree in this study, raising the possibility that self-fruitfulness in ‘Sunflower’ could have resulted in greater fruit set in this selection. Pollinizer relationships between pawpaw varieties and PPF advanced selections have not been examined. Hand pollination of pawpaw would be expensive and time consuming; however, this could also lead to greater yields in the PRVT selections being tested.
Pawpaws have few disease problems. Pawpaw leaves can exhibit leaf spot, principally Mycocentrospora aiminae (Farr et al., 1989; Peterson, 1991) and some trees in the PRVT planting in Frankfort have exhibited signs of this foliar disease. The pawpaw peduncle borer (Talponia plummeriana) is a small moth larva [about 5 mm (0.2 inch) long] that burrows into the fleshy tissues of the flower causing the flower to wither and drop (Heinrich, 1926; MacKay, 1959; Peterson, 1991). Signs of the pawpaw peduncle borer have been observed in pawpaw orchards in at the University of Maryland Experiment Station at Wye, Md. (R.N. Peterson, personal communication), but not in the PRVT planting in Frankfort. The zebra swallowtail butterfly (Eurytides marcellus), whose larvae feed exclusively on young pawpaw foliage, will damage leaves, but this damage has been negligible at the PRVT plantings. In 2000, six trees in the PRVT orchard at Frankfort were damaged severely by male deer rubbing their antlers on trees in winter. Deer will not generally eat the leaves or twigs, but they will eat fruit that has dropped on the ground in the KSU orchards. Finally, japanese beetles (Popillia japonica) damaged many young leaves on pawpaw trees in the Frankfort PRVT orchard in July 2001.
planting in Frankfort. The zebra swallowtail butterfly (Eurytides marcellus), whose larvae feed exclusively on young pawpaw foliage, will damage leaves, but this damage has been negligible at the PRVT plantings. In 2000, six trees in the PRVT orchard at Frankfort were damaged severely by male deer rubbing their antlers on trees in winter. Deer will not generally eat the leaves or twigs, but they will eat fruit that has dropped on the ground in the KSU orchards. Finally, japanese beetles (Popillia japonica) damaged many young leaves on pawpaw trees in the Frankfort PRVT orchard in July 2001.
In conclusion, the selections ‘Sunflower’, ‘PA-Golden’, ‘NC-1’, ‘Wilson’, 1-23, 8-20, and 9-58 showed the best fruit production and survival rates (>63%) in 2001. Based on limited data collected so far in the Kentucky trials, ‘PA-Golden’ and ‘Sunflower’ have at least performed well in the two locations and other varieties and PPF selections show promise. Orchard performance will continue to be examined at each site in terms of pests, growth, flowering, yield, year-to-year consistency, and fruit characteristics in the coming years at the PRVT plantings.
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