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Pear Maturity Indices
Pear maturity indices are not as reliable or consistent as those used for apples. Indices similar to those used for apples historically have not been as consistent for different years or orchards. The exception is firmness and possibly days after full bloom.
A combination of two or more of the following indices will give a better indication of fruit maturity. As with any measurement used to predict fruit maturity, expect variations from year to year, block to block, and by tree and growing conditions. The best method is to select several tests and repeat them every year to develop a track record for your orchard.
Days after full bloom (DAFB)
DAFB can give an approximate harvest date or a "ballpark guess." The major problem with this type of measurement is that there is little consistency from year to year and a wide range in suggested DAFB values. For example, for D'Anjou the range can be 120 to 150 days, for Bartlett 110 to 133, for Bosc 130 to 145, and for some of the new Asian pears 112 to 150. Firmness in pears can be measured with the same device as apples, but with an 8-mm tip to a depth of 7.9 mm.
Firmness
In pears, fruit firmness is probably the most reliable indicator of maturity. Fruit to be sold immediately or held only for a short time can be harvested at a much softer stage than fruit to be stored for a longer time. Firmness is not a good indicator of maturity for Asian pears. These types are best when ripened on the tree where fruit pressures will run 8 to 12 pounds. Color and taste are better indices for the Asian types. The recommended ranges for firmness measured by a pressure tester are as follows: D'Anjou 13 to 15 pounds, Bartlett 15 to 17 pounds, and Bosc 14 to 16 pounds.
Fruit appearance
Although it is a subjective evaluation, fruit color and finish can be a valuable maturity indicator. In Bartlett, look for a change from green to a white green, blotchy appearance at the fruit neck and finally a light yellow. Any pink coloration at the calyx end probably indicates a premature ripening problem in Bartlett. For D'Anjou, look for a change in ground color. Russetted Asian pears change from green to brown to orange or gold. Yellow-fruited varieties change from grass green to light green to yellow green.
Fruit finish is another means of judging maturity. For D'Anjou and Bartlett, look for smooth, waxy skin. As the fruit matures, corking of the lenticels is related to fruit maturity. An immature fruit has white lenticels that become brown and shallow. The brown color in lenticels is a good indicator that the fruit will ripen without shriveling.
Other methods
Amount of soluble solids is often not a good indicator of maturity in traditional varieties because of the need to harvest the fruit before it is ripe. A minimum of 11 percent for Bartlett and of 10 percent for all other varieties is recommended, except in Asian pears, where 12 percent is recommended.
Measuring the amount of starch in fruit is a "new" technique that has worked very well for apples but only with limited success for pears. As the fruit matures, starch is converted to sugars. Reports from the Pacific Northwest indicate that that the starch iodine test may be a reliable indicator and that fruit should be harvested when 60 percent of the cut fruit surface still contains starch.