Butternut Squash and Growth Cracks.

As autumn approaches butternut and other winter squash (to include pumpkin) develop a hard skin. This permits the storage of these fruits for several months. Once this hardening process starts anything that encourages further growth of the fruit may result in splitting of the fruit as is seen in these photos. A heavy rain or application of water after the fruit starts to harden its skin can stimulate growth and result in the cracking of the fruit. Applying nitrogen at the wrong time can also cause splitting.

Vine crops like butternut squash should be side-dressed in midseason as they start to vine. At that time 2.5 ounces of nitrogen should be applied for each 250 feet of row. Fertilizing much later or with more than recommended above can stimulate growth resulting in cracking. See http://www.coopext.colostate.edu/TRA/PLANTS/Nitrogen%20Recommendations%20-%20Vegetables.pdf for details on fertilizing vegetables in the summer.

The crystalline substance on the edge of the cracks is due to plant juices that oozed from the damaged tissue.