Mechanical & Field Injury

The Mechanical & Field Injury section of the card set includes many of the injuries that occur to apples prior to harvest. This includes problems such as bruising and weather-induced defects, except sunburn, which is covered in the Fruit Finish section. The upcoming revision of the Defects & Disorders Guide should include any emerging or reclassified disorders. To navigate directly to the pest damage of interest use the links below this text block.  The card images shown on this site are slightly modified from their original form to accommodate web formatting. Any reproduction of the card images or content without permission is in violation of WSU Copyright policies.

Bruising   Chemical burn   Frost   Hail


Bruises are the most common type of mechanical damage. Fruit can be bruised on the tree during hand thinning, or during picking. They can also be bruised by adjacent fruit or tree limbs.  Once harvested, fruit bruise easily in the bins though rough handling. Loading fruit in the dump tank and running on packing line equipment can also bruise fruit. Although mostly considered a cosmetic down grade, bruises can make fruit susceptible to rot. 

Chemical Burn

Chemical burns originating in the orchard may appear differently depending on the varieties susceptibility to the chemical and which chemical is responsible. Any chemical applied in or around an orchard can cause fruit burns. This includes oils, pesticides, herbicides, fertilizers and growth regulators depending on how it was applied. Unfortunately, the resulting burns may be hard to identify because the damage may take time to develop and may look like insect or other types of damage.

Figure 1. The burns shown here were caused by a nutrient spray that left large droplets on the fruit surface.

Frost Injury

Frost is a serious problem both early in the season and late season. Frost occurring around blossom or fruit set can cause complete fruit loss. Late season frost effects mostly late season varieties leaving the effected fruit with a characteristic ring russet scar from where the frost settled on the fruit. It can be confused with the russetting caused by powdery mildew. However, mildew russet is more net-like across the fruit. 

Hail Injury

Hail damage can occur any time during the growing season. What the damage looks like at harvest will depend on how mature the fruit was and how large and hard the hail was it struck. A hard impact early in the season could cause a very deep depression and deformation of the fruit. Later season damage could appear more bruise-like.

Figure 1. Damage to this Red Delicious probably occurred mid-summer leaving a noticeable depression. Cracking is not uncommon. A mark like this can be confused with insect damage. Notice that this fruit also has a large bin bruise unrelated to the hail mark.