Pests & Diseases
Strawberry bud weevils, also called ‘clippers,’ can cause considerable damage. The females lay eggs once a year inside buds then ‘clip’ them to prevent flowering and exposure of the eggs. Leafrollers hide in cocoon-like enclosures secured with silky, white, thread-like webbing. They feed while enfolded in the leaves and then as the plant matures, work their way to the fruit, leaving tiny holes.
Strawberry aphid waste is referred to as honeydew and is the cause of sooty molds. The aphids shed their skin, which sticks to the mold and contaminates fruit. Strawberry yields can also be impacted by mites, rootworms, sap beetles, strawberry crown borers, tarnished plant bugs, thrips, and white grubs.
Botrytis rot or grey mold will grow at 32°F, albeit very slowly. Grey mold is the most common cause of postharvest fruit loss and starts as white in color, but quickly turns grey. Rhizopus rot is easily spread through airborne spores and characterized by black spots. Infected fruit will become soft and leak sticky red juice. The disease will not grow in temperatures below 41°F, so proper storage temperatures can prevent losses.
Mucor and rhizopus rot both produce soft, leaky fruit, while red stele root rot causes damage in wet winter and spring months. Plants will appear stunted and dull, with younger leaves displaying a blue-green pall. Other diseases that challenge strawberry cultivation include black root rot, leaf rot, fruit rot, blossom blight, powdery mildew, leaf scorch, and verticillium.
Storage & Packaging
After picking, strawberries are gently packed in the field and fruit should be cooled as soon as possible to maximize shelf life. Optimum storage temperature is between 32° and 34°F with 90 to 95% humidity for 5 to 7 days.
Berries will shrivel or lose color if stored too long. Mold growth is accelerated in temperatures above 36°F; modified atmosphere packaging with 10 to 15% carbon dioxide can reduce respiration, control mold, and extend shelf life.
References: Agricultural Marketing Resource Center, Cornell Cooperative Extension, Iowa State University Extension, PennState Extension, Purdue Extension, UC Davis Postharvest Technology Center, University of Illinois Extension, USDA, Washington State University.
GRADES & GOOD ARRIVAL
Strawberries are classified as U.S. No. 1, U.S. Combination, or U.S. No. 2 based on characteristics such as size, firmness, ripeness, development, and coloring, as well as being free from damage caused by mold, decay, dirt, moisture, disease, pests, and mechanical harm.
Generally speaking, the percentage of defects shown on a timely government inspection certificate should not exceed the
percentage of allowable defects, provided: (1) transportation conditions were normal; (2) the USDA or CFIA inspection was timely; and (3) the entire lot was inspected.
|U.S. Grade Standards||Days Since Shipment||% of Defects Allowed||Optimum Transit Temp. (°F)|
Canadian good arrival guidelines (unless otherwise noted) are broken down into five parts as follows: maximum percentage of defects, maximum percentage of permanent defects, maximum percentage for any single permanent defect, maximum percentage for any single condition defect, and maximum for decay. Canadian destination guidelines are 15-10-5-10-3.
References: DRC, PACA, USDA.
• If any amount of decay or mold affects a strawberry, it is scored as defective; a berry with surface mold is scored against the 5% tolerance for serious damage, while a berry with decay is scored against the 2% decay tolerance
• Sound strawberries with juice from bruised or decayed berries are also scored as defective, against the 5% tolerance for serious damage (moisture from condensation is not to be scored as a defect)
• Strawberries will be scored as defective unless there is a minimum of 75% of the surface being at least a pink color.
Source: Tom Yawman, International Produce Training, www.ipt.us.com.