Black Spots on Raspberries | Causes, Prevention and Concerns
For many gardeners, early summer marks beginning of raspberry season. Those juicy, red berries begin to appear all over raspberry bushes ready to be harvested and consumed. While nothing beats an abundant harvest of juicy, tart and sweet raspberries, sometimes black spots can appear on your berries making them an eyesore and more importantly, having you question if they should even be consumed.
So what are those black spots on raspberries? Black spots on your raspberries are just dead or decaying areas of the berry most likely caused by a fungal or bacterial infection. When an infection begins attacking the raspberry bush, it will create toxins and proteins that will kill the plant’s immune system. As a result, many of the plant’s cells die off leaving black spots on the berries.
You’re probably wondering: Are raspberries with black spots safe to eat? The short answer is yes. The bacterial or fungal infection that have caused the raspberries to gain black spots have evolved to harm a plant’s immune system, but not a human’s.
The only downside to consuming raspberries with black spots on them is that it may not taste very good. After all, you are consuming dead or decayed parts of the berry, but that is really the only concern when it comes to eating raspberries with black spots.
As long as you rinse off your raspberries with some water prior to eating them, you should be fine. The real threat is the dirt and debris on produce that may be harboring harmful bacteria such as E. coli on its surface. However, this threat applies to most all fruits and vegetables. As long as you give your produce a good rinse off, you should be fine.
Discolored or rotten raspberries, however, are never a pleasant sight to see. But, with the right treatment and diagnosis of the plant, you can prevent your raspberry bush from producing anymore defective raspberries in the future.
Fungal infections are notorious for causing discolored spots on raspberries as well as other fruits and vegetables for that matter. Harmful fungi can be harbored in the surrounding soil, weeds or even bugs and insects in and around your raspberries.
Not all fungi is necessarily bad for you raspberry bush. In fact, some fungi such as mychorrizal fungi can be beneficial for plants in your garden by helping the roots take in more nutrients from the soil.
While some fungi can be good for your raspberry bush, many are harmful. Some of the more common fungal infections that negatively affect your raspberry plants and give the berries black spots include the following:
This is a fungal infection caused by a fungus called Leptosphaeria coniothyrium. Black raspberries are especially susceptible to the fungus.
Cane blight occurs in the first year of growth. It affects any present wounds on the raspberry canes.
The fungus then grows into the vascular system of the plant. The affected cane overwinters, and in spring, the fungus spores are released. These spores thrive in wet weather. Factors like irrigation and splashing rain help to distribute the fungal spores to other uninfected canes
The spores then germinate in any present wounds and produce new infections. Cane blight symptoms are likely to appear beyond the wound in fall. Therefore, you are more likely to notice cane blight on pruning wounds when you peel back the cane.
The presence of vascular discoloration should confirm that your raspberries have cane blight. Also, if the infection is present, the lesions will have dark red spots with irregular purple borders and gray centers.
In the second year of growth, cane blight will prevent buds and flowers from growing. You can also experience raspberry fruits that are sunken and black. They often look like tiny peppercorns.
Managing and Treating Cane Blight