Virus Decline

Are your strawberry plants looking pitiful? Do they fail to produce big, luscious fruits? It may be virus decline. [And those berries are not really berries, they are accessory fruits, but I digress.]

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Virus decline is a combination of multiple viral infections that leave strawberry plants looking like they’ve missed too many meals.


Causes of virus decline

Virus decline is a combination of viruses: Strawberry pallidosis associated virus (SPaV) or Beet pseudo yellows virus (BPYV), both which are spread by whiteflies, combined with any one of several other viruses commonly spread by aphids. Because virus decline is a combination of infections, plants may look fine one day, even though they’ve already been infected by SPaV or BPYV, and then look bad a few days later, having become infected with another of the relevant viruses. These aphid-borne viruses include:

• strawberry crinkle virus
• strawberry mild yellow edge virus
• strawberry mottle virus
• strawberry vein banding virus

Strawberry latent ringspot and Fragaria chiloensis latent viruses may also play a role. Research is currently underway. 


Virus decline symtoms

Plants infected with virus decline are often stunted, sometimes severely. Leaves turn purple or red, though new growth that forms near the center of the plant may remain green. There is little or no fruit production, and the roots are brittle and reduced. These plants will never be productive.

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Control of virus decline

You cannot know for sure if your strawberry plants have virus decline without sending a sample in for lab testing (which your County Agriculture Office may offer for free). but declining plants are best removed and replaced, preferably in a new location. 


One way you can reduce the likelihood of virus decline occurring in your strawberry patch is to keep other plants that might host these viruses at a safe distance. The SPaV virus favors strawberries and its cousins, and a few weeds, such as nettle, creeping sibbaldia, mock strawberry, sharp leaf groundcherry, and cheeseweed. BPYV, however, has a taste for your melons, squashes, lettuces, cucumbers, endive, and spinach, along with marigolds, zinnia, dandelions, and cheeseweed.


To reduce the possibility of virus decline in your strawberries:

• only buy certified disease-free plants
• place new plants in quarantine
• control whiteflies and aphids
• remove nearby weeds
• plant strawberries away from potential host plants

These steps are no guarantee, but they will significantly reduce the chance of your plants becoming infected.