Last summer /early fall (september) when I was ready to pull my mature beets for consumption and storage, I was shocked that the beets were hollowed out by something. They grew into good size mature beets but the flesh had been eaten. I live in Brechin on the east shore of Lake Simcoe. I do not have a photo.
Do you know what kind of grub or beetle this might be?
Also, what precautions I should take for planting them this year?
That’s a tough one, most of the information I have talks about pests and disease that attack the leaves and not the actual beet root. However, there are some issues regarding cultivation that may help prevent what you are experiencing.
Firstly, the white grub that attacks many roots in the garden is a member of the scarab family and is commonly called the June Beetle / Bug larvae. The large mature black or reddish brown June Beetle next month will begin to lay eggs in or on the ground. These eggs will turn into fat, white to bluish white, C shaped grubs that are 3/4 – 1 inch long with brown heads. These grubs hatch in 2-3 weeks and feed on root vegetables and other plant roots, right around the time your beets would be maturing. The eggs are protected by the detritus that gets left behind in the fall, so early spring clean up is important to remove any leaf debris along with any eggs before they have a chance to emerge.
If you suspect you have grubs, they can be treated with beneficial nematodes. These tiny, soil-dwelling parasitic worms live in the soil and target & kill grubs. Nematodes can be purchased at or ordered through most reputable nurseries or large garden centres. Apply on an overcast day to soil or lawn that has been rained upon or recently watered. Follow the directions on the container carefully and use the correct amount for the square footage of your garden.
There are other cultivation practices that may have affected your beets and possibly hollowed them out or cracked them:
1. Beets need regular, even watering for optimal growth. Uneven watering over their growing period can cause cracking or misshaping of the root. Roots also grow best when fertilized with a higher phosphorus number, the “P” in the fertilizer system. Too high a nitrogen (N) level produces leaves and poorly formed or no beet roots.
2. Beets are a cool weather crop – it is recommended they be planted in early spring rather than late spring or summer, for harvest in the fall. Perhaps they were planted a little late and if harvest was in mid-September, they were over mature, and cracked. The greens can be cut early when the leaves are young and tender. Young roots are the most tender, about the size of a golf ball and can be harvested about 6 weeks after sowing. Wait a bit longer for larger roots. Beets that mature in hot weather will be poorly flavored. Lift spring beets before daytime temperatures average greater than 21 degrees Celsius. To harvest in the fall, daytime temperatures should consistently be around 10 degrees. See the article below that recommends harvest time for spring and fall beet crops.
3. Although there are sandy areas around Lake Simcoe, Brechin is on clay plain, so it is possible that you are planting beets in a heavier soil which they don’t like. Beets prefer a lighter soil so to lighten your soil, mix in plenty of organic matter such as compost or well rotted manure. This will allow water and air to penetrate more easily and will also add vital nutrients. This will improve beet production and prevent misshapen roots.
On a final note, consider creating and using raised beds where you can have greater control of the soil as you introduce all of it. These would also give you the advantage of earlier spring planting of your beets as the soil would warm up sooner. Also, rotating your beet crop to a different section of your vegetable garden is advisable.
With early spring clean up of debris, applying nematodes, amending the soil, creating raised beds, crop rotation, planting at the proper time, increasing phosphorus feeding and consistent watering, should lead to a healthier and larger beet crop..