Blueberry Growers Warned about Cherry Fruit Worm

While the pest is a localized species, pressures can be high if it takes up residence.

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By its name, one would logically think cherry fruitworm is a cherry pest. It is, but like many pests with diverse appetites, the larvae (a caterpillar) has more than one preferred food source. The primary hosts are cherries (sweet and sour) and blueberries. In other regions, other hosts have included various tree fruits and even roses.

Destruction of crops

Cherry fruitworm will render blueberries unsaleable and the pest has been found in the Fraser Valley, according to Dru Yates, vegetable and blueberry IPM supervisor with E.S. CropConsult. The fruitworm is not widespread through the Fraser Valley, but is a serious problem for growers who have it.

Starting in May of 2019, Yates set up field traps in the Fraser Valley to assess how widespread the cherry fruitworm was in blueberries.

“The moth catches we had were quite low,” she says. “But the pest is very localized and so where it is found, the pressure can be high.”

The first and highest catch areas were in Glen Valley with three to five moths per trap. Spraying was recommended. The only other moth catch was in Matsqui, but larvae was found for the first time in Pitt Meadows where there were no traps set up at the time.

Export impact

Exports of blueberries have been an increasing option for BC growers, but there is a need to follow certain specifications for China and South Korea as there is a trapping and monitoring protocol for growers when it comes to Cherry fruitworm. India has a quarantine and inspection program and recently the European Union announced requirements similar to China’s.

For those growers hoping to find international markets for their berries, identification and control of cherry fruitworm is a serious and ongoing issue.

Cherry fruitworm lifecycle

In BC, the Cherry fruitworm has one generation per year. The moth is present in May to June and lays near-microscopic eggs on green berry fruit in June and July. From August to April, larvae can be seen which then pupae in April and May to prepare for egg laying.

“What you are going to see is the larvae,” explains Yates.

These larvae eat through berries in order to overwinter and move into adulthood. Like a lot of teenagers they are messy, with no regard for anyone else. “Even after the larvae has left the berry, that mess is still left,” Yates explains.

The mess left behind is frass (more commonly known as caterpillar poop) inside the berry.

“You may only see this once you’ve begun harvesting,” she says.

Larvae leave tiny holes as they enter one berry, feast their way through it, then exit and head into a neighbouring berry.

“That’s quite common,” Yates notes of the travel between berries without a gap in between.

Berry damage can be identified in June or July by spotting the tiny entry and exit holes as well as premature ripening during green berry stage and berry shriveling.

Identification of moths and larvae

Yates recommends growers in Glen Valley, Matsqui and Pitt Meadows to put traps up in May to assist in pest monitoring. False codling moth traps are preferred as the cherry fruit worm lure is ineffective in BC.

“Try to monitor that pest as it increases in pressure,” she explains. “Moths are quite small in size.”

This makes it harder to distinguish the moths as they are just five to 10 millimeters long. The wings are different from other moths, in that they have dark gray and black stripes along their forewings, but when they are stuck to a trap on their back, it’s near impossible to see.

Thus, growers should look for larvae in order to make an accurate identification. While the feeding damage is similar to that of cranberry fruitworm, this pest hasn’t been found in blueberries in BC, though it has been identified in blueberries in Ontario. Damage is also similar to spanworms and leafrollers, but fortunately, identification of the Cherry fruitworm larvae is relatively easy.

Young larvae are white with a black head, while more mature caterpillars are about 7.5 to 9 millimeters long, pale pink and feature a light brown head. They overwinter in bark wounds.

Control of Cherry fruitworm

“Timing of control is important if you’re going to have any efficacy. Only spray if the pest has been detected in your field, unless you are exporting, then you must follow [that country’s] specifications,” Yates says. “But it’s very important to know you have this pest before you take action. You must spray the egg and larvae before they bore into the fruit.”

The caterpillars are quite protected once they are inside the fruit.

Chemical controls are the major management method. The first spray is advised for nine to 10 days after trap catches with one to three follow-up sprays at 10 to 14 day intervals. Registered products include Altacor, Assail, Confirm, Rimon, Malathion and DiPel.

Yates stresses that the first step is to detect and confirm cherry fruitworm. The second step is to use that information during the next season for spraying (unless exporting).