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Spider Mites
Mites have a love for all kinds of berries and some of these pests are finding their way to new territories in terms of berry plants. Identification is the first step, then knowing how to best deal with the pests follows, says entomologist Tracey Hueppelsheuser with the Ministry of Agriculture.
“Damage caused by mites is quite broad-reaching,” says Hueppelsheuser.
There is a range of mite families and the pests within these groups will cause damage by feeding and pushing toxins into plants. Mites are actually arthropods with four or eight legs (sometimes having two or six legs at different life stages), and aren’t insects as commonly believed.
Two-spotted Spider Mite
The two-spotted spider mite is perhaps the most commonly known and comes from the tetranychidea family.
“It’s actually the poster-child mite we think of,” Hueppelsheuser says.
These mites use their webbing as highways to move their large colonies. While destructive during spring and summer, the adults turn orange pre-winter and don’t do any damage in the late fall. Their preference seems to be cane berries, but the pest is exploring new worlds in BC
“We don’t really see spider mites in blueberries, but we found they can live in blueberries,” she notes. “It doesn’t seem to be on the increase, but keep an eye out for it.”
The flare-ups in blueberries seem to be minimal and she says the same controls used for spider mites in other berry crops will work for blueberries. In order to determine if control is necessary in cane berries, Hueppelsheuser advises collecting ten leaflets per growing location in June (pre-harvest) and examine them. If spider mites are approaching 10 or more per leaflet (and there are few or no predators – ie, less than one predator to 10 mites) or there are numerous eggs, spraying may be necessary. However, she advises to do the check more than once per site in order to establish trends and see if mite populations are growing and if action is required pre-harvest.
Other Mites
Yellow mites are relatively new to BC and differ from spider mites in that they are more yellow/green, come out earlier in the season and tend to focus on cane berry plants.
The European red mite is more common in drier zones, but has been seen in the Lower Mainland. This mite is redder than the spider mite, but its eggs over-winter.
The McDaniel spider mite is very similar to the two-spotted spider mite so for proper identification, Hueppelsheuser points to guidelines from WSU as well as the berry production guide.
Cyclamen mites in strawberries can be a costly pest for growers.
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Stethorus punctillum
The stethorus punctillum is described as a spider mite destroyer.
“It does cause growth deformation,” she says, adding that it will stunt growth points of the plant. “If you see anything that looks like sand it could be mites.”
Red berry mites are also aggressive and make use of Himalayan blackberries as refuge areas while hosts are wild and cultivated blackberries. Canes infested with red berry mite will have berries that don’t ripen. Instead, berries will stay green, red or two-toned and crops can be lost within three years of the first detection of the pest.
“What you see is non-ripening fruit,” she says. “They overwinter under bud scales, come out to flowers and ultimately to the fruit. There is nothing you can do this year [if you find it].”
She advises to use lime Sulphur or sprayable Sulphur early the following spring.
The currant big bud mite only seems to damage black currants and again Sulphur, combined with pruning, is the best control.
“The buds basically become mite hotels,” she explains, so to get rid of the mites, you have to demolish their ‘hotels’.
Along with cyclamen mites, broad mites are part of the tarsonemidae family. Broad mites enjoy blackberries but are not common in BC, but the Ministry is advising growers to watch for them. They tunnel into the plant similar to the cyclamen mite’s behaviour in strawberries. “It likes warm and moist,” says Hueppelsheuser.
Finally, the blueberry bud mite is also not seen in BC at this time, but is in Eastern Canada and the Southeastern U.S. It behaves in blueberries similarly to how the currant big bud mite behaves in currants.
Plan of Attack
With the ability to identify mites comes the next step – the approach to knocking them down.
“We are fortunate in BC to have lots of beneficials,” Hueppelsheuser says of insect helpers.
A tiny ladybug known as the stethorus punctillum is what she describes as a spider mite destroyer. It starts working early and continues to prey on mites throughout the season.
Another naturally occurring beneficial is the pirate bug. “They will eat pretty much what they can catch on your plant,” she notes.
While both insects are native, they can also be purchased to supplement existing populations.
The neoseiulus (amblysieus) fallacis will also eat all species of pest mites.
For chemical approaches, Hueppelsheuser says the majority are for spider mites, but there are options for other mites as well. In cranberries, Acramite and Kanemite are labeled for spider mites as is Agri-Mek which will also control broad mites. In blueberries, Envidor is labeled for bud mite and also controls spider mites. Strawberries have Nealta and Oberon for spider mites as well as Agri-Mek which is also labeled for cyclamen mite. In currants, oils, Sulphur and lime Sulphur are labeled for big bud mite.
Those growers in a fight against mites will do best to first identify the pest they are dealing with, then determine the plan of attack to better win the battle and save the berry crop for next year.