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Monday, March 15, 2010

As the covers come off...

Those strawberry growers who have had row covers on their plants all winter are now removing them and performing sanitation on the plants (removing dead leaves and stray weeds). As these covers come off, I am getting reports of lots of arthropods appearing.

Spider mite management begins in earnest now, and growers should begin their weekly sampling of 10 leaflets/acre. The undersides of these leaflets should be examined for spider mites with a 10x hand lens (or microscope if you're well equipped). If the average number of mites/leaflet is 5 or great, miticide treatments should be applied. Scouting should continue post treatment to ensure they are effective and to determine if and when re treatment is needed.

Twospotted spider mite female and eggs on the underside of a strawberry leaf. Photo: HJB

Threshold based treatments are helpful because not only do they often reduce the number of applications, but they also allow us to select the best material for the job by providing a weekly pattern of information. This means we have a better idea if populations are small and newly established (best treated with an ovicide/larvicide) or are already large (best treated with an adulticide plus ovicide/larvicide).

Cast aphid skins (white) and dead aphids (brown) on tunnel strawberries at the Piedmont Research Station, Salisbury, NC. Photo: HJB
Click to enlarge this image for a much better view.

Aphids are also showing up as covers are removed, but I have yet to hear about damaging numbers in NC. It takes a lot of aphids to reduce yield in strawberries, and we have excellent native biological control agents. In fact, also found under the covers have been lady beetle larvae, feeding on the captive aphid buffet. Most of the aphids that were present under the covers morphed to winged (alate) forms, and have dispersed off the plants leaving only their cast skins. These cast skins appear white against the plastic or leaves.

Lady beetle larvae found on newly uncovered strawberries in the Sandhills. Photo: David Dycus.

As the weather warms and spring is finally here, the real fun begins!

A note about pesticide recommendations.

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