Ross Mountain Farm
Ross Mountain Farm

Of weevils and nematodes

Oct 26, 2015

Of weevils and nematodes….

Harvest 2015 came a full month earlier than last year, and we were ready – the bird net up in plenty of time, our team of awesome pickers hired and ready to go, customers waiting. With the bushes loaded with ripening fruit, it looked like our third harvest would be another good one.

But as we got into the harvest season, we started noticing some blueberry plants looked weak, their fruit was small and generally showed a lack of vigor.

I surmised these plants simply needed more fertilizer than I had given them. Easy enough to remedy, right?


This summer we noticed weevil-feeding activity on the leaves of the bushes. Their distinctive chewing habit creates a notched pattern around the leaf edges.  Our suspicions were confirmed via a midnight walk through the blueberry field, flashlights in hand. Black vine weevils caught in the act - busted!bvw.jpgnotches.JPG

No big deal, we thought - they were just eating leaf edges, plenty of green left… let ‘em snack. We figured Mother Nature would respond in good time with a clever balancing act, without our intervention. This naïve optimism was based on an experience from three years ago: in our first harvest year we had lots (lots!) of aphids on some of the blueberry bushes. The following spring there was a major ladybug hatch all over the back of our house. Brilliant!

Meanwhile, some of the plants really started to decline, leading me to finally consult the experts at the Ministry of Agriculture Plant Health Department.

Diagnosis: black vine weevil larvae. While the adults were eating leaves above the ground, the larvae of the little buggers had been feeding on the blueberry roots all summer long. Yikes!

I suffered immediate and utter disappointment for not realizing how much damage weevils (larvae) could cause below the surface of the soil. But, no time for that, this situation called for immediate action. Inquiries and online sources suggested nematodes can be effective and are acceptable to use on an organic operation. Nematodes are microscopic single-celled worm type critters, and there are two common strains that are used for weevil larvae.

Under the correct conditions, the nematodes find and enter the weevil larvae, bacteria within the nematodes are released and the host weevil larvae dies, becoming food for the nematodes. Fortunately, our September weather cooperated and we managed to get two applications of the nematodes on the whole blueberry field.

A third application is planned for the spring, once the soil has warmed up again. Unfortunately, it’s hard to tell if/ how effective the treatments have been until next year. Early next summer we hope to see much lower weevil leaf munching in the field.

I have learned another lesson – the hard way of course. And I can guarantee there will be a whole new ‘issue’ to learn next year, and the year after that.

The joy of farming!



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