July 26, 2017

Collaborator Visit & Pest Update

Hello again strawberry growers! In this post I will recap a trip to two of our farmer collaborator’s sites, in addition to an update on the pest problem on our research plot this year.

Last week I visited 2 farms that are serving as collaborators on our research project- Berry Ridge Farm in Alexandria, MN and Fairhaven farm in South Haven, MN. I arrived at Berry Ridge first and met Ron Branch, who showed me his low tunnel strawberry row that we installed earlier this year.

Low tunnel row at Berry Ridge.

Low tunnel row at Berry Ridge.

Ron’s row looked great, as did the rest of his operation, which utilizes high tunnels as well. Even though he never fertigated the fruit still looked healthy. There was some moderate damage from tarnished plant bug (TPB), similar to what we have in our low tunnel rows in St Paul. Ron made a simple but important innovation in the tunnel system as well. One of the most consistent nuisances we’ve observed in these low tunnels from Dubois Agrinovation is that the black end hoops on each row tend to collapse inwards. Ron solved this problem by tying thick blue twine from the anchor onto the end hoops, keeping them from being pushed inwards.

Blue twine attached from anchor to end hoop.

Blue twine attached from anchor to end hoop.

Next I traveled to Fairhaven farm and met up with managers Dave and Marsha. Dave showed me his low tunnel row, which was placed in an area with thick natural windblocks. Because of this Dave mentioned that they’ve never had to deal with the plastic or hoops being blown over. However, as in the past Fairhaven encountered a considerable amount of TPB, and the damage was quite apparent on the fruit.

Developing fruit at Fairhaven with heavy TPB damage.

Developing fruit at Fairhaven with heavy TPB damage.

After meeting with Marsha (who was making jam in the farm’s kitchen), she told me that while the fruit was very sweet, the TPB damage made it nearly unsaleable as a whole fruit. Fortunately Marsha is an experienced canner, and was able to process the fruit into jams which apparently are selling well. It is nice to see how farmers can alter their product in order to mitigate damages. What I took from my visits is that the low tunnels themselves are holding up quite well, but pressure from TPB this year is both widespread and heavy.

Speaking of pest pressures, lets revisit our plot in St Paul and see what we’ve been dealing with. I’ve gone into depth about TPB before, but recently 2 other pressures have presented themselves. The first is a fungus Phytophthora cactorum, commonly known as leather rot. Leather rot presents itself in poorly drained, wet soils, and here in St Paul we’ve had quite a few rainy nights on our silty clay soils. The fungus is known as leather rot because of the infected tissue turning brown and leathery, shown below.

Leather rot on strawberry fruit.

Leather rot on strawberry fruit.

Honestly I’m not too worried about leather rot because it doesn’t affect a lot of fruit (maybe 1 in 150 so far) and tends to go away once soils dry. The more worrisome problem is one we’ve touched on before, the dreaded spotted wing drosophila (SWD), Drosophila suzukii. This invasive fruit fly has finally reared its ugly head and we’re beginning to see the damage on our fruit. Fortunately the damage is quite obvious (sunken, soft flesh) so there is little risk of infected fruit making it to market. The scary part is that this pest can lay its eggs even on undamaged flesh, so diligent harvesting will not suppress it and once arrived it is very hard to control organically.

SWD larvae feasting inside ripe fruit, shown by blue arrows.

SWD larvae feasting inside ripe fruit, shown by blue arrows.

So far this pressure is also fairly low, much lower than the damage caused by TPB, but we’ll monitor it through the rest of the season and keep you updated.