Predators

Basic Types

Predation on blueberries can come in various forms.  These pages describe my attempts to combat predation by a couple of strategies.  For example to guard against bird predation my basic strategy is to cover the blueberries with netting and thus shield them from avian predation.  In the case of insect predation, my strategy is primarily to eradicate the insect predator either by using an organic insecticide or by using biologicals -- organisms that eat the insect predator either in the adult, larva, or egg stage.

Guarding Against Bird Predators:  Erecting and Maintaining a Netting System

Birding Netting System for Established Blueberries: Summer 2010

As a trial test, I redesigned a frame-work and netting system for our old blueberries -- six bushes that we planted back in 2000.  These bushes have been productive over the years, but we have had to battle with birds to prevent them from eating practically all the blueberries.  For many years we have simply draped a bird netting over the bushes when the berries began to ripen.  However, when we wanted to pick the berries, we had to remove or throw back the netting from the bush.  This wasn't the easiest task, since the netting tended to stick to the bush and pulling on the netting typically dislodged ripe blueberries.

Initially I constructed a frame work made of 3/4 inch PVC pipe.  Starting with 10 foot pipes, I cut those in half producing five foot pieces.  The top cross bars were three feet long.  Using a combination of cross-pieces, elbows, I created repeading five foot long sections.  Overall dimensions were 5x3x30 feet.

Overall bird-netting frame created from3/4 inch PVC pipe and covered with bird netting.  This row of blueberries are planted on the side of a hill and the plants lean toward the right side giving a sideways look to the structure.

The top of the structure consists of three pieces of pipe that extend lengthwise: one at the middle of the top and two at each side of the top.  The top cross pieces are three feet wide.

Side view of bird netting structure with net in place.

Bird Netting

A great diversity of bird netting types and prices are available.  I looked at numerous companies and tried to compare quality, netting size, size of openings, costs, etc.  Finally as a trial I purchased the following: Dewitt 14-Foot by 45-Foot Bird Barricade Deluxe Netting 1/4-Inch Mesh #BB1445DLX .  The cheapest source that I could find for this netting was through Amazon.com.

Photograph of the Dewitt Bird Netting with 0.25 inch mesh.

This netting handles well, is lightweight, and appears to be durable.  Time will tell about its suitability.  The price for a 14x45 foot piece was $78.  Other netting with larger mesh sizes, i.e. 1 inch or 3/4 inch are considerably cheaper.  I hope this netting will "retard" Japanese beetles, but I'm afraid the mesh is not fine enough for that.

Constructing a Framework for Netting Commercial Blueberries

My next project which I hope to "complete" by July is to construct a post and suspension wire framework around the organic blueberry plots and the conventional blueberry plot.  For the organic plot, I purchased squared black locust posts (4x6 inch x 10 feet) which I will set at the top and bottom of each row.  I plan to put the posts two feet into the ground leaving eight foot exposed.  Using 2x6" lumber I want to tie the tops of these posts together (row centers are 8 feet) and then stretch strands of high tensile fence wire between the posts paralleling the length of the rows.  Then I plan to drape bird netting over the entire structure.

Above is a view of the organic blueberry plots.  Note the perimeter locust posts that are installed at the head of each row.  During the spring of 2011, I will install the wooden framing and strands of high tensile fence wire.

Install Dura-Line as Support

In June 2011, with the help of Zoya and Elva, we installed Dura-Line as the supporting wire for the netting that is planned.  Dura-Line is sold by Dubois Agrinovation and is a high-tensile polyamide monofilament with low elongation.  Breaking elongation is about 20-24%.  Supports long-term temperature extremes.  Is UV and chemical resistant, lightweight, non conductive.  I used 8 gauge wire which is 4 mm in diameter.  A role of Dura-Line that is 2796 feet long weighs 25 lb.

Installation Photos

Starting to stretch the Dura =Line with a Come-a-long.

Dura-Line is now stretched and ready to be tied off at the end post

Finished Knot on the stretched side

 

Stretched Line -- Another View!

Bird/Insect Protection Netting

 

 

 

 

 

 

 

 

This netting was purchased this season from Smart Net Systems and arrived in June 2011.  To cover our plots, I calculated that I needed 2 rolls of 15' x 300' to cover the plots and 7 rolls of 7' x 100' to provide the surrounding side curtains.  Cost including shipping was $1300.  Last year, I installed support posts at the ends of each row for netting support.  At the beginning of this season, I installed a wire support (Dura Line) about 7 feet above each row to hold the netting.  Since the stretched wire put pressure on the posts, I added board braces to counteract the pressure of the wire.  (See the above photograph showing the support wires in place for the bird/insect netting as well as the support board braces.)  The Dura-Line runs along the middle of each row between the posts that are planted at the ends of each row.  These parallel wires are designed to support the netting like a tent about seven feet above the ground.  In addition a perimeter wire is installed for a net curtain that can be drawn to the side to gain access.

For economic reasons, we decided to store the netting this season and not install it until next season when the extent of the blueberry crop will make it economically viable to put up the netting.  This netting is estimated to last for about seven seasons which means that the cost per season is roughly $185.  Since our crop is small this first year, it doesn’t make economic sense to waste a year of the netting’s life to protect a very small crop. 

The consequence of the above decision to not net the first year resulting in losing about 30% of our 2011 summer blueberry crop to the birds.  The birds became a real problem in early July and consumed the berries as rapidly as they ripened. 

We plan to install the stored netting in June 2012.