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Anchors Away: Keeping Support Systems From Failing

Support System Failure in Apple

Support System Failure in Apple. Image: Dan Donahue

The crop load of late varieties appears to be robust in most orchards this season. Predictions are for a record crop in the Hudson Valley with many blocks exceeding 1000 bushels to the acre. In tall spindle systems with trees in their 4th leaf and older, many growers are pushing the upper limits of support systems designed for a 10′ tall tree. At 12′ to 14′ row spacing, gaining an additional 5-15% fruit load above the top wire is enticing but not without considerable stress. Without additional support in years with a heavy crop, these systems are increasingly at risk for failure.

Over the past 24 hours we have had 2.99″ of rain at the Hudson Valley Lab. Continued rainfall, albeit at lower rates, are expected through the weekend. Under conditions such as what we are now experiencing, anticipating 11-13 mph winds over the next 5 days, the added crop load above the top wire of support systems may cause significant stress to the system. If we add to this significantly higher winds, many systems could begin to fail.

As hurricane Joaquin moves north, tree fruit growers should continue monitoring the weather pattern to determine the need to reinforce high density production systems. Presently NOAA weather is forecasting a 30% probability of sustained winds up to 39 MPH in the lower Hudson Valley by Monday-Tuesday of next week. Shoring up anchors, tightening up wire and adding in-line support should be strongly considered if foul weather predictions increase in probability.

NOAA Tracking of Joaquin

NOAA Tracking of Joaquin

System Failure and Support:
Dan Donahue & Anna Wallis; CCE ENY Horticulture Team

Stress Factors
• 2 – 4” of rain over the next several days, possible more if the hurricane hits.
• High winds, increasing in severity if Hurricane Joaquim turns inland this weekend.
• Heavier than average crop
• Fruit size has increased dramatically due to recent rains and favorable temperatures
• Some mature tall spindle blocks have become too tall for the supporting trellis structure.
• Undersized support posts (even if they are closely spaced)
• Ineffective anchor systems
• Trellis wire(s) not adequately tensioned
• While it may seem that trellis on hillsides would be most vulnerable, this is not necessarily the case. The quality of trellis construction, stability of the underlying soil, strength of prevailing winds, deviation of the trellis structure from true vertical (plumb), and the extent that trees have been allowed to grow beyond the top wire are more important considerations. Trellis’s fail on perfectly flat sites if the forces acting on the structure move from vertical towards horizontal.

Stress Failures
• Anchors giving away in soft ground
• Trellis posts giving away in soft ground
• Trellis posts snapping at the base
• Top wire breading under load (not very common)

Quick Fixes to Shore Up a Weak Trellis System
• Identify your weakest, at risk trellis systems.
o Inspect anchors
o Check for broken posts & heaving posts
o Check wire tension
• Re-set weak anchors or reinforce with some heavy weight (large block, equipment, etc.)
• Set 2”x6” studs as crutches on leaning posts to reduce sideways movement
• Re-tension trellis wires, starting with the top wire (as long as the anchors can handle it)
• Tie off the top of a failing post to a stronger post on the opposite the direction of movement. Tying off to the base of the post in the adjacent row would be strongest, but will effectively block that row middle to wheeled traffic, and could be dangerous if not very well marked with high-visibility flagging. It would be best to entirely block traffic from the affected row middle.

Concrete anchors (buried) used to support end posts.

Concrete anchors (buried) used to support end posts.

Use of heavy gauge wire for system support

Use of heavy gauge wire for system support

Increasing Post Length for Higher Canopy Yield.

Increasing Post Length for Higher Canopy Yield.