Sunday, March 15, 2015

Pest Traps Key Tool for Battling NOW in Almonds This Season

Spring officially arrives this Friday. That means it’s time to step up bug watch in almond orchards.

Field scout Jenna Horine has been busy visiting orchards throughout the San Joaquin Valley and setting out traps for navel orangeworm (NOW) monitoring. She should have all in place soon.
Field scout Jenna Horine holds a navel 0rangeworm trap,

These traps play an important role in treatment decisions for the   battle against NOW infestation. Jenna will check the traps, record eggs laid in the traps and rely that information to growers throughout the season.

Long-time almond expert and UC IPM emeritus Walt Bentley has worked with Jenna over the years about the placement locations of traps. Usually, Jenna places traps in three corner locations of an orchard block, depending on prevailing wind direction, nearby fields or orchards when pests may migrate from and grower advice.

The traps are placed about at least five trees from the orchard edge, 6 to 7 feet above the ground, 1 to 3 feet inside a tree drip line and in the shade away from water. As a rule, there never are less than three traps per orchard. For orchards of 20 to 80 acres, UC IPM recommends 1 trap per 10 acres for acres 20 to 80 acres in size. For orchards over 80 acres, the rule is 1 trap for every 20 acres.

Here’s what UC IPM says about using the traps:
  • Check twice weekly to determine the bio fix – this is the first of two dates in which egg laying increases in 75 percent of the traps in a given location.
  • Record the biofix date.
  • Continue monitoring traps, counting and recording egg numbers of a monitoring form. Remove eggs as you monitor.
  • NOW trap should be 6 to 7 feet above ground.
  • Change bait – a mixture of almond meal and almond oil – about every four weeks.
  • Look for flat eggs that are laid mostly on the ridges of the trap or on the raised lettering on the top and bottom of the trap. Eggs will be white when first laid but turn orange-red before hatching.
  • Graph numbers of eggs laid at each trap reading on the monitoring form. This will give you an idea of when new generations of navel orangeworm are laying eggs.
  • Use this information to verify degree-day calculations. If you wish to use this information for timing a hullsplit spray, continue monitoring for the entire season.
Degree-Day Calculations
  • Use the biofix determined by egg trap monitoring to start accumulating degree days for following navel orangeworm development and to time hullsplit treatments.
  • Egg laying by the second flight of moths is predicted to begin 1056 DD after the biofix.
  • Shake trees before third generation egg laying takes place.
  • Early stage of NOW development.
  • If treatments are planned and hullsplit begins before egg laying predicted, apply the hull split spray at the beginning of egg laying. If hull split begins after egg laying is predicted, apply the spray at the beginning of hull split. Back up degree-day predictions by checking egg traps.
Of course, UC IPM officials point out the need to treat for NOW is based on three factors:
  • Whether there was significant loss the previous three years.
  • The prospects of infestation from nearby orchards, including pistachios.
  •  Orchard sanitation, meaning trees had two or less mummy nuts.
Jenna is quick to point out she already can spot troublesome orchards likely to experience NOW problems this season. These are the ones that have had a poor track record in removing mummy nuts.
In one orchard with lax sanitation regularly, for example, Jenna sees lots of mummy nuts that have fallen to the ground. “You can see the worms in the mummies,” she says. It’s going to be another tough year in that orchard.

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