Monday, March 27, 2017

Now is the Time to Put Out Pest Traps in Almond Orchards

Drive around almonds orchards across the Valley and you’ll see growers and their crews busy on spring chores.

Except for a few rainy days, everyone has been busy applying fungicidesto tackle fungus and other diseases brought about by the wet weather and adding fertilizers and nitrogen to the soil.

Mummy nuts left on the ground over the winter.
Field scout Jenna Mayfield has been out and about as well, visiting orchards and setting up pest traps for the upcoming season. While walking through the orchards, she’s noticed a common theme.

“Many growers left so many mummy nuts on the trees,” she says.

That could spell trouble with navel orangeworm (NOW) down the road. NOW is the main pest of almonds. The mummy nuts serve as a winter home for NOW larvae.

That’s why Jenna stresses the importance of growers launching an aggressive mummy nut removal program during the fall and early winter. Without such a program, growers may wind up treating for NOW at hullsplit.

However, orchard sanitation apparently hasn’t been high on the to-do list for a number of growers.  That means Jenna will be watching closely for NOW – as well as other pests throughout the season. To prepare, she has spent the past couple weeks placing traps for NOW and peach twig borer (PTB). (PTB is another pest, which overwinters in cracked bark and trunks of trees.)

This is a PTB trap in placed in an almond orchard.
UC IPM notes that egg traps will help follow NOW development and determine when “navel orangeworm eggs will hatch in relation to hullsplit so treatment can be timed precisely.”

For growers setting out their own traps, here’s a checklist from UC IPM:


  • After setting the traps in early spring, check twice weekly to determine the biofix—this is the first of two dates in which egg laying increases in 75 percent of the traps in a given location.Jenna will set her traps seven trees deep from the edge and spaces them apart based on wind direction.
  • Record the biofix date.


  • Use traps baited with almond meal and 10 percent (by weight) crude almond oil. Black traps work best, but their caps do not need to be black.
  • Place one trap per every 10 acres, for at least four traps per orchard.
  • Choose trees that are at least seven trees in from the edge of the orchard.
  • Hang traps at head height on the north side of nonpareil trees, one to three feet inside the drip line of the tree. Avoid areas where traps will be hit with sprinkler irrigation.
This is one of the NOW traps Jenna will be monitoring.

Trap reading

Continue monitoring traps, counting and recording egg numbers on an egg trap monitoring form.
  • Change baits 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.
Meanwhile, Jenna says many trees remain in bloom. “It has been one of the longest bloom periods in a long time.” Last year, the Valley saw what was described as a “flash bloom” – a very short bloom period.

Growers are hoping the extended bloom will lead to a good fruit set, which could translate into a good yield at harvest. Ah yes, spring does bring optimism.

FIELD DAY: Almond growers will learn about honey bee health and receive valuable disease, fungicide and pest management tips at a field day on Tuesday. The free event will be from 10 a.m. to noon at the Cook Orchard, 15640 Avenue 22 1/2, Chowchilla. David Doll, a Merced County UCCE pomologist, will review bloomtime diseases found in almonds, chemical treatments, including the proper selection of fungicides and nitrogen applications. FlorentTrouillas, UCCE fruit and nut specialist at the UC Kearny Ag Center, will explain the complexities of many wood cankers found in almond trees. He also will offer tips about treating the problem, including chemical and mechanical management practices. Sponsored by San Joaquin Sustainable Farming Project, the field day offers one hour of continuing education credit. For more information contact Project Director Marcia Gibbs at (530) 370-5325 or at


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