When Will Almonds Hulls Split? Here’s a Hint: Look Back to Winter, Early Spring Weather

 It may be the Fourth of July holiday tomorrow, but growers will still be out during the morning hours to double check the progress of their orchards.

Field scout Jenna Mayfield says growers have little time to rest and fully enjoy the holiday. They are quickly preparing for the start of the harvest season.

Hull split will be starting in the Valley.

Indeed, this is the time hull splitoften takes place – the first week of July.  There are many factors that influence the splitting of the green hull enveloping the shell: weather, the amount of stress on the trees and almond variety.

You might think the late spring and early summer weather greatly influences the start of hull split. But University of California, Davis researcher Ted DeJong found in a study that weather during the first 90 days after bloom is the best forecaster. Simply put: cooler weather during this period will translate into a later hull split while warmer conditions lead to an earlier split. You can learn more online about DeJong’s model on hull split predictions.

Late winter and early spring conditions influence hull split.

Now on to tree stress. Merced County’s UC Cooperative Extension farm advisor David Doll says there are indications the amount of stress and nutrients in trees influences hull split duration. For example, let’s say the trees are stressed in June. This will decrease the amount of water in the hulls, which means drying time is faster as they start to split.

Normally, the Valley experiences heavy heat in June – think the prolonged triple-digit heat wave we just went through. This extreme heat leads to stress because of the inability to manage irrigation properly.

Almond trees showing major signs of stress.

The nitrogen level in trees also influences the rate of split. Trees with a higher amount of nitrogen will have a longer period of hull split, Doll says.

Of course, you have to consider the overall health of the orchard. Orchards with trees that are growing vigorously experience less stress and have higher nitrogen levels. This can lead to an uneven ripening of the nuts on the trees. The result can be the nuts in the top part of the tree will split two to three weeks before the almonds on the bottom half. Uneven ripening isn’t good. This condition will delay harvest, which increases the risk of pest and disease infestations.

The lesson here, according to Doll, is the value of embracing best management practices such as proper irrigation techniques and nitrogen management. The payoff is an easier time during shaking and harvest.

Meanwhile, field scout Damien Jelen says growers are wrapping up another alfalfa cutting – which is good because worms counts had been on the upswing.

The story is different in cotton. As expected, lygus bugs continue to be worrisome. Damien reports seeing some damage to squares.

Lygus damage found in cotton squares.

“The southeast part of the Valley is getting hit pretty hard,” he said.  In one field, for example, Damien recorded 36 lygus bugs per 50 sweeps of his net. UC Integrated Pest Management guidelines put the treatment threshold at 2 bugs per 50 sweeps in late June. The threshold at the beginning of July bumps up to 7 to 10 lygus per 50 sweeps.

Damien says one grower already has treated for lygus. His advice to cotton growers: stay vigilant because it’s already shaping up to be a big year for lygus.