Irrigation

(originally published May 2018)

 

 

Don’t Play A Guessing Game

Farm advisors and professionals in orchard water management emphasize that tools to determine soil moisture in relation to water holding capacity of the soils and tree water stress in your walnut orchards are critical to irrigation decisions.

Allan Fulton, University of California Cooperative Extension (UCCE) irrigation and water resources advisor in Tehama County, said, many walnut growers and managers in the Central Valley are using some combination of soil moisture sensors, water budgeting, and tree stress indicators to determine initial irrigation needs and they also use them to make sure trees have adequate moisture throughout the growing season.

Proper use of those tools can prevent over or under irrigation, and stress on trees, ultimately improving production, consistency and potential.

Why would a grower risk guessing on such a critical piece (plant available water) in the complex environment that makes up their soil profile, asked Brian Bassett of H2O Optimizer. 

Bassett said his company’s clients ended the year by recharging the soil profile to about 70 percent of field capacity, in the event that winter rains arrive. Leaching doesn’t take place in a dry soil, he noted, so having some level of moisture allows rainfall to create the leaching as opposed to filling the soil profile.

Growing degree-days are compared to historical bud break or bloom to determine bloom or bud break for the current year. Initial irrigations are to refill soil profiles determined by the sensors. Depending on growing region, soil profile and weather conditions, Bassett said winter irrigations in walnut begin the second week of February.

Soil profile is important, he noted because clays are slow to fill. Irrigations on sandy soils are closer to bloom or bud break to avoid water leaching.

Correct timing and length of irrigations is important because depletion or excess soil moisture in orchards can lower plant vigor or create an environment for the spread of fungal diseases. Nutrient uptake can also be affected.

 

Sterile Insect

(originally published May 2018)

 

Aiming to suppress burgeoning navel orangeworm (NOW) populations in California pistachio orchards, the pistachio industry is following in the footsteps of the cotton industry and continues to pursue a sterile insect program adding another control tool for growers.

Delivered to a 1,250 acre test plot in western Kern County this spring will be five million sterile navel orangeworm adults. Taking a page from the cotton industry’s successful pink bollworm eradication program, the project is aimed a reducing numbers of NOW early in the season to head off much larger crop damaging NOW populations later.

Sterile Insect Releases

The release plan, said Bob Klein director of the California Pistachio Research Board, is for one million moths per day to be delivered via fixed wing aircraft, to the test plot. The releases will be made in the early morning hours from 500 feet up. Another 1,250 acre block of pistachios will be used as a control. Both blocks will continue to receive standard NOW control with sanitation, mating disruption and pesticide applications.

These releases, Klein said, are the first in a three year program focused on NOW suppression and lowering crop damage percentage and to determine success of the delivery method.

Sterile insect releases are being scheduled to match emergence of native adult NOW moths from overwintering sites. The aim is to end the reproduction cycle for as many NOW adults as possible by releasing sterile NOW when males are seeking females to mate. High numbers of sterile insects are needed to out-compete native NOW.

Klein said the sterile insect releases are believed to work best early in the season when NOW populations are lower. The sterile Insect program is a suppression program, Klein stressed, and if it proves successful, can be another tool for growers to protect their pistachio crops.

Best Pest Managments against (PFB) and (BMSB)

(originally published June 2018)

 

Hazelnut acres are surging in Oregon despite the challenges being raised by two significant insect pests.

The opportunistic Pacific flathead borer (PFB) preys on newly planted hazelnut trees while the invasive brown marmorated stinkbug (BMSB) continues to infest orchards and destroy nut crops.

BMSB

The brown marmorated stinkbug, a native of Asia, was introduced on the east coast in the 1990s and by 2004 was detected in Oregon. Nik Wiman, Oregon State University (OSU) orchard specialist, said BMSB damage to hazelnut crops was confirmed in 2012.

This pest has also been found in California, but mostly in urban areas. There has been speculation by researchers that the prolonged high summer temperatures in California may be a limiting factor with this pest. Oregon, with forested areas adjacent to many orchard crops, may have a bigger challenge with this tree-loving pest.

Adult BMSB has a typical stinkbug shape, white bands on its antennae and legs, rounded shoulders and a prominent light-dark banding pattern on its abdomen. BMSB eggs are barrel shaped, white to pale green in color and can be found as masses on leaves. Newly hatched nymphs are difficult to distinguish from native stinkbug nymphs.

 shutterstock 98565563

(originally published July 2017)

 

Farm advisors and professionals in orchard water management emphasize that tools to determine soil moisture in relation to water holding capacity of the soils and tree water stress in your walnut orchards are critical to irrigation decisions.

Allan Fulton, University of California Cooperative Extension (UCCE) irrigation and water resources advisor in Tehama County, said, many walnut growers and managers in the Central Valley are using some combination of soil moisture sensors, water budgeting, and tree stress indicators to determine initial irrigation needs and they also use them to make sure trees have adequate moisture throughout the growing season.