World OJ demand, open hydroponics and psyllid control top Citrus Industry Conference

07/14/2011 04:01:00 PM
Vicky Boyd

• an update on open hydroponics, sometimes called the “advanced citrus production system,” at the Gapway Grove near Lake Alfred.

Open hydroponics involves intensive fertigation, balanced and complete nutrition, high tree density, a rootstock capable of developing compact trees and an efficient root system to maximum nutrient uptake.

Arnold Schumann, an associate professor at the Citrus Research and Education in Lake Alfred, is leading the team conducting the research with cooperator John Strang.

The goal is to see if growers can replant an existing grove with a high-density one and bring it into production in this day and age of huanglongbing, also known as HLB or citrus greening.

The grove was planted in January 2009. A computer, hooked up to soil moisture sensors, keeps the root zone near waterholding capacity with short water pulses.

Fertilizer is injected during most pulses. The project also is comparing the open hydroponic system, which uses two rows of drip emitters, to balanced fertigation with a conventional microsprinkler system and a grower standard granular fertilizer and microsprinkler program.

The grower standard involves applying granular fertilizer six times per year and infrequent irrigations.

Already, the plots on drip and microsprinkler fertigated with the balanced nutrition program appear more vigorous and have a larger canopy, Schumann says.

In the end, Schumann says the team hopes to see reduced fertilizer and water use, faster growth and earlier production with the open hydroponic system compared with the grower standard program.

To take a digital tour of the Gapway Grove, visit

• aggressive Asian citrus psyllid control in young trees. Michael Rogers, an entomologist at the CREC, looked at psyllid control from three different soil-applied neonicotinoids: Admire Pro, Platinum 75SG and Belay 50. Belay is registered only for non-bearing trees and has a 12-month pre-harvest interval, something Rogers says Valent USA, the product registrant, hopes to change by 2012.

The neonicotinoids actually disrupt psyllid feeding, reducing HLB transmission, he says. They also provide long-lasting systemic control and target both leafminer, which spreads citrus canker, and Asian citrus psyllid.

Rogers also looked at psyllid control in three different sized trees: resets less than 3 feet tall; 1- to 2-year-old trees 3 to 5 feet tall; and 3- to 5-year-old trees 5 to 9 feet tall. “In young trees up to 5 feet, it takes about two weeks to get consistent control, and you can expect it to last 60 days [after application]” Rogers says.

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