Mexican Organic Orchards Offer Better Psyllid Control

A wider diversity of weeds and insects in organic Mexican citrus orchards compared to conventional orchards aids in control of the HLB-spreading Asian citrus psyllid (ACP/Diaphorina citri), a Mexican scientist reported recently. HLB is also known as citrus greening disease. 

“In the organic orchard, there are almost double the species of weeds compared to the conventional orchard,” Carlos Castillejos Cruz stated. “The organic orchard has higher abundance in all order of insects,” including ACP predators, he added. The professor of plant morphogenesis and physiology at National Autonomous University of Mexico said a conventional orchard had 700% the ACP population of an organic grove at the time of tree sprouting.

A slide that Cruz presented offered the following conclusions regarding biodiversity management for ACP control:

• Organic management promotes the biological density of insects and weeds, which allows the orchard to be more resistant to pest proliferation. Therefore, biological control is active and effective against Diaphorina citri.
• If herbicides are not applied, and weeds (especially broadleaf weeds) are allowed to develop, the population of Diaphorina citri is reduced. This is also applicable to conventional orchards.

Cruz also reported that “alternate cutting” of weeds (see photo) in organic orchards favors the control of ACP and prevents HLB from spreading. Alternate cutting also reduces the cost of managing weeds, he reported. Other forms of weed control that researchers experimented with were “low cut,” “grower’s cut” and “conventional management.”

Cruz made his presentation, titled “Biodiversity management for the control of Diaphorinacitri in organic citrus production,” as part of an international webinar on HLB. The Switzerland-based Research Institute of Organic Agriculture hosted the webinar. The institute has facilities in Switzerland, Germany, Austria, France and Belgium. Founded in 1973, it has 290 employees engaged in research, consulting, continuing education and development cooperation. It started a citrus greening research program in 2011.

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