In previous field studies in Northern Mexico, we found the wasp Brachygastra mellifica (Say 1837) (Hymenoptera: Vespidae) preying voraciously the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae), the vector of the bacteria Ca. Liberibacter spp., the putative agent of Huanglongbing, one of the most devastating citrus disease in the world.   As in Mexico, the ACP management considers the use of pest biological control, the availability of potential agents for the control of the vector remains as a priority.  The objective of this study was to determine the predation preference of the wasp for the different developmental stages of D. citri. During 2011-2012, we performed experiments in field where we exposed manually to the predator new citrus flushes infested by eggs and diverse ACP nymphal instars.  The predation behavior was recorded in videos and posteriorly analyzed in the lab. Other observations on its feeding attack were made directly on infested flushes in the trees, during the foraging activity of the wasp. Results indicated that B. mellifica preferred for predation 4^th and 5^th instar nymphs, and posteriorly 2^nd and 3^rd instars. Due to their size and position in the flush, eggs and first instar nymphs were practically discriminated by the wasp. Occasionally, B. mellifica consumed D. citri adults. This predator represents a potential agent for natural control of D. citri in the North of Mexico, and South of the USA, mainly through conservation strategies of beneficial insects.

Entomopathogenic fungi are natural enemies of D. citri adults in Mexico. Natural prevalence (%) of fungi on live adults in central Veracruz (summer) and southern Tamaulipas (fall) were: Hirsutella citriformis (7-35); Isaria fumosorosea (5-15); Lecanicillium (2 in Tamaulipas), and Beauveria (<1). Torrubiella (=Sporothrix) is a hyperparasite of Hirsutella. In inland Tamaulipas only Isaria was found. Entomophthora (<2%), a new report for Diaphorina, was found at Veracruz in October 2012.

Diaphorina citri, the vector of the pathogen causing Huanglongbing, has been found infected by the entomopathogenic fungus Hirsutella citriformis Speare in the Mexican citrus industry.  The objective of this study was to characterize morphologically eight H. citriformis isolates and evaluate their potential for the control of D. citri adults. The fungal isolates were obtained from citrus groves located in the Mexican states of Campeche, Chiapas, Colima, Quintana Roo, San Luis Potosí, Tabasco, Veracruz, and Yucatán.  The fungi showed mycelium composed by delicate hyphae measuring 1.18-1.88 µm in diameter; phialides 30.7-40.9 µm in lenght and neck length of 24.7-35.8 µm.  Conidia measured 5.83-5.92 µm in length and 1.43-1.99 in diameter.  The mucilaginous layer was 7.83-8.12 X 5.86-5.99 µm.  The morphological characterization indicated that the isolates were related to H. citriformis.  The experiments for the evaluation of pathogenicity were conducted under controlled conditions (25±2°C, 76±4% RH and 16:8 h L:D).  Insects were inoculated by contact with sporulated cultures of the isolates.  For each H. citriformis isolate, 15 adults of D. citri received the spores of the fungus.  The results showed that mortality of the psyllids by the fungus began six days after inoculation; occurrence of the first H. citriformis sinnemata in the D. citri specimens was observed 10 days after inoculation.  In the first bioassay, the final record of survivorship was performed 27 days after the beginning of the experiments; the mean rate of mortality was 98 and 70% for the Tabasco, and San Luis Potosi H. citriformis isolates, respectively.