POTENCIAL DE Heterorhabditis indica (RHABDITIDA: HETERORHABDITIDAE) COMO ESTRATEGIA DE MANEJO DE Copturus aguacatae (COL: CURCULIONIDAE) y Phyllophaga spp. (COL: MELOLONTHIDAE).

Abstract

The borer branches Copturus aguacatae Kissinger (Coleoptera: Curculionidae) is an important pest of avocados in Mexico. Its control, based on chemicals brings significant economic and environmental costs. An alternative is biological control, where entomopathogenic nematodes which would be important candidates as they have proven their efficiency in controlling other pests drill. For its part the species complex white grubs Phyllophaga spp. is an agricultural pest of major economic importance in Mexico, mainly due to their polyphagous habits and wide distribution. As inhabitants of the soil, entomopathogenic nematodes (EN) is an environmentally sustainable alternative to control white grubs. For to know the potential of the nematode Heterorhabditis indica Poinar strain Tab-03 in the control of the pest, larval bioassays, inside and outside of branches were implemented. Four concentrations outside of branches were evaluated: 1% (2500 nematodes m-1), 0.1% (250 nematodes m-1), 0.01% (25 nematodes m-1) and 0.001% (2.5 nematodes m-1). The best dose and the time where 50% of the larvae died (LT50) were estimated. Bioassays inside of branches included four application strategies: sap ("baba") of “nopal”, gelatin, water, and water + plastic cover. Sponge strips of 5 x 6 cm were soaked with nematode suspension concentrations of 500 nematodes ml-1 + the corresponding treatment. The branches were wrapped with sponges and incubated at 25 ± 1 ° C for 15 days. To Phyllophaga spp. bioassays with larvae and adults collected in northwestern Michoacán were developed. Larvae of 3° instars were placed into plastic containers of 5 x 6 cm with substrate (soil or composta). Concentrations of 2 500 nematodes ml-1 were added and incubated at 25 ± 1 °C. Daily Readings mortality started 24 h after and passed during five days. Additional studies included the effect of three types of regional soil on the infectivity of H. indica: two of the Purepecha Plateau ("topure" and "Charanda") and one representative of the Cienega of Chapala (Vertisol-saline). Bioassays for adults were similar to the larvae; the difference was that here was used one sponge as substrate. Results for C. aguacatae showed high virulence of H. indica on larvae of the pest; the estimated LT50 was 28.8 h, whereas 100% mortality was reached 44 h later. The optimal dose was 0.1% (250 nematodes ml-1) with 93.3 ± 5.7% of mortality. The emergence of juveniles ranged from 386 to 3426.66. However, under the study conditions, the results indicate strong constraints of H. indica to penetrate and infect C. aguacatae inside the galleries. Although there was a trend of higher mortality in treatments than the control, only juveniles were xiv obtained in the treatment water + plastic cover. Apparently H. indica entry to the galleries is highly influenced by the presence of sawdust in them and the application technique used, which could be minimized by early applications. Future work should focus on the evaluation of the time, dose and different application techniques. With respect to the results to Phyllophaga the larval mortality was similar in soil and composta (46% and 40%). “topure” and “Charanda” soils had the best physical-chemical activity of the EN, which was consistent with the higher mortality in larvae of Galleria mellonella in both soils (88.09% and 88.33%) compared with saline-clay soil, where the lowest mortality occurred (18.75%). Unlike larvae, adults of Phyllophaga were highly susceptible to H. indica. The LT50 was estimated at 49 h while 99% mortality was reached at 86.6%. However, never was registered nematodes emergency in the treatments. Based on the results it can be concluded that the nematode H. indica could be a good candidate for the management of Phyllophaga spp. they caused mortality in larvae and adults. In adults could be using the technique of autodiseminación by light traps baited with nematodes.