Scyphophorus acupunctatus is the main pest of Agave tequilana. Its adults are vectors of Erwinia carotovora, which causes plant destruction. The susceptibility of S. acupunctatus larvae to various strains of entomopathogenic nematodes has been demonstrated previously (Molina et al., 2004). In the current paper, the use of seven different concentrations: 0, 10, 20, 50, 100, 200, and 500, of infected juveniles per larva in petri dishes containing a filter paper against Steinernema carpocapsae strains All, Ca, and Fl, and also against native insolated N1, N2, N4, belonging to the genera Steinernema sp. The studies were conducted under laboratory conditions to determine the susceptibility of S. acupunctatus larvae to entomopathogenic nematodes. One hundred percent mortality of S. acupunctatus larvae was achieved by S. carpocapsae strains All, Ca, and Fl with exposure to 100 infected juveniles. In the case of native isolates, N2 registered 95% mortality, and for N4 and N1, mortality registered was 75%. An analysis of variance was conducted in order to determine whether strain or isolate had the highest virulence against S. acupunctatus larvae. Means for S. acupunctatus larvae by entomopathogenic nematodes presented significant differences (F = 57.01; df = 55, 223; P < 0.0001), resulting in two levels. At the first level, S. carpocapsae All, Fl, and Ca are statistically the same as isolate N4. At the second level, the isolates N4 and N1 are statistically the same. The results indicate the high susceptibility of S. acupunctatus larvae. The infectivity of native isolates as well as S. carpocapsae strains All, Fl, and Ca are associated with the symbiotic bacterium Xenorharbdus sp., suggesting they have potential for use against S. acupunctatus larvae.
Eva Judith Hueso, Jaime Molina-Ochoa, Jalil Fallad-Chávez, Roberto Roberto Lezama-Gutiérrez, Marilú López-Edwards, and Javier Farías-Larios
Jaime Molina-Ochoa*, Eva Judith Hueso-Guerrero, Roberto Lezama-Gutiérrez, Javier Farías-Larios, Francisco Radillo-Juárez, Abraham García-Berbe, and Jalil Fallad-Chávez
The agave weevil (Scyphophorus acupunctatus Gyllenhal) (AW) is widely distributed and is severe pest of plants in the Order Liliales, Familiy Agavaceae, such as Agave tequilana, A. fourcroydes, A. sisalana, A. sp., Polianthes tuberosa, and Yucca sp. Some of these species have importance as ornamental, medicinal, fragrant essence, and raw fiber. AW is controlled with insecticides, but insecticides are unable to reach the larvae in the galleries where the larvae borrows the agave crowns. Galleries are cryptic habitats where the entomopathogenic nematodes are able to infect instars of the AW. Recently, Hueso-Guerrero, and Molina-Ochoa (2004) reported the occurrence of native steinernematid nematodes naturally infecting the AW larvae. Virulence of isolates and strains of steinernematid and heterorhabditid nematodes against AW larvae was determined under laboratory conditions. Three native steinernematid isolates obtained from naturally infected AW larvae (A1, A2, and A3) were bioassayed a concentration of 100 nematodes/mL and petri dish (60 × 10 mm) arenas. Native isolates were isolated from AW larvae attacking agave crowns. Other strains evaluated were: S. carpocapsae All and Mexican, S. riobrave, and Heterorhabditis bacteriophora NC2. Native steinernematid isolates caused 100% mortality, however exotic strains caused mortality ranges between 90%, and 40%. Steinernema carpocapsae All strain, S. riobrave, H. bacteriophora NC2, and S. carpocapsae Mexican strains caused 90%, 60%, 50%, and 40% mortality, respectively. Results suggest that native steinernematid isolates, and S. carpocapsae All strain have potential as biological control agents against the AW weevil.