Susceptibility of the cactus weevil Metamasius spinolae to Beauveria bassiana and Metarhizium anisopliae under laboratory and field conditions.

AIMS: To evaluate different entomopathogenic fungal isolates against the cactus weevil Metamasius spinolae under laboratory and field conditions, and select an isolate to be used as a tool in the management of this insect pest. METHODS AND RESULTS: Four experiments were carried out. The effect of temperature on the in vitro growth of eight isolates of entomopathogenic fungi (two Metarhizium anisopliae and six Beauveria bassiana) was assessed. The susceptibility of adult M. spinolae to the same isolates was evaluated. Using three selected isolates, the interaction between susceptibility and sex of the insect was studied. Finally, a field experiment was carried out to evaluate infection of adult M. spinolae by the same three isolates under natural abiotic conditions. Overall, growth rate was greatest at 25°C for all the isolates. In vitro growth of M. anisopliae was greater than B. bassiana. Mortality of adult M. spinolae was greater when inoculated with B. bassiana compared with isolates of M. anisopliae. Susceptibility had no interaction with the sex of the insect. The proportion of insects succumbing to infection was smaller when incubated under field conditions than when incubated under laboratory conditions. CONCLUSIONS: The experiments described here showed a complex interaction between entomopathogenic fungi and M. spinolae, and these data allows us to select isolate Bb107 as a first step towards its use in the management of this pest insect. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results showed that entomopathogenic fungi can be used for the control of M. spinolae, which may help reduce the use of chemical insecticides and, therefore, the exposure of Opuntia ficus-indica producers to pesticides.

Does Foraging Experience Affect the Responses of the Predator Dicyphus hesperus Knight to Prey-Induced Volatiles?

The predatory mirid bug Dicyphus hesperus Knight (Hemiptera: Miridae) is a native North America species with high potential as biological control agent of the potato psyllid, Bactericera cockerelli Sulcer (Hemiptera: Triozidae), which is a major solanaceous pest. Olfactory responses of D. hesperus to volatiles from plants infested with the potato psyllid and the effect of foraging experience on search efficacy were studied. Using a Y-tube olfactometer, we found that naïve females had no preference in choice tests between either uninfested tomato plants, or Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs-infested plants, and clean air. Naïve females showed an innate positive response to B. cockerelli-infested plants, but no preference when given a choice between uninfested tomato plants and E. kuehniella eggs-infested plants. However, females with experience of foraging on B. cockerelli-infested plants showed a strong preference for B. cockerelli-infested plants (78% response) in choice tests with uninfested tomato plants and E. kuehniella eggs-infested plants. Implications of learning for augmentative biological control are discussed.

Improved Sweetpotato Whitefly and Potato Psyllid Control in Tomato by Combining the Mirid Dicyphus hesperus (Heteroptera: Miridae) With Specialist Parasitic Wasps.

Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) and Bactericera cockerelli Sulcer (Hemiptera: Psyllidae) are important pests in tomato, and the mirid Dicyphus hesperus Knight (Heteroptera: Miridae) has been shown as an effective predator of both pests. Although the predator was able to suppress populations of both pests, the remaining levels could still exceed tolerable levels. Thus, we here hypothesized whether the combination of D. hesperus with the specialist parasitoids Eretmocerus eremicus Rose y Zolnerowich (Hymenoptera: Aphelinidae) (whitefly) and Tamarixia triozae (Burks) (Hymenoptera: Eulophidae) (psyllid) would result in better pest control on a greenhouse scale. For that, we conducted a trial in which we compared the results against B. tabaci and B. cockerelli in greenhouses treated with D. hesperus alone or the predator in combination with the specialist parasitoids. The results showed that the predator was able to establish and suppress B. tabaci and B. cockerelli in tomato, but the addition of the specialist parasitoids resulted in better and more cost-effective pest control. Implementation of this method would therefore increase the robustness and reliability of biocontrol-based integrated pest management programmes for tomato crops, over methods based exclusively on D. hesperus release.

Specific Diversity of Metarhizium Isolates Infecting Aeneolamia spp. (Hemiptera: Cercopidae) in Sugarcane Plantations.

Spittlebugs from the genus Aeneolamia are important pests of sugarcane. Although the use of the entomopathogenic fungus Metarhizum anisopliae s.l. for control of this pest is becoming more common in Mexico, fundamental information regarding M. anisopliae in sugarcane plantations is practically non-existent. Using phylogenetic analysis, we determined the specific diversity of Metarhizium spp. infecting adult spittlebugs in sugarcane plantations from four Mexican states. We obtained 29 isolates of M. anisopliae s.str. Haplotype network analysis revealed the existence of eight haplotypes. Eight selected isolates, representing the four Mexican states, were grown at different temperatures in vitro; isolates from Oaxaca achieved the greatest growth followed by isolates from Veracruz, San Luis Potosi and Tabasco. No relationship was found between in vitro growth and haplotype diversity. Our results represent a significant contribution to the better understanding of the ecology of Metarhizum spp. in the sugarcane agroecosystem.