Gabriel Otero-Colina

Resistance to amitraz and flumethrin in Varroa destructor populations from Veracruz, Mexico

SUMMARY Dose response curves were determined for amitraz and flumethrin for Varroa destructor collected near Veracruz city, Mexico. Both pesticides were sprayed at known concentrations on female mites using a Burgerjons tower. Probit analysis was performed to calculate mean lethal concentrations (LC50). We estimated the LC50 for amitraz to be 0.526 mg/litre; this estimate is 2.3-times higher than the LC50 baseline established nine years earlier in Mexico. The LC50 for flumethrin was estimated as 0.286 mg/litre, 327-times higher than the LC50 baseline, suggesting the development of resistance.

Comparing effects of three acaricides on Varroa jacobsoni (Acari: Varroidae) and Apis mellifera (Hymenoptera: Apidae) using two application techniques.

Two bioassays were administered to determine the dose-lethality response of Varroa jacobsoni Oudemans and the honey bee, Apis mellifera L., to amitraz, flumethrin and fluvalinate. The first bioassay method was spraying by means of the Potter-Bourgerjons tower. The results are expressed in mean lethal concentrations (LC50). The second method was topical application by means of microsyringe and manual applicator. The results are expressed in mean lethal doses (LD50). Both LC50 and LD50 values were considerably higher in honey bees than in varroa mites, showing that a wide margin of safety exists between effective doses against mites and harmful doses for honey bees. Both methods gave similar confidence intervals; they showed a comparable sensitivity to changes in dose or concentration of pesticides.

Susceptibility of Varroa destructor (Gamasida: Varroidae) to four pesticides used in three Mexican apicultural regions under two different management systems

ABSTRACT Mexico has five apicultural regions wich are defined according to their blooming period and geography. Varroa destructor Anderson and Trueman is controlled with pesticides and alternative treatments in all these regions. To determine the concentration-mortality response lines of V. destructor, bioassays with four pesticides that are used for its control in the Gulf of Mexico, Yucatan Peninsula and Central-Highland regions were conducted. The Burgerjon spraying tower was used to apply known concentrations of flumethrin, fluvalinate, amitraz and coumaphos. Lethal concentrations 50 (LC50) and resistance indexes were calculated with Probit analyses. In the Gulf region, the resistance indexes were: flumethrin, 659.43; fluvalinate, 21.83; amitraz, 12.77; coumaphos, 1.49×. In the Central-Highland region: flumethrin, 243.43; fluvalinate, 19.04; amitraz, 8.56; coumaphos, 1.22 x. In the Yucatan Peninsula region: flumethrin, 4057.32; fluvalinate, 199.57; amitraz, 26.55; coumaphos, 3.93×. These results suggest a resistance to flumethrin, fluvalinate and amitraz, with similar values in migratory beekeeping regions, and higher values in the non-migratory region. Coumaphos remained effective in V. destructor populations of the Gulf and Central-Highland regions.

Life tables and thermal constants of Pediculaster mesembrinae (Acari: Siteroptidae) fed on the Fungus, Trichoderma harzianum Rifai

Abstract Life and fecundity table studies on Pediculaster mesembrinae (Canestrini) (Acari: Siteroptidae) were conducted under controlled conditions (15, 20, 25 and 30°C, relative humidity 60 ± 5 %), using cohorts of 40 individually confined mites in observation arenas. Fermented wheat straw (compost) previously inoculated with Trichoderma harzianum Rifai spores was used as substrate and food source. The study started with mite eggs approximately 5 h old. The life cycle of P. mesembrinae included the stages of egg, larva, quiescent larva or nymphocrysalis, and adult; only females were observed in our population. The length of the life cycle, as well as total longevity, showed an inverse (linear) relation with temperature. Values of rm (intrinsic rate of increase) were 0.146, 0.132, 0.170 and 0.204, for 15, 20, 25 and 30°C, respectively. Developmental rates had a direct and linear relationship with temperature; and threshold temperatures ranged between -0.53 and -3.22°C. Development from egg to adult required 152 degree days.

Transmission of viruses associated with cytoplasmic and nuclear leprosis symptoms by Brevipalpus yothersi and B. californicus

Two groups of viruses cause the citrus disease complex known as leprosis: the cytoplasmic type, of the genera Cilevirus and Higrevirus, and the nuclear type, of the genus Dichorhavirus. It has been shown that the cilevirus Citrus leprosis virus C (CiLV-C) is transmitted by Brevipalpus yothersi. Within the genus Dichorhavirus, CiLV-N is a recently described and distinct species present in Brazil and transmitted by B. phoenicis sensu stricto, whereas the species found in Mexico and Colombia are strains of Orchid fleck virus (OFV-citrus), suspected to be vectored by B. californicus. A study was conducted to determine whether B. californicus and B. yothersi can acquire and inoculate Mexican isolates of CiLV-C and OFV-citrus to sweet and acid citrus species (sweet orange, mandarin, grapefruit, sour orange, Persian lime and Mexican lime) in experiments set up in areas in Mexico with prevalence of the respective viruses. Brevipalpus californicus acquired OFV-citrus and transmitted it to all the citrus cultivars included in the experiment, while B. yothersi acquired CiLV-C and transmitted it only to sweet citrus cultivars (sweet orange, mandarin, and grapefruit). Both mite species were able to become established and reproduce in the experimental plants for nearly a year. This study represents the first experimental evidence of OFV-citrus transmission by B. californicus, as well as evidence that B. yothersi cannot transmit this virus.

Effects of neem (Azadirachta indica) on honey bee workers and queens, while applied to control Varroa destructor

The objective of this study was to determine the effect of neem (Azadirachta indica) oil on mortality and development of honey bee worker brood, queen oviposition, colony performance, and Varroa destructor mortality. As a hypothesis it was indicated that adequate concentrations of neem oil may control V. destructor without affecting bee colonies. Neem oil at concentrations of 0.33–21.1%, with 7.26–464.64 mg l−1 azadirachtin, was sprayed on bee (Apis mellifera) combs. Their effects on mortality and developmental time of the brood, worker bee response on feeding and capping the larvae, and number of eggs laid by the queen were quantified. A 21.1% oil concentration resulted in 100% egg mortality, but lower concentrations resulted in minimal egg mortality. Larvae that reached the fifth instar were capped and survived the presence of the oil, but when 21.1% was applied, their development was delayed one to two days. With concentrations of 5.3 and 10.6% (116.2 and 232.3 mg l−1 of azadirachtin, respectively), queen oviposition was not significantly different from the control, but 10.6% slightly decreased oviposition. The highest V. destructor mortality (85%) was proportional to the concentration and number of spray applications. When neem oil was applied to hives, none of the concentrations used decreased bee population, capped worker larvae or the reserves of honey and pollen. However, two queens died after one application of 5.3% and three applications of 10.6%.