Rafael A. Calderón

Reproductive biology of Varroa destructor in Africanized honey bees (Apis mellifera)

Since its first contact with Apis mellifera, the population dynamics of the parasitic mite Varroa destructor varies from one region to another. In many regions of the world, apiculture has come to depend on the use of acaricides, because of the extensive damage caused by varroa to bee colonies. At present, the mite is considered to contribute to the recent decline of honey bee colonies in North America and Europe. Because in tropical climates worker brood rearing and varroa reproduction occurs all year round, it could be expected that here the impact of the parasite will be even more devastating. Yet, this has not been the case in tropical areas of South America. In Brazil, varroa was introduced more than 30 years ago and got established at low levels of infestation, without causing apparent damage to apiculture with Africanized honey bees (AHB). The tolerance of AHB to varroa is apparently attributable, at least in part, to resistance in the bees. The low fertility of this parasite in Africanized worker brood and the grooming and hygienic behavior of the bees are referred as important factors in keeping mite infestation low in the colonies. It has also been suggested that the type of mite influences the level of tolerance in a honey bee population. The Korea haplotype is predominant in unbalanced host-parasite systems, as exist in Europe, whereas in stable systems, as in Brazil, the Japan haplotype used to predominate. However, the patterns of varroa genetic variation have changed in Brazil. All recently sampled mites were of the Korea haplotype, regardless whether the mites had reproduced or not. The fertile mites on AHB in Brazil significantly increased from 56% in the 1980s to 86% in recent years. Nevertheless, despite the increased fertility, no increase in mite infestation rates in the colonies has been detected so far. A comprehensive literature review of varroa reproduction data, focusing on fertility and production of viable female mites, was conducted to provide insight into the Africanized bee host-parasite relationship.

Presence of deformed wing virus and Kashmir bee virus in Africanized honey bee colonies in Costa Rica infested with Varroa destructor

Newly emerged bees with damaged wings, bees crawling in front of the hive and unusually severe adult bee mortality were observed in Africanized honey bee colonies in Costa Rica. A large proportion of the adult bee population in most of these colonies was infested with Varroa destructor. Adult bee samples were sent to the Department of Entomology, Penn state university, for virus analysis. This analysis showed the presence of deformed wing virus and Kashmir bee virus. The occurrence of adult bee mortality and the detection of these viruses in Africanized colonies in Costa Rica infested with V. destructor, should be considered as a cause of concern.

The reproductive ability of Varroa destructor in worker brood of Africanized and hybrid honey bees in Costa Rica

SUMMARY From February to July 2001, the reproductive ability of Varroa destructor in artificially infested worker brood cells of Africanized honey bees (AHB) (Apis mellifera) and hybrids (HF1) of AHB X European honey bees was investigated in Costa Rica. No significant differences were found between AHB and HF1 in the percentage of fertile foundress mites (AHB = 69.8%, HF1 = 76.5%), the percentage of foundress mites that produced mature female offspring (AHB = 28%, HF1 = 25.4%), the mean number of offspring per foundress (AHB = 3.4, HF1 = 3.5) and the percentage of foundress mites that produced only immature stages (AHB = 17.3%, HF1 = 18.2%). Nevertheless, the percentage of foundress mites that did not reproduce at all tended to be greater in AHB than in HF1 colonies (AHB = 30.2%, HF1 = 23.5%; P = 0.06). In both groups of bees, the number of fertile mites was higher than that reported in other studies for AHB in Brazil (49–55%). Furthermore, the percentage of non-reproducing mites was greater than the percentage reported for mites in European bees and lower than the percentage reported for mites in AHB in Brazil. Thus, the AHB population we monitored in this study may be less tolerant to varroa than AHB populations in Brazil.

Chalkbrood (Ascosphaera apis) and some other fungi associated with Africanized honey bees (Apis mellifera) in Costa Rica

fungal diseases in Africanized honey bees (AHB) in Costa Rica. Chalkbrood is a fungal disease that occurs in larvae of the honey bee (Apis mellifera). It is caused by Ascosphaera apis, a heterothallic organism that sporulates only when mycelia of opposite strain come together (Gilliam & Vandenberg, 1990). This fungal disease is not considered a serious problem in many countries, and it is generally reported as a transient condition (Gilliam & Vandenberg, 1990). Although experiments have shown that brood is most susceptible to infection when it has been chilled, chalkbrood can occur even in warm climates when colonies have insufficient adult bees to incubate their brood adequately (Bailey & Ball, 1991). The sudden loss of adult bees following infestation with Varroa destructor may, as a consequence, indirectly increase chalkbrood even in the warmer climates (Medina & Mejia, 1999).

Detection of the mite Varroa destructor in honey bee cells by video sequence processing

It is presented an algorithm for detecting and tracking a mite, from videos provided by the Centro de Investigación Apícola Tropical (CINAT-Costa Rica). These registrations correspond to the presence of the Varroa destructor mite in an Africanized honey bee cell, in a controlled environment. The main objective in this paper is to present the various stages of development of the algorithm and show the results obtained in the percentage of success in detecting. Therefore, we have implemented a calibration system in order to have a frame more enhanced versus the original video. This calibration is done by the searching of the Movement Active Area and definition of our object (the mite V destructor), and finally, an automatic detection and tracking are done. We have reached up to 93.75% for right detection and tracking, working on real time under a Matlab environment.

The reproductive rate of Varroa destructor in drone brood of Africanized honey bees

Summary The reproductive rate of Varroa destructor was measured in drone brood of Africanized honey bees (AHB) in Costa Rica. One mature female mite was introduced into a drone cell within 6 h of the cell being capped. Data were obtained from 304 artificially singly infested drone cells from six colonies. Fertility of varroa mites (i.e., those that produced any offspring) was 95.1%. Fifty-three percent of the foundress mites produced viable female offspring. The number of potentially mated female offspring produced per foundress was 2.6 ± 1.0. Eight percent of foundresses produced only immature offspring, 26.5% produced only a female offspring and 7.6% produced only a male offspring. In cells with both female and male offspring, the male or the female was found dead in 8.7% of the cases; male mortality was 6.1%. Although varroa fertility in drone brood was significant in AHB colonies, factors that limited mite reproduction were the absence of a male and the mortality of a male in more than 26.0% of the drone cells.

Cognitive Modeling of the Natural Behavior of the Varroa destructor Mite on Video

The present work offers an innovative and automatic approach for detecting, tracking, analyzing, and reporting the natural behavior of the Varroa destructor mite and its activity from videos provided by the Tropical Apicultural Research Center (CINAT) in Costa Rica. These videos correspond to the presence of V. destructor in capped Africanized worker honeybee cells in a controlled environment. The main objective of this paper is to present an automatic report of the identification of the mite behavior based on mite information (bioinspired information). First, a calibration system was implemented to enhance the frame. This calibration was achieved by searching the movement-active area (MAA) and the geometrical definition of the V. destructor mite. Then, an automatic detection and tracking was applied. Finally, an automatic classification was used to establish the mite activity. This approach reached up to 92.83% for all processes: detection, tracking, behavior analysis, and activity reporting, in real time and showing a cognitive model of the mite. The proposed approach provides an automatic tool and objective measurement against manual and qualitative methods traditionally applied in this kind of analysis, with a significant potential to be used as a reference in the modeling of the behavior of the V. destructor mite.

Control del ácaro Varroa destructor en cría sellada de obrera al utilizar ácido fórmico y timol, en colmenas de abejas africanizadas, bajo condiciones tropicales. Nota Técnica

The mortality of the Varroa destructor mite was evaluated in capped worker brood cells by using formic acid and thymol in Africanized honey bee colonies. The apiary was located in Atenas, Alajuela, Costa Rica, and was randomly arranged in three groups: A, B and C. Group A was treated with 150 g formic acid at 65%, while group B received two applications of 25 g thymol, and group C was used as a control group. Mortality of the Varroa’s different stages was evaluated in capped worker brood cells by checking the pupa and the bottom of the cell for mites. Eighty-six percent mite mortality occurred in capped brood cells in colonies treated with formic acid, while Varroa mortality was less than 10% in capped cells for control colonies and colonies treated with thymol. In conclusion, high mortality of Varroa mites was observed in capped brood cells after applying formic acid, while mortality was low in control colonies and colonies treated with thymol. The foregoing could imply a direct effect of formic acid over mites in capped brood cells.