Print version ISSN 0103-9016
Sci. agric. vol. 54 n. 1-2 Piracicaba Jan./Aug. 1997
FLIGHT RANGE OF AFRICANIZED HONEYBEES, Apis mellifera L. 1758 (Hymenoptera: Apidae) IN AN APPLE GROVE
B.A.J. PARANHOS1; J.M.M. WALDER2; J. CHAUD NETO1
1Instituto de Biociências, UNESP, C.P. 199, CEP: 13506-900 - Rio Claro, S.P.
2Centro de Energia Nuclear na Agricultura-USP, C.P. 96, CEP: 13400-970 - Piracicaba, S.P.
SUMMARY: Africanized honeybees from five colonies were marked with P-32 and taken to an apple grove for a flight behavior study. The method used to determine the flight range was to put out an array of tagged trees in a cross pattern with the colonies arranged in the center point of a 0.8 ha test area. The tagged trees were located 10 meters apart in the 4 rows of 50 meters each, arranged according to the North, South, East, and West directions. Bees were collected while visiting the tagged tree flowers twice a day, during a ten-day period. The number of honeybees marked decreased in relation to the distance from the hives. Analysis of variance showed that a linear regression was highly significant to describe the process. Geographic directions did not affect the activity of the bees.
Key Words: honeybees, flight range, radiophosphorus
RAIO DE VÔO DE ABELHAS AFRICANIZADAS Apis mellifera L. 1758 (Hymenoptera: Apidae) EM POMAR DE MAÇÃ
RESUMO: O estudo do raio de ação das abelhas na coleta de néctar e pólen é de extrema importância para se saber até que distância a polinização por este inseto é promovida com eficiência. Para tanto, cinco colônias de abelhas africanizadas marcadas com 32P foram levadas a um pomar de maçã, sendo agrupadas no centro de uma área de 0,8 ha, a partir do qual foram colocadas estacas a cada 10m, formando quatro alas correspondentes às direções Norte, Sul, Leste e Oeste. As abelhas foram capturadas duas vezes por dia e por dez dias consecutivos, quando visitavam as flores das macieiras, até 50m do centro. Verificou-se que o número de abelhas marcadas coletadas, diminuiu linearmente à medida em que as mesmas se afastavam das colméias. Não houve interferência das orientações geográficas no comportamento de vôo das abelhas.
Descritores: abelhas, raio de vôo, radiofósforo.
Bees are among the most important beneficial insects due to honey production and flower pollination. Studies by Brittain (1933) showed that the bee visits decrease, the further the colony is from the plant. But, according to Free (1960) the scope area of a colony depends on factors such as: amount of available pollen and nectar per unit area; different species attractiveness and cultivars present; climate conditions; and physical characteristics of the site. That author recommends that the beehives should be placed as close to blossom as possible in order to obtain a higher number of visits.
According to the observations of Krezdorn (1972), for hives located 150 to 200 m apart, the bee flight foragers can be doubled. Benedek et al. (1972) studying the influence of bees on apple pollination, using screened and non screened branches at different distances (20, 60, 150, 300 and 600 m) from hives, observed a higher number of fruits on non screened branches, but decreasing in number according to the higher distances. The covered branches yielded less but heavier fruits.
While working with radio-labeled bees in different environments Amaral (1972) and Pacheco (1982) observed a similar decrease in flight activity up to 100m distance. Also, according to Waller (1980) bees may travel several miles for foraging, but the probability of a visit to certain crops decreases as the distance from the apiary increases. By placing beehives at 100 and 900m from an alfalfa crop Kozin & Reznitskii (1980) reported a production twice as high as in the closer site. Farkas (1981) obtained higher cherry yield when honeybees hives were at 50 m than when 105 m from the orchard. The author also estimated losses of 1.2 kg of cherry yield for each 14 m from the hives.
Orlowski et al. (1982) studying cabbage pollination by honeybees observed a decrease in production related to the distance of the apiary from the cabbage field. A yield of 1920 kg/ha of cabbages was obtained for crops 20 m away from the hives, and those 1700 m the production was 1270 kg/ha.
Jankovic & Kulincevic (1985) observing the effects of bees on crop production and fruit quality in a pear grove, found that the production was higher when the beehives were located 50 to 100 m from the trees but, for higher distances, the production decreased.
Mijacika & Konstantinivic (1986) testing the effect of the hive distances (5 to 440 m) from an apple orchard on flower pollination, observed that the fertilization index, fruit establishment, seed numbers per fruit and fruit production were all adversely affected by distance from hives. Similar results were found by Garcia (1987) who observed high pollination efficiency in trees located no more than 125 m from the hives. Ferrari (1990) also observed the preference of bees to forage trees located 90 to 150 m from hives.
MATERIAL AND METHODS
Five hives, of about 35,000 bees each, were labeled using a Boardman feeder with radioactive phosphorus in a 50% w/v sugar solution. Each hive received 300 mL of the syrup with 2.5 mCi/mL of 32P (Sodium phosphate monoacid). The radioactive syrup was completely consumed by the bees within 48 hours and, thereafter, the hives were taken to the blossomed orchard of apple cv "Anna". Inside the grove, a 100 m diameter circle area (0,8ha) was chosen as the experimental site. The tagged trees were located 10 m apart in 4 rows of 50 m each, arranged according to North / South and East / West directions. Wide opening glass containers with ether soaked filter paper inside were used to collect the bees during a 5 minutes period while visiting the tagged tree flowers two times a day. This pattern was repeated during 10 consecutive days.
In the laboratory the labeled insects were separated from the not labeled through the measurement of radioactivity, as counts per minute less background, using the Cerenkov effect in a liquid scintillation spectrometer (Beckman LS 230).
The experimental design was a split plot experiment, plots being the directions (4), sub-plots the distances (5) with 20 replications (2 collections per day during 10 days period) and the variables were the labeled and wild bees captured.
Bee capture data were transformed (square root of x + 0.5) for the analysis of variance (ANOVA). Once significant, the capture data were analyzed using polynomial regression (SAS, 1990). Correlation between bee capture and distance or directions was examined by Pearson correlation matrix (SYSTAT).
RESULTS AN DISCUSSION
The analysis of variance indicated a significant statistical difference between the number of marked bees collected at the chosen distances (F = 7.22**; P >0.001). On the other hand, the factor direction was not significant, indicating that the bees had no preferential direction. The distribution of the radio-marked bees within the experimental area fits in a linear model (F = 26.55*). The calculated equation is: Yi = 51.47 - 0.477 Xi (r2 = 0.62), where Y is the mean number of bees captured and X is the distance from the hives. These results are in agreement with those reported by Brittain (1933), Amaral (1972), Benedek et al. (1972), Farkas (1981), Pacheco (1982) and Mijacika & Konstantinovic (1986).
For a broader view of the relationship between marked bees (32P) and wild bees, a correlation matrix of Pearson type was constructed (TABLE 1).
The analysis presented in TABLE 1 reveals an inverse response for (32P) bees and wild bees, indicating that as the distance increases, the number of marked bees decreases, while that of wild bees increases (Figure 1). No significant correlation occurred between geographic directions and bee capture data, suggesting a random flowers bee visit (Figure 2). This was expected since the wild bees had to come from close apiaries, and the longest distance flown by the marked bees was the shorter for the wild bees in the studied site.
Figure 1 - Marked and wild bees captured on flowers as a function of proximity to apiary.
Figure 2 - Distribution of honeybees in North, South, East and West direction.
Bees prefer to collect nectar and pollen from flowers closer to their hives and their activity decreases following a linear model. There was no preference of the bees concerning the North, South, East or West directions.
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Recebido para publicação em 30.01.96
Aceito para publicação em 09.12.96