The effect of nectar production to the gathering behaviour of honeybees and to the foraging activity of wild bees at apple flowers

Intensity of bee visitation (honeybees and wild bees), foraging behaviour of honeybees and nectar parameters (nectar production, sugar concentration, sugar content in nectars) were inspected at 18 apple cultivars for three consecutive years. Honeybee visitation was calculated to be some 3.07 bee visits at a single apple flower a day but wild bee activity was very low, only some 0.11 wild bee visits per flower per day.

The nectar production (nectar content) of apple flowers was fairly different according to the cultivars and the nectar production (nectar content) of flowers was negatively correlated with the sugar concentration in nectar. Interestingly, at the majority of the inspected 18 cultivars the nectar production has shown minor or no changes in the morning and at the afternoon. The nectar production (nectar content) of flowers clearly encouraged the total bee activity at the inspected cultivars (r = 0.54). Bees visited abundant nectars with greater sugar concentration most intensely than lees abundant nectars with smaller sugar concentration.

Nectar parameters, however, affected the activity of honeybees with different types of gathering behaviour in different way. More intense activity by pollen gatherer and mixed behaviour honeybees was observed at cultivars producing abundant nectar (pollen gatherers: r = 0.65, mixed behaviour: r = 0.79). The activity of pollen gatherer honeybees and of mixed behaviour bees, on the other hand, was negatively correlated to the sugar concentration in nectar (pollen gatherers: r = -0.51, mixed behaviour: r = -0.73). This can be explained by the fact that their behaviour was much more affected by the amount of pollen than by any nectar parameters. Accordingly, "mixed behaviour honeybees" should probably rather be called as "pollen gatherers with nectar load" instead of "nectar gatherers with pollen load", as widely used in literature. The activity of ineffective side worker nectar gatherers was greatly encouraged by the sugar concentration in nectar (p = 0.63), similarly to the pure (top) nectar gatherer honeybees (r = 0.72). There was a negative relationship between the nectar production (nectar content) of flowers and the activity of these behaviour classes (nectar gatherers: r = -0.47, side workers: r = -0.36).

Concluding the findings we can state that the activity of pollen gatherers and mixed behaviour honeybees is strongly encouraged by greater nectar production (greater nectar content) of apple flowers. Their activity, however, is mostly dependent firstly on the amount of pollen. This is the reason why the sugar concentration is in a negative relationship to the activity of pure pollen gatherers and mixed behaviour bee. On the other hand, pure nectar gatherers and side worker nectar gatherers are greatly encouraged by the sugar concentration of apple nectar the amount of nectar was not a definite influence on their activity.

Side worker honeybees occurred at each cultivar inspected, however, their ratio varied widely among cultivars. So we can draw the conclusion that, in contradiction with earlier believes, side worker nectar gathering is a general phenomenon at apple flowers. The activity of side workers depends first of all on the relative position of stamens and petals; however, low sugar concentration of nectars can probably moderate their activity but probably do not affect pollen gatherers and mixed behaviour bees.

Wild bee visitation was very low; the wild bee species observed (Osmia cornuta, Andrena flavipes, Anthophora acervorum, Bombus terrestris, Bombus lapidarius and Halictus simplex) comprised some 3.44 per cent of the total bee visitation at apple flowers only. Wild bee visitation was in a positive correlation with the nectar production (nectar amount) of flowers (r = 0,4) and with the sugar content of nectar (r = 0.46) but it was negatively correlated with the sugar concentration in nectar (r = -0,27).

Our result calls the attention to the importance of nectar parameters in the effective honeybee pollination of apple plantations. Most effective pollinating activity of honeybees can be expected in plantations with cultivars of high nectar production because this feature seem so encourage the activity of those behaviour classes (pure pollen gatherers and mixed behaviour bees) that are the most effective pollinating agents among honeybees.

Consumer buying behaviour of fruit and vegetables in the Netherlands

The Dutch Households bought in 2010 compared with the year before a little less vegetables and less fruit. However because of a higher price level the supermarket sales of fruits and vegetables increased with 7% to almost €3 billion. A Dutch household bought 72.4 kilo fresh vegetables in 2010. This is 2% less than in 2009. Tomatoes are the most bought vegetable followed by onion and cucumber. Although the Dutch households bought less vegetables, the spending increased with 5%. The average price of vegetables was 7% higher than in 2009. In 2010 a Dutch household bought almost 88 kilo fresh fruit. Compared with 2009 this was 2% less. Apple is far out the most popular, followed by orange and banana. Also the spending on fruit decreased a little, specially on strawberry, kiwi and banana. The sales of vegetables is realized for almost 90% by the supermarket channel. Albert Heijn has a market share of 38%, followed by Superunie and C1000. Also for fruit the supermarket is the most important retail channel. However fruit is also sold for 20% in grocery stores and markets. The total turnover from supermarkets of vegetables was in 2010 over €2 billion, 8% more than in 2009. 85% of this is fresh product (fresh and pre-treated). Canned vegetables become less popular. The turnover was decreasing 2% to just under €200 million. Green beans are the most popular, followed by peas and carrots. However more money was spend on frozen vegetables (+5%) and pickles (+1%). Over 40% of the supermarket turnover of frozen vegetables is spend on spinach. The supermarket turnover of fruit increased in 2010 with 3% to €1,25 billion. From this 93% is fresh unprocessed fruit. The turnover of pre-treated (washed and sliced) is increasing, but still not more than 3%. Although with a modest share, the spending on frozen fruit also increased in 2010 to €5,5 million. The turnover of canned fruit however was decreasing with 6% compared with 2009. The supermarket turnover of pre-treated fruit was €35 million. Albert Heijn is the absolute market leader for pretreated fruit. In 2010 70% of the sales was realized by Albert Heijn. Mixed fresh pre-treated fruit, mainly fruit salads, account for 40% of the total supermarket turnover of processed fruit. Canned pineapple is the most important canned fruit in supermarkets, followed by fruit cocktail and peach. There is a high degree of awareness of consumers regarding the “must” to use enough fruit and vegetables. Despite of this, consumers do not always eat enough healthy products. Reasons for this are the busy life of the modern young people and the perception that vegetables are “not easy” to use. Therefore preparing a meal has to be easy and fast with suitable products Here is an important task for concept and product development.

Honeybee (Apis mellifera L.) visitation at the flowers of quince cultivars (Cydonia oblonga Mill.)

Studies were made on the bee visitation of 6 quince cultivars and on the foraging behaviour of honeybees at quince flowers for 3 consecutive years. The bee visitation was highly intense because both the plantation and its surrounding was overpopulated by honeybee colonies. Some 5.5 bee visits were counted in average at 50 opening quince flowers in 10 minutes and some 9.7 flowers were visited of the 50 ones observed meanwhile. This equals some 7 bee visits per flower per day per in good weather. Bee visitation, however, was variable and it was greatly different in the three consecutive years with fairly favourable weather. Some cultivars tended to be more and others less visited by honeybees than the others but these differences were not consequent at each occasion. No consequent relationship between the weather and the bee visitation of quince trees could be recognised. It was concluded that .other factors were responsible for the variable nature of the bee activity at quince. Most honeybees tended to collect pollen (51.6% in average for the 3 years) and usually much less gathered for nectar only (19.9%), and the rest of them were mixed behaviour foragers gathering for both (28.5%). There were some slight differences in the foraging behaviour of honeybees at some cultivars but these differences were not always consequent in consecutive years. Also the nectar production of flowers failed to affect the bee visitation and the foraging behaviour of honeybees definitely. For the variable nature of bee visitation and bee behaviour at quince flowers, supplementary pollination is needed to achieve as high set of fruits as high is required to a good crop at quince (at least 20-25% because the flower density is low of this fruit tree species). Since the intensity of bee visitation at the flowers is the only reliable estimate of the necessity of supplementary bee pollination further research is needed to explore the relationship between the number of honeybee visits and the consequent fruit set at quince.


Flower constancy of honeybees (Apis mellifera L.) to blooming pear plantations

Studies were made on the composition of pollen loads of honeybees captured at the flowers of blooming pear trees in pear plantations. Also the foraging behaviour of honeybees was observed. Overwhelming majority of honeybees visiting the flowers of 13 pear cultivars in 1996 were pollen gatherers (95.6 per cent). Proportion of pure nectar gatherers was as low as some 3.7 per cent and no more than 0.7 per cent performed mixed behaviour. The analysis of pollen loads of bees collected at pear flowers in blooming pear plantations showed that fidelity was as high as 89-90 per cent towards pear, higher than for another fruit species in other studies. Even those plant species that are regarded to be strong competitors of blooming fruit trees in the literature (Taraxacum officinale, Stellaria media, Lamium purpureum) were scarcely represented in the loads. Accordingly, honeybees can be much more important and more effective pollinating agents of pear cultivars than generally believed.


Flower characters and self-fertilization capacity in relation to the bee pollination at sour cherry cultivars

Detailed studies and comparisons were carried out on those flower characters of sour cherry cultivars that may affect bee pollination of flowers. Flower characters of sour cherry are fairly similar to other temperate zone fruit tree species. Their relatively small flowers distinguish the Cigánymeggy-types of cultivars from the flowers of tart cherries cultivars that are conspicuously larger, almost as large as the sweet cherry flowers. The relative position of flower organs was much more variable according to the season than according to the cultivars. So the differences were rather the consequences of seasonal effects than of variety features of sour cherry cultivars. As far as individual cultivars are concerned differences in the nectar production and the sugar concentration are revealed rather between groups of cultivars than between individual cultivars. The pollen production of flowers was extremely changeable in consecutive years. Most honeybees collected nectar at sour cherry flowers; pure pollen gatherers and mixed behaviour bees were half as frequent but differences among the behaviour of honeybees according to cultivars cannot be stated. The fidelity of honeybees to sour cherry is less expressed than to some other fruit tree species. Accordingly, it is very strongly suggested to take the competitive effect other plant species (weeds) flowering in and around the orchard carefully into account when organizing additional bee pollination in sour cherry plantations. Several sour cherry cultivars possess more or less self-fertilization capacity but this is greatly changeable according to the season. It has been proved that self-sterile sour cherry cultivars are sensitive even on the partial restriction of the effective time of bee pollination and it is to be stressed too that even in the case of partly self-fruitful cultivars bee pollination is also vital in yield formation because medium or strong restriction of the effective bee pollination period is of a definite negative effect on their fruit set and yield. In years with unfavourable weather the yield can dramatically be reduced sometimes down to nil. However, very high fruit set is also unfavourable because a negative correlation was detected between the final set and the mean mass of fruits.

Effect of intensity of bee visitation and the foraging behaviour of honeybees on the fruit set and yield of apple (Malus domestica Borkh.)

Based on the results of our experiments, both the relative and the effective intensity of bee visitation were rather different depending on the cultivars as well as the time of the day. While it varied between relatively extreme values (40-80%) in the morning for the varieties examined, there were much smaller differences between the intensity of bee visitation at the afternoon, because the relative bee visitation attained 70-90% at each cultivar. These results showed that the differences arising from intensity of bee visitation of different cultivars should be taken into consideration more carefully in the morning in orchard planning and in estimating the number of honeybee colonies required.

The results showed that the greatest percentage of fruit set and the highest number of viable seeds per fruit were measured on branches of those cultivars that were most frequently visited by pure pollen gatherer bees as well as by bees collecting both nectar and pollen (mixed behaviour). The effect of pure pollen gatherers and of bees with mixed behaviour was highly significant from the statistical point of view on the fruit set and the number of viable seeds per fruit.

Those bees that were sucking nectar only from apple flowers did not proved to be effective pollinators at all. Relationship between their number and the fruit set as well as the number of viable seed per fruit were not significant because the coefficient of correlation was close to nil.

The ratio of side worker nectar gatherers was negatively correlated with the fruit set and the seed content of fruits of apple cultivars examined at both of our experimental sites, at Mosonmagyaróvár and Feketeerdő as well. The presence of side worker nectar gatherers resulted in higher decrease of fruit set and seed content of fruits at Feketeerd6 than at Mosonmagyaróvár, especially in the morning.

The effect of flower visiting intensity by other pollinating insects was found to be fairly variable according to the time of the day. In the morning they had no effect on the fruit set as well as on the seed content of fruits either at Mosonmagyaróvár or at Feketeerdo. However, at the afternoon, when their intensity was greater, the correlation was a bit stronger.