Bee Culture - April, 2003

by Joe Traynor

I have been a student of pollination for a number of years. When I first got started, I would attend meetings and read books on the subject. One of the first things I learned was that bees increased the seed set and yield of fruit with multiple ovules. There are a number of examples: apples, pears, cantaloupes, watermelons and certain varieties of tangerines.

Pictures and tables show a dramatic correlation between the size, shape and weight of a fruit and the number of seeds that fruit contains. A perfectly shaped apple, for example, will have a full complement of seeds, as will a perfectly shaped melon. Slice a lopsided fruit in half and you will invariably find fewer seeds on the puny side, more on the fully developed side. Each seed represents the union of a pollen tube from a single pollen grain with a single ovule. The more pollen that is transferred by bees, the more seeds in a fruit and the larger and more uniform the size and shape of the fruit. It was a concept I could grasp fairly easily, and one that growers could also grasp. Once grasped, it was not difficult to convince growers that more bees or stronger colonies was a good investment if high yields of well-shaped fruit were desired.

California tangerine growers bought into this concept, and 25 years ago I was paid by a tangerine grower to place bees in his grove during bloom in order to assure a good set of fruit (he had a variety that required cross-pollination to set a commercial crop). The grower was happy with his crop and received a good price for it even though the tangerines contained numerous seeds.

Things have changed since that time and in today's market place seedy mandarins (tangerines are in the mandarin family) are a liability - the consumer doesn't want seedy fruit. A mandarin with over two seeds is considered "seedy" by many packing houses and if they accept the fruit at all, they pay a reduced price for it. The unstoppable shift in consumer preference toward seedless produce (e.g., grapes and watermelons) makes it a whole new ball game for today's mandarin grower.


This mandarin (Encore variety) will be difficult or impossible to sell. (photo from U.C. Bulletin 814)​

The Clementine mandarin has proven popular in recent years due to its intense flavor and zipper skin. The U.S. imports many Clementines from Spain, Morocco and New Zealand. Unfortunately, Clementine mandarins produce seeds when bees are present (although they also produce a lot of seedless fruit, even in the presence of bees - see side bar).

California mandarin growers are now attempting to keep honey bees two miles away from their groves -a difficult task in the San Joaquin valley where citrus groves are checker boarded on the east side of the valley from Bakersfield to Fresno. Beekeepers are losing long-held locations even when not directly parked on a mandarin planting because the owners of the property the bees are on want to get along with their mandarin neighbors. Citrus honey is the backbone of California's bee industry and if mandarin growers are successful in displacing beekeepers, the results would be devastating to beekeepers.

This mandarin (Pixie variety) will command a premium price in the market. (photo from U.C. Bulletin 814)​

Perhaps California mandarin growers took their cue from Spain where legislation in the Valencia district requires the bees to be kept three miles from any Clementine mandarin planting. In contrast, mandarin growers in Morocco have come up with a botanical solution: certain pollen producing varieties must be removed from Clementine mandarin areas.

It will be interesting to see how the current imbroglio plays out. A botanical solution seems the most likely since there are now a number of mandarin varieties that produce close to 100% seedless fruit, even in the presence of bees and other pollen sources - these seedless varieties have sterile ovules. Growers with seedy fruit can graft over to these seedless varieties. There is a precedent for such a solution: seeded grape varieties have been grafted over (or replanted) to seedless varieties. Twenty years ago many thought it impossible to develop a seedless red grape or a seedless watermelon. Today, both dominate in the marketplace over seeded varieties. Mandarin varieties that are seedless, even in the presence of bees, should dominate the U.S. mandarin market. What is needed is a mandarin with the market qualities of Clementines that also has sterile ovules.


Kern county, California, is a major watermelon area. Melons are planted early each Spring so that they are harvested by the July 4 holiday market. Twenty years ago, I tried to convince watermelon growers to use bees, plying them with literature and university studies showing that watermelon fields on which bees were placed had higher yields due to the increased size of melons which in turn was due to a greater number of seeds.

All watermelon varieties had seeds at that time and most growers didn't place bees. The one grower I convinced to try bees did so for only one year because his melons got too big and the trade wanted a melon that would fit handily in a refrigerator (the monster melons of years past are difficult to find today).

Today, virtually all watermelon growers in Kern county plant seedless varieties and, ironically, all of them use bees. In order to set marketable fruit, seedless watermelons must have the stimulus of pollen. As Roger Morse put it "Apparently, pollen carried to a female watermelon flower's stigma by a bee grows and reaches the seed, but at that point the seed aborts; however the growing pollen has done its work and stimulated fruit growth" (Bee Culture, April 2000, p. 14). There is no need to sell seedless watermelon growers on the need for bees because seed companies do the selling job for the beekeeper. Seedless watermelon seed is quite expensive and seed companies insist that growers use bees if they want a commercial crop. Quite a change from 20 years ago.

The same stimulus from pollen increases set and size on seedless mandarin varieties including an increased set of seedless fruit on the popular Clementine variety (Ann. Abeille, 1964, 7:63-80). Growers desiring this stimulus should be encouraging beekeepers to place bees by their plantings. If so, beekeepers currently treated as a pariah by mandarin growers could have growers bidding for their bees. Beekeepers could then be in the position of the "soup Nazi" of Seinfeld fame, and, if mandarin growers didn't show the proper respect, beekeepers would tell them "No bees for you! Next."

Joe Traynor is a crop consultant and pollination broker in Bakersfield, California.