Grafting

Grafting (larva transfer) is the transfer, one by one with a grafting tool, of newly hatched worker larvae taken from a comb of the breeder colony into artificial queen cell cups. It is the task that most determines quality in queen rearing: larvae of the right age must be transferred with a quick hand, without drying out or being turned over. This page covers the materials needed, choosing larvae, the grafting technique step by step, the difference between dry and wet grafting, and the causes of poor acceptance.

What is grafting and why is it done?

A queen and a worker develop from the same fertilised egg; the difference comes from feeding. If a newly hatched worker larva is placed in a vertical queen cell (cell cup, queen cup) and given to a queenless, crowded colony, the bees feed it with plenty of royal jelly and the larva develops into a queen. Grafting is the way to put this biological fact to work according to the beekeeper's plan.

Compared with queens raised naturally, grafting has three big advantages: the beekeeper decides which queen the larvae come from, how many cells are made and on which day the work is done. That is why grafting is the basic method of commercial and breeding-oriented queen rearing; in English the technique is known as grafting, larva transfer or queen grafting.

What materials do you need for grafting?

• Grafting tool: A fine-tipped implement that slides under the larva and lifts it together with its jelly. There are flexible-tongue (Chinese), rigid metal-tipped and push-type (plunger) versions.
• Cups and bars: Plastic or beeswax cups, ready and waiting, mounted on the bars of the grafting frame.
• Light: Strong, direct light that illuminates the bottom of the comb cell (head torch, hand torch or desk lamp).
• Magnifier: A head-mounted magnifier or reading glasses; a great help, especially for those who have difficulty seeing close up.
• Damp cloth: A clean, damp cloth or towel to cover the breeder comb and bars waiting to be grafted.
• Royal jelly or lukewarm water (optional): For the drop placed at the bottom of the cup if wet grafting.

How do you choose the right larva for grafting?

The most important variable determining queen quality is the age of the larva put in the cup. The target is a newly hatched larva less than 24 hours old. As the larva grows, it begins developing in the worker direction; a queen raised from an older larva has fewer ovarioles and a smaller spermatheca.

• Size: A larva not much bigger than an egg, slightly larger than a pinhead.
• Shape: Crescent- or comma-shaped; a larva that has closed into a full "C" and fills the cell floor is too old.
• Pool of jelly: The larva should be floating in a shiny pool of jelly at the bottom of the cell. Do not take a larva from a cell that looks dry.
• Comb: A light brown comb that has reared brood once or twice reflects light well and makes it easier for the tool to reach the bottom of the cell. Very old, dark combs with narrow cells make the work harder.

To know the age of the larvae rather than guess, give the breeder queen an empty comb on a set date, or confine the queen to that comb for a day or two with a frame cage. About 4 days after laying, the comb will contain young larvae suitable for grafting.

How do you graft, step by step?

1. Prepare the starter: The day before grafting, the starter colony is made queenless, its open brood removed and it is made crowded. The cups are placed in a colony a day before so the bees can clean them.
2. Choose the workspace: A cool, shaded, wind-free spot; if possible a warm, humid room or the inside of a vehicle. Direct sun dries a larva within minutes.
3. Take the breeder comb: The bees are gently brushed off the comb rather than shaken; hard shaking can dislodge the larvae in their cells. Cover the comb immediately with a damp cloth.
4. Get the light to the bottom of the cell: Holding the comb at a slight angle, direct the light onto the cell floor; see clearly how the larva is lying.
5. Go in behind the back: The tip of the tool slides down the back (outer) wall of the cell and goes in under the larva's back, lifting it with the jelly beneath it. Do not press on the larva with the tip.
6. Release it the same way up: Lower the tool to the bottom of the cup, touch the tip to the base and draw it back gently; the larva stays on the jelly in the same position it was lifted in. A larva turned upside down drowns.
7. Finish quickly and cover: Cover each completed bar with a damp cloth, and once the frame is full give it to the starter without delay. Write the grafting date and batch number on the frame.

Dry grafting or wet grafting?

The method in which the larva is placed directly into the cup is called dry grafting; the method in which a small drop is first placed at the bottom of the cup is called wet grafting. Royal jelly diluted with water is mostly used for the drop.

Some producers get good results with each method. What matters is to choose one, apply it consistently and record the results. The royal jelly used must be clean and fresh, and must not carry disease from another colony.

What is double grafting?

Double grafting means removing the larva from each accepted cup a day after the first grafting and replacing it with a new, young larva; the aim is for the larva to be surrounded by plenty of jelly from its first hour. It takes extra work and opinions on its benefit differ; for a start, single grafting is enough.

Common grafting mistakes

• Taking older larvae: A larva that fills the cell floor, even if accepted, produces a poor-quality queen.
• Turning the larva over: The larva's breathing holes (spiracles) are buried in the jelly and it dies; the most common beginner's mistake.
• Crushing or injuring the larva: Do not press the tool onto the larva; replace a worn or split tool tip with a new one.
• Letting it dry out: Working in sun or wind, or leaving larvae waiting too long, kills them.
• Dirty or smelly cups: The smell of detergent, treatments or new plastic lowers acceptance.
• Not writing the date: If the grafting day is not known, distribution on day 10 is missed and the first queen to emerge kills the others in their cells.

How can you improve the acceptance rate?

About 24 hours after grafting, the frame is gently lifted out and acceptance is checked. An accepted cup has started to be extended with wax at the mouth and is shiny inside and full of jelly; the larva floats on top of the jelly. A cup that has not been accepted looks empty or dried out.

• Starter: It should be queenless, without open brood, and packed with enough young bees to overflow the spaces between frames.
• Food: If there is no natural flow, start syrup and pollen feeding a few days in advance.
• Larvae: The youngest possible, floating in a pool of jelly.
• Warmth: Do not let the bars chill, and do not leave them in sun or wind.
• Practice: Low acceptance is normal in the first attempts; after a few batches your hand gets quicker and the rate rises markedly.

If acceptance is persistently low, rule out the causes one by one: larval age, larvae drying out or being turned over, the strength of the starter, the presence of open brood, the food situation and the weather.