Oxalic acid strips are suitable for a wide range of temperatures from 15 -35 degrees Celsius. Since oxalic acid works by contact, below 15 degrees we have low movement of bees in the frames and therefore less contact of different bees with the tapes, which delays and perhaps reduces the effectiveness of the treatment with possible negative consequences in failure. At temperatures above 35 degrees we have a faster release of oxalic acid from the strips with possible negative consequences for the health of the colony. In summary, we avoid using Winter in low temperatures and during periods of intense heat.

The number of strips placed per colony depends on its population size. Below is a helpful table:

Especially during the spring period when the beehives is in development, we are careful not to apply more strips than necessary, we do not want to “pressure” the bee by affecting its development.

Oxalate strips to be effective must ALWAYS be placed in the frames where brood is present. This is due to the fact that Varroa reproduces in the brood and young bees and queen bees always have the highest infestation and since the oxalic acid works in contact in this way we maximize the spread of the active substance in the infected population. However, we do not need to place absolutely in the center of the frame disturbing the movement of the bees. We can place them in a ¨Λ¨ formation 5-7 cm from the imaginary center of the frame and alternately. We fold the strips and “wear” them in the frame that has a brood.

Also we can cut them in half and place 2 halves hanging with a toothpick, instead of one whole folded. The difference is that when they are half balanced in the gap of the frames it leaves a better corridor for the bees and the queen to pass through. It also reduces “dimpling” of the wax in the frames. However, the disadvantage is that it takes significantly more time to place them in the colonies.

Although nothing changes in efficiency, the beekeeper will personally decide which position serves him best.

INDICATIVE PICTURES OF INSTALLATION OF OXALIC TAPES

Although in beekeeping there are exceptions and from season to season the parameters change, as a general rule we set the moments when the temperatures are suitable and especially when the colonies have the least brood for each season. This is usually right after a honey harvest. Our apiaries to fill with honey, reduce the food to the queen to reduce the brood rate, as a result they keep fewer frames with brood and many more with honey. Practically then, the varroa has fewer brood cells to enter and “cover”, so it is more vulnerable and necessarily crowded into a smaller space (4-0 maybe, frames) to reproduce within the hive. At those moments the strips of oxalic acid make a “great work” with a rate that reaches <90%.

An important think that the beekeeper must have in mind is that the treatment must be applied on the day of harvest or in the next 2-3 days. Why;

Because after a honey harvest the colony tends to increase the queen laying rate, especially if we practice nomadic beekeeping and move our hives to area with blossom for a re-growth of the Beehive. Given that:

1) Usually 2-3 days after harvest beehive organized and the queen start lays eggs again

2) That the day just before the brood is sealed the varroa enters the cell

it means we have about 10 days where the varroa is “severely exposed”. In these 10 days that should ALREADY have the treatment applied at the earliest to kill the mite varroa at higher rates. If we do not do timely treatment and we are late, then after 10 days the varroa has already entered in brood and the application of the treatment  is less effective and also the varroa has already done damage to the colonies without us being able to do anything. A good beekeeper does not miss the right timing, this one is VERY SERIOUS.  We take advantage of these opportune moments!

Normally only one course of treatment is needed. However, there are some cases where it may be necessary to repeat the treatment with new strips after 15-20 days.

This is needed in the following 2 cases:

1. A) If the varroa infestation is particularly high in our colonies. Eg a colony with 1,000 varroa infested, even if 90% of the mites are killed, the remaining 10% is 100 varroa. These 100 varroa if we don’t reduce them with 2 applications then in a few months they will reach close to their original number again and we don’t want that. Of course, in order to realize this, we have to measure the varroa fall over a period of 20 days in beehives ¨indicators¨ and if the sum is high enough, a second application is needed. Also with the alcohol test method we can have an indication of the rate of varroa infestation before the treatment.

*(For more information on varroa growth rate see section: Varroa Reproduction and Life Cycle (Examples).

1. B) If some strips are destroyed in 15 days by the bees. This happens ussaly in large bees because of the cleaning instinct, then we don’t necessarily do 2 application cycles, we can just selectively replace the damaged tapes with new ones.

In most cases where an application cycle is performed the oxalate strips should remain in the cell for up to 30 days. Then if they haven’t already been destroyed by the bees, we have to remove them.

However, when there are 2 treatment cycles then we can make them shorter in 20 days for the first application and another 20 days for the second application. A total of 40 days.

In the offshoots it is a very good opportunity to clean them almost completely of the varroa by doing the following tactic:

Counting 15 days from the day we created the offshoot we apply ½ -1 strip of oxalate according to size of new colony (2-5 frames) for only 20 days. During this time the scion is almost broodless because most of the brood has already come out from the frames and the new queen will not lay eggs yet. So the varroa is almost completely exposed to the action of the oxalic acid strips. With this tips we achieve very good fighting results with minimal financial costs and give our new bee a very good and “clean”start!