IPM
with
APINOVAR

A Simple Guide

By Jean-Pierre Chapleau

Novembre 2004


Here is a quick guide for a successful non chemical control of varroa with the help of APINOVAR. The strategy we propose relies on being adequately informed of your infestation levels at key moments during the season and treating your colonies when definite thresholds are reached.

General guidelines

For sampling we use natural mites fall

For treating we use basically “flash”(1) applications of formic acid.

The success this IPM strategy depends mainly on not exceeding the following levels (table 1) of natural mites fall just before the fall treatment is started:

Maximum mites fall before the fall treatment

Maximum average mites fall for all colonies
25

Maximum mites fall for individual colonies

75

Table 1

Exceeding these thresholds leads to higher than normal winter loss and/or weaker colonies the next spring.

At the end of the season we lower rapidly the infestation level with repeated “flash” applications. Our target is to obtain a very low level of infestation for the winter. This insures that:
• The wintering bees are not weakened and secondary viral secondary infections don’t have much chances to develop
• A low level of infestation in the fall also means a low level the next Spring and chances are good that we will not have to treat before the next fall.

Until further experience suggest differently, we target the following result from our treatments:

Maximum mites fall 2 weeks after last “flash”
0.5 to 1

Table 2


The use of bee stock that has been improved(2) for resistance to varroa will help reduce the number of treatments required during the whole season.

Nevertheless sampling should be performed at two other times during the season to make sure the fall threshold will not be exceeded. Table 3 suggests tentative thresholds for spring and mid-season.

Spring and mid-season suggested thresholds
1st week of May
0.5 to 1
50 days before the fall treatment
6.25
25 days before the fall treatment
12.5

Table 3


We suggest sampling in early May and at another time in mid-season at a convenient moment for the beekeeper. Sampling should be done just before a time window where one or more flash application can be done. In areas where it is not possible or desirable to take off the honey supers at mid-season, it will be essential to make sure that the spring natural mortality is lowered to the acceptable level before the honey supers are put on. (Until you know more about your bee stock capability etc. , prefer the 0.5 treshold.)

“FLASH” treatments

You will find in this section the basic information concerning the “flash” application of formic acid.

As opposed to the methods currently used here in Canada, all based on the slow release of the formic vapours, “flash” relies on the fast volatilisation of the acid in the hive over a very short time (6-12 hours). Fast volatilisation methods are very popular in Europe.

Here are the main advantages of this method, when it is used in conjunction with APINOVAR:

• High efficiency over a short time period, mainly because some mites in the brood are killed.
• The colonies are disturbed only for a very short period and resume rapidly their normal activities.
• No need to open the hive: the application is extremely fast.
• Dosage can be adapted to suit colony size and temperature conditions.
• No special material is needed although using a drench gun is a plus. (Dosage is very accurate and application is faster).
• This is the most economical way of delivering formic to colonies.

Method
We “flash” our colonies from the bottom, more exactly from the sampling drawer of the APÌNOVAR board. We use a drench gun to inject the formic on a paper towel placed in the sampling drawer. We use one single section of paper towel for singles and 2 sections (folded to form a double layer) for doubles.

Table 4 presents the dosages we actually use:

Formic Dosages for FLASH
Maximum temperature anticipated in the next 6 hours
DOUBLES
SINGLES
20 – 26
Celsius
40 ML
(35 ml if weak )
20 ML
(15-17 ml if weak)
16 - 19
Celsius
45 ML
(40 ml if weak)
22 ML
(17-19 ml if weak)
10 – 15
Celsius
55 ML
(45 ml if weak)
27 ML
(20-22 ml if weak)

Table 4


Basically applications of formic acid by the fast volatilisation method based on this table give us approximately a 60% reduction of the natural mites fall measured 14 days after the treatment . The dosages in table 4 result from a 2 years large scale testing period with the APINOVAR board. These dosages are safe to our knowledge and should not cause queen loss or significant brood damage. Higher efficiency can be obtained with higher dosages but the risk of damage increases also. Despite this potential damage it could be wise to use higher dosages in emergency situations to save otherwise endangered colonies.

Caution

-In order to avoid important drifting, flash the whole yard at the same time. If you want to treat individual colonies flash them at the end of the day, or when bees are not flying.

-We repeat: you have to be careful with the dosages you are using. Overdosing can result in damage to the colony.

  • Remember that the same dosage will have a stronger effect if applied at higher temperatures.
  • Weak colonies (colonies that do not fill their super) will not stand the same dosage as strong colonies. Please consult table 4. We have little experience for the moment with very small colonies like nucs. We think it is preferable to treat your colonies when they are strong. If you have to treat weak colonies we suggest to start with a dosage of 2 ml per frame of bees.

- The dosages in table 4 will not be valid with other bottom boards as their different design will change the formic concentration and distribution pattern in the hive.

- Never flash your colonies with honey supers on.

- Always wear appropriate clothing, rubber gloves and safety glasses when working with formic.

We used flash for fall, mid-summer and spring treatment.

Flash as a fall treatment
For two consecutive years we have used repeated flash as our main fall treatment. An average natural mites fall of 20-25 varroas/day or more in early September will require 4 applications to completely clean the hive. We suggest knocking down rapidly most of the mites with 2 early applications at 4-5 days interval. We do a third application approximately a week later. We hold the fourth application until early October when there is very little brood in the hives. This way a very high efficiency can be obtained with this last treatment. Lower average mites fall may require fewer applications. More on that later.

Flash as a mid-summer treatment
We had very good results with one single application in early August. Colonies can be flashed as the first crop is removed. There should be no honey super on the hives when the application is done..

Flash as a spring treatment
We have limited experience with spring flash. This is not the option we favour. We really prefer to treat colonies when they are strong. I you want to do it make sure you adapt the dosages accordingly. Many factors suggest avoiding spring treatments whenever possible:
• colonies weakened by the winter are more vulnerable to formic vapours;
• there is usually an important variation in the strength of the colonies and it is difficult to apply a uniform dosage;
• a high proportion of the varroas are in the brood and brood is in expansion;
• outside temperatures are seldom ideal.

Nevertheless, if mites fall justifies, you will have to do something. If you can afford, wait until the brood chambers are pretty much filled up with bees. Remember 2 things:
• fall is the time where you really want to clean the hive;
• and using resistant stock will help you avoid the spring treatment.


Sampling

Sampling is your information tool. Your treatment decisions will be based on your sampling results. Too many times, sampling is not done right. Here are a few hints.

Preparation
• As a sampling carton we suggest you cut pieces of “corroplast”(3) that will fit the sampling drawer (full dimension). These can be cleaned out after each sampling. They can be reused indefinitely.
• It will be much easier to do the counting if you draw lines on your cardboard. Draw them perpendicular to the longest side of the carton and a few centimetres apart.
• Coat your cartons with melted vegetable grease ("Crisco") using a paint roller. It is not necessary to protect the carton as the bees do not have access to the sampling drawer.


How many days should we sample?

Low infestation levels require longer sampling periods to obtain a reasonable precision and vice versa. Here are some suggestions:

Suggested Duration of the Sampling Period
May
July-August
just before fall treatment
15 days
after fall treatment
4 - 7 days
3 - 4 days
1 - 3 days
4 - 7 days

Table 5

Keep in mind that very long sampling period will make very dirty cardboards that will be very difficult to read. So if you can sample a fair number of hives, do not necessarily go for the longest period. You may not obtain super high accuracy at individual colony level but you will be able to trust the averaged results.

Always express your results on a 24 hour basis as the recommendations are commonly provided in this format.

IMPORTANT WARNING

Put all the necessary attention when you do the counting. By experience I can tell you that the great majority of beekeepers are overconfident and obtain counts on average 50% lower than reality! You must count all the varroas that have some coloration. The ones that are not fully pigmented are more difficult to see and they could be easily taken for hive debris. So use a magnifier lamp and… take your time. It may be wise to have your counts checked by somebody else. Younger people have more facility seeing all the varroas on the carton. Once you learned to do it correctly counting is easy… but you have to get the proper training.


Further reading on FLASH with APINOVAR:

 

notes:

(1) In this text "flash" refers to a method of using formic acid to treat bee colonies. Formic acid is poured on a paper towel deposited in the sampling drawer of the APINOVAR bottom board. Volatilisation of the acid is very fast as opposed to the other slow release methods commonly used in Canada.

(2) For average bee stock, varroa population seems in our conditions to double more or less every 15 days. Our experience of selection for varroa resistance shows that the lenght of the doubling period can easily be extended to 25 days and more. Such stock will take 124 days or more to reach the fall threshold (spring natural mortality level of 1 assumed) and no treatments other than the fall treatment will be required in most areas.

(3) Cardboard like plastic sheets