A honeybee IPM program for pollinator health in blueberry production

A honeybee IPM program for pollinator health in blueberry production

Summary

Major NJ beekeepers who pollinate NJ blueberries experienced severe bee mortality in 2014. We experienced up to 40% brood death along with queenless hives that needed to be rebuilt throughout the season. This damage not only contributes to a lack of sustainability for NJ beekeepers, but will also contribute to increased pollination costs for NJ blueberry growers, who require about 16,000 hives per year to produce the crop. The proposed program brings our staff together with Rutgers IPM program assistance to establish a monitoring system to assess bee mortality, pesticide use, brood health and pesticide residues in hives, as contributing factors in colony decline. We established a monitoring program during the blueberry pollination period to assess acute pesticide toxicity by using dead bee trays.

In 2016 monitored hives were placed on 8 commercial blueberry farms during blueberry pollination. Data was collected by monitoring hive ejected dead bees (1 – 7 day count), percent brood coverage (2 counts), and pesticide residue analyses. Hives were marked for sampling (101 hives). A subset (16) was outfitted with new comb foundation and queens for pesticide residue analyses at the end of pollination. A total of 15 active ingredients were found in pollen and comb samples. One twilight meeting presentation was made to commercial blueberry growers in the spring, and two presentations were made in 2016 winter grower meetings in Atlantic City and Hammonton (total 190 grower and beekeeper contacts).

Objectives/Performance Targets

Objectives – 1) Establish an acute bee mortality monitoring system during blueberry pollination. 2) Identify pesticide use during the early part of the season up to bee removal. 3) Correlate hive damage, brood and queen mortality with possible pesticide factors, using a combined pesticide use survey and laboratory screening tests. 4) Create an “off season” communication system with blueberry growers that inform them of beekeeper issues related to pesticide use, and how those issues may relate to blueberry crop yield.

Accomplishments/Milestones

In the subset of 16 new comb hives 12 of the 16 showed growth and 4 showed “0” growth or shrinkage. Analyses for pesticide residues showed up to 15 active ingredients were present in sampled hives. Some of these such as DMPF, Coumaphos and Fluvalinate were common and are attributable to the products used for Varroa mite control. Fungicide residues included Azoxystrobin, Fenbuconazole, Metalaxyl, Boscalid, Pyraclostrobin, Captan and the Captan metabolite, THPI. All of these are normally used in blueberries, including just before and during pollination. Other insecticide residues included Esfenvalerate, Imidacloprid, Phosmet, and Chlorpyrifos. Atrazine was found in 3 hives.

Impacts and Contributions/Outcomes

The 7 day dead bee count averaged 27.7 bees per hive and ranged from 0 to 114 dead bees per hive. Most hives had between 10 to 30 dead bees per hive. The percent brood coverage was averaged for all 6 comb counts per date, and sampled hives compared by date. The reading on the first date (5/7) was used as the base. Therefore hives should show an increase in brood coverage by the second date (5/29). By 5/29 59 hives out of 101 (58.4%) showed an increase in brood coverage. There was “0” growth or less coverage in 42 hives (41.6%) (Figure 1)2016Figure 1. The goal for the beekeeper was to see at least 30% increase in brood strength during the pollination period. Over 90% of the hives did not make this goal.

In the subset of 16 new comb hives 12 of the 16 showed growth and 4 showed “0” growth or shrinkage. Hives rated as queenless were hives where the queen had died and/or a new queen had not been produced. Where farm sites had at least 7 monitored hives, the percent queenless hives at the beginning vs. the end of pollination were compared (Figure 2)2016Figure2. In most cases the number of queenless hives significantly increased throughout the pollination period. Analyses for pesticide residues showed up to 15 active ingredients were present in sampled hives. Some of these such as DMPF, Coumaphos and Fluvalinate were common and are attributable to the products used for varroa mite control. Fungicide residues included Azoxystrobin, Fenbuconazole, Metalaxyl, Boscalid, Pyraclostrobin, Captan and the Captan metabolite, THPI. All of these are normally used in blueberries, including just before and during pollination. Other insecticide residues included Esfenvalerate, Imidacloprid, Phosmet, and Chlorpyrifos. Atrazine was found in 3 hives.

Two pesticide residues, Chlorpyrifos and Atrazine are not labeled in blueberries and could have been used on other crops within the foraging range of the bees. This area-wide issue of pesticide use and honey bee management needs to be further explored.

This data did show that a significant number of hives showed no growth in brood, and even decreased in strength. This was partly do to an increased level in queen mortality and lack of queen replacement. While varroa mites were present in most hives, along with some disease, many pesticide residues were also found. Fluvalinate is a known toxicant to bees, formerly used as a varroa miticide. Regression analyses were performed on various pesticides vs. percent brood change. This was a small data set with no clean controls and multiple factors influencing survival and mortality. None of the fungicides as related in his data showed a significant correlation with lack of brood growth (Figure 3)2016Figure 3. Insecticide residues did show a correlation with negative brood growth (Figure 4)2016Figure 4. Grower pesticide use records were collected from those growers where hives were placed, and compared with residues found. However, honey bees do not know the boundaries of the farms where they are placed and forage wherever suitable nectar and pollen is found. Two pesticide residues, Chlorpyrifos and Atrazine are not labeled in blueberries and could have been used on other crops within the foraging range of the bees. This area-wide issue of pesticide use and honeybee management needs to be further explored. Phosmet (Imidan) was found in most of the samples. This is an insecticide that was commonly used immediately after the bees are removed. The presence of phosmet in the samples may be due to continued bee foraging to sprayed fields from their removal (bee yard) site.

The fact that when a number of beekeepers removed hives from blueberry fields after pollination, only to bee yards that were very close to blueberry fields, permitted bees to forage back to blueberries during times that post pollination insecticides were used. This practice was changed as a result of this project. The fact that fluvalinate was found in every new hive, and not used by the beekeeper, indicates that at least one foreign residue is present in beeswax comb. The fact that multiple residues were present, some not even used by blueberry growers, combined with other hive stressors like varroa mites and disease, indicates the highly stressed conditions of the hives. Additionally, new work is showing that certain pesticides can exhibit different toxicological properties on brood as compared to adults alone. Some combined compounds have been shown to synergize toxic properties within the hive. These factors and others point to the need for further work in more controlled conditions.

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