Landscape effects on spatial distribution and movement of brown marmorated stink bug in peach orchards

Landscape effects on spatial distribution and movement of brown marmorated stink bug in peach orchards

Summary

The spatial patterns of the brown marmorated stink bug (BMSB), Halyomorpha halys (Stål), in peach orchards was investigated in the summer of 2014. Orchards at two commercial farms and two research stations were monitored weekly for H. halys from May through September. All locations had been sampled in previous years and were confirmed to have H. halys through visual sampling. The search area focused on peach orchards but also included some adjacent habitat including lilacs and small apple trees. Assessments for damage were conducted as peaches ripened. These consisted of visual assessments for stings and catfacing damage. Closer to fruit ripening, peaches were peeled to assess and compare damage on the inside and outside of each peach. ArcMap was used to visually display H. halys populations and damage levels in each orchard. Data was analyzed with semivariograms to determine spatial autocorrelation. A hierarchical Bayesian model is being developed to analyze the influence of landscape features to the number of H. halys on individual trees in the orchard.

Objectives/Performance Targets

Objective 1. Determine if BMSB are more prevalent in peach orchards in northern or southern New Jersey, when they increase in population, and what landscape factors contribute to population buildups.

• • In 2012, 23 orchards were sampled, 13 sampled in northern New Jersey and 10 sampled in southern New Jersey. Low populations occurred throughout the multiple orchards sampled, with none found in peach orchards in southern New Jersey. Less than 100 adults were found in orchards in northern New Jersey.

• • In 2014, orchards at two commercial farms, one in northern New Jersey (Farm 1) and one in southern New Jersey (Farm 2), and at two research stations, one in central New Jersey (Cream Ridge) and one in southern New Jersey (RAREC), were monitored for halys. Sampling in the two previous years indicated the presence of H. halys at these sites.

• • Populations in the commercial farms were very low. At Farm 1, 7 egg masses, 8 nymphs, and 3 adults were found throughout the sampling period in 345 trees. However, lilacs bordering the orchard harbored 113 nymphs and 11 adults found through July and August. At farm 2, 6 egg masses and 6 adults were found in over 500 sampled trees.

• • At the beginning of the sampling season, fruit at the sampled orchard at RAREC was heavily damaged by a hail storm. There was significant fruit loss at the orchard, most likely contributing to the low populations of halys found at the site. 216 nymphs and 12 adults were found over the sampling season.

• • As with previous years, Cream Ridge exhibited populations of halys that peaked from late July through August (Figure 1). There were low numbers of adults in comparison to the number of nymphs found in the orchard. The number of H. halys was also counted in a nearby planting of lilacs. There were high numbers of adults early in the sampling season. High numbers of nymphs were seen later in the season (Figure 2).

Objective 2. Determine where high BMSB populations are located within peach orchards, and what landscape factors contribute to this.

• • Sampled trees in the orchards were displayed on maps in ArcMap.

• • Due to low populations of halys at Farms 1 and 2, maps were not created. One date of peak populations of nymphs at RAREC was selected for mapping (Figure 3) and two dates of populations of nymphs at Cream Ridge were selected for mapping (Figure 4).

• • Semivariograms used to determine the degree of spatial autocorrelation in the field were developed. Semivariograms were created for the Cream Ridge sampling dates 7/31/14 and 8/26/14 and displayed in Figure 5. The semivariogram for 7/31 indicates spatial autocorrelation of the population at distances less than 10 feet, while the semivariogram for 8/26 indicated varying levels of autocorrelation through the field.

• • A conditional autoregressive hierarchical Bayesian model will be used to analyze how landscape factors such as distance from wooded edge or variety contribute to populations within the fields.

Objective 3. Determine what landscape factors contribute to high levels of fruit damage by H. halys.

• • Damage to fruit was assessed in 2014. The orchards at Farms 1 and 2, Cream Ridge and RAREC were sampled once every two weeks to evaluate the number of externally damaged, undamaged, and catfaced fruit using visual counts. The total number of fruit was also counted. These data were displayed on a map (Figure 6).

• • In August at Cream Ridge, 20 fruit per tree were picked and peeled to assess damage found on the exterior of the fruit before and after peeling.

Objective 4. Determine what locations/habitats near a peach orchard might contribute to H. halys immigration into orchards.

• • Data of populations of halys has been inputted and mapped. The contribution of landscape features to the initial population levels within the field will be examined with a conditional autoregressive model. The parameters of ripeness, variety and distance from edge are to be incorporated into the model.

• Figs 1-6

Accomplishments/Milestones

            Field sites monitored in 2014 were selected from farms monitored in 2012 and 2013 that exhibited populations of H. halys confirmed through trapping or visual sampling. All orchards either participated in the Rutgers fruit IPM program or were Rutgers agricultural research stations.

            Sampled orchards were surveyed weekly for eggs, nymphs, and adults using visual sampling from May through August. H. halys populations remained low in all orchards; the cause of this is unknown. However, at RAREC, there were a hailstorm at the beginning of the growing season that caused significant damage to all of the fruit, leading to partial or complete fruit loss. There was also some land-use change in and around certain orchards. At Farm 2, there were 11 rows of peach trees were removed, totaling more than 500 trees. At Cream Ridge, several rows of older trees had been removed within sampled orchards, and a large block of unused ornamental trees that harbored a large population of H. halys was also removed.

For objectives 2 through 4, a second year of sampling in multiple orchards will improve the power of the statistical models and tests used to relate landscape features to populations of H. halys in the field. In 2014, not enough adults were found to mark individuals in situ to assess how they move around a field. For objective 3, a second year of damage assessments was conducted. Visual assessments for damage were more frequent, and the number of fruit sampled for peeling at the end of the season was 20, double the number sampled in 2013. These data will strengthen the analysis of the correlation between damage and H. halys population in the field.

Impacts and Contributions/Outcomes

            All data have been recorded and inputted, and much of the data has been mapped. The analysis of the impact of landscape features will be conducted with the conditional autoregressive model. As with previous years, low populations within all orchards may make it difficult to draw conclusions of the spatial arrangement of populations in the field. However, three years of data will strengthen the analysis and the power of the statistical tests. Examining the maps of the populations visually, the populations of H. halys seem to be congregating in similar areas to previous years.

            I hope that my analysis of the clustering of H. halys populations and the landscape features that contribute to this will be useful to growers in their future management plans.

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