Limits...
Living on the Edges: Spatial Niche Occupation of Asian Citrus Psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), in Citrus Groves.

Sétamou M, Bartels DW - PLoS ONE (2015)

Bottom Line: In both cultivars, significantly more psyllids were found on perimeter trees throughout the study period suggesting a strong edge effect in D. citri distribution in the groves.Citrus groves located at the outer edge of the study with at least one side non-surrounded to other citrus groves harbored significantly more D. citri than groves located within the block cluster and entirely surrounded by other groves.In addition, psyllid densities decreased significantly with increasing distance from the grove edge.

View Article: PubMed Central - PubMed

Affiliation: Department of Agriculture, Agribusiness and Environmental Sciences, Texas A&M University-Kingsville Citrus Center, Weslaco, Texas, United States of America.

ABSTRACT
The spatial niche occupation of the Asian citrus psyllid, Diaphorina citri Kuwayama, 1908, was evaluated to determine its field colonization and food resource exploitation strategies in citrus groves. Mature grapefruit and sweet orange groves were surveyed as part of an area-wide program in 2009-2010 to determine D. citri population densities and between-tree distribution. In both cultivars, significantly more psyllids were found on perimeter trees throughout the study period suggesting a strong edge effect in D. citri distribution in the groves. D. citri densities and infestation levels gradually declined from the edge to the center of grove. Higher numbers of D. citri were recorded on trees located on the east and south sides of the groves than those on the west and north sides. Citrus groves located at the outer edge of the study with at least one side non-surrounded to other citrus groves harbored significantly more D. citri than groves located within the block cluster and entirely surrounded by other groves. In detailed field studies during 2012, infestation of D. citri started from border trees in the grove where possibly one generation is completed before inner trees become infested. In addition, psyllid densities decreased significantly with increasing distance from the grove edge. Using the selection index, D citri exhibited a strong niche occupation preference for border trees.

No MeSH data available.


Related in: MedlinePlus

Mean number of D. citri life stages per flush shoot and percent flush infestation level in relation to tree location in grapefruit and sweet orange groves during area-wide surveys (2009–2010).
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4507854&req=5

pone.0131917.g003: Mean number of D. citri life stages per flush shoot and percent flush infestation level in relation to tree location in grapefruit and sweet orange groves during area-wide surveys (2009–2010).

Mentions: Independent of host plant species and grove location in the survey area, D. citri densities for egg, nymph and adult (F > 14.73, 99.45, 179.72; df = 2, 35,000; P < 0.0001) and flush shoot infestation level (F = 221.72; df = 2, 35,000; P < 0.0001) varied with tree position in the grove (Table 1). Flush shoot infestation levels and D. citri densities in citrus trees gradually declined from the edge of the grove to the interior. Least square mean discrimination using Tukey’s test showed three distinct groups for each D. citri variable recorded. The highest infestation levels and densities of D. citri were recorded on perimeter trees followed by adjacent trees, while interior trees harbored the least numbers of D. citri (Fig 3). The rate of decline in D. citri densities and flush infestation levels from the edge to the interior of the grove was similar for grapefruit and sweet orange, and was well described by an exponential decay function (y = a*exp [-bx], where x is the distance of tree position in meter from the edge of the grove and y the density of D. citri life stage) (Table 2). Based on these equations, D. citri flush shoot infestation level fell to one half of that recorded on perimeter trees within 33 m and 29 m of the grove edge in grapefruit and sweet orange, respectively. With the exception of the number of eggs on sweet orange, all D. citri developmental stages on interior trees decreased to 50% of their densities recorded on perimeter trees within 22 to 29 m of the grove edge (Table 2). Simple regression analysis between D. citri adult densities at different tree positions revealed good fits of models for both grapefruit and sweet orange (See S1 Appendix). About 90% and 76% of total variation in adult D. citri densities found on adjacent trees were explained by the number of adult psyllids recorded on perimeter trees for grapefruit and sweet orange, respectively. Similarly, 60–82% of the total variation in psyllid densities on interior trees was explained by psyllid densities on adjacent trees or perimeter trees. The slope of the regression lines indicated that each increase of 1 adult psyllid on perimeter trees resulted on only 0.4–0.5 and ∼0.3 psyllid increases on adjacent and interior trees, respectively (See S1 Appendix).


Living on the Edges: Spatial Niche Occupation of Asian Citrus Psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), in Citrus Groves.

Sétamou M, Bartels DW - PLoS ONE (2015)

Mean number of D. citri life stages per flush shoot and percent flush infestation level in relation to tree location in grapefruit and sweet orange groves during area-wide surveys (2009–2010).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507854&req=5

pone.0131917.g003: Mean number of D. citri life stages per flush shoot and percent flush infestation level in relation to tree location in grapefruit and sweet orange groves during area-wide surveys (2009–2010).
Mentions: Independent of host plant species and grove location in the survey area, D. citri densities for egg, nymph and adult (F > 14.73, 99.45, 179.72; df = 2, 35,000; P < 0.0001) and flush shoot infestation level (F = 221.72; df = 2, 35,000; P < 0.0001) varied with tree position in the grove (Table 1). Flush shoot infestation levels and D. citri densities in citrus trees gradually declined from the edge of the grove to the interior. Least square mean discrimination using Tukey’s test showed three distinct groups for each D. citri variable recorded. The highest infestation levels and densities of D. citri were recorded on perimeter trees followed by adjacent trees, while interior trees harbored the least numbers of D. citri (Fig 3). The rate of decline in D. citri densities and flush infestation levels from the edge to the interior of the grove was similar for grapefruit and sweet orange, and was well described by an exponential decay function (y = a*exp [-bx], where x is the distance of tree position in meter from the edge of the grove and y the density of D. citri life stage) (Table 2). Based on these equations, D. citri flush shoot infestation level fell to one half of that recorded on perimeter trees within 33 m and 29 m of the grove edge in grapefruit and sweet orange, respectively. With the exception of the number of eggs on sweet orange, all D. citri developmental stages on interior trees decreased to 50% of their densities recorded on perimeter trees within 22 to 29 m of the grove edge (Table 2). Simple regression analysis between D. citri adult densities at different tree positions revealed good fits of models for both grapefruit and sweet orange (See S1 Appendix). About 90% and 76% of total variation in adult D. citri densities found on adjacent trees were explained by the number of adult psyllids recorded on perimeter trees for grapefruit and sweet orange, respectively. Similarly, 60–82% of the total variation in psyllid densities on interior trees was explained by psyllid densities on adjacent trees or perimeter trees. The slope of the regression lines indicated that each increase of 1 adult psyllid on perimeter trees resulted on only 0.4–0.5 and ∼0.3 psyllid increases on adjacent and interior trees, respectively (See S1 Appendix).

Bottom Line: In both cultivars, significantly more psyllids were found on perimeter trees throughout the study period suggesting a strong edge effect in D. citri distribution in the groves.Citrus groves located at the outer edge of the study with at least one side non-surrounded to other citrus groves harbored significantly more D. citri than groves located within the block cluster and entirely surrounded by other groves.In addition, psyllid densities decreased significantly with increasing distance from the grove edge.

View Article: PubMed Central - PubMed

Affiliation: Department of Agriculture, Agribusiness and Environmental Sciences, Texas A&M University-Kingsville Citrus Center, Weslaco, Texas, United States of America.

ABSTRACT
The spatial niche occupation of the Asian citrus psyllid, Diaphorina citri Kuwayama, 1908, was evaluated to determine its field colonization and food resource exploitation strategies in citrus groves. Mature grapefruit and sweet orange groves were surveyed as part of an area-wide program in 2009-2010 to determine D. citri population densities and between-tree distribution. In both cultivars, significantly more psyllids were found on perimeter trees throughout the study period suggesting a strong edge effect in D. citri distribution in the groves. D. citri densities and infestation levels gradually declined from the edge to the center of grove. Higher numbers of D. citri were recorded on trees located on the east and south sides of the groves than those on the west and north sides. Citrus groves located at the outer edge of the study with at least one side non-surrounded to other citrus groves harbored significantly more D. citri than groves located within the block cluster and entirely surrounded by other groves. In detailed field studies during 2012, infestation of D. citri started from border trees in the grove where possibly one generation is completed before inner trees become infested. In addition, psyllid densities decreased significantly with increasing distance from the grove edge. Using the selection index, D citri exhibited a strong niche occupation preference for border trees.

No MeSH data available.


Related in: MedlinePlus