Spatial relationships among natural enemies and four insect pests over two consecutive years
Author of the article:ZHANG Shu-Ping;YU Yan; LI Shang;WANG Zhen-Xing;WANG Jian-Pan;ZHOU Xia-Zhi
Author's Workplace:School of Forestry and Landscape Architecture, Anhui Agricultural University, Hefei 230036, China; School of Science, Anhui Agricultural University, Hefei 230036, China
Key Words: 4 kinds of pests, 8 kinds of natural enemies, spatial relationship geostatistics, gray system analysis
Abstract:
[Objectives] To protect and utilize natural enemies, and
develop more scientific sampling methods, spatial relationships among natural
enemies of Ricania speculum, Ectropis
obliqua, Frankliniella intonsa and Toxoptera aurantii Boyer were investigated in the “Baihaozao” tea
gardens in suburban Hefei, China in 2015 and 2016. [Methods]
Ranges of spatial dependence (RSDs) of natural enemies were
calculated using geostatistics and the spatial relationships among predators
and pests were analyzed using grey relational analysis. This paper analyzes why
the spatial distribution of natural enemies of insect pests closely match that
of their hosts. [Results] Relational grade analysis
indicated that the spatial distribution of the three main natural enemies, Clubiona japonicola (0.859 3), Oxyopes sertatus (0.805
8) and Erigonidium graminicolum
(0.804 7) closely
matched that of Ricania speculum in
the “baihaozao” tea garden in 2015. However, in 2016, the three main enemies
were Erigonidium graminicolum (0.806
2), Tetragnatha squamata (0.792 9) and
Neoscona theisi (0.792 2), i.e. only one of the top
three predators was the same in both years. The spatial distribution of Clubiona japonicola (0.790 9); Theridion octomaculatum (0.790 4) and Oxyopes sertatus (0.789
4) also closely matched that of Ectropis
obliqua in 2015, but in 2016 the three main enemies were Neoscona theisi (0.877 7), Erigonidium
graminicolum (0.872 0) and Clubiona japonicola (0.823
0). Again, only one of the top three predators was the same in both years. The
spatial distribution of Oxyopes sertatus (0.890
0), Theridion octomaculatum (0.878
9) and Clubiona japonicola (0.843 5)
closely matched that of Frankliniella intonsa in 2015, but in 2016 the three
main enemies included Tetragnatha maxillosa (0.879
7), Theridion octomaculatum (0.866
5) and Clubiona japonicola (0.855 3);
only two of the top three predators was the same in both years although their
relative ranking was the same. The spatial distribution of Tetragnatha
maxillosa (0.819 9), Neoscona theisi (0.816
4) and Tetragnatha
squamata (0.814 2), closely matched that of T. aurantii in 2015. However, in 2016 the three main enemies were Neoscona theisi (0.840 7), Misumenops
tricuspidatus (0.814 7) and Theridion
octomaculatum (0.806 8); i.e. only one of the top three predators
was the same in both years. [Conclusion] The main reason for the observed changes
in the relative abundance of natural enemies of pests in different years is
annual variation in climate. The smaller the ratio between numbers of pests and
their natural enemies the closer the spatial relationship between them should
be because of greater competition among natural enemies for prey.