Damage caused by two kinds of scale insect on Pyrus sinkangensis
Author of the article:ZHANG Bei1** Adil·Sattar1*** Yasin·Ghopur2 ZHOU Wei-Feng
Author's Workplace:1. College of Forestry, Xinjiang Agricultural University, Urumqi 830052, China; 2. Korla Harayama Forestry Station, Korla 841000, China
Key Words: Quadraspidiotus slavonicus (Green); Quadraspidiotus perniciosus (Comstock); damaging characteristics; harm stage; diffusion pattern
Abstract:
[Objectives] To clarify the cause of the red spot on Pyrus sinkangensis, identify the scale insects that damage the fruit
of this species and how these spread. [Methods] The damage caused by two kinds of scale insect
were observed during the development of pear fruit by artificially
inoculating P. sinkangensis at fixed points.
The subsequent spread of these pests was monitored using the hanging yellow
board method. [Results] During
the the fruit growing period, second generation nymphs of Quadraspidiotus
perniciosus crawl onto the fruit and cause the spots visible on the surface
of fruit in the middle of July. Dark red spots occur where the fruit is reddish
and dark green spots when damage occurs in unpigmented areas. Early stage fruit
are harmed by 1st instar nymphs of Quadraspidiotus slavonicus (Green).
1st instar nymphs of this species drift on the wind to pear leaves
and fruits from adjacent poplar forests causing red spots to appear on the
surface of fruit in late May and early June. When the wind scale was about 2-3,
1st instar nymphs of Q. slavonicus dispersed a maximum of 50
m and the mean number caught on yellow sticky boards under these conditions was
0.011 per one cm2. When
the wind scale was about 5-6, 1st instar nymph could disperse up to
150 m, and the mean number caught on yellow sticky boards was 0.239 per one cm2. [Conclusion] The red spots on
young fruit of P. sinkangensis are caused by 1st instar
nymphs of Q. slavonicus. Important factors influencing the spread of
this pest to P. sinkangensis orchards are the height of the poplar
forest zone, the wind force, and the number of insects. Spots on pears during
the P. sinkangensis fruit growing period (mid-July) were caused by 2nd generation nymphs of Q. perniciosus.