What are the control methods for the tortoise wax scale on jujube trees
In recent years, the tortoise wax scale (Ceroplastes japonicus) has spread through the counties of our city, causing serious damage, which has generally weakened the vigor of jujube trees, significantly reduced yields, and even caused total crop failure. In order to effectively carry out chemical control of the tortoise wax scale on jujube, since 1996 we have carried out trials on controlling the tortoise wax scale on jujube for 4 consecutive years, and achieved notable benefits.
1. Determining the favorable period for spraying to control the scale
On the 4th-5th day after the eggs of the tortoise wax scale hatch into nymphs, the nymphs become covered with a white waxy layer, which grows thicker day by day and is difficult to control with chemicals. Therefore, the most effective period for chemical control of the scale is within 3-5 days after the eggs hatch into nymphs, before the nymphs become covered with wax. However, because this pest lays a large number of eggs and reproduces in great numbers, and its eggs hatch into nymphs over a relatively long period, it is very difficult to determine the spraying period for controlling this pest. In the choice of chemicals, they must both eliminate newly hatched nymphs and kill eggs, and must also have a strong penetrating killing effect on nymphs that have just become covered with wax.
In order to determine the most effective period for chemical control of the tortoise wax scale, in 1996-1997 we set up 9 trial sites in 8 counties (districts) and observed for two consecutive years, and concluded that the early hatching stage of this pest in our city is July 5-7, the peak stage is July 12-15, and the late stage is July 19-23. Therefore, the effective period for control should be these three periods.
2. Chemical control results
In 1997, we carried out chemical control trials at each trial site during these three periods, using 40% isocarbophos at 1000 times dilution plus the adjuvant Hailiping at 1000 times dilution. At each site, 2 trees were fixed, and on each tree 5 branch segments 10 cm long were randomly selected from five positions, east, west, south, north and top, tagged and fixed, and the number of pests before and after spraying was investigated.
The results showed that before spraying there were on average 64 pests per branch segment, and after three chemical control applications there were 2.3 pests remaining per branch segment, a reduction in pest population density of 96%.
The trial results show that the chemical control of the scale carried out as required was suitable and effective both in terms of timing and chemical selection.
3. Effect of scale control on restoring tree vigor and yield
While controlling the scale, at each trial site we selected 4 jujube trees of similar age and vigor, sprayed 2 trees and left 2 trees unsprayed as a control, and the following year investigated the number of new jujube heads and permanent secondary branches as well as the yield.
The results showed that the treated trees had on average 103.75 new jujube heads per tree, an increase of 96.7% over the control's 52.75, and 12 permanent secondary branches per jujube head, an increase of 58.6% over the control's 7.75, and the yield was 40.75 kg, an increase of 162.1% over the control's 15.55 kg.
The trial results show that after chemical control of the scale, there was a clear effect on the recovery of tree vigor and yield in the second year.