0633-B3

The Mathematical-Relation Between Pests and Their hosts Wood-Loss

Guo kai-yueh ¹, Wu qiao-ming ², Li chang-zhi ³

Abstract:

The result obtained by analysing the data from the observation trials of capacity for eating of the two pests, and from the measurement experiences of masson pines wood--loss when it suffers simulant attack of the pests by pinching its leaves both of which have been done in several trial plots in Guizhou province from 19971999 shows:

1. one pine caterpillar (Dendrolimus punctatus Walker) can eat off 52.122 grams of pine leaf, or 6,090.05cm and one yellowhindwinged tussock moth (Dasychira axutha Collenette) 75.047 g, or 9,072.451 cm in one year.

2. the relation between length (L) and weight (W) of pine leaf is linear one. So is the relation between the population(n) of the pests and its hosts wood-loss(V, unit: m3) (for detail, look at the following tables, please). This paper, I think, will be useful for all of us to control the pests on masson pine more scientifically and to protect environments from pollution.

Preface

With the characteristics of fast growing, highquality wood etc. masson pine (Pinus massoniana Lamb.) is one of the most important trees for afforestation in poorer areas of Guizhou pronvince as well as in other southern pronvinces in China. But masson pine is often attacked by many pests such as pine caterpillar (Dendrolimus punctatus) yellowhindwinged tussock moth (Dasychira axutha) etc., which results in damage of more than £ 1 million (about $130,000) only in Guizhou every year. To make pest control of masson pine more economical reasonable and scientific, we have done some researches on this subject.

What and How

Object pests and trial plots:

1. pests: pine caterpillar (Dendrolimus punctatus) yellowhindwinged tussock moth (Dasychira axutha)

2. Trial plots: the Guizhou Zazuo Forest Farm the Guizhou Longli Forest Farm the Guiyang Qingyan Forest Farm the Guiyang Xifeng Forest Farm.

Procedure of the research

1. measurement of capacities for eating of the pests: the data about the capacities for eating of each pest are got by averaging the ones of four replications which are obtained by observing and recording the number of the leaves eaten by the pests every other day from March ¨CDec. 1997 (there are 1015 object pests in each replication) and summing them up.

Collecting the data about leaf of masson pine:

1. measure the total length and weight of fifty pine leaves pinched from the normal sample tree belonging to each of four agegroups(510 1115 1620 and older than 20 years) on 1st and 15th of every months.
2. make regression formular with the data about weight and length of the pine leaves

Measure woodloss of the sample trees when their leaves are pinched in different levels

1. General information: For each of the four agegroups of masson pine(same as previous ones), set a trial stand with three leafpinched sample trees as well as three normal ones at each of five leafpinching levels.
2. The five leafpinching levels:
One leaf pinching level is that the quantity of the pinched leaves should account for about 75% of total leaves of a sample tree, the second level about 65%, the third about 50% and the fourth about 25%.
3. Measure the weights of the pinched leaves of each of the sample trees at each of the five leafpinching levels.
4. Measure the diametes at the height of 1.3m and the weights of each of the pinched and normal sample trees before the trees are pinched in March as well as in December when the sample trees stop growing.
5. Measure current annual increments (CAI) of the normal sample trees by doing stem analysis.
6. Obtain CAI (a) of the normal sample trees during trial by minusing the CAI in March from the CAI in Dec.
7. Obtain the average of the CAI(a).
8. Obtain the CAI(b) of the leafªpinching sample trees and the average of CAI(b) in the same way
9. CAI(a)CAI(b) means the wood loss resulting from the pinched leaves.
10. Make a mathematical regression equation between the wood loss and the quantity of pinched leaves

Result obtained

For the results obtained in detail, please look at the table No.1---5.

Conclusion

Based the results obtained, we can come to the conclusion that: 1. the relation between population of the pests and their hosts woodloss(unit: m3) is a linear one with at least a correlation coefficient(R) of 0.80. 2. a young tree is much more sensitive to the pests attack than elder one.

The pests attacking from March will do much larger damage to their host than one from September.

Discussion

1. Because the places the trial is carried out are limited within the territory of Guizhou province, China, the regression equation , Im afraid, may not suit to other distribution areas of masson pine.

2. For masson pine at age of 25 years or older one, each of the regression equation maybe is not the best one.

Reference materials:

1. Chen J.L. etc. 1987, Economics for control of pests, the Publish House of Chongqing University.

2. The compilers of < mathematical statistics>, 1980, mathematical statistics, the Forestry Publish House of China.

3. The Forestry Department of Anhui Agriculture Institute, 1982, the masson pine, the Publish House of China.

4. The compilers of < Forest mensuration >, 1992, Forest mensuration, the Forestry Publish House of China.

5. Yang S.Y. & Zhou Z. X. 1989, Division of productive areas of masson pine in Guizhou province, Collection of Guizhou Agricultural College -----research on masson pine, Vol. 1213 (ò): 6076.

table 1 the relation between L and W of pine leaf unit: g, cm

table 2 the relation between the number(n) of pine caterpillar and wood-loss(V, unit: m3)

table 3 the relation between the number (n) of yellow-hindwinged tussock moth and wood-loss(V, unit: m3)

table 4 the relation between the number of pine caterpillar (n) and wood-loss(V, unit: m3)

table 5 the relation between the number(n) of yellow-hindwinged tussock moth and wood-loss(V, unit: m3)

¹ The Forestry Secondary School of Guizhou, Zazuo, Xiuwen county, Guiyang city, Guizhou province, the Peoles Republic of China, zipcode: 550201,
Phone: 08512354037.
E-mail: [email protected].

² (same as above) phone: 0851¡2354120
E-mail: [email protected].

³ (same as above)
phone: 0851¡2354136