Salicylates effiectiveness against termites

Tests to evaluate the effect of salicylates against termites were performed against the species Reticulitermes lucifugus (Rossi) and K.flavicollis (Fabricius).

As concerns R.lucifugus, mortality of individuals exposed to treated wood samples (5 repicates for each thesis) was the first parameter considered. Data obtained from the four theses (Control i.e. water, linseed oil, Zn-salicylate in linseed oil, Cu-salicylate in linseed oil) were statistically analyzed as dead termite percentage on the total inserted in each container (50). As variances were not homogeneous, ANOVA could not be applied. The results of non-parametrical analysis (Kruskal –Wallis), reported in the box-plot (Figure 114), show an extreme variability in the control samples, that could contribute to influence the esit of non-significative differences among theses. The 100%

mortality was observed for temites exposed to Cu-salicylate in linseed oil treated samples, but mortality is not a suitable parameter to stress possible differences among the theses since total mortality was reached by some replicates of each thesis, with a wide variability especially in case of the control samples.

The observation of the behaviour of individuals and of their interaction with wood resulted much more interesting.

Figure 114 Mortality percentage results of efficacy tests against R.lucifugus. Water=control samples;

Linseed= wood treated by immersion with linseed oil solution; Cu-Lin= wood treated with copper salicylate in linseed oil solution; Zn-Lin= wood treated with zinc salicylate in linseed oil solution.

Table 49 shows the distribution of termites within each container at the tenth day.

Termites exposed to treated wood were less attracted from the samples. This was evidenced especially in samples treated with copper salycilate where almost all the individuals were found in the surrounding sand rather than on wood. The Cu-salicylate in linseed oil formulation seems to have repellent properties against the termitical specie.

This behaviour was also evidenced by Zn-salicylate treated samples, but in this case a high mortality was also noticed, accompainied by bad health of the remaining indiviuals (cracked abdomen): as concerns Zn-salicylate formulation, the biocidal effect seems to prevail.

Finally, the mass loss data of wood samples are reported in Table 50, Figure 115.

Compared to the control samples, linseed oil samples showed a mass loss reduction, especially with the addition of copper or zinc salicylate.

Table 49 Behaviour of termites after ten days from exposition to the wood samples. Distribtion among wood and the surrounding sand. C= control; L= linseed oil; Zn= Zinc salicylate in linseed oil; Cu= Copper salicylate in linseed oil

*= cracked abdomen; O = almost all dead.

R. lucifugus behaviour (day 10)

Sample Treatment Termites on sand Termites in wood mortality

C96 Control (untreated) 7 43

C97 Control (untreated) 28 22

C98 Control (untreated) 17 33

C99 Control (untreated) 30 20

C100 Control (untreated) 37 13

Li116 Linseed oil 50 0

Li117 Linseed oil 48 2 ^*

Li118 Linseed oil 47 3

Li119 Linseed oil 45 5

Li120 Linseed oil 37 13

Zn131 ZnSAL in linseed oil 43 7 *

Zn132 ZnSAL in linseed oil 42 8 *

Zn133 ZnSAL in linseed oil 0 O

Zn134 ZnSAL in linseed oil 1 O

Zn135 ZnSAL in linseed oil 0 O

Cu146 CuSAL in linseed oil 50 0

Cu147 CuSAL in linseed oil 36 4

Cu148 CuSAL in linseed oil 33 7

Cu149 CuSAL in linseed oil 50 0 *

Cu150 CuSAL in linseed oil 49 1 *

Temperature 26,6 C

Data are in agreement with the observations of termite behaviour, since the scarce permanence of termites in treated samples caused a reduction of eaten wood. Being the variance homogeneity violated, the non-parametric analysis (Kruskal–Wallis test) was performed on weight loss data (Figure 116).

From the multiple comparison analysis significant differences only emerge between Water and Cu-Lin (z= 3.34, p= 0.005).

Table 50 Wood samples Mass loss percentage (ML%) after exposure to the termites R.lucifugus. Water=

control; Linseed= linseed oil Cu-Lin= Copper salicylate in linseed oil; Zn-Lin= Zinc salicylate in linseed oil.

Thesis (number of replicates) Average ML % (st.dev.)

1 Water (4) 2.59±0.79

2 Linseed (5) 1.10±0.06

3 Zn-Lin (5) 0.70±0.35

4 Cu-Lin (5) 0.31±0.09

Mass Loss%

0.0 1.0 2.0 3.0 4.0

C L ZN-L CU-L

Figure 115 Histogram showing the wood samples mass loss % caused by termites R.lucifugus. C= control;

L= linseed oil; Zn-L= Zinc salicylate in linseed oil; Cu-L= Copper salicylate in linseed oil.

Figure 116 Kruskal–Wallis test results histogram showing the wood samples mass loss % caused by termites R.lucifugus. C= control; L= linseed oil; Zn-L= Zinc salicylate in linseed oil; Cu-L= copper salicylate in linseed oil.

The tests with K.flavicollis shown gave worse results: the tested treatments didn’t produce significant mortality: two termites are dead in the case of samples impregnated with zinc salicylate, in copper salicylate tests too, and one dead in the test control, but in all cases the cause of death is not attributable to the action of the biocide chemicals, infact these termites were damaged at the beginning of the test.

As concernes termites behaviour, table 51 shows the distribution of termites within each container at day 15. No differences were noticed between untreated and treated samples, despite a slightly lower termites feeding activity on wood treated with copper salycilate, not sufficient to indicate preferential feeding.

Average Mass loss % data (Table 52) and histogram (Figure 117) show that termites exposed to treated wood feed the samples; this is less evident for the samples with copper salycilate. Infact, compared to the control samples, linseed oil samples didn’t show a great mass loss reduction, only the sample with the addiction of copper salicylate presents some differences. However, from the sum of mortality, behaviour and mass loss data, neither copper salicylate in linseed oil can be considered as having repellent or biocide activity against K.flavicollis at the tested concentration: the Cu-salicylate in linseed oil formulation seems morepromising than the corresponding formulation with zinc. In both cases, higher concentration values should be evaluated.

Table 51 Behaviour of termites after 15 days from exposition to the wood samples. Distribution among wood and the surrounding sand. C= control; L= linseed oil; Zn= Zinc salicylate in linseed oil; Cu= Copper salicylate in linseed oil

K. flavicollis behaviour (day 15)

Sample Treatment Termites on sand Termites in wood

C81 Control (untreated) 2 26

C82 Control (untreated) 4 24

C83 Control (untreated) 5 23

C84 Control (untreated) 0 28

C85 Control (untreated) 2 26

C86 Control (untreated) 7 21

C87 Control (untreated) 3 25

C88 Control (untreated) 4 24

C89 Control (untreated) 4 24

C90 Control (untreated) 5 23

K. flavicollis behaviour (day 15)