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152 Rodr�guez-Navarro et al. 2008 Table 1. Monthly temperature and humidity in the glasshouse. ments with nine replications were evaluated. In the first three treatments, mites were transferred manually (50, 150 and 200 individuals) to the stems of field bindweed (McClay et al., 1999); in another three treatments infested stems with 3, 5 or 7 galls were twisted around healthy stems of field bindweed (Rodr�guez et al., 2004; Lauriault et al., 2002). For the final treatment, no plants were infested as the controls. Fifteen days after infestations a random sample was taken to check for the presence of symptoms on the treated plants. Mite specimens were mounted on slides using Hoyer’s medium and identified by comparison with A. malherbae characteristics (Nuzzaci et al., 1985). Sampling - The number of galls and the number of stems with galls were counted from all samples taken at 15 day intervals from each of the pots. Mean temperature and humidity data for the duration of the trial were obtained from sensors connected to a Hobo H21-001 climatologic station. Statistical analyses - To corroborate the normal distribution of data, the Kolmogorov-Smirnov; Cramervon Mises and Anderson-Darling (SAS, 2001) methods were used. Subsequently differences between sample means were tested by ANOVA and a regression analysis was done. RESULTS AND DISCUSSION Because sample data did not represent a normal distribution despite transformation, the analysis of variance was not applied to the mean values, and instead the non-parametric Kruskal-Wallis (Zar, 1996) method was applied. According to Fig. 1, the selected ranges of the samples used in the comparison representing the various infested stems were not statistically different. Nevertheless a positive response was observed with all the treatments except for the controls and the treatment with infested stems with three galls each. The treatment with 150 mites, overall, produced the highest number of infested stems (Fig. 2). The non-parametric tests used for the variation of galls per plant, again, did not indicate any statistical differences between the treatments. Similarly, as mentioned before, the number of galls per plant in the controls and in the treatment using 3 galls per stem showed no response. The treatment with 150 mites again presented the highest number of galls per plant. As was the case in the controls, the absence of any response to the treatment using three galls per stem could have been the result of the low survival of A. malherbae. The regression analysis (Fig. 3) to determine the relation between the number of infested stems and the num- Fig. 1. Infested stems for the various treatments (mean values). Bars with the same letter indicate no statistical differences between treatments.
Vol. 34, No. 2 Internat. J. Acarol. 153 Fig. 2. Galls per plant (mean values). Bars with the same letter indicate no statistical difference between treatments. ber of galls per plant showed a positive linear tendency (R² = 0.969) indicating that the increase in the number of galls attached to plants resulted in a 96.9% increase in the number of infested stems: the more infested stems, the more galls are formed on them. The conditions under which the experiments were conducted could have limited the infestations and damage caused to field bindweed. Hammon (2007) mentioned an inverse relationship between the amount of irrigated water applied and the success of infestations. The daily application to each pot of 320 ml of water and the high humidity (Table 1) which occurred during the experiments could have affected the settling success of the mites, negatively. In these experiments the damage caused by A. malherbae on the leaves of field bindweed was similar to the damage observed by McClay et al. (1999) who reported that over a period of one to four years, A. malherbae caused light to severe damage to field bindweed under field conditions. Another important consideration is that when the eriophyids are transferred one by one, it is guaranteed that only A. malherbae is present in the new colony. However, this method may cause dehydration if the mites are exposed to direct heat or they may be injured while being transferred. Also, when transfering by galls it is necessary to clean the galls to avoid thrips, white flies, or spider mites. The advantages of using this method are a higher Fig. 3. Positive linear relationship in the number of galls dependent on the number of infested stems.
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