Paper presented at the 52nd CFCS Annual Meeting, Guadeloupe, July 10-16, 2016 75 WP) and four received no insecticide but were drenched with water. The imidacloprid solution was prepared according to the label rate of 0.7-1.4 teaspoon per foot height. Each plant measured approximately one foot. A total of 2.25 g of imidacholprid was mixed with 2 liters of water in a plastic bottle. Each plant received a total of 200 ml of solution that was applied to each pot by pouring over the soil surface. Each pot was slowly drenched with the insecticide solution in a way to prevent dripping from the bottom of the pots. The control plants were drenched with the same amount of water. Leaves were removed and placed in petri dishes, one adult per plate, and examined 24 hours after treatment. This was repeated 2, 3 and 7 days after treatment with fresh beetles and fresh leaves, and replicated a week later. Second and Third Instar Beetle Larvae. The three experiments described for adults were repeated using second and third instar beetles. All other procedures were the same. Indirect Contact – Treated Scales. A total of 10 plants infested with different stages of croton scale were divided into two groups (five plants each). The first group was sprayed with bifenthrin (Talstar P) and second group (control) was treated with water only. The bifenthrin solution was prepared according to the label rate (0.16 oz/gal) for ornamental trees as described above. This test was repeated one week later with a new set of plants. A second experiment was done with imidacloprid (Merit 75 WP), using the above-mentioned protocol and rate for trees and ornamentals. A third experiment used the drench method of application of imidacloprid (Merit 75 WP) following the same protocol previously described. Scales were removed from either control or treated plant three hours after treatment, and were placed in petri dishes with one adult beetle each; the experiment was repeated with second and third instar beetle larvae. Monitoring was done at 3, 6, 12, 18, 24 and 48 hours to determine if the beetles had died after exposure to the treated scales. This test was repeated one week later with a new set of plants. Statistical Analysis. Statistical analysis was carried out using SAS 9.1 (SAS, 1996). Average mortality data were collected for each test. The data from the initial and repeated tests (T1) and (T2) were combined because there were no differences between the results of the two tests. ANOVA was used to analyze the data to determine the effect of insecticide exposure and method of application on the predatory beetle. Response of adult T. montezumae to two different insecticides was subjected to Probit analysis using the POLO program (Russell et al. 1977). The responses were considered not significant if the 90% confidence limits at the LT50 overlapped. A likelihood ratio test of equality of parallelism was run to determine whether the regression lines were parallel (Robertson and Priesler 1992). Main results Biology of Thalassa montezumae Thalassa montezumae has a holometabolous life cycle that includes four larval instars (Figure 1). Under laboratory conditions, they can complete their life cycle in 28 to 37 days (Table 1). At a constant temperature of 27¹2°C on a diet of P. howertoni, the mean duration of each stage was as follows: egg 8.2 days, first instar 4.7 days, second instar 2.8 days, third instar 2.8 days, fourth instar 6.3 days, and pupae 9.3 days. Development from egg to adult was 34 days on average.
Figure 1. Immature Stages of T. montezumae. Photo by Netalie L. Francis.
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