2. CAPITULO II: PROCESO DE INGENIERÍA DE REQUISITOS
2.5 GESTIÓN
2.5.3 SELECCIÓN DE REQUISITOS O TRIAGE
The experiments were carried out in a low-speed laminar-flow wind tunnel located at Plant & Food Research, Lincoln, between November 2010 and August 2011. For full description of
Passive dispensers. Polyethylene bags (150 micron in thickness) were made from
polyethylene layflat tubing (50 mm wide) (Accord Plastics Ltd, New Zealand). The tubing was cut into 75 mm long strips and heat sealed twice at one end using an industrial heat sealer (Accolade Packaging Ltd, New Zealand). A piece of white acrylic felt (Spotlight, New
Zealand) measuring 40 x 12 mm (for 0.5 ml MI), 40 x 25mm (for 1.0 ml MI) or 40 x 40 mm (for 0 and 2.5 ml of MI) (Fig. 2.1 a) was placed inside the tubing/bag. Commercially
available kairomone sachets (LUREM-TR lures emptied of the contents) (Koppert Biological Systems, the Netherlands) were prepared prior to the experiment by placing the sachets in a fume hood for 6 weeks at room temperature, followed by freeze-drying to exhaust the sachet of the original kairomone. In addition to these dispensers, the release rate of the commercially available thrips lure LUREM-TR (Koppert Biological Systems, the Netherlands) was tested. The commercial sachet and the LUREM-TR dispensers measured 105 x 44 x 6 mm with the centre part (50 x 34 x 5 mm) containing a white piece of absorbent material (40 x 25 x 3 mm) covered with a perforated membrane on one side (Fig. 2.1 a,b). The final dispenser type used comprised of uncovered cotton dental rolls (size 2) (Biomedics, New Zealand). The cotton dental rolls were not modified (Fig. 2.1 c).
Figure 2.1 Passive dispenser systems tested; (a) polyethylene bags (without and with methyl
isonicotinate (MI)), (b) commercial sachet (without (permeable side shown) and with (non-permeable side shown) MI), (c) LUREM-TR with MI (permeable and non-permeable side shown) and (c) cotton dental rolls (with and without MI). (Photo: M-C Nielsen).
(a) (b)
Treatments.The release rates were tested at 15+1, 25+1 and 35+2oC and under 0.1–0.15 m/s air flow (air flow I) and 0.25–0.3 m/s air flow (air flow II). The experiment was carried out under ambient relative humidity that was recorded. The cotton dental rolls were tested using 0 (control), 0.5 and 1.0 ml MI. The emptied commercially available sachet and the 150 micron polyethylene bag were tested using 0 (control), 0.5, 1.0 and 2.5 ml MI. The commercially available thrips lure LUREM-TR contains approximately 2.69 ml MI (F. Griepink 2013, pers. comm. to M-C Nielsen, 22 June 2013). The emptied commercial sachet with 0 ml MI was also used as the control treatment for LUREM-TR as the dispensers are similar. The physical and chemical properties of MI can be found in Appendix II.
Assay and design layout.The release rate was determined gravimetrically by recording weight loss (g/day). Each of the dispensers were weighed before and after adding the liquid MI (+0.001 g) to establish the weight of the added volumes (0.5, 1.0 or 2.5 ml MI). The MI was added to the cotton dental rolls and the polyethylene bags using a 3ml disposable plastic pipette (Sarstedt, Global Science, New Zealand). The top of the polyethylene bags were immediately sealed after adding the MI. Adding the MI to the emptied commercial sachets was done by directly injecting the MI through one of the existing premade holes in the perforated membrane using a 1 ml insulin syringe (BD New Zealand Ltd), thereby not puncturing the sachet. A twist tie was added to each dispenser to hang them from a wire frame within the wind-tunnel. The experiment was a split-plot design, with each temperature by air flow combination (six runs) in randomised blocks. Each run contained three sets of 12 treatments (randomised split-split plot) with each set positioned randomly within a run thus comprising a split-plot 'pseudo' treatment to increase replication. The layout is illustrated in Fig 2.2 below.
Figure 2.2 Experimental design of MI release rate experiment. The experiment comprised six runs; each run was one temperature by one air flow combination (air flow I (0.1–0.15 m/s) or II (0.25–0.3 m/s). Each run included three sets, each set comprising 150 micron polyethylene bags containing 0 (P0), 0.5 (P0.5), 1 (P1.0) or 2.5(P2.5) ml MI, emptied commercial sachet containing 0 (C0), 0.5 (C0.5), 1 (C1.0) or 2.5 (C2.5) ml MI, cotton dental rolls (CR) containing 0 (CR0), 0.5 (CR0.5) or 1 (CR1.0) ml MI and LUREM-TR containing 2.67 (L2.5) ml MI.
The dispensers were weighed daily (24+2 h) for all treatments run at 35oC. At 25 and 15oC the dispensers were weighed daily (24+2 h) for the first 3 days, then every 2 days (48+2 h). The observations for each dispenser were stopped at day 42 or earlier when the dispenser’s weight was within 5% of its original weight.
2.2.1 Data analyses
Rates of release were calculated from the average daily loss in weight (g). The data were graphed to show trends of the release rates and to examine the hypotheses to be tested. Linear regression was used to fit straight lines to the linear part of each curve, with a separate
analysis for each dispenser by temperature combination (including both air flows). The linear
Run Temp (°C) Air flow Layout of treatments and sets within windtunnel for each individual run
1 35 II Set 1 Set 3 Set 2
1C0 4 CR1 7P2.5 10 CR0 1L2.5 4 CR0 7 P0 10 C0 1 C1 4CR0.5 7 C2.5 10C0 2P0.5 5 CR0.5 8P1 11 C2.5 2P2.5 5 C1 8 C2.5 11 CR1 2 CR0 5P2.5 8 C0.5 11P0 3C0.5 6 C1 9L2.5 12 P0 3C0.5 6 P1 9 CR0.5 12 P0.5 3 L2.5 6P0.5 9 P1 12CR1
2 25 I Set 2 Set 3 Set 1
1C1 4 C0.5 7L2.5 10 CR1 1P0 4 P2.5 7 C2.5 10 P1 1 CR0 4L2.5 7 P1 10CR1 2P0 5 CR0 8C2.5 11 C0 2CR0 5 C1 8 P0.5 11 C0 2 C0.5 5C2.5 8 CR0.5 11P0.5 3P1 6 P2.5 9CR0.5 12 P0.5 3CR0.5 6 CR1 9 L2.5 12 C0.5 3 C1 6P2.5 9 C0 12P0
3 25 I Set 3 Set 1 Set 2
1P2.5 4 P0.5 7P0 10 L2.5 1P0 4 C1 7 C2.5 10 CR0 1 C0.5 4C0 7 P2.5 10P0.5 2C0.5 5 CR0 8CR0.5 11 C2.5 2L2.5 5 P2.5 8 P0.5 11 C0 2 C1 5P0 8 CR0.5 11C2.5 3C0 6 P1 9C1 12 CR1 3CR0.5 6 P1 9 CR1 12 C0.5 3 L2.5 6CR0 9 CR1 12P1
4 35 I Set 1 Set 3 Set 2
1CR0 4 CR1 7P1 10 L2.5 1C1 4 C0 7 P0.5 10 P2.5 1 C2.5 4P1 7 CR1 10C0 2C1 5 P2.5 8P0.5 11 C0.5 2CR1 5 C2.5 8 P1 11 L2.5 2 L2.5 5P0.5 8 C1 11CR0.5 3C0 6 P0 9C2.5 12 CR0.5 3C0.5 6 P0 9 CR0.5 12 CR0 3 P2.5 6CR0 9 P0 12C0.5
5 15 II Set 2 Set 3 Set 1
1L2.5 4 P0.5 7CR0 10 P0 1C0 4 P2.5 7 C1 10 P0 1 L2.5 4C0 7 C1 10P0 2CR0.5 5 C1 8P2.5 11 C0.5 2P0.5 5 CR1 8 CR0 11 L2.5 2 CR0 5CR1 8 CR0.5 11C0.5 3C2.5 6 P1 9C0 12 CR1 3C2.5 6 P1 9 C0.5 12 CR0.5 3 P0.5 6P2.5 9 C2.5 12P1
6 15 II Set 3 Set 1 Set 2
1P0 4 CR0.5 7P2.5 10 CR1 1C2.5 4 P0.5 7 L2.5 10 C1 1 CR1 4P1 7 L2.5 10C0.5 2P0.5 5 L2.5 8C0.5 11 CR0 2C0 5 C0.5 8 CR1 11 P0 2 C2.5 5P2.5 8 P0.5 11CR0 3C0 6 C1 9P1 12 C2.5 3CR0.5 6 P2.5 9 P1 12 CR0 3 P0 6C0 9 CR0.5 12C1
part of the data was identified by including only data above 0.1 g of MI remaining. For each dispenser by temperature combination, separate constants (y-intercepts) were estimated for each initial amount (as the constant estimates the initial amount), but with a single slope estimated. The slope of these regressions gave the estimated average release rate for each dispenser by temperature combination. Because the treatments involved an element of
pseudo-replication where all replicates were tested over time within the same wind tunnel, no other formal statistical analyses were applied to the data.