evaluation of mediterranean fruit-fly traps for use in sterile-insect-technique programmes

J. Appl. Ent. 11 8 (1994), 442452 0 1994 Blackwell Wissenschafts-Verlag, Berlin ISSN 0931-2048

University of Thessaloniki, Department ofAgriculture, Laboratory of Applied Zoology and Parasitology, Thessaloniki, Greece

Evaluation of Mediterranean fruit-fly traps for use in sterile- insect-technique programmes

By B. I. KATSOYANNOS

Abstract

This paper contains information on a 5-year experimental programme, coordinated by the International Atomic Energy Agency (I.A.E.A.), on Mediterranean fruit-fly (medfly); Ceratztic ca ztata (Diptera,

sterile-insect-technique programmes under various climatic and ecological conditions. The experiments were conducted in Greece during the months July-Se tember, 1987-1991, in a citrus orchard on the island of Chios. Seven different trap types and severaftrap treatments consisting of combinations of visual and olfactory (food, sexual) attractants were tested according to the coordinated protocol. Additional trap types and treatments were also assessed in additional experiments. Among the treatments tested, the most effective in terms of total captures was the International Pheromones' Plastic McPhail Trap (IPMT), baited with a water solution containing the protein Nulure" 9 %, borax 3 % and having a Trimedlure (TML) plug in a basket hung from the trap ceiling. This treatment captured predominantly males and was relatively selective for medflies since, apparently, TML has repellent effects on non-target insects and in part, on medfly females. The same treatment without TML was almost as effective as the above treatment, capturing predominantly females but also a large number of non-target insects which renders it problematic. The IPMT was as effective as the other McPhail Trap version tested, including the classical glass trap. The international1 used Jackson Tra baited with a TML plug was the most convenient in terms of handling and perf?mned well under pow to medium population densities. However, with high populations, its sticky surface was too small to capture the corresponding proportions of males. Under high population densities, larger sticky traps or dry traps with a much bigger carrying capacity are more suitable. Some of the Nadel-type traps such as a Hawaiian and a Moroccan version (the Ma hrebmed trap), or even a dry IPMT baited with TML and DDVP, were very effective and are probabk suitable for dry and dusty areas. However, with some of the traps, such as the Hawaiian type, most of the captured flies were frequently removed by yellowjacket wasps (Vespula germanica L.) entering into the trap.

Tephritidae) trapping. The aim of the experiments was to standardize trapping met R ods for use in

1 Introduction

Although several effective trapping systems for the Mediterranean fruit fly (medfly) Ceratitis capitara (Wied.; Dipt., Tephritidae) have been developed (BAKER et al. 1988; VILLEDA et al. 1988; HENDRICHS et al. 1989), a standard trapping system suitable for use in sterile- insect-technique (SIT) programmes under different climatic and other ecological conditions throughout the world is apparently unavailable.

In order to evaluate existing or newly developed traps for use in medfly SIT programmes, a 5-year coordinated research programme was initiated and supported by the International Atomic Energy Agency (I.A.E.A.). Researchers from nine different European countries, as well as northern Africa and Central America, assessed, under their particular conditions, new and existing medfly trapping systems using standard experimental protocols. In some cases, additional questions that arose during the trapping experiments were also addressed.

This paper reports on the main findings of that study and on some additional related experiments conducted on the island of Chios in Greece.

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Evaluation of Mediterranean fruit-fly traps 443

Tdble 1. Climatic data from the island of Chios, Greece, taken from t h e meteorological station a t Chios airport, 2 km from the experimental area. Average values over 10 years (1966-1976)

Month Average air temperature ("C) Precipitation Avg. no. of Avg. rel. Avg. Min. Max. (mm) days with rain humidity (%)

January February March April

June

August September October November December

Total

May

July

9.9 6.9 10.0 7.5 11.6 8.8 15.2 12.1 19.2 15.9 24.3 20.7 26.5 22.8 26.7 22.9 22.8 19.4 18.7 16.2 16.0 13.6 12.7 10.5 - -

12.9 13.0 14.5 18.8 23.7 28.5 31.2 31.3 26.6 22.0 18.8 15.1 -

133.5 101.4 76.2 24.0 34.2

3.2 0.3 0.1

11.0 23.7 90.8

151.2

649.6

15.9 12.8 11.3 8.5 5.8 3.4 0.7 0.5 3.0 6.9

10.2 16.4

95.4

71.8 70.3 67.7 65.4 63.3 53.6 48.4 48.0 56.0 64.3 71.8 74.7 -

2 Materials and methods

2.1 Generalities

The experiments were conducted from July to September in 1987-1991, in the island of Chios, Greece, which is located in the central Aegean sea, about I0 km off the west coast of Turkey. The weather on the island is typically Mediterranean. During the experimental period, it was characterized by moderate to high tern eratures, moderate humidity, and moderate to strong wind, usually from the north (Table 1). No raini l l occurred during the 5 years of the experiment. The experimental area was approximately 1 km west of the eastern coast of the island at an altitude of 1-2 m above sea level, in the middle of a 20 kmz area mostly cultivated with various Citrus spp. trees, especially mandarins and oranges. In the same area, medfly host trees other than citrus are present, such as apricots, pears, and, especially, figs which are a host of preference. In figs, the fly breeds from mid August until late October. The experimental farm consisted of ca. 4 ha planted with various host trees, mostly citrus, and non-host trees and vegetables. It has been used several times for medfly experimentation (KATSOYANNOS 1983, 1987, 1989). For the experiments, the citrus trees in the orchard were used while, for some additional experiments conducted at the same time, other trees were also used.

2.2 Research coordinated experiments

The traps and materials used were purchased and rovided by the I.A.E.A. The ex eriments were conducted according to the experimental rotocol Bescribed by the I.A.E.A. for the Erst year of the experiments and remained almost unmodigd over the entire 5 years. In brief, the experiments consisted of cornlaring, each year, 5-6 trap treatments in five experimental blocks using a complete randomized block esign, with three replicates in a time sequence, each replicate lasting 2 weeks. The t r y types and the attractants used each year (except the first one) were decided during research coor inatlon meetings in which the results of the previous year(s) were evaluated and discussed.

The tra placement and other experimental details were as described by the experimental protocol provided the I.A.E.A. In all years, the traps were sus ended either on orange o r mandarin trees, 1- 2 m from t e ground, at a distance of 10-15 m from eacLother, in the shade, and in the southeast part of the tree canopy. During the experiment, all citrus trees bore unripe, green, hard fruit which were unsuitable for oviposition and remained uninfested during the experimental period. The fruit diameter was 3-8 cm for oranges and 2-4 cm for mandarins and increased with time from the first to the last replicate. Apart from that normal crop and usually at the beginning of the first replicate in July, a few mandarin, orange, and sour-orange trees also bore some ripe old-crop fruit that were infested with medfly and fell to the ground during the time of the first replicate. Flies captured in July mainly originated from late (May-late June) ripenin infested oranges and sour oranges, while those captured in August and September originated mainly from figs.

All traps were checked twice a week and the number of medfly males and females was recorded. In

444 B. I . Katsoyannos

addition, other insects captured were also recorded. During the 5 years of experimentation, the following combinations of trap types (Fig. la-g), and attractants were assessed:

1987 experiments: Conducted August 17-Se,ptember 28. 1 .JT (TML): Jackson Trap (JT) provided with a white sticky insert and baited with 2.0 m liquid Trimedlure“ TML on a 1 cm diameter, 4 cm long cotton wick; 2. IPST (TML): triangular, yellow-coloured sticky trap containing a sticky surface about double the size of that of the Jackson trap, provided by International Pheromones Ltd, baited in the same way as trap T1; 3. IPMT (TML+NU+B): International Pheromones’ Plastic McPhail Trap baited with 300 ml solution containing rotein Nulure@ 9 % (NU), borax 5 % (B), and 86 % water (by weight), plus a cotton wick impregnate!with TML as in T1 and 2, and suspended by a wire from the tra ceiling; 4. IPMT (NU+B): As with T3 but without the TML; and 5. IPMT (AS): IPMT trap baited witg a water solution containing 5 % ammonium sulfate salt.

1988 experiments: Conducted Iuly 22-September 2. 1. JT, w (TMLP): as with T t in 1987 but baited with a TML-impregnated plug (Magneto Trimedlure 70-0 Plug, 2g Active; provided by AgriSense Inc., Fresno, C A 93722, USA) that was placed in a 2 x 3 cm plastic basket hung inside the trap in the middle of the horizontal wire hanger; 2. JT, y (TMLP): as with T1 but with a yellow-coloured sticky insert (provided by the I.A.E.A.) suggested to be more effective than the white one; 3. IPMT (TMLP- + N U + B): IPMT trap baited with a 300 ml solution containing 9 % Nulure, 3 % borax and 88 % water, plus a Trimedlure plug hung by a wire at a third of the distance from the trap-ceilin centre to the trap opening; 4. IPMT (TMLP + NU + B + DDVP): as with T 3 but including a DDVP (&hlorvos) plug hun on the same wire with the TML plug but near the trap ceiling; 5. IPMT (NU+B): as with T 3 but wit lout the TMLP; and 6. IPMT (NU+B+AS): as with T 5 but including 5 % ammonium salt in the solution.

1989 experiments: Conducted July 21-September 1. 1. JT, w (TMLP): as with T 1 in 1988 experiments; 2. JT, y (TMLP): as with T 2 in 1988 experiments; 3. IPMT (NU+B): as with T 5 in 1988 experiments; 4. IPMT (TMLPc + N U + B): as with T 3 in 1988 experiments but with the TML plug hung near the trap ceiling; 5. IPMT (TMLPo + NU+B): as with T 4 but with the TML plug hung near the rim of the internal trap opening; and 6 . SDT (TMLP + DDVP): dry trap (Nadel type, Spanish version known as ‘mosquer6’) baited with a TML and a DDVP plug, both in the same basket, hung from the trap ceiling midway between the trap ceiling and floor.

1990 experiments: Conducted July 6-August 17. 1. J T (TMLP): as with T 1 in the 1988 experiments; 2. IPMT (NU+B): as with T2 in the previous 2 years; 3. IPMT (TMLPo+NU+B): as with T 5 in the previous year; 4. HDT (TMLNALP): dry trap (Nadel type, a Hawaiian version) baited with Trimedlure and naled as a killing agent, combined in the same plug (Trimedlurenaled) placed in a plastic basket fixed in the interior of the trap cover; and 5. HDT (TMLP + NALP): as in previous years but with TML and naled in separate plugs put into the same basket.

1991 Experiments: Conducted July 19-August 30. 1. J’r (TMLP): as with T1 in the 1988 experiments; 2. IPMT (NU+B): as with T 5 in the 1988 experiments; 3. G M T (NU+B): Glass McPhail Trap (like those used in the USA, provided by the I.A.E.A.), baited as in T 2; 4. HDT (TMLP + DDVP): Hawaiian type of dry Nadel trap, as with T 4 and 5 in the 1990 experiments, baited with a T M L plug and provided with a DDVP plug in the same basket as a killing agent; and 5. M D T (TMLP + DDVP): Moroccan version of Nadel dry trap (Maghrebmed type) trap baited as in T 4. In all experimental years the three replicates were run one after the other in the same blocks by re- randomizing the trap position within the blocks. At the beginning of each replicate, new TML and DDVP (or naled in 1990) plugs were used and the liquid bait of the McPhail Trap types was renewed at each trap check, i.e. twice a week.

The trap capture data of each year were analysed using the non-parametric test for multiple com- parisons as described by WILCOXON and WILCOX (1964).

2.3 Additional experiments

In most years, along with the coordinated experiment, additional ex eriments were conducted. The purpose of these experiments was either to answer questions arising {om the results obtained during the coordinated experiment or to extent the coordinated experiment by testing additional trap types (fig. h,i) and/or treatments.

Most of the additional experiments were conducted in the same area with, and during the same eriod or immediately after the termination of the coordinated experiment. In the former case, other

gost o r non-host trees outside of the experimental citrus orchard were used while, in the latter case, the citrus trees in the experimental orchard were also used. When two treatments were to be compared, the two traps of each pair were hung either on the same tree (when big fig trees were used) 2-5 m a art, or in nearby trees of the same species, 5-10 m apart. Each replicate consisted of the total captures [om two consecutive checks of a pair of traps. At the first check, the positions of the traps were interchanged.


17

d

P

e

n

C

A i

Fig. 1. Various trap types tested during the coordinated (a-g) experiments and other types tested during the additional experiments (h-i): a. (JT). Jackson Trap provided with a white sticky insert and baited with 2.0 ml liquid Trimedlure @ (TML) on 1 cm diameter, 4 cm long cotton wick (1987), or, with TML- impregnated plug (‘Magnet’@ Trimedlure 70-0 Plug, 2g Active provided by AgriSense Ltd, Fresno, CA 93722, USA,) placed into a special plastic basket hung inside the trap in the middle of the horizontal wire hanger (1988-1991); b. (IPST). Triangular, yellow-coloured sticky trap with a sticky surface about double that of the Jackson Trap, provided by International Pheromones Ltd, baited with 2.0 ml liquid TrimedlureO (TML) on 1 cm diameter, 4 cm long cotton wick (used in 1987 experiments); c. (IPMT). International Pheromones’ plastic McPhail Trap type. In its standard use it was baited with a 300 ml solution containing protein Nulure@ 9 Yo (NU), borax 3 % (B), and 86 % water (by weight); d. (SDT). Dry trap (Nadel type, Spanish version, trap known as ‘mosquero’) baited with a TMLP and DDVP plug, both in the same basket, hung from the center of the trap ceiling at midway between trap ceiling and floor; e. (HDT). Dry trap (Nadel type, Hawaiian version) usually baited with Trimedlure and DDVP placed in a plastic basket hung from the center of trap ceiling near the trap opening holes or stuck in the center of the trap cover; f. (GMT). Glass McPhail Trap (like those used in the USA), baited as with IPMT; g. (MDT). Moroccan version of Nadel dry trap (‘Maghrebmed’ type), baited withTMLP and DDVP in the same basket hung in the middle of the trap; h. (UNI-trap). Modified Universal Moth Funnel trap by International Pheromones Ltd, baited with TMLP and DDVP hung near the trap ceiling or placed in trap bottom; i. New ‘Dome’ trap. Plastic McPhail Trap version provided by AgriSense Ltd and baited as with the IPMT

446 B. I . Katsoyannos

Table 2. Medfly captures per treatment during 1987. Experimental period: August 18-September 28. Data of five blocks with four counts in each 2-week test; three replicates

Treatment Captures per trap per replicate' 0% of % % Males Females Total total males females

1 . JT(TML) 26.3"b 0.2̂ 26.5= 6.1 99.2 0.8 2. IPST (TML) 107.2" 0.5a 107.7"b 24.7 99.5 0.5 3. IPMT (TML+NU+B) 61.0" 68.4' 129.4bc 29.6 47.1 52.9 4. IPMT (NU+B) 4.9h' 148.3' 153.3' 35.1 3.2 96.8 5. IPMT (AS) 1.5' 18.2b 19.7" 4.5 7.8 92.2

' Means in each column followed by the same letters are not significantly different at P < 0.05.

The time between tra checks varied, according to the population densities, from 1-5 days. A similar approach was used wten three treatments, were com ared but, in this case, the position of the tra s

group of treatments. Details concerning each particular test in the most relevant additional experiments are iven below.

Tke trap-capture data from the experiments in which three treatments were compared were analysed using the non-parametric test described by WILCOXON and WILCOX (1964), and those in which two treatments were compared using the WILCOXON signed-rank test.

was rotated at each check and a replicate consisted orthe total captures from a full trap rotation o P a

3 Results

3.1 Co-ordinated experiments

3.1.1 1987 experiments

The results obtained are given in table 2. In terms of total captures, the most effective trap was the IPMT baited with Nulure (NU) and Borax (B) (T 4), followed by the same trap type in which Trimedlure (TML) was added (T 3), and then the IPST (T 2). The Jackson Trap was less effective (T 1) and the IPMT baited with ammonium salt solution was even less effective (T 5). This latter treatment seems to be unsuitable for medfly trapping and was excluded from further testing. For males, the most effective trap was the sticky TML- baited IPST, followed by T 3 (IPMT baited with TML, NU and B), and then the Jackson Trap. Concerning females, by far the most effective trap was the IPMT baited with N U and B, followed by T 3. Sticky traps baited with only TML captured almost exclusively males (about 99 % of the total flies captured) whereas the IPMT baited with NU and B captured mostly females (92.2 % of the total captures by this treatment) and 2-3 times more females than the same treatment when TML was added. The reduced number of females captured in T 3 as compared with T 4 indicates that TML had a repellent effect on medfly females, as suggested by ZERVAS (1987), and also on other insects, especially Diptera.

Sticky traps baited with TML captured a very limited number of non-target insects whereas IMPT traps captured large numbers of non-target insects, especially in the case of those baited with only NU and B (T 4). Thus, during the three replicates, 41, 81, 5401, 11268, and 2832 non-target insects were captured by T 1 to T 5 , respectively. The high number of non-target insects captured by Nulure-baited IPMTs, not only during 1987 but also in the following years (up to IOOO per trap per check day in some cases), render segregation and counting of medflies difficult, especially with high medfly populations.


As shown in table 3, IMPT baited with NU, B, and TML (T 3) was the most effective for males, which were probably for the most part attracted by the TML, while the presence of

Evaluation of Mediterranean Jruit-fly traps 447

Table 3. Medfly captures per treatment during 1988. Experimental period: July 22-September 2. Data of five blocks with four counts in each 2-week test; three replicates

Treatment Captures per trap per replicate' "A of % % Males Females Total total males females

1. JT,w.(TMLP) 61.5ah 0.6" 62.1b' 11.6 99.0 0.1

3. IPMT (TMLP+NU+B) 146.9& 15.7b 162.6& 30.4 90.3 9.7 4. IPMT(TMLP+NU B+DDVP) 103.7' l l . l h 114.9" 21.4 90.3 9.7

2. JT,y.(TMLP) 50.7ab 0.3" 50.9" 9.5 99.3 0.7

5. IPMT (NU+B) 20.9J' 94.7' 115.6"' 21.6 18.1 81.9 6. IPMT (NU+B+AS) 6.1' 23.5& 29.6' 5.5 20.7 79.3

Significance see table 2.

NU in the trap also attracted some females. However, the number of females was much smaller than that of the same trap type without TML (T 5). This confirms the repellent effect of TML to the females, also found in 1987. The limited number of females captured by T 3, if added to the large number of males, rendered this treatment the most effective in terms of total captures (30.4 % of the total of the 6 treatments). The addition of a DDVP plug in this treatment (T 4) reduced the captures, perhaps because DDVP had some repcllent effects on the flies. Similar to the previous year, IPMT with NU and B (T 5) was the most effective for females and selectively captured flies of this sex (81.9 % females). Addition of ammonium salt in the solution (T 6) rendered the combination quite ineffective. Concerning the two Jackson Trap treatments, the use of a yellow sticky insert had no positive effect on trap performance.


The overall captures in 1989 (table 4), were almost equally high in all treatments except T 6 (the Spanish version of the Nadel dry-trap type). For males, Jackson Traps with a yellow insert again performed no better than those with a white one. This result was confirmed by additional experiments conducted in this and in the following years (see below). The overall results of the three IPMT treatments were more or less the same, with T 3 (only Nulure and Borax) capturing, as expected, predominantly females (about five times more females than males), while the treatments with the addition of a TML plug captured mostly males. T 5 (TML plug near trap opening) was no more effective than the treatment with the TML plug near the trap ceiling (T 4).

Table 4. Medfly captures per trap-treatment per replicate during 1989. Experimental period: July 21-September 1. Data of five blocks with four counts in each 2-week test; three replicates

Treatment Captures per trap per replicate' Males Females Total

Y" of Yo total males

% females

1. JT,w. (TMLP) 2. JT,y. (TMLP) 3. IPMT (NU+B) 4. IPMT (TMLP'+NU+B) 5. IPMT (TMLP"+NU+B) 6. SDT (TMLP+DDVP)

' Significance see table 2.

141.0" O.la 141.1% 130.3" 0.3" 130.5^ 36.7' 182.5" 219.3h

1 3 4 2 35.0' 169.2" 186.6" 30.7' 217.3ah 53.5b 0.5a 53.9'

15.2 99.9 14.0 99.8 23.5 16.8 18.2 79.3 23.3 85.9

5.8 99.4

0.1 0.2

83.2 20.7 14.1 0.6

448 B. I. Katsoyannos

Table 5. Medfly captures per trap-treatment per replicate during 1990. Experimental period: July 6-August 17. Data of five blocks with four counts in each 2-week test; three replicates

Treatment Captures per trap per replicate' % of Y" % Males Females Total total males females

1. J T (TMLP) 156.2b' 0.03 156.2" 19.5 100 0.0

4. H D T (TMLNALP) 127.6b 0.0" 127.6a 15.9 100 0.0 5. HDT (TMLP+NALP) 207.7h' 0.1' 2O7.Xab 26.0 99.9 0.1

2. IMPT (NU+B) 37.0" 245.0b 282.0b' 4.6 13.1 86.9 3. IPMT (TMLP"+NU+B) 271.7' 90.8' 362.4' 34.0 74.9 25.1

I During 1990, severe predation by yellow jacket wasps was observed in T 4 and 5. In 23 checks out of the total 60 checks made in each treatment, almost no flies were found in these traps due to predation. All data from these checks are excluded from the table.

Significance see table 2.

In contrast to previous years, Jackson Traps captured almost as many males as IPMTs with the TML plug. The low efficacy of the SDT trap (T 6) is apparently due to its constructional details since a similar dry trap (the Hawaiian type) performed well during the additional experiments conducted in 1989 and during the coordinated experiments in the following years.


In 1990, severe predation in the dry traps (T 4 and 5) by yellow jacket (YJ) wasps (Vespulu germanicu) and, to a lesser extent by ants, was observed. During the course of the three replicates, a total of 23 individual trap-checks were rejected because of this predation. Thus, in table 5, only those results in which predation was not observed are given. Concerning the first three treatments, the same tendency as in previous years was obvious. Dry traps with the TML in a separate plug from the killing agent (T 5) performed somewhat better than T 4 (TML and naled in the same plug) and better than the Jackson Trap in capturing males. There were also indications that the killing agent used was not as efficient as DDVP in killing medflies quickly.


During 1991, the medfly population in the experimental orchard was lower than 1990. Probably for this reason, despite the presence of the YJ wasps in the orchard, no predation was observed in the dry traps. The results of 1991 are given in Table 6. The Hawaiian and Moroccan versions of the Nadel trap type (T 4 and 5), baited with Trimedlure and provided with a DDVP plug as a killing agent, were the most effective traps, capturing twice as many males as the Jackson Traps. Both versions seem equally effective. Furthermore, the two Nulure-baited McPhail Trap versions (Glass, IPMT, T 2 and 3), seemed equally effective and, as expected, captured more females than males. However, contrary to the results obtained in the previous years, they captured a rather limited total number of flies, even fewer than the Jackson Traps.

The 1991 results show that as long as the medfly population is not high enough to provoke predation by wasps and other predators, the two dry traps tested (Hawaiian and Moroccan types) are very effective in capturing medfly males. In cases of predation, however, other dry traps, e.g. dry IPMTs baited with TML and DDVP, such as those tested in the additional experiments (see additional experiments below), could be useful.


Table 6. Medfly captures per trap-treatment per replicate during 1991. Experimental period: July 19-August 30. Data of five blocks with four counts in each 2-week test; three replicates

Treatment Captures per trap per replicate' % of Yo % Males Females Total total males females

1. JT (TMLP) 37.3" 0.0" 37.3" 14.2 100 0.0

4. HDT (TMLP+DDVP) 92.6' O.Oa 92.6b 35.3 100 0.0 5. MDT (TMLP+DDVP) 84.0' 0.0' 84.0h 32.0 100 0.0

2. IPMT (NU+B) 6.6' 18.3b 24.9" 9.5 26.5 73.5 3. GMT (NU+B) 6.7h 16.5' 23.3" 8.9 28.9 71.1

' Significance see table 2.

3.2 Additional experiments

3.2.1 Evaluation of the UNI trap

Modified International Pheromones' Universal Moth traps (UNI traps) were tested for their effectiveness as a dry trap for medfly (fig. h). The traps were baited with a TML plug and provided with a DDVP toxicant stripe as a killing agent. In one treatment (A), the TMLP was placed near the trap opening and the DDVP near the trap floor, whereas, in the other treatment (B), both TMLP and DDVP were placed near the trap floor. These treatments were compared with a dry (without water solution) IPMT baited with a TMLP and a DDVP stripe and were both put in a special holding basket hung by a wire in the middle of the trap. The experiment was conducted from July 26 to August 31, 1988, on mulberry, pear and olive trees.

The results (table 7, experiment 1) show that all three treatments were more or less equally effective in capturing medfly males. In all three treatments a limited number of females was also captured. Because the dry version of the IPMT has proven very effective (table 7, experiment 4) it can be concluded that the U N I trap tested is also very effective. However, it is more complicated to service and more expensive, making the U N I trap less desirable for use in SIT programmes.

3.2.2 Comparison of the Hawaiian version of the dry Nadel trap with other trap types

During the coordinated experiment of 1989, the Spanish version of the Nadel dry-trap type was found to be ineffective in capturing medfly males. During the same year, a Hawaiian version of the same trap type was provided by the I.A.E.A. and was tested in three additional experiments conducted between July 20 and September 6, 1989, on mulberry, pear, fig and mandarin trees. In the first experiment, the Hawaiian trap was compared with the Spanish version, in the second with the standard Jackson Trap, and in the third with the dry version of the IPMT reForted above.

The results are given in table 7 (experiments 2 - 4 ) . As shown, the Hawaiian version of the Nadel-trap type was much more effective than the Spanish version, capturing about four times more males (experiment 4). More females (17 vs.1) were also captured by that type of trap. Because the two traps function in a similar way, the differences in efficiency between the two trap types are probably due to their constructional differences. The Spanish type (fig. d) is basically opaque, 13 cm long with a 7.5 cm-diameter-base plastic box, with eight, equidistantly spaced, 1 cm-diameter holes for the evaporation of the attractant and the entrance of the attracted flies. O n the other hand, the Hawaiian version (fig. e) IS ' a trans- parent, 11.5 cm long plastic box, with a 9 cm-diameter floor and 11 cm-diameter top. It has four large, 2.5 cm-diameter opening holes for the evaporation of the attractant and the

450 B. I. Katsoyannos

Table 7. Medfly captures per treatment during some additional experiments conducted between 1988 and 1992

Experiment Trcatments compared’ No. of Mean medflies’.’ % of replicates captured per total

replicate

1 UNI-trap-A(TMLP, up+DDVP, down) 10 139.2= 36.2 UNI-trap-B(TMLP+DDVP, down) 127.3“ 33.1 IPMT, dry (TMLP+DDVP) 118.3” 30.7

2 DT, Spanish version (TMLP+DDVP) 9 31.3” 18.5 DT, Hawaiian version (TMLP+DDVP) 137.7& 81.5

DT, Hawaiian version (TMLP+DDVP) 3 55.7” 64.5

4 IPMT, dry (TMLP+DDVP) 9 149.4& 48.2 DT, Hawaiian version (TMLP+DDVP) 160.7” 51.8

5 IPMT(NU+B) 10 227.4“ 51.5

6 JT(TMLP) 6 657.5a 28.9 IPST (TMLP) 1620.3b 71.1

3 JT(TMLP) 9 196.1” 35.5

‘Dome’ trap (NU+B) 213.8’ 48.5

For explanations on the treatments see text. Significance see Table 2. ’ When only TML was used, almost all of the captured flies were males whereas, when Nulure was used, females were 1-3 times more prevalent than the males.

entrance of the attracted flies. The higher effectiveness of the Hawaiian trap is probably due to the size of these holes. However, these large holes, and probably its transparency, may be responsible for the severe predation of the attracted medfly males by yellow jacket wasps observed during the coordinated experiment of 1990 and in certain additional experiments in the following years (unpubl. data).

The Hawaiian trap was also found to be more effective than the Jackson Trap (experiment 3 ) , capturing twice as many flies, and almost as attractive as the dry version of the IPMT (experiment 4).

3.2.3 Comparison of the standard I P M T with the ‘Dome’ plastic McPhail Trap

Five pairs of traps using two McPhail Trap treatments, the standard IPMT, and the ‘Dome’ trap, a new, pear-shaped version of the same trap type provided by AgriSense Ltd (fig. i), baited with Nulure and borax as in the coordinated experiment, were tested between July 27 and August 12, 1991, in a citrus orchard harbouring a large medfly population.

As shown by the results (table 7, experiment 5) , both trap types captured almost the same number of predominantly female flies (777 males and 1497 females were captured by the IPMT, whereas 710 males and 1428 females were captured by the Dome trap).

3.2.4 Comparison of Jackson Trap with the IPST under high population densities

To determine the carrying capacity of the Jackson Trap and to compare it with a similar trap of a larger sticky surface, the Jackson Trap was tested against the IPST (T 2 in the 1987 coordinated experiment) in an orchard with a very high population between July 25 and August 25, 1992. Two pairs of traps were checked six times at intervals of 5 days.

The results (table 7, experiment 6) show that IPST captured about three times more males

Evaluation of Mediterranean fruit-fly traps 45 1

than the Jackson Trap. O n average, 810 males were captured per trap check using the IPSTs (max. about 1300) whereas, on average, 328 males (max. 485) were caught in Jackson traps. The carrying capacity of the Jackson trap seems to be about 300400 flies but it obviously functions optimally at lower population densities (up to 200 flies per trap).

4 Discussion

The overall results demonstrate that, of the treatments tested, the IPMT baited with N U , B, and TML was the most effective in total captures. The system attracted predominantly males but also caught a large number of females. Furthermore, apparently due to the repellent effects of TML, this treatment was much more selective for medflies than the same trap type baited with only NU and B. This latter treatment was, in general, also very effective for medflies showing a very high attractiveness for females. However, it also attracted large numbers of non-target insects. This is a disadvantage because of the time involved in segregating medflies from non-target insects. Because of the inherent difficulties in servicing a liquid-baited trap, both the aforementioned treatments seem rather incon- venient for use in SIT programs. Sticky or dry trap types are preferred. In this respect, the standard Jackson trap, baited with a long lasting TML plug which eases its maintenance, seemed to be the most convenient and showed a consistent performance with minimal problems. This trap type is the most suitable for use in low to moderate population densities. It has the disadvantage that its sticky surface is small and hence its capacity is limited to 300-400 flies per trap. At high population densities, this number of males can be captured within a few hours of the trap’s installation (unpubl. data), hence, traps which are serviced once or twice per week cannot reflect the actual size of high populations. In such cases, sticky traps with larger sticky surface such as the IPSTs, or even dry-trap types, are preferable. Two of the dry traps tested (Hawaiian and Moroccan Nadel-trap types) are not only very effective in capturing mefly males and have a big carrying capacity, but are also very convenient, easy to service, and inexpensive. However, as shown by these results, these traps are sometimes confronted with unexpected problems such as severe predation by yellow jacket wasps. In such cases, another type of dry trap should be employed such as the dry version of the IPMT tested in the additional experiments. With this trap, predation was not observed and is unlikely to occur because any wasps that enter the trap cannot easily find their way out and are usually killed by the DDVP (unpubl. data).

Acknowledgements

This study was conducted within the framework of the research coordinated project ‘Standardization of medfly trapping for use in the Sterile Insect Technique programmes’ under research contract GRE, no. 4443/Rl-R4/RB, of the International Atomic Energy Agency (I.A.E.A.). Many thanks are due the I.A.E.A. staff members for providing materials and solving administrative and financial problems. Special thanks are due to Dr. A. P. ECONOMOPOULOS, who coordinated the project, for his continuous and enthusiastic support. Thanks go also to Prof. Dr. M. E. TZANAKAKIS, University of Thessaloniki and Dr. D. R. LANCE, USDA-APHIS, Hawaii, for critically reading the manuscript.

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Author’s uddresst Dr BYRON KATSOYANNOS, University of Thessaloniki, De artment of Agriculture, Laboratory of Applied Zoology and Parasitology, 540 06 Tiessaloniki, Greece

evaluation of mediterranean fruit-fly traps for use in sterile-insect-technique programmes

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