Plant Protection Research Institute

Key words: Liriomyza spp., Diglyphus isaea,, Trialeurodes vaporariorum, Macrolophus caliginosus, Macrosiphum euphorbi, Aculops lycopersici, Pronematus ubiquitus

The population was followed during the spring, autumn and single crop growing seasons in İzmir and single crop growing season in Muğla. Leaf miners were seen at the beginning of the crop and then disapperead. Whitefly increased locally in early autumn in autumn and single crop growing, and late spring in spring crop growing. Aphid appeared only in the early sprig when the rational humidity was high. Spidermites appeared at the end of the vegetation in a low density. Thrips was found at a very low level at the beginning of the crop. Adult of the Cicadellidae species was captured on the yellow traps but any adult and nimph was found on the plants. Aculops lycopersici (Massee) was seen at the end of the vegetation in the spring growing, in early spring with the single crop growing. Noctuids were found at the beginning of the crop in a low infestation level in autumn. It was found that parasites controlled leaf miners, predators controlled whitefly, A. lycopersici, thrips, aphids, spidermites,noctuids naturally.

1.Introduction

The protected vegetable crops has been cultivated in 17,865 ha area in Turkey. Vegetables are grown 95% of the glasshouses. Of this, tomato has grown in 57%, cucumber in 27%, pepper 8%, the others 8%. In Aegean region, vegetable glasshouses occupy 19,783 ha, the production is 233,599 t. The concentration of greenhouse and outdoor crops in an area provides continuous cropping and the continuous presence of pests with carry-over and build-up taking place during the year. These circumstances are also valid for the beneficials. It is therefore necessary to follow the population growth of pests and their incidence throughout the season and also their beneficials in each locality. This study will provide population trends and determine the strategy to set up a sound method of integrated control in all cropping periods.

The project was carried out with spring, autumn and single crop growing in İzmir, and single crop growing in Muğla between 1995-1997 in the Aegean region of Turkey. Details of the greenhouses are given in table 1. The population development of whitefly (Trialeurodes vaporariorum (Westw)), leafminers (Liriomyza trifolii (Burgess)), L. bryoniae (Kaltenbach)), aphid (Macrosiphum euphorbia (Thomas)), thrips (Thrips tabaci Lindeman), tomato rust mite(Aculops lycopersici(Massee)) and leafhopper (E. decipiens and A. Decedens) were followed in 1000-1200 m² glasshouses. The adults of winged pests which were whitefly, leafminers, leafhoppers and the beneficials (Coccinellidae, Chyrysopidae, Syrphidae) were captured by yellow sticky traps (20x25 cm), placed 2 traps/da, at 15-30 cm above the plants. The adults were counted and recorded then taken from trap surface.

The larval population development of whitefly, leafminers, larva and adult aphids, spidermites and thrips were counted on 20 plants randomly selected. For each plant a top, middle and bottom leaf was taken and checked for the numbers of pests with a binocular in the laboratory. Counts were the means of larvae or individuals (adult+nimph) per leaf. The larva or nymph of the predators were counted on 50 randomly chosen leaves in the glasshouses. The larvae of Chrysoperla sp., Shyrphidae, Coccinellidae, and Aphidoletes sp., the adults of Orius niger (W.), the adults and nymphs of M. caliginosus were recorded. The parasitism ratios of leafminers, whitefly and aphids were found.

In the single and spring crop growing in İzmir and Muğla, whitefly appeared in autumn and winter at a very low level and began to increase from mid April to the end of the crop, and reached the highest incidence in mid May (fig. 1). Although large number of adults were captured (max. 1510(NO:1); 607(NO:2); 738(NO:3)adults/trap/week) the larval population was very low (max. 4,76(NO:1); 1,6(NO:2); 3(NO:3)larva/leaf) in April and May. M. caliginosus was found in the greenhouses with the appearance of the whitefly larva. The predator activity was effective (at a level of 0,03-1; 0,20-17.90; 0,2-1,52 individuals/leaf) on the whitefly larval population (at a level of 0,2-4,76; 0,03-1,6; 0,03-3 individuals/leaf). When the crop period lasted in summer, the adult population gave a second and higher peak but the larval population was at a lower level (0,01-0.3 larva/leaf) and the predator population was higher (0,3-1,5 individuals/leaf) than previously. The whitefly population was suppressed beneath the treatment threshold(5 larva/leaf), while the expected trend was an increase in whitefly population with the favorable temperature (20-30C⁰) and relative humidity (50-75%), and the high adult population in the greenhouses. In the autumn crop growing, the whitefly population was over the treatment threshold from the beginning. The source of the pests were neighboring cucumber plastic tunnels in which the plants were left for a long time after the last harvest. There was continuous and large migration of whitefly from this source. The population on the rows near the infestation source was very high (max. 138 larva/leaf). However, the population was about 5-11 larva/leaf throughout the season in the middle and the other side of the plastic tunnels. The average incidence level of the larval population was between (8-98 larva/leaf) in the greenhouses. The predator was effective in the middle and other side of the greenhouses but it remains too weak on the rows exposed the continuous and abundant migration from the cucumber tunnels.

Leaf miners were found at the beginning of the crop in all growing periods (fig 1). In the single crop growing, the adult and larval population (max. 125 adult/trap/week), 1,68 larva/leaf) was high at the beginning in Muğla. Parasitised larva (13-66%) were recorded in the period of increasing larval population. Afterwards larval population decreased gradually and disappeared in winter. Larva were not found between February-June although a few adults were captured on yellow sticky traps. In İzmir, the adult and larval populations (max. 78 adults/trap/week; 1 larva/leaf), and the parasitism ratio (1-5%) were relatively low. The larva disappeared after parasitism occurred and larval population developed again in spring at a low level (5,5 larva/leaf). In this period, no parasitised larva were found but larval and adult populations decreased at the end of the crop. Adults and larvae (max. 145 adults/trap; 0,10 larva/leaf) were recorded from the beginning of the spring crop. After the parasitised larva (6-56%) were recorded, the larval population decreased and then disappeared while adults (45 adults/trap) were captured on the trap. In the autumn crop, the larva of leafminers reached a maximum level (16.8.1995) at the beginning of the crop and then decreased rapidly and disappeared by 11.10.1995 and increased (0,30 larva/leaf) towards the end of the crop, while the adult population decreased. The larval parasitism was between (6-100%). The larval populations in all growing periods did not exceed the treatment threshold (10 larva/leaf).

Leafhopper adults were captured on the yellow sticky traps in all crop growing period but any nymph or adult was found on plant (fig. 2). Adults were found in October-December and April- June in the single crop in İzmir (max. 98 and 144 adult/trap/week) and Muğla (max. 8 and 5 adult/trap/week). They were found between August-November(325 adult/trap/week) in the autumn crop and April-June (341 adult/trap/week) in the spring crop.,

Aculops lycopersici (Massee) appeared in mid June in the spring crop.Their predator, Pronematus ubiquitus (Mc.G.) (max. 19 individuals/leaf) also began to appear with the population growth of A. lycopersici (max. 97 individuals/leaf) and suppressed the pest after a short time. In single crop A. lycopersici appeared at the beginning of May and reached the maximum level (550 individual/leaf) in Muğla, and (458,2 individuals/leaf) in İzmir towards the end of the single crop (fig. 2). The predator was not found in his crop growing period and A. lycopersici caused a severe demage.

Aphids also appeared at a low level (Max. 4 (No:1); 5,9 (No:2); 12 (No:3); 1,53 (No:1) individuals/leaf ) in humid weather conditions (autumn and spring) and did not exceed the treatment threshold (20 individual/leaf) (fig. 2). There was parasitism at a rate of 2-15% (No 1),1-5%(No 2), 15-100%(No 3), 15-56%(No 4). The predator of the aphid such as Syrphidae, Coccinellidae, Chrysoperla spp appeared and parasitism was recodede whenever aphid began to appear on the crop. Therefore aphid population was suppressed by its natural enemies.

Heliothis armigera Hübn. was only found between October-February at a rate of 2-10% infestation only in the single crop in İzmir (fig. 2). Although the infestation level was low, egg parasites (Thricogramma spp) and the larval parasitoid (Hyposotar spp.) were found and the parasitism ratios were 75% and 85%, respectively.

Thrips appeared in the autumn crop between 16.8.1997-14.9.1997 at 0,01-0,05 individuals/leaf (fig. 2, No: 3). Its predator Scolothrips longicornis Priesner, was found at a very low level 0,01 individuals/leaf in two week. Spidermites were found through to the end of the crop (0,02-0,05 individuals/leaf).

The common predators; adult Syrphidae (between 20.11.1996-11.12.1996 at level of 0,01-1 individuals/trap), adult Coccinellidae (C. semptempunctata and A.. variegata)(between 23.4.1997-02.7.1997 at level of 1-5 individuals/trap), and adult Chrysoperla spp. (in 19.02.1997 at a level of 1 adult/trap) were recorded in MuğlaChrysoperla sp (between 9.6.1996-24.6.1996 at a level of 8-20 adults/trap.), Coccinellidae (between 9.6.1996-02.7.1996 at a level of 0,35-2 adults/trap), Syrphidae (between 9.6.1996-17.6.1996 at a level of 0,02-0,2 adults/ trap) were found in the single crop (fig. 2). In the spring crop, Syrphidae (between 26.4.1995-7.6.1995 at a level of 1-7 adults/trap), Chrysoperla (between 19.4.1995- 02.5.1995 at a level of 1-3 adults/trap) appeared. In the autumn crop, Coccinellidae (1 adult/trap/week in 31.8.1995 and 25.10.1995), Syrphidae (between 31.8.1995-17.10.1995 at a level of 1-2 adults/trap/week), Chrsoperla sp (1 adult/trap/week on 31.8.1995) were recorded. Larvae were not recorded in any of the growing periods.

4. Conclusion

Whitefly occurred at the beginning of the crop in the autumn and towards the end of the crop in spring. The low infestation level at the beginning of the crop can be suppressed by M. caliginosus but continuous infestations caused the whitefly density on rows near the source to exceed the treatment threshold, but the density remained constant in the middle and other side of the greenhouse due to predator activity. It is necesssary to release adequate amounts of M. caliginosus in the highly infested parts. Leafminers were suppressed throughout the crop by its parasitoid if there wasn’t any disturbance of natural balance, although the infestation of adults was continous. A. lycopersici was suppressed when its predator was established earlier in the greenhouses with the spring crop. If A.. lycopersici increased early in spring before the predator appeared , it caused a severe damage locally to the single crop. Aphids and spidermites were found at low population levels and locally. The parasitoid of aphids (A.matricariae and L. fabarum) and the predators (C. semptempunctata and A.. variegata) were the major beneficials. They controlled the aphid population in all growing periods of tomato. Thrips , leaf hopper, spidermite, bollworm are found at a very low level and their natural enemies were found when peste appeared on the crop and suppressed the pests population.

Natural control generally suppressed leaf miners, thrips and to some extent A. lycopersici and whitefly if there was no disturbance of the natural balance. Thus, the major beneficials of the pests, Diglyphus isae Walker for leafminers, Macrolophus caliginosus Wgn. for whitefly, Aphidius matricariae Haliday or A. Variegata for aphid, Pronematus ubiquitus (McG.) for A. lycopersici, should be studied in order to support them when they are needed. The possibilities of biological control should be investigated. If preventive measures can be applied the infestation period and the level, augmentation of the pest populations can generally be prevented.

The control of insects can be achieved generally by preventive measures such as covering the ventilation opening, and using well constructed greenhouses to manipulate the temperature, humidity and ventilation. The environment should be kept clear from plant debris and infested plants. Crop should be planned to give a sound crop rotation in order to monitor the population of pests and their beneficials.