Itzhak Secker-Esquira
State Greenhouse Extension Specialist
Ministry of Agriculture, Israel

Abstract: UV-absorbing covers can prevent greenhouses from infections caused by insects, and associated viral diseases distributed by them. Nevertheless, using the UV-absorbing cover is liable to cause malfunction of the main pollinators such as - honeybees and bumblebees.

Experiments were conducted in two sites (north and south of Israel) Two plastic films were studied in each site, regular thermal film 150 (Ginegar Co.) and UV absorbing thermal film 150µ (Ginegar Co.). The covering materials had equal properties for excluding the ability of absorbing in the UV range. The greenhouses sidewalls were protected with 50 mesh insect proof net (Meteor Co.) Tomatoes (cv. 191, Zeraim) were planted on 2/9/98.and seven yellow sticky traps (14 x 20 cm) were placed to monitor insects. The traps were replaced every week. Trap installation was initiated on 10/9/98 and ended on 7/1/99. During February, mapping conducted TLYCV infection.

Observation of bee activity was performed on fixed days: during two weeks following installation of the beehive in the greenhouse every two days then - once in a week.

The total amount of insects in greenhouses covered with regular cover was twice more than in greenhouse covered with UV-absorbing cover. Mapping of tomato viral infection caused by TYLCV led to viral infection detection levels in 463 plants in a greenhouse covered with regular cover, compared with 98 plants infected in the greenhouse, covered with UV-absorbing cover. The model for scattering of infected plants in two greenhouses was significantly different. No significant difference in bumblebee activity was observed due to greenhouse cover material. Total yield was not significantly different between the treatments except on clusters with 5 fruits.

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