Integrated control of aphids on lettuce [Lactuca virosa] varieties resistant to Nasonovia ribisnigri
1999
Aarts, R. | Schut, J.W. | Driessen, R. | Reinink, K. (Rijk Zwaan Zaadteelt en Zaadhandel, De Lier (Netherlands))
The aphid Nasonovia ribisnigri was found to be the most frequently occurring aphid on lettuce in northwest and central Europe. Because it can be found in closed lettuce heads, it is difficult to control with insecticides. In 1978 a Lactuca virosa accession with resistance against this aphid species was discovered. The resistance was introgressed in L. sativa. In 1997 Rijk Zwaan was the first breeding company to introduce commercial lettuce varieties comprising this new resistance. This study investigates the possible reduction of insecticide use by growing these varieties. For this purpose we performed five experiments distributed over one season (1997) and two locations. Resistant and susceptible crisphead lettuce varieties were grown and treated on the basis of a fixed application schedule (T2) or in the case of aphids observed in the crop (T1). Both treatments were compared with an untreated control (T0). At the harvestable stage of the lettuce we observed the number of aphids per head. This number is an indication for the marketability of the head. In general the untreated resistant varieties contained less aphids than the treated susceptible varieties. We conclude that only one or two insecticide treatments are necessary, i.e. cost-effective, when growing Nasonovia-resistant lettuce varieties. This may reduce the use of insecticides in the production of crisphead lettuce by 60-90/.
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