Abstract
Western flower thrips [Frankliniella occidentalis (Pergande)] is a worldwide pest insect that causes damage in pepper cultivation, so growers would benefit from host plant resistance. The objectives of this study were (1) to evaluate the effect of plant age on thrips resistance using nine Capsicum accessions with different levels of thrips resistance at three different plant ages, and (2) to study the effect of leaf age on thrips resistance in a resistant and a susceptible pepper accession. The fraction of first instar larvae that did not develop into second instar was used as a measure for thrips resistance. Our results show that plants start to develop thrips resistance when they are between 4 and 8 weeks old. This transition was most marked on the resistant accession CGN16975, on which about 50% of the L1 larvae developed into the next stage on 4-week-old plants, whereas none of them developed beyond the L1 stage on 8- or 12-week-old plants. Furthermore, it is shown that youngest fully opened leaves of the resistant accession CGN16975 are significantly more resistant to thrips than older leaves; 89% of the L1 larvae did not develop into the next stage on the youngest leaves, whereas 57% did not develop beyond the L1 stage on the oldest leaves. Young leaves of the susceptible accession CGN17219 are more susceptible than older leaves; 9 versus 52% of the L1 larvae did not develop into the next stage on young and old leaves, respectively. These findings can be used to improve integrated pest management strategies.
Highlights
Thrips is a worldwide pest insect in agricultural and horticultural crops (Kirk and Terry 2003)
We showed that on 4-week-old plants of all accessions L1 larvae can develop to the L2 stage, there are significant differences between the accessions
Between plant ages of 4 and 8 weeks, we observed an increased resistance in five of the accessions (Table 3). This transition was most marked on CGN16975, the most resistant accession included in this study, on which about half of the L1 larvae were able to develop into the stage on 4 weeks old plants; whereas on 8- or 12-week-old plants they did not develop at all beyond the L1 stage
Summary
Thrips is a worldwide pest insect in agricultural and horticultural crops (Kirk and Terry 2003). Thrips can damage plants both directly and indirectly. It is difficult to control thrips because of their high reproductive rate, short life cycle and cryptic behaviour (Cloyd 2009). Monitoring the thrips population and limiting its growth to prevent an outbreak is important. This can at least partly be accomplished by using cultural, mechanical, physical and biological control (Mouden et al 2017). In addition to these protective measures, it is highly desirable to identify plants that have a natural source of resistance against thrips, either constitutive or induced. Host plant resistance can be found in several plant species and in several forms (Smith 2005; Broekgaarden et al 2011), for example, by the presence of a modified epicuticular wax
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