In this project, locally sourced entomopathogenic nematodes (EPNs) were assessed for their potential as a biological control agent for mealybugs. The intention is to determine if it could be used in an integrated pest management system and to provide an alternative for chemical control.
- Four local EPN species were screened for their efficacy against female mealy bugs;
- The most potent species were Heterorhabditis noenieputensis and Steinernema yirgalemense;
- Since S. yirgalemense was previously shown to be highly effective against a range of pests, the effects of temperature and humidity on the infectivity of S. yirgalemense to female mealybugs were also assessed;
- The project was carried out under optimal conditions in a lab.
- The application of S. yirgalemense at 25°C yielded the highest mortality, of 72%, followed by 45% mortality at 30°C, and only 9% mortality when applied at 15°C;
- S. yirgalemense performed best at 100% relative humidity (RH), resulting in 70% mortality;
- Decreasing RH levels resulted in decreased mortality;
- As a soil-based organism, S. yirgalemense is most effective as a biocontrol agent of mealybugs under conditions of moderate temperature and high humidity;
- This EPN shows promise as a potential biocontrol agent against mealybugs because it is indigenous and highly lethal to mealybugs.
SIGNIFICANCE OF STUDY:
EPNs are soil-adapted and consequently require high levels of relative humidity in order to infect their hosts and a thin film of water to enable movement. Each EPN species is also sensitive to different temperatures and relative humidities. In this study, two of these species proved to be good candidates for biological control agents against mealybugs. In order to use them as a foliar application, an application method that preserves ideal conditions to prolong their persistence and allow for optimum activity and infectivity will need to be optimized. Once the EPN infected the mealybug, they survive easily.
- Platt, N.F. Stokwe, A.P. Malan. S. Afr. J. Enol. Vitic., Vol. 39, No. 2, 2018, p 208-215