Document Type : Research Article
Ferdowsi University of Mashhad
Ferdowsi University of mashhad
Introduction. Pomegranate carob moth with the scientific name Ectomyelois ceratoniae Zeller ( Lep. :Pyralidae) is a key pest of pomegaranate and cause an economic damage to the quantity and quality of pomegranate fruits. According to reports, more than 80% of the pomegranate fruits in the garden and warehouse is attacked by the carob moth and suffers damage (Fotouhi et al., 2021).
Different methods include chemical control, use of optical traps, use of fabric nets, flag removal, use of repellent compounds such as processed kaolin with a concentration of 5% and at an interval of 20 days in four stages, collection and destruction of infected fruits on the tree and garden floor, the use of resistant cultivars and the use of Trichogramma wasps have been recommended to control the Pomegranate carob moth (Shojaei and Esmaili 1366), but so far none of these methods have been able to cause a decisive reduction in the population of the pest. Considering the importance of organic pomegranate production, the necessity of further studies on non-chemical pest control methods, especially biological control using Trichogramma wasps, is emphasized (Fotouhi et al., 2021).
Field observations indicate that the release of Trichogramma wasps is influenced by various factors, including arthropods that prey on parasitized eggs on Trichocards. So far, only a handful of studies have examined the effect of predators on the emergence rate of Trichogramma wasps on Trichocards during the release stage. For example, Al Rouechdi, and Voegele (1981) reported that after installing trichocards on plants due to the phenomenon of predation, a considerable number of wasps were destroyed before hatching and emergence of adult wasps. Also, Bento et al. (1998) and Bento (1999) announced the reduction of Trichogramma wasps (T.cacoeciae) efficiency due to the activity of predators. According to Gomes et al. (1998), ants are one of the important predators of parasitized eggs of cereal willow and thus reduce the efficiency of biological control. Suh et al. (2000) also announced the low efficiency of Trichogramma species (T.exiguum) in controlling cotton pests due to the activity of ants on parasitized eggs during the release of Trichogramma. Perira et al. (2004) evaluated the destructive effects of predators on the Trichogramma wasps (T.cacoeciae) biocontrol agent of olive willow in Portugal and reported that more than 99% of the predators of released parasite eggs are ants. Kerguntiol et al. (2013) in a research in Uruguay on reducing the destructive effect of predators on the emergence rate of Trichogramma wasps from Trichocards, considered two species of ants responsible for the destruction and destruction of parasitized eggs and with changes in the packaging of release units to somewhat reduced the effect of ants.
Despite the destructive role of predators in release stage of Trichoramma wasps for controlling plant pests, so far, no research has been done in Iran on the identification of the predators of parasitized eggs on trichocards and the extent of their influence during the release stage of Trichogramma wasps for the biological control of carob moth (Ectomyelois ceratoniae Zeller). The present research aims to identify different groups of predators of parasitized eggs and estimate the effect of predators on the loss rate of Trichogramma wasps during the release phase in pomegranate orchards.
Material and methods. A research was conducted in a pomegranate orchard with an area of two hectares located in the village of Hoz Sarkh, in the central district of Torbat-e- Heydarieh, in Razavi Khorasan province of Iran, in 2019 in form of a factorial two-factor experiment, each factor at two levels on a completely randomized basis with 5 replications.
Results. In this study, a total of six species of ants namely Pheidole pallidula (Nylander, 1849), Crematogaster subdentata Mayr, 1877, Tapinoma erraticum (Latreille, 1798), Lepisiota frauenfeldi (Mayr, 1855), and Camponotus sanctus Forel, 1904 from three subfamilies including Formicinae, Dolichoderinae, Myrmicinae, of Formicidae family, and one species of Dermaptera (Forficula auricularia L), a species of Hemiptera (Geocoris sp.) as well as a few spiders were collected and identified from the surveyed trichocards. Also, the results of this study showed that ants and other predators destroy a significant number of the parasitized eggs on trichocards and this cause a significant decrease in the efficiency of this egg parasitoid. The mortality rate of aprasitized eggs on trichocards embedded with grease was significantly lower than those tichocards without grease. In this study, the height of the installation of trichocards also showed a significant effect on the loss rate of Trichogramma wasps. In addition, the height of installation of trichocards also showed a significant effect on the loss rate of Trichogramma wasps. So that at high altitude in both the grease and non-grease treatments at different times, the loss rate of Trichogramma wasps was lower.
Conclusion. Therefore, according to the results of this research, in order to protect the trichocards from ants' attacks and reduce the damage caused by them, it is necessary to pay attention to the release plan of Trichogramma wasps in such a way that the maximum number of wasps emerge in less than 24 hours of the initial installation of the trichocards. Also, trichocards should be installed at a higher altitude (150 centimetrs above the ground level) by using a wire coated with a sticky substance such as grease.
Key words: Biological control, Trichogramma brassicae, Predator, Ant, Trichocard.