Abundance and phenology of two pest species, Cacoecimorpha pronubana and Epiphyas postvittana (Lepidoptera: Tortricidae)

Cacoecimorpha pronubana (Hübner, [1799]) and Epiphyas postvittana (Walker, 1863) are economically important polyphagous pest species. The larvae of these moths affect a wide range of horticultural crops. We evaluated the seasonal abundance and population dynamics of these two species, hypothesising that both species of moth exhibit similar patterns in their seasonal abundance and respond to abiotic factors. The study was carried out on a wide range of protected ornamental crops grown on a total area of one hectare at a commercial nursery. The study was completed over 5 consecutive years from 2015 to 2019, where both populations were monitored weekly during the months of moth activity, from April to November, using sex pheromone traps to trap the males of both species. The timing and abundance of catches were analysed in relation to local meteorological data. The mean yearly abundance of adult males was 604 ± 23.89 (mean ± SE; C. pronubana) and 1706 ± 167.18 (E. postvittana) also differing significantly between years for both species. There was no influence of any weather measures on the abundance of E. postvittana, but sunshine duration (4.84 ± 0.26 h) and temperature (13.04 ± 0.57°C) affected the mean seasonal abundance of C. pronubana. There was an overall difference in the seasonal pattern of abundance between the species studied. While we demonstrate a seasonal abundance difference between years for C. pronubana, we found no significant seasonal differences for E. postvittana. Improved understanding of seasonal abundance, phenological patterns and inter‐seasonal variations in population dynamics of these two species may be useful in developing forecasting models that can be used in improving integrated pest management strategies for these two pests

Life history traits of two important lepidopteran pests, the carnation tortrix (Cacoecimorpha pronubana) and the light brown apple moth (Epiphyas postvittana)

Cacoecimorpha pronubana (Hübner, [1799]) and Epiphyas postvittana (Walker, 1863) are economically important polyphagous pest species. Larvae of these moths affect a wide range of horticultural crops. The larva produces silk which it uses to roll leaves creating a shelter against predators and natural enemies, and feeds of the foliage. The main hypothesis of this study was that different host plant species affect life history traits of C. pronubana and E. postvittana differently, and that there are differences in life history traits between these two polyphagous species. In order to test the main hypothesis, there were objectives formulated analysing overall abundance and phenology of C. pronubana and E. postvittana, their oviposition preference, relative performance, and effect of host plants on life history of these two herbivorous species. The main aim of this study was that improved understanding of the life history traits of these two herbivore pest species will help in developing improved integrated pest management systems within horticultural crop habitats. For this, the effect of abiotic factors on population dynamics and abundance of these species of moth in the ornamental crop habitats was analysed. Further studies involved investigating the life history traits of these two Lepidopterans under controlled environmental conditions at 20°C, relative humidity of 60% and a 16L:8D photoperiod. These included analyses on oviposition preference towards six different ornamental host plant species, the effect of six different host plant species on the larval development and the relationships between different life stages of the insect, as well as the effect of intergenerational dietary changes on the life history traits of both species of moth originating from two different diets. Noticeable differences were observed between these two species in terms of population dynamics and seasonal appearance based on a five-year study period (2015-2019). Further study showed that oviposition preference in terms of clutch size differed neither between the moth species, nor between the host plants. Larval host plants, however, affected the survival, duration of larval stage, pupal weight and fecundity. It was shown that the longer the duration of larval stage is, the greater the negative effect on female development. Change in larval diet affected oviposition behaviour of both species. Interesting results, however, were identified in the oviposition behaviour in terms of the change in the clutch size, which was affected by transgenerational change in a diet. It was concluded that better understanding of the population dynamics and the behaviour of these two tortricid (Lepidoptera: Tortricidae) species may be useful in developing forecasting models and in determining crop specific dynamics of these two generalists in developing improved IPM strategies within horticultural crop habitat

Effect of host plant on the life history of the carnation tortrix moth Cacoecimorpha pronubana (Lepidoptera: Tortricidae)

The carnation tortrix moth, Cacoecimorpha pronubana (Hübner, [1799]) (Lepidoptera: Tortricidae), is one of the most economically important insect species affecting the horticultural industry in the UK. The larvae consume foliage, flowers or fruits, and/or rolls leaves together with silken threads, negatively affecting the growth and/or aesthetics of the crop. In order to understand the polyphagous behaviour of this species within an ornamental crop habitat, we hypothesized that different host plant species affect its life history traits differently. This study investigated the effects of the host plant species on larval and pupal durations and sizes, and fecundity (the number of eggs and the number and size of egg clutches). At 20°C, 60% RH and a 16L:8D photoperiod larvae developed 10, 14, 20 and 36 days faster when reared on Christmas berry, Photinia (Rosaceae), than on cherry laurel, Prunus laurocerasus (Rosaceae), New Zealand broadleaf, Griselinia littoralis (Griseliniaceae), Mexican orange, Choisya ternata (Rutaceae), and firethorn, Pyracantha angustifolia (Rosaceae), respectively. Female pupae were 23.8 mg heavier than male pupae, and pupal weight was significantly correlated with the duration of larval development. The lowest and the highest mean numbers of eggs were produced by females reared on Pyracantha (41) and Photinia (202), respectively. Clutch size differed significantly among moths reared on different host plants, although the total number of eggs did not differ. This study showed that different ornamental host plants affect the development of C. pronubana differently. Improved understanding of the influence of host plant on the moth's life history parameters measured here will help in determining the economic impact that this species may have within the ornamental plant production environment, and may be used in developing more accurate crop protection methodologies within integrated pest management of this insect

Transgenerational effect of host plant on growth and reproduction in two species of moth, Cacoecimorpha pronubana and Epiphyas postvittana (Lepidoptera: Tortricidae)

The carnation tortrix moth, Cacoecimorpha pronubana (Roelofs & Brown, 1982), and the light brown apple moth, Epiphyas postvittana (Walker, 1863) (Lepidoptera: Tortricidae) are two important polyphagous pest species affecting a wide range of plant species many of which are horticultural crops. Crop damage is caused by the larvae of these two moths rolling leaves together and feeding on the foliage. In order to understand how these two species are affected by a host plant through transgenerational dietary changes, we hypothesised that larval parental pre-treatment diet affects growth and reproduction of offspring. We tested the performance of developmental traits of C. pronubana and E. postvittana on three host plant species (larval diet treatment) – Prunus (Rosaceae), Choisya (Rutaceae) and Griselinia (Griseliniaceae). For the experiment we used larvae from a second generation of C. pronubana and E. postvittana reared either exclusively on Prunus, or reared exclusively on Griselinia (pre-treatment). Regardless of whether moths had been reared on Prunus or Griselinia both species of host plant had a significant average effect on the duration of larval development and the pupal size of both species of moth, for E. postvittana, and for C. pronubana. Although, neither pre-treatment, nor treatment had a significant overall effect on fecundity (number of eggs per clutch laid) in either species of moth, there was a significant interaction effect observed between the pre- and post-treatment on fecundity for both species of moth. Our results suggest that changes of host plant species composition can affect the performance of offspring of both these polyphagous pest species intergenerationally in complex ways which are relevant to agroecosystems. Such phenomena may be important when developing new strategies for the integrated pest management of these two important pest species