Host preferences of the cocoa pod borer, Conopomorpha cramerella, the main threat to cocoa production in Southeast Asia

Abstract

Insects ensure the survival of their offspring by depositing their eggs in suitable environments. Even generalist egg-laying insects often show preferences for specific host plants. The cocoa pod borer (CPB), Conopomorpha cramerella (Snellen) (Lepidoptera: Gracillariidae), successfully infests and reproduces on relatively few host plants, but has a major economic impact only on cocoa, Theobroma cacao L. (Malvaceae). Choice tests were performed in the laboratory to compare the frequency of insect visits, the duration of the visits, and the number of eggs laid on the fruits for each combination of host plants testedthat is, cocoa clones or fruits of rambutan (Nephelium lappaceum L.), Fijian longan (Pometia pinnata JR Forst & G Forst, both Sapindaceae), and langsat (Lansium domesticum Corrêa, Malvaceae). Our laboratory study showed that, when given the choice, CPB significantly favored cocoa pods over other host fruits (rambutan, langsat, or Fijian longan). Females also deposited more eggs on unripe fruits than on ripe fruits of similar size. The preference to lay eggs on specific cocoa clones in the bioassays did not reflect the level of the clone resistance to CPB damage reported from the field. Consequently, oviposition preference of female CPB does not seem to be the main factor explaining field resistance of some cocoa clones to CPB infestation.

DNA barcode identification of Conopomorpha cramerella (Snellen, 1904) (Lepidoptera: Gracillariidae) and other moths affecting cacao in Papua New Guinea

“…Conopomorpha cramerella show a strong preference for oviposition on introduced cacao over its native plant hosts (Gende 2012; Niogret et al . 2020). This is surprising given that cacao was introduced during the 16th century to South‐East Asia from the new world (Day 1985) where Conopomorpha is absent (De Prins & De Prins 2019).…”

Influence of host plants on the development, survivorship, and fecundity of the summer fruit tortrix moth, Adoxophyes orana (Lepidoptera: Tortricidae)

“…2018; Niogret et al . 2020), and the intrinsic population growth rate is ≥0 (Wang et al . 2020; Zalucki et al .…”

Evaluation of yield and pest and disease resistance of cocoa clones in Kolaka District, Southeast Sulawesi, Indonesia

“…The preference for laying egg and the number of visits varied depending on host plants. The most recently introduced host plants are likely preferred by CFB (Niogret 2020). Pests (butterfly pests) usually lay eggs on young cocoa pods aged 2-3 months.…”

“…To resolve the problem of low productivity of cocoa requires technological improvements, such as high-yielding clones with high productivity (Rubiyo and Siswanto 2012;Witjaksono and Asmin 2016), pest and disease management (Daymond et al 2017), fertilization (Abdulai et al 2020), and pruning management (Tothmihaly and Verina 2017;Effendy et al 2019). Planting resistant clones is a promising strategy (McMahon et al 2010b;Adu-Acheampong et al (2015) although it is difficult to find cocoa clones fully resistant to CPB (Niogret 2020). The selection process requires adequate knowledge of environmental and genetic factors and a reliable process for screening for resistance, for example, the leaf disc and detached pod tests (Efombagn 2011).…”