By sintu alemayhu
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Host-range study on the stem-boring weevil ( Listronotus setosipennis ( Coleoptera : Curculionidae ) for the control of Parthenium hysterophorus in Ethiopia . By Sintu Alemayhu. Objective. To evaluate the safety of the stem-boring weevil, Listronotus setosipennis non-target plant species.

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By sintu alemayhu

Host-rangestudy on the stem-boring weevil (Listronotussetosipennis (Coleoptera: Curculionidae) for the control ofPartheniumhysterophorus in Ethiopia

By Sintu Alemayhu


Objective

Objective

  • To evaluate the safety of the stem-boring weevil, Listronotus setosipennisnon-target plant species


Description and life cycle

Description and life cycle

  • stem boring weevil Listronotus setosipennis (Hustache) [Coleoptera: Curculionidae] originally from Argentina, were introduced from Agricultural Research Council-Plant Protection Research Institute (ARC-PPRI) of South Africa in December 2009, to be used for studies in Ethiopia


By sintu alemayhu

Listronotussetosipennis (Coleoptera: Curculionidae

Lay eggs in flower heads or leaf bases

Nocturnal adults feed on leaves and flowers

hatch 3-5 days later

Complete life cycle of Listronotustakes30-35 days.

pupate in soil inside fibrous capsules


Damage

damage

  • Adult feeding damage is negligible.

  • Larval feeding has the ability to kill or prevent further development of parthenium seedlings.

  • In glasshouse conditions, infestation by Listronotus weevil at high densities significantly reduced the plant biomass by 21.9% and flower production by 75%.


Host specificity

Host specificity

  • Host specificity testing is a critically important step in the process of introducing natural enemies for classical weed biological control.

  • It provides information upon which the suitability of a proposed biological control agent can be assessed (Marohasy1998).


By sintu alemayhu

Cont…

  • Evaluation of the host range of any bioagent comprises of no-choice tests (test plant species only), followed by choice tests (test plant with Parthenium) if feeding, oviposition or development is observed under no-choice testing on non-target species

  • The safety of Listronotussetosipennis (Hustache) to non-target plants was tested under quarantine on economically important members of the Asteraceae family and indigenous weed species through no-choice tests


Selection of non target species

Selection of non-target species

  • The selection of non-target species for host preference testing was made by a taxonomist from Addis Ababa University.

  • The centrifugal phylogenetic method was followed in selecting test plants for testing candidate control agents

  • The test plant species were identified based on how closely related they are to Parthenium, whether they are strictly endemic, near endemic, cultivated, or indigenous to Ethiopia.


By sintu alemayhu

Figure 1. Diagrammatic representation of the tribe Heliantheae and some crop plants (adapted by Lorraine Strathie from Wapshere, A. J. 1974).


Materials and methods

Materials and Methods

Area description

  • The experiment was conducted under quarantine condition at Ambo Plant Protection Research Center (APPRC) 109km West of Addis Ababa.

  • The average temperature is ranges from 10o to 30o C and relative humidity at 50-87 % in the quarantine facility


Culturing of l setosipennis

Culturing of L. setosipennis

  • Adult feeding and oviposition were tested using nylon mesh test cages with metal frames(0.5m x 0.5m x 1m), with two holes for potted plants.

  • All corners and joints were sealed with silicone to prevent escape of weevils through gaps.


By sintu alemayhu

  • The safety of Listronotus setosipennis (Hustache) to 39 non-target plants consisting of

    • nineteen major crop species mostly used as food and export

    • Twenty crops and other plant species, belonging to the family Asteraceae which includes two species of Helianthus annus , six species Guizotia abyssinica, both of which are important oil crops in the country . and four species of Bidens


By sintu alemayhu

Cont…

  • No-choice tests were designed to test whether the bio-agent feeds, lay eggs and survive on a test plant when it has no access to target weed Parthenium.

  • All the test plants were grown or transplanted into plastic pots(22cm X 18 cm), containing the mixture of sand 25%, compost/humus 25% and 50% soil

  • grown up to the required test stage by providing every agronomic management under lath-house


By sintu alemayhu

Cont…

  • Healthy and similar size Plant with flowers, were selected and placed in a cage after being washed

  • Five mating pairs of adult L. setosipennis, obtained from same age group of adults that had been kept for 2-3 weeks, were released into each cage.

  • Sodium hypochlorite solution (2%) was sprayed on the leaves and soil to prevent any disease occurrence.

  • The experiment was replicated three times in CRD and one plant per cage was used.


By sintu alemayhu

Cont…

  • After 7 days of exposure all adults were removed from each test plant and the number of adults that survived, died and missed was recorded

  • All plant parts, including leaf axils, stems and petioles, were carefully examined for ovipostion and feeding. Eggs were counted after dissecting flowers and examining plants under a microscope.


By sintu alemayhu

  • The blue arrow shows frass

  • The read arrow shows egg


By sintu alemayhu

Bidens pachyloma

Tagetes minuta

Helianthus annus (oissa)

G.abysinica (kuyyu)

Vernonia galamensis


By sintu alemayhu

Table 1. Result of Host-Specificity of Listronotus setosipennis (Hustache) on major crops


By sintu alemayhu

Evaluation of species related to Parthenium


Conclusion

Conclusion

  • The concern that the agent, Listronotus setosipennis, might attack non- target crops and plants was resolved through a quarantine test against crops and plants that are closely related to Parthenium and others that are economically important and indigenous to Ethiopia.

  • Therefore there was no need to go for choice test since no oviposition took place in no choice test


By sintu alemayhu

Thank You


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