Entomopathogenic fungi for control of soil-borne life stages of false codling moth, Thaumatotibia leucotreta (Meyrick) (1912) (Lepidoptera: Tortricidae)
- Authors: Coombes, Candice Anne
- Date: 2013
- Subjects: Tortricidae , Lepidoptera , Cryptophlebia leucotreta , Insect pests -- Biological control -- South Africa -- Eastern Cape , Tortricidae -- Biological control -- South Africa -- Eastern Cape , Citrus -- Diseases and pests -- Biological control -- South Africa -- Eastern Cape , Entomopathogenic fungi , Fungi as biological pest control agents , Biological pest control agents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5607 , http://hdl.handle.net/10962/d1002057 , Tortricidae , Lepidoptera , Cryptophlebia leucotreta , Insect pests -- Biological control -- South Africa -- Eastern Cape , Tortricidae -- Biological control -- South Africa -- Eastern Cape , Citrus -- Diseases and pests -- Biological control -- South Africa -- Eastern Cape , Entomopathogenic fungi , Fungi as biological pest control agents , Biological pest control agents
- Description: False codling moth (FCM), Thaumatotibia leucotreta is an extremely important pest of citrus in South Africa and with the shift away from the use of chemicals, alternate control options are needed. One avenue of control which has only recently been investigated against the soil-borne life stages of FCM is the use of entomopathogenic fungi (EPF). In 2009, 12 entomopathogenic fungal isolates collected from South African citrus orchards showed good control potential during laboratory conducted bioassays. The aim of this study was to further analyse the potential of these isolates through concentration-dose and exposure-time response bioassays. After initial re-screening, concentration-dose response and exposure-time response sandconidial bioassays, three isolates were identified as exhibiting the greatest control potential against FCM in soil, Metarhizium anisopliae var. anisopliae (G 11 3 L6 and FCM Ar 23 B3) and Beauveria bassiana (G Ar 17 B3). Percentage mycosis was found to be directly related to fungal concentration as well as the amount of time FCM 5th instar larvae were exposed to the fungal conidia. LC50 values for the three isolates were not greater than 1.92 x 10⁶ conidia.ml⁻ₑ and at the LC₅₀, FCM 5th instar larvae would need to be exposed to the fungus for a maximum of 13 days to ensure a high mortality level. These isolates along with two commercially available EPF products were subjected to field persistence trials whereby net bags filled with a mixture of autoclaved sand and formulated fungal product were buried in an Eastern Cape citrus orchard. The viability of each isolate was measured on a monthly basis for a period of six months. All isolates were capable of persisting in the soil for six months with the collected isolates persisting far better than the commercially used isolates. Two of the isolates, G 11 3 L6 and G Ar 17 B3, were subjected to small scale laboratory application trials. Two formulations were investigated at two concentrations. For each isolate, each formulation and each concentration, FCM 5th instar larvae were applied and allowed to burrow into the soil to pupate before fungal application or after fungal application. Contact between fungi and FCM host is essential as, in contrast to pre-larval treatments, percentage mortality in post-larval treatments was low for both formulations and both isolates. For isolate G Ar 17 B3, a conidial suspension applied as a spray at a concentration of 1 x 10⁷ conidia.ml⁻ₑ obtained the highest percentage mortality (80 %). For isolate G 11 3 L6 however, both formulations performed equally well at a high, 1 x10⁷ conidia.ml⁻ₑ concentration (conidial suspension: 60 %; granular: 65 %) The results obtained thus far are promising for the control of FCM in citrus, but if these EPFs are to successfully integrate into current FCM control practices more research, some of which is discussed, is essential
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Agathis bishopi (Nixon) (Hymenoptera: braconidae) its biology and usefulness as a biological control agent for false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: tortricidae), on citrus bishopi (Nixon) (Hymenoptera: braconidae) its biology and usefulness as a biological control agent for false codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: tortricidae), on citrus
- Authors: Gendall, Kierryn Leigh
- Date: 2008
- Subjects: Cryptophlebia leucotreta -- Parasites , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Tortricidae , Braconidae , Citrus -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5635 , http://hdl.handle.net/10962/d1005317 , Cryptophlebia leucotreta -- Parasites , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Tortricidae , Braconidae , Citrus -- Diseases and pests
- Description: The false codling moth, Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), is one of the major pests of citrus in South Africa, the others being mealybug, Mediterranean fruit fly, bollworm and some mites. Due to problems such as the expense of pesticides, insects evolving pesticide resistance (Hogsette 1999), chemical residue on the skin of export fruit and the negative impact of pesticides on the environment, it became necessary to find alternative methods for pest control (Viggiani 2000). Agathis bishopi (Nixon) (Hymenoptera: Braconidae), a larval parasitoid of false codling moth known only from the Sundays River Valley area (Sishuba 2003), offers a means of control for the pest. A total of 11 389 navel oranges were collected from various orchards in the Addo/Kirkwood area, and false codling moth larvae infested 36.09% of the fruit. A single parasitoid species, A. bishopi, was reared from these larvae. In 2006 the highest parasitism rate, 11.43%, was recorded in May and in 2007, the highest parasitism rate, 13.27%, was in April. Agathis bishopi parasitizes larvae in instars 2 and 3, possibly due to the accessibility of these younger instars to the female parasitoid and possibly due to the length of the life cycle of this koinobiont. Second instar hosts yielded the highest number of parasitoids, and there was no emergence of parasitoids from fifth instar larvae. Females of A. bishopi live for 18.5 days (n = 20; S.E. = 3.1) and males for 8.25 days (n = 20; S.E. = 1.23). Females produce an average of 23 offspring in a lifetime, while female false codling moths produce about 800 eggs each. A high number of parasitoids will be required per hectare to reduce the population of false codling moth. Captive rearing of A. bishopi proved difficult due to viral and fungal contamination. Agathis bishopi has potential for use in an integrated pest management programme once the hurdle of mass-rearing has been overcome.
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Investigation of the larval parasitoids of the false codling moth, Cryptophlebia Leucotreta (Meyrick) (Lepidoptera: Tortricidae), on citrus in South Africa
- Authors: Sishuba, Nomahlubi
- Date: 2004
- Subjects: Cryptophlebia leucotreta , Tortricidae , Cryptophlebia leucotreta -- Control , Pests -- Biological control , Parasitoids , Citrus -- Diseases and pests
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5918 , http://hdl.handle.net/10962/d1016267
- Description: The study examined the larval parasitoids of Cryptophlebia leucotreta (Meyrick) on citrus in South Africa and aimed to improve the existing rearing techniques of C. leucotreta with a view to mass rearing of biological control agents. The biological characteristics of Agathis bishopi Nixon (Hymenoptera: Braconidae) were studied, with an emphasis on parasitism rates in the field, host stage preference, developmental rate, life span and offspring sex ratios. Two larval parasitoids, A. bishopi and Apophua leucotretae (Wilkinson) (Hymenoptera: Ichneumonidae), and an egg parasitoid, Trichogrammatoidea cryptophlebiae Nagaraja (Hymenoptera: Trichogrammatidae), were recorded on C. leucotreta on citrus. A. bishopi was the more abundant of the larval parasitoids and exhibited density dependent parasitism. The highest parasitism rates were observed in December with up to 38% in Sundays River Valley and 34% in Gamtoos River Valley, at a time when the highest false codling moth infestations were observed. Agathis bishopi was recorded only in the Eastern Cape Province. The sex ratio of A. bishopi was biased towards females throughout the study (77% in Gamtoos River Valley and 72% in Sundays River Valley). Agathis bishopi is a solitary, koinobiont, larval-pupal endoparasitoid. The species showed a preference for 1st and 2"d instar hosts. Females regulate the sex of their progeny according to the size and larval stage of the host, ovipositing unfertilised eggs in younger, smaller larvae (1st instars) and fertilised eggs in older, larger larvae (2nd instars). The developmental rate of A. bishopi is in synchrony with that of the moth and adults emerge when adult moths that have escaped parasitism emerge. Agathis bishopi and T. cryptophlebiae compliment each other because they have different niches and strategies of attack. Integrating A. bishopi and T. cryptophlebiae into the management of citrus orchards has potential to suppress false codling moth. Larger rearing containers seemed ideal for large-scale rearing of false codling moth. A higher percentage of adults was obtained from larvae reared in larger containers than in smaller ones. The width of the sponges used as stoppers prevented escape of the larvae. Media prepared in larger containers are easier and simpler to prepare than in smaller ones, thus eliminating many precautions otherwise necessary to prevent contamination. Moth production was greatly reduced by the high concentration of Sporekill used for egg decontamination.
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