One or more of the features that are needed to show you the maps functionality are not available in the web browser that you are using.
Please consider upgrading your browser to the latest version or installing a new browser.
More information about modern web browsers can be found at http://browsehappy.com/
Symptoms vary according to host. On oranges there is sometimes a scar on the fruit surface, on most other crops, the habit of internal feeding leaves few symptoms.
There is currently a wide range of effective control options available (Moore and Hattingh, 2016; Malan et al., 2018). However, as T. leucotreta is indigenous wherever it occurs, with the exception of Israel, the occurrence of alternative wild hosts can lead to reinfestation, if growing in close proximity to the crop. However, T. leucotreta is a poor disperser and coloniser (Newton, 1998; Stotter et al., 2014) so this reinfestation would be a slow process. Additionally, a plethora of natural enemies would maintain suppression of the pest, if undisrupted within an IPM approach.
T. leucotreta is monitored using a combination of pheromone traps and fruit infestation (Moore et al., 2008). Amongst others, Newton et al. (1993) identified the female pheromone and Hofmeyr and Burger (1995) developed the original pheromone dispenser. However, due to the phytosanitary status of T. leucotreta for many export markets, traps are no longer used to determine whether intervention is necessary, but rather to assist with accurate timing and prioritisation of treatments (Moore et al., 2008).
Reed (1974) and Byaruhanga and De Lima (1977) showed that late-sown crops of cotton in Uganda were worst affected, but the difference was not great. As T. leucotreta is primarily a fruit feeder, it is suggested by Glas (1991) that crops of cotton grown close to fruit trees may be less affected. Ullyett and Bishop (1938) found that weekly sanitation in citrus orchards (picking up and destruction of fallen fruit) reduced fruit loss from 6.1 to 3.3%. Stofberg (1954) found that a programme of regular sanitation could save between 24 and 60 fruit per tree from T. leucotreta infestation. He concluded that at that time, the cost of twice-weekly sanitation would be justified if T. leucotreta infestation was reduced by half. Moore and Kirkman (2008) showed that weekly orchard sanitation from December to June removed an average of 75% of T. leucotreta larvae infesting fruit. Orchard sanitation is considered as the backbone for effective control of T. leucotreta.
Parasitoids of T. leucotreta have been identified, and mass release of Trichogrammoide acryptophlebiae has been shown to be effective (Newton and Odendaal, 1990). Parasitoids are currently commercially available for augmentation (Malan et al., 2018) and have been shown to reduce T. leucotreta infestation by up to 60% (Newton and Odendaal, 1990; Moore and Hattingh, 2016).
Cryptophlebia leucotreta granulovirus (CrleGV) has been used commercially for more than 15 years, reducing T. leucotreta by up to more than 90%, with a residual efficacy from one spray of up to 17 weeks (Moore et al., 2015a). Currently, there are three commercially available CrleGV products on the market (Hatting et al., 2019).
Entomopathogenic fungi, Beauveria bassiana and Metarhizium anisopliae, isolated from citrus orchards (Goble et al., 2010, 2011; Coombes et al., 2013, 2015) reduced T. leucotreta infestation of citrus fruit by over 80% during a full season, from a single spring application to the soil (Moore et al., 2013; Coombes et al., 2016). However, these isolates are still to be commercially developed, and currently, the only EPF registered for control of T. leucotreta in southern Africa are applied to the tree for control of the egg and neonate larval stages.
An EPN product, with its active ingredient Heterorhabditis bacteriophora, is registered for use against the soil-dwelling life stage of T. leucotreta in South Africa (Malan et al., 2018). Application of H. bacteriophora to a citrus orchard floor, reduced T. leucotreta infestation of fruit by up to 81% (Moore et al., 2013).
Sterile Insect Technique
The Sterile Insect Technique (SIT), as a stand-alone treatment in a semi-commercial trial, reduced T. leucotreta infestation in 35 ha of Navel orange orchards by 95.2%, relative to an untreated control orchard (Hofmeyr et al., 2016a). These initial findings led to commercial implementation for control of T. leucotreta within an integrated programme in citrus, since 2007. The programme is proving extremely effective (Hofmeyr et al., 2015), having reduced moth catches by 99%, fruit infestation by 96% and export rejections by 89% since the inception of the programme (Barnes et al., 2015). After orchard sanitation, area-wide techniques, such as SIT and mating disruption, are considered as the most important control tactics for T. leucotreta.
Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:
This moth has the potential to be a serious economic pest of some citrus types and pomegranates in southern Africa, peppers and flowers particularly in East Africa, and of cotton in many parts of Africa. It also affects maize in West Africa. Historically, citrus crop losses of 10-20% were reported in South Africa (Glas, 1991). However, pest status varies considerably across citrus cultivars and production regions (EPPO, 2013; Moore et al., 2017). Reed (1974) described losses of between 42 and 90% in late crops of cotton in Uganda. It also used to be a significant pest of macadamia in Israel (Wysoki, 1986); however, macadamia is no longer grown commercially in this country (EPPO, 2013). Blomefield (1989) reported losses of up to 28% in a late peach crop in South Africa. Begemann and Schoeman (1999) calculated citrus crop loss in South Africa specifically due to T. leucotreta was 1.6% in Navels and 0.3% in Valencias. Currently, where high populations occur on preferred hosts, and where these are uncontrolled or the effective natural enemy complex is disrupted, T. leucotreta can still reduce crop yields (Newton, 1998; Moore, 2002). However, T. leucotreta is now very effectively controlled in citrus orchards in southern Africa, using an integrated suite of control options (Moore and Hattingh, 2012, 2016; Barnes et al., 2015; Moore et al., 2015a; Moore et al., 2017). Reduction in infestation of between 95 and 97% has been reported with currently available pre-harvest control options (Moore and Hattingh, 2012; Moore et al., 2015a). The sterile insect technique (SIT) has been used for control of T. leucotreta in several regions in South Africa since 2007 and is proving extremely effective, having reduced moth catches by 98% and fruit infestation by 99% since the inception of the programme (Barnes et al., 2015). Consequently, the pest status of T. leucotreta is now chiefly phytosanitary in nature, due to its endemism to southern Africa and regulations imposed by importing markets (Grout and Moore, 2015; South African Department of Agriculture Forestry and Fisheries, 2015; Moore et al., 2017).