Bb-Protec is a biological insecticide that has the fungus Beauveria bassiana strain R444 as the active ingredient. Compared to conventional insecticides, Bb-Protec has a narrow target range, but when compared to other biological insecticides, its target range is considered broad. This makes it a viable solution for different growers that are challenged by different pests. Bb-Protec (known as Eco-Bb in South Africa), has been registered in South Africa since 2011 and is used by various tree crop growers, including citrus, pome fruit, stone fruit, macadamia nut and avocado growers. Bb-Protec is used mostly against red spider mite, white fly, mealybug and false coddling moth, and trials are underway around the world to evaluate its potential against other targets.
South Africa is the world’s second largest exporter of citrus, with 158.7 million cartons shipped in 2021. This is up 22% from 2019 and the citrus industry in South Africa is expected to grow rapidly in the coming years (Citrus Industry, 2021). It is estimated that over a million households in South Africa depend on the citrus industry for their livelihoods (DARLLD, 2020). The industry does however face challenges, such as rising fuel and fertiliser prices and delays that are affecting ports in South Africa and around the world (Produce Report, 2022). In order to access the lucrative international markets now and in future, Maximum Reside Limits (MRLs) need to be strictly adhered to and therefore the products available for pest management at certain times during the crop cycle are limited.
May was the start of harvest time for certain citrus cultivars in the Eastern Cape and pest pressure was still prevalent, especially from the citrus mealybug (Planococcus citri). An adult female citrus mealybug can lay between 300 and 600 eggs in its lifetime and on average 29 eggs per day. Under the right conditions, Citrus Mealybug can move from first instars to egg laying adults within four weeks. Therefore, the potential for the mealybug colonies to grow exponentially in a short period of time is high, which puts fruits destined for export at risk. One of the advantages of Bb-Protec is that it has no MRL constraints, and therefore it can be used up until the day of harvest.
Andermatt Madumbi, our sister distribution company in South Africa, worked closely with lemon growers this season to manage mealybug populations near the time of harvest. According to Andermatt Madumbi field agent Pete Thorpe, growers were able to significantly reduce mealybug colony size and keep populations at a low level. Pete’s photographs of fruit from a treated and an untreated block show the effect that Eco-Bb had in maintaining a low mealybug infestation. Growers also noticed natural mealybug enemies such as lacewing larvae and parasitic wasps at work in the orchard after Bb-Protec applications.
Mealybug is a difficult insect to target, as the later instars and female adults develop a waxy cuticle, which provides protection from fungal, bacterial and viral infection, and even protects the insects from certain chemical insecticides. For this reason, the first instars, known as crawlers, are the most susceptible to Bb-Protec, and by targeting this life stage, a low mealybug population can be maintained, and undamaged fruit can be protected.
For use against mealybug, we recommend at least 3 applications at a seven-to-14-day interval. As mentioned, the adult female mealybug is protected from fungal infection by its waxy layer, and therefore egg laying will continue after Bb-Protec applications. Multiple applications are therefore needed to target new crawlers entering the population, so that these individuals are removed before they can start up new mealybug colonies. It is also important that the first application is made as early as possible, before there are high numbers of female adults in the population.
Citrus growers in South Africa will face further challenges next season, as certain conventional mealybug products will be removed from the market. We are confident that Bb-Protec will be a valuable tool to our growers who are aiming to produce high quality and safe fruit for local and international consumers.
References
Citrus industry, 2021. South Africa Citrus Exports to Break Record. Online [Available]: https://citrusindustry.net/2021/04/02/south-africa-citrus-exports-to-break-record/ . Accessed 08 June 2022.06.13
Department of Agricultural, Land Reform and Rural Development (DALRRD), 2020. A Profile of the South African Citrus Market Value Chain. Online [Available]: https://www.dalrrd.gov.za/doaDev/sideMenu/Marketing/Annual%20Publications/Citrus%20Market%20Value%20Chain%20Profile%202020.pdf Accessed: 08 June 2022.06.13
Produce Report, 2022. South African Citrus Exports Forecast to Rise in 2022. Online [Available]: https://www.producereport.com/article/south-african-citrus-exports-forecast-rise-2022#:~:text=South%20Africa’s%20soft%20citrus%20exports,463%2C500%20metric%20tons%20%E2%80%94%20last%20season. Accessed 08 June 2022.06.13