By Grethe Roets
Marketing & Communication
Koppert

Partnering with nature has unending innovation as a result – we must just discover it! Entering 2022, Koppert South Africa is not only celebrating a decade of investing in the health, safety, and productivity of South African soil, but we are also moving forward with a value-driven new international visual identity. We believe that every problem in agriculture and horticulture has a solution, and we know that the search must start within nature. So, we partner with nature and never stop innovating.

As the company’s founder, Jan Koppert, was a cucumber grower himself 50 years ago, our roots are grounded in working for growers and farmers. We understand the challenges and offer an integrated system of natural solutions to cultivate healthier crops and improve quality and yield. We use natural enemies to combat pests, microbials, and biostimulants that support, protect and strengthen crops and improve plant health, above and underground.

In this pursuit of helping our clients partner with nature, we are excited to introduce theewest member of our team. Rhyzobug (Rhyzo-bius lophanthae) is a classic biological control agent which preys on most armoured scale species plus selected mealybug species for crops including citrus, mango, avocado, berries, apples, pears, and stone fruit. This small ladybird offers a solution for California red scale, Coconut scale, Florida red scale, Brown soft scale, Pernicious scale, Purple scale, Citrus black scale and Mango white scale.

Population development

As for most coccinellids, Rhyzobug has a long development time at lower temperatures. Though they are relatively well adapted to low temperatures with a minimum threshold for development of around 8 degrees Celsius, optimal temperatures are around 25 degrees Celsius. Eggs are laid under the scale of the
prey in small groups of one to five eggs.

A maximum of 16-18 eggs per day can be produced, with a total of around 600 eggs. The lifespan for mated females is around two months. Total prey consumption from first larvae until death of an adult on A.nerii is around 400 for males and 700 for females. All stages of the beetle can overwinter. No diapause has been observed.

Life cycle and appearance

The adults are on average 2.5 mm long and 1.8 mm wide. They are metallic brown-black coloured. The head is reddish-brown.

Application

• Approach and dose: Release 500 adult Rhyzobug per hectare early in season. Once pest pressure is high, doses can be increased to up to 1000 adults.
• Various strategies exist: Either determine levels of infestation to release 1 adult per 250 scale or;
• Alternatively release 10 adults per tree.
• Commercially available in a 100 ml shaker bottle containing 250 adult beetles.

Effectiveness

In a field experiment in outdoor summer conditions, Koppert evaluated the effectiveness of adult and larvae of Rhyzobius lophanthae for Aspidiotus nerii control. A. nerii is a common pest in citrus and R. lophanthae is known as a predator of this and other scale insect pests. A previous cage trial, conducted by Koppert Spain, demonstrated that both, larvae, and adults of R. lophanthae, were able to significantly suppress A. nerii populations, although adults were more effective.

However, it was not confirmed whether larvae or adult releases of the predator are more suitable under realistic conditions, particularly because the adults of the predator may fly away after the release. It was, therefore, important to confirm this to know which instar is more suitable to be used for augmentative biocontrol under realistic crop conditions. Evaluations started one week after the predator release
and continued weekly for 6 weeks thereafter.

Overall results showed an abundance of A. nerii increased during the first weeks of the experiment in untreated plots and decreased during the last week, presumably due to the population that started to collapse due to the lack of space to settle i.e., food.

Differently, progressively fewer insects were recorded in all plots receiving the predator during the experiment, although treatments receiving adults were more effective as the abundance of the pest was significantly lowest in plots receiving adults or adults and larvae.

Dynamics of larvae were similar in all treatments with predator release and thus no differences were observed in the number of larvae per leaf among treatments. In all of them, progressively higher numbers of larvae were observed over the first three weeks of the experiment, decreasing afterwards until the end.

Similar numbers of R. lophanthae adults were recorded in all treatments with predator release over the entire experimental period and consequently, abundance of adults was similar among all of them.

Results clearly demonstrated that R. lophanthae is effective as a predator of A. nerii, especially when adults are released. Additionally, the results demonstrated that the predator remains on the infected trees after the release. Contact us to learn more about Rhyzobug and the rest of our comprehensive offering for biological control.

We look forward to helping you partner with nature in the upcoming seasons.