Scarab-Solutions We’re changing how the world targets crop pests and diseases... Tue, 06 Apr 2021 10:32:49 +0000 en-GB hourly 1 Striking back against thrips: Prevention strategies to regain the greenhouse Wed, 14 Apr 2021 12:30:17 +0000 Striking back against thrips: Prevention strategies to regain the greenhouse

Figure 1: Frankliniella occidentalis – western flower thrips (Image source: Frank Peairs, Colorado State University,, CC BY 3.0 <>, via Wikimedia Commons)

Thrips is a pest to be reckoned with – its polyphagous appetite, alarming reproduction rate and ability to vector plant viruses presents significant threats to greenhouse growers looking to take their products to market. Tackling these pests is no easy matter but, with 15 years of experience in cut roses, Scarab Solutions experts have found that several intervention actions, when combined, can help growers effectively manage and control the destructive power of thrips and avoid a costly infestation:

1. A fundamental hygiene process

Initial efforts must start in the production area, where cleanliness is a necessity. To prevent introducing a new infestation into the greenhouse, new crops must be clean and free of ‘resident thrips’ that multiply within the crop. ‘Immigrant thrips’ come in from outside and derive from either ‘migratory thrips’, or ‘local flyers’, the latter flying within the hight of the canopy and being guided by visual cues – and these are the type of ‘migrants’ that are most likely to find their way into the greenhouse crops.

2. Identify the hotspots – think ‘the leeward side’ and hunt in the right places

The risk of thrips entering greenhouses from the leeward side than from the windward side is more than double – verified by research on wind vanes that found 75% of thrips caught on the leeward side.[1] We recommend identifying the prevailing wind direction on the farm’s location, with the intent of stopping thrips entering on the leeward side.

Sticky traps, usually placed above the crop canopy, would benefit being nearer to the ground level. Growers will yield more reliable data and support mass capturing – and research confirms that 70% of flying thrips adults are captured at a height lower than 1 meter from the ground.[2]

3. Strengthen your defences and limit infiltration

Nearby grass should be frequently mowed and never allowed to flower, as this will help reduce the build-up of thrips populations in the greenhouse vicinity. We recommended a thorough examination of all outdoor plants on the farm, replacing any plants and trees that are attractive to thrips – particularly those on the leeward side. For the growers who wish to apply repellent measures, we recommend placing these near to the ground to target the local flyers.

The installation of double doors to create a small airlocked room connected to the entrance of a greenhouse can limit thrips entrance – but don’t forget to close the first door before opening the next!

4. Schedule predatory mites and scout accordingly

Predatory mites can be a crucial biological control for thrips population management but be mindful – different predatory mite species are only effective at certain stages in the thrips lifecycle. Neoseiulus cucumeris, Amblyseius swirskii, Amblydromalus limonicus and Transeius montdorensis only predate the larval stages, which means that they will only feed on the ‘resident thrips’ offspring and help keep the resident population low.[3] Soil dwelling predatory mites, Stratiolaelaps scimitus (formerly Hypoaspis mites) and Macrocheles robustulus feed on thrips pupae in the soil and the predatory bug, Orius laevigatus, feeds on both adults and larvae.

A good scouting system can calculate the proportion between thrips adults and thrips larvae, giving growers insight into the type of thrips population (residents or migrants) they have – and helps decide which will be the most effective means to control the thrips population.

5. Enhance entomopathogens effectiveness

Fungi attacking insects (entomopathogens) such as Verticillium lecanii are another biological control for supressing the thrips population. The effectiveness of certain entomopathogens (Paecilomyces and Beauveria bassiana) is amplified when combined with a mixture of insecticides or natural insecticides, such as neem extract.[4]

6. A new thrips generation equals a new Mode of Action (MoA)

For growers who are allowed chemical sprays, a spray at least once a week can control the ‘resident thrips’ but it is important growers change to a new chemical with a different MoA for every thrips life cycle, i.e., about every two weeks, as they can build up a chemical resistance.

Some sprays rely on contact with thrips in order to be effective, so timing is important. Thrips are most actively flying between 8:00AM – 10:00AM and 2:00PM – 4:00PM, so avoid spraying during these periods and instead, concentrate sprays when thrips are settled on the plant.[5] Mixing with liquid sugar additives like those used in beehives (as opposed to dissolved solid sugar) at a dosage between 0.125% to 0.25% has been found to enhance efficacy significantly.[6] Ensure thorough coverage of all plant parts and be careful of spraying during strong midday sunlight as this can increase the risk of scorching.

7. Filter the light to confuse and disorient

As thrips orientate themselves to the sunlight, filtering out some UV light will help to control activity and movement. UV-absorbing plastics will discourage thrips from moving into the perceived dark spaces[7] and highly reflective, metalized ground mulch at the greenhouse circumference can disorientate the thrips, limiting the likeliness of invasion.[8]

It’s time to fight back!

Detecting thrips is a difficult task and can sometimes be too little too late. But by consistently using a combination of prevention and intervention processes, growers can strike back and protect their crops and plants from this destructive pest.

By Lisbeth Riis, CEO, Scarab Solutions


[1]  Ansari, M.A. et al. (2007). Control of western flower thrips (Frankliniella occidentalis) pupae with Metarhizium anisopliae in peat and peat alternative growing media. Biological Control 40, 293–297

[2] Ben-Yakir, D. and Chen, M. (2011). Characteristics of the migratory flight of the onion thrips (Thrips tabaci) and their relevance for pest management. Entomological Society of America Annual Meeting 2011. Dept. Entomol. Inst. of Plant Protection, Agricultural Research Organization, Bet Dagan, Israel

[3] Labbé, R.M. et al. (2019). Comparison of Transeius montdorensis (Acari: Phytoseiidae) to Other Phytoseiid Mites for the Short-Season Suppression of Western Flower Thrips, Frankliniella occidentalis (Thysanoptera: Thripidae). Environmental Entomology, Volume 48, Issue 2, April 2019, Pages 335-342

[4] Wakil, W. et al.(2012). Toxicity of Paecilomyces lilacinus blended with non-conventional agents to control cotton thrips (Thrips tabaci Lind.) (Insecta: Thysanoptera: Thripidae). Journal of Microbiology Research Vol. 6 (3), pp. 526-533; Al Mazraáwi, M. S. (2007) Interaction effects between Beauveria bassiana and imidacloprid against Thrips tabaci (Thysanoptera: Thripidae). Commun Agric Appl Biol Sci. 72 (3):549-55

[5] Liang, X.H. et. al. (2010). The diurnal flight activity and influential factors of Frankliniella occidentalis in the greenhouse. Insect Science 29 November 2010. Zhong‐Ren Lei, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China. Email:


[7] Masami S. and Honda K. (2013). Insect reactions to light and its applications to pest management.  Appl. Entomol. Zool. 48:413–421

[8] Giles, F. (2010). Keep Out Greenhouse Pests. Growing Produce. May 1, 2010

How to tackle Mealybug infestations in rose greenhouses – and why early intervention is a must Mon, 15 Mar 2021 13:00:24 +0000 How to tackle Mealybug infestations in rose greenhouses – and why early intervention is a must

Figure 1: Mealybugs on a plant in a glasshouse (Image source: CSIRO, CC BY 3.0 <>, via Wikimedia Commons)

Unfortunately for growers around the world, the increase in more sustainable pest management strategies has seen an unintentional rise in unwanted pests such as Mealybugs on greenhouse crops. This destructive pest, once contained by strong miticides to treat spider mites, is now able to thrive in greenhouse conditions as growers increase their reliance on biological controls. In Kenya, the recent arrival and rapid spread of the Papaya mealybug, Paracoccus marginatus is a development that rose growers around the world need to monitor closely. Just like the Coffee mealybug, Planococcus kenyae, the Papaya mealybug species is a quarantine pest that can spread viruses along fresh cut flower pathways and significantly affect crop productivity, quality and quantity.

But it doesn’t have to be a losing battle – with early integrated pest management strategies, you can contain Mealybug infestations before they become too widespread and costly to resolve. Here’s five essential control methods that rose growers can use to manage Mealybugs.

1. Act fast with early detection

One of the main challenges in the management of Mealybugs is the pest’s ability to hide in crevices between branches and the underside of plant leaves. Out of sight, these Mealybugs can reach damaging population levels quickly as adult females lay up to 600 eggs. But that’s only half the problem – once the eggs hatch, immature scale crawlers can spread to new plant parts and new hosts and at this stage, your situation becomes uncontrollable.

This is where a deep understanding of the insect’s biology can make a significant difference. Scouts can learn to check for early Mealybug signs such as the appearance of sticky honeydews on plant material and take immediate action to alert management before it’s too late. If steps like this are missed however, Mealybug’s toxic saliva can go on to support the growth of black sooty mould, which interferes with plant respiration and transpiration.

2. Keep your greenhouse clean and tidy

Practicing good hygiene is important and should start on the greenhouse floor. To limit Mealybug development, you can regularly sweep debris away as these tend to be egg sac hotspots. Unwanted material such as weeds, dead foliage, and hanging leaves should also be cut to allow the crop to open up during the early stages of plant development. This increases the level of coverage and can improve the effectiveness of intervention methods, such as spraying, that might be used in later stages.

If you want to minimize Mealybug build-up and reduce the chances of reinfection, you may also need to use cultural and mechanical controls. Any affected crops and plant material will need to be immediately removed to protect clean areas of the greenhouse. If agrobacterium tumefaciens sets in, you should regularly monitor the rose crop for any fresh crown galls that might attract Mealybugs, and follow this step with a disinfection of the contaminated area. But don’t forget to keep physical contact with infested plants to a minimum as Mealybugs easily attach to clothing and implements.

3. Target intervention on a granular level – with the help of digital mapping

More often than not, Mealybugs can prove to be very resistant and require further intervention. A good tip is to start when Mealybugs are in the crawler stage and have yet to develop their white wax.

For small infestations, a small paint brush coated in undiluted alcohol should do the trick. If the infestation is more widespread, high volume spraying can achieve good coverage of the infected area. While the volume can vary, it is important to disturb Mealybugs from their colonies.

But knowing where to target your intervention can sometimes be a challenge in itself, especially when you have to cover extensive ground. This is where Scarab’s accurate mealybug mapping can help guide your scouts to hotspots that require immediate attention.

4. Follow up with a rinse and repeat

At this stage, your situation may require a reliable spraying routine. To start, apply soapy water or detergent to crack the waxy layer of the pest – but focus on the hard leaves to avoid scorching the younger and less developed leaves. Then it’s time for a rinse. To be more precise, you will need a high-water volume and a suggested size 16 or 18 nozzle to achieve effective coverage.

As an extra precautionary measure, you can follow up with a chemical spray with a pH between 5.0 and 6.0. In cases where the Mealybug infestation is well-established, weekly or semi-weekly intervals between sprays is suggested for effective management. To achieve widespread coverage, you should apply the chemical spray, two or three hours after the crop has been washed with soapy water or detergent.

5. Rethink long-term plans with sustainable practices

With demand for sustainable practices continuing to increase, now is the time to include biological controls in your long-term strategies. As the production of parasitoids starts to increase, natural enemies of the Mealybug such as the predatory ladybird beetle, Cryptolaemus montrouzieri can play a crucial role. These beetles can feed on Mealybug eggs from the beginning of their larvae stage and help growers reduce the population density of the pest.

A relatively new option, which is showing great promise, is the use of insecticides such as Neem Oil. This biological control can prevent Mealybug resurgences and has the potential to significantly alter future control strategies. Already many Integrated Pest Management companies are developing biopesticides that minimize the development of resistance in key insect pests and protect non-target biodiversity.

Investment in the right tools and training will pay off

While early intervention methods such as the use of undiluted alcohol, soapy water, and chemical sprays can be critical in reducing the size of the infestation, most sprays do not give industrial growers the contact needed to eradicate the Mealybugs entirely. This is why investing in a knowledgeable team and an accurate scouting system to detect infestations early on is key to immediate intervention and will help you win the battle against the insatiable pest!

Dr Geoffrey M. Macharia, Managing Director for East Africa, Scarab Solutions

Humans still crucial as AI image analysis for crop pest and disease management has a long way to go Wed, 17 Feb 2021 13:00:04 +0000 Humans still crucial as AI image analysis for crop pest and disease management has a long way to go

Figure 1: Scarab Solutions was able to use AI image analysis to identify a large percentage of spider mites on a leaf but the results were insufficient for routine scouting efforts. In a greenhouse setting, the scouting team could move around more freely and inspect the situation more accurately and efficiently than the AI tools.

Effective pest and disease management is not only time consuming, as many know, it often comes at a price. According to the Food and Agriculture Organization of the United Nations, pests such as thrips and leaf miners along with diseases such as blights and mildews cost around $220 billion to the global economy annually – equating to between 20% and 40% of annual global crop production.

To improve horticultural industry efficiency, crop management strategies will inevitably require improved techniques and technology. With technological advances in scouting already set to transform the sector, is artificial intelligence (AI) the answer?

In early development, AI promises to make a difference, but will this happen in practice? Here’s one agriculturalist’s opinion on why growers shouldn’t be too quick to completely replace their existing processes with drones and robots.

When AI meets horticulture – a promising start

As AI’s potential grows, developers set their sights on horticulture with the belief AI-driven image analysis can automate crop management operations – but are we at this stage already?

Recent developments include a ‘robot scout’ equipped with near-infrared image cameras to detect powdery mildew and image analysis to predict bud and flower yields, and the IRIS Scout Robot. With the latest remote pest monitoring system that uses machine learning (ML), growers can receive pheromone trap image analysis – crucial to real time intervention strategies.

More wide-spread cases promote using smartphone applications to scan photos for pests and diseases, often presented as or nearly ready for prime time use. So, growers using smartphone image analysis for crop pest and diseases identification cannot be far off?

A rosy picture at odds with reality

As it stands, studies suggest image analysis falls short of its promises. According to a recent Scientific American article, the effectiveness of image analysis statistics is often misleading at best. The most common ‘pairing test’, testing the ability to compare two plant images and state which has the pest or disease, gives more accuracy than multiple image analysis with no information on whether any have the pest or disease.

 … with the added challenge of false positives

The false positive issue is all the evidence needed to caution against using inaccurate or skewed AI generated results as a basis for potentially damaging pesticide use.

Consider an imaging system giving a five-percent false positive reading for blight – a conservative figure, even by current app accuracy claims. In a full field of blight, this would not pose an issue, but in a field with zero blight occurrences, a slightly different story emerges. If you take 2,000 images in that field – the number of observation points a skilled scout manages per day – you would yield 100 positive results!

You must then decide whether to act or inspect the “positive” locations to verify whether they are indeed affected. Multiply this by other pests and diseases the image analysis system is checking for, with perhaps an even higher false-positive rate, and the results speak for themselves. The higher the number of false positives, the more resources are required to verify the results and all automation gains are lost.

Figure 2: AI image analysis can generate inaccurate or skewed results such as false positives, which causes growers to use more resources such as pesticide. This can create more damage than good and significantly reverse the gains of automation.

Man vs machine – an unequal comparison

The context should not be lost. Studies comparing scenarios where there is AI or no crop scouting technology at all, do not paint a realistic picture because in some cases, a system already exists which effectively records and analyzes scout-collected data. In a greenhouse setting, a scout can move their head, turn leaves, and use a magnifying glass – giving a significantly better view of the issue than smartphone image analysis ever could.

Upskill your team with the support of mobile technologies

Now is not the time to replace scouts with AI. Instead, growers should focus on supporting and enhancing human capabilities. The right digital tools should help scouts work more accurately, faster and to a greater result – not ignore their expertise.

Smartphones will continue to be key – but not primarily as an AI tool. A more realistic and proven application is data collection and mapping. Crop protection managers should empower scouts to use their inspection skills and record results as they go – building a wealth of accurate data for comparison.

This is where effective training makes a difference. Correct identification and scoring of pests and diseases, thorough sampling protocol knowledge and techniques to expedite the process harmonize the performance and accuracy of scouts’ farm-wide and are key for success.

AI may guide scouts towards correctly identifying unknown pests or diseases, but most crop scouting is about tracking the dynamic distribution of a well-known set of pests and diseases.

Working together, not apart – digital technologies can offer new insights

By combining scout-recorded data with geographical information, the results create datasets which provide an audit trail for traceability and visualization options, such as digital maps, charts, and graphs. These prove invaluable for easy identification of unique and recurring problems and patterns with few, if any, false positives.

Digital mapping combines pest and disease scouting with human expertise to optimize outcomes. Scarab Solutions sees this daily as clients use Scarab Precision crop pest and disease scouting and mapping solutions to provide a solid basis to pinpoint infestation hotspots, determine correct pesticide use, and reduce crop losses through enhanced farm management.

As datasets grow, crop protection managers can benchmark their progress against regional figures, using anonymized data from other farms.

AI can wait – humans are still the most vital commodity

An industry talking point, AI-driven image analysis still has a long way to go. For now, GPS-tracking, mobile data collection and interpretation tools are the most effective and lucrative technological solutions for crop pest and disease management. There is no doubt AI can be a real asset to extend human intelligence and enable more efficient task completion – but let’s save AI-driven image analysis on drones and robots for another time.

Dr Mikkel Grum is Research and Development Director at Scarab Solutions

How to keep control of your greenhouse to combat Downy Mildew on rose stems Fri, 29 Jan 2021 13:00:46 +0000 How to keep control of your greenhouse to combat Downy Mildew on rose stems

Few diseases strike more fear into industrial rose growers across the highland tropics than downy mildew, Peronospora sparsa. The disease can appear quickly when cool temperatures (10-18°C), high relative humidity (> 85%, > 3-4 hrs) and excess moisture on leaves combine particularly on young apical tissue – the weakest point in a plant. There is only one way to combat downy mildew, by taking a zero-tolerance approach across every greenhouse on a farm, and that means taking appropriate prevention methods, combined with early detection and rapid intervention when necessary.

Key indicators of downy mildew

One of the primary signs of downy mildew are purplish red, brown or blackish angular spots on the upper side of a leaf, particularly in areas between major veins. In fact, in humid environments (>85% RH), grey to brownish erect sporangiophores will form on the underside of the leaf and conidia will spread from here by any air currents and water splashes.

Sporulation will not always be visible underneath the leaves, but the risk of this taking hold  when environmental conditions are favourable is high. Purple patches can also be identified on stems, peduncles, floral sepals and petals.

Zeroing in on downy mildew in rose stems

In this blog we will focus on the consequences of downy mildew on rose stems, from identification through to establishing control. This will serve as an excellent best practice guide for the control and management of the disease.

Easily recognisable purple patches of 2 cm or more can be observed on affected stems, often alongside longitudinal cracking of the stem. Under very humid and moist conditions, white mycelial growth may also be observed. Although Aegerter et al. (2002) has shown that symptomatic rose stems are extensively colonized within the stem cortex tissue, researchers have not been able to unanimously confirm whether downy mildew is a systemic disease in the rose plant. Many farm technicians have posited that downy mildew in stem can be dealt with by cutting off the sick part of the harvested stem, in order to meet production expectations. But this comes with long-term issues after harvest.

Short-term gain, long term pain – the false economy of trimming stems

There is significant evidence to show that removing the impacted part of a rose stem only serves to postpone the repercussions of downy mildew. Ing. Roberto Toscano of Hoja Verde Cia. Ltda., Ecuador shared his experiences with downy mildew in stem affecting vase life significantly, even after chopping off the symptomatic part of the stem and rescuing the remaining, although shorter, stem for sale. After two days, the heads of the rescued stems started hanging and did not open up like the heads on the healthy stems harvested within the same bed.

This is why the Scarab Precision monitoring system takes downy mildew in stem very seriously and provides growers with the knowledge and strategy to track the status of downy mildew in the rose crop before harvest. Its findings put farms on high alert, so that they can put in place a proactive strategy to avoid the full impact of downy mildew.

Five steps to establish control

Rose varieties differ greatly in their susceptibility and tolerance to downy mildew, but many of the susceptible varieties are in high demand and fetch a good market price. Here are the five stages to reduce the likelihood or minimize the impact of downy mildew in rose greenhouses:

  1. Prior Prevention
    Prevention by means of climate control is ideal, but for those without such technology, prevention relies on good hygiene and ventilation (except during downy mildew sporulation). Fungicides, such as potassium phosphites, copper phosphites or fosetyl-aluminium, also important in the plant’s early life, help suppress outbreaks of this disease to a certain extent.
  2. Thorough Hygiene
    Hygiene is critical to reduce the presence of downy mildew, as sporangia can remain viable on dried fallen leaves for up to one month and carefully removing the debris around the plants, without stirring up the sporangia into the air, can help reduce the presence of spores.
  3. Adequate Ventilation
    Providing good air movement and keeping the greenhouse well ventilated through appropriate plant spacing, raised roofs, raising curtain walls during times of water condensation in the air, and installing industrial fans (except during downy mildew sporulation) to keep the relative humidity below 85% is key, but difficult during rainy and cool conditions.
  4. Quick Cut and Disposal
    Beyond the preventive measures, when detected, it is vital to spray curatively to avoid the spread of spores and then cut and carefully remove any affected plant parts directly into bags, which should be immediately sealed.
  5. Focus on Fungicides
    For those who don’t have climate management, the control of downy mildew relies heavily on chemicals and to avoid the build-up of resistance, it is critical to apply different active ingredients with different modes of action, as established by the Fungicide Resistance Action Committee (FRAC).

High-volume sprays of fosetyl-aluminium (FRAC 33) or tank mixtures of cymoxanil, mancozeb, and fluazinam (FRAC 27/ FRAC M 03/ FRAC 29) have proven good control. Also, good control has been observed rotating cyazofamid (FRAC 21), dimethomorph (FRAC 40), mancozeb/copper hydroxide (FRAC M 03/FRAC M05), phosphonate fungicides (FRAC 33) and oxathiapiprolin (FRAC 49) according to Salgado-Salazar et al. (2018). Phenylamides (FRAC 4), on the other hand, should be excluded as these are prone to develop resistance.


Active ingredients to be rotated in an effective downy mildew control programme:
Phosphonate fungicides (FRAC 33) work as protectants by boosting the plant’s own natural defences and may be applied in form of Potasium phosphite, Copper phosphite, Calcium phosphite and Magnesium phosphit
Fosetyl-aluminium (FRAC 33) has a systemic mode of action and provides a long-lasting, broad spectrum preventative control of diseases
Cymoxanil (FRAC 27) is a contact and locally systemic fungicide that has curative activity when applied immediately after spore germination
Mancozeb (FRAC M 03) is a protectant fungicide
Fluazinam (FRAC 29) has protective activity with very good residual effect, and limited curative or systemic activity
Cyazofamid (FRAC 21) is a protectant fungicide
Dimethomorph (FRAC 40) is a systemic fungicide with protectant, curative and anti-sporulating activity
Copper hydroxide (FRAC M05) is a protectant fungicide. Caution: There is a high risk of causing phytotoxicity when applied in spray water with a pH of less than 6.5 and/or mixed with fosetyl-aluminium
Oxathiapiprolin (FRAC 49) is a protectant fungicide
Phenylamides (FRAC 4) should be excluded as these are prone to develop resistance


Winning the battle against downy mildew in rose stems

Growers must take an all-encompassing approach to combat downy mildew. Simply removing the affected part of a stem does not solve the issue and can actually do long-term damage to a grower’s reputation through very short vase life.

Controlling downy mildew in rose greenhouses means turning knowledge into action, from scouting to prevention strategies and intervention to regular control. 

By Lisbeth Riis, CEO, Scarab Solutions


Major sources:

Aegerter et al. (2002) Detection and management of Downy mildew in rose rootstock. Plant Disease 86:1363-1368

Salgado-Salazar et al. (2018) Downy Mildew: A serious disease threat to rose health worldwide. Plant Disease, 102:1873-1882

Thanks to:

Ing. Roberto Toscano of Hoja Verde Cia. Ltda., Ecuador, for sharing his experiences.

How to wage war on the two-spotted spider mite in rose growing – lessons learnt from biological control Mon, 17 Feb 2020 16:01:50 +0000 How to wage war on the two-spotted spider mite in rose growing – lessons learnt from biological control

It has taken time for rose growers to learn crucial lessons on biological control of the two-spotted spider mites, Tetranychus urticae[1]. These lessons have taught us that, yes, you can apply phytoseiid predatory mites to a rose crop and get your spider mites under control, but it is not the classical biological control where you release predators which then feed on the prey, multiply and reduce the prey population until the two populations eventually oscillate into a balance. Whereas Colombian rose growers might just be getting the grip of it, there are still lessons to be learnt from their Kenyan counterparts, many of whom now have biological control incorporated in their DNA.

Think “biopesticide”

Predatory mites are put to work in industrially grown rose crops in much the same way as a biopesticide. Predatory mites reproduce very little in industrial rose production and growers do best when applying an appropriate release methodology. You, the grower, release the predatory mites, they then feed on the spider mite prey, Tetranychus urticae. However, the authors[2] of this paper have witnessed over 15 years that predator reproduction in industrial greenhouse roses is low – probably due to the direct and accumulative effect of other necessary pesticides and fungicides used in the crop. So, you, the grower, will need to keep applying predators just as if they were a biopesticide. The good news is that it will pay off with when you get it right.

Here’s a simple three step formula to succeed with your biological control of spider mites.

  1. Start when the pest population is low

The first lesson in doing it right is to start the release of predatory mites when and where the pest population is low. Don´t challenge your supplier of predatory mites by starting in your worst spider mite infested house. Neither you nor the predatory mites will win such battle. Why? Because the reproduction of the predatory mites in industrial rose greenhouses won’t be what you would expect according to classical biological control.

The predators will feed on the spider mites, but they produce comparatively few offspring. So, rule number one is first to bring down your population of spider mites with compatible chemicals, i.e. chemicals with short-lived persistence in the crop. For example, Organo-silicone adjuvants, such as Silwet Gold, are a good option but make sure you don’t spray in direct sunlight. Your supplier can also provide you with a list of compatible chemicals. Remember, at this stage, it is the short-lived persistence that matters and not whether the product kills your predatory mites because this is before predatory mites are released.

  1. Excellent scouting and analysis

There is a cost to the use of predatory mites. Excellent scouting and mapping of the locations with predator deficiencies will help you to significantly reduce that cost by spatially targeted release of the predatory mites only where there are spider mites and insufficient numbers of predators. This helps avoid wasting predatory mites where there are no spider mites or where there are sufficient numbers of predators. This requires good scouting and a good analytical tool, which is a cornerstone in biological control.

Most of the scout’s time is spent on (1) walking diligently through the crop, (2) searching thoroughly for the pests and diseases in each observation point and (3) recording observations. But if the scout simply records presence you will only get information about the pest incidence and will not get the full understanding of the spatial distribution of the pest severity.

Even if the scout records pests on a scoring scale, spends a little extra time on counting the pest in a pre-defined sampling unit and then concludes which severity score level to record, these classified scores are not of continuous data like our number system – and are therefore no good for statistical analysis. Instead of having the scout spending time on figuring out which score class to record, the same amount of time is much better invested in recording the real counts. There are excellent methods for quick counting that a good scouting company can train your workforce to implement.

  1. Map, monitor, manage

Recording the counts spatially allows the corresponding spatial analysis to map the deficiency and sufficiency of the predatory mites. Continuous spatially targeted release of predatory mites in the locations with predator deficiency should come next. Releasing in numbers that bring the ratio of predators to spider mites below 1:10 will significantly reduce the time taken to get the spider mites under control.

These targeted spot releases will be most effective when applying the strong hunter of the specialist predatory mites, Phytoseiulus persimilis, which specifically and exclusively feeds on the two-spotted spider mites, Tetranychus urticae.

Blanket releases should be carried out  applying the resilient, more ‘generalist’ and more cost effective Neoseiulus californicus (formerly known as Amblyseius californicus) which can survive on alternative preys such as other mites and pollen, where or when the spider mite population is very low and the great hunter Phytoseiulus persimilis won’t have many feeding options.

Excellent record keeping of the scouting analytical results allows for a crucial evaluation of the interventions. Evaluation of the effectiveness of control measures ensures that lessons are learnt quickly, expensive wasted effort is avoided and irregularities are spotted early.

Playing the waiting game doesn’t pay – don’t extend the pain

If you release too few predatory mites, rather than taking enough ‘soldiers’ to the war, you will extend the time of the battle. If you are an industrial rose grower and you intend to wait for the classical biological control dynamics to kick in, you are waiting in vain. If you apply the strategy of going in with an abundant army of predatory mites and control the process with excellent monitoring and analytical tools, you’ll win the war quickly rather than extending the pain.

On one hand, when you replace your miticides with predatory mites, other pests that were suppressed by the miticides before may now inevitably flare up. This is an uncomfortable challenge for the growers who use biological control. On the other hand, as you may need to spray pesticides against these ‘new’ pest problems, these pesticides are likely to negatively affect your predatory mite population. Hence, you find yourself between the devil and the deep blue sea.

But there is another huge gain from this strategy. First, you need to get your spider mite population to zero and, yes, that’s possible if you diligently execute the war strategy outlined above. Once your spider mite population is as good as zero, you’re no longer so sensitive about your predatory mite population because there won’t be many of them left – they have done the job anyway. You can calmly spray your other pests as long as you choose pesticides with short residual effects, which will allow you to come back with the resilient and cost effective Neoseiulus californicus if you see signs of spider mites returning.

Clean up the house

The above strategy can allow growers to successfully clean up one greenhouse from spider mites and move on to the next. It is indispensable that you apply the same strategy simultaneously in the houses that share the same workers and keep other workers away from other spider mite infested houses in order minimize the reintroduction of spider mites from elsewhere. On many rose farms, the same group of workers operates in two houses, so pair these houses and apply the same strategy in these at the same time.

Clean up a pair of houses and let them go into ‘maintenance mode’ with occasional blanket releases of your resilient friend Neoseiulus californicus, combined with continuous scouting and spatial analysis as you continue your warfare strategy in the next houses and eventually clean up the entire farm.

Until the last spidermite!

You can never relax, but it is easy when you setup a solid work structure. Identify a serious and determined biological control ‘specialist’ among your personnel and dedicate him/her the task of leading the predator releases and keep the war going until the last spider mite falls. The key is to combine target releases in hot spots with the great hunter (Phytoseiulus persimilis) and blanket releases for maintenance with your resilient friend (Neoseiulus californicus).

The reason to continue until the last spider mite is because that is when it gets cost effective. You will have taken a great burden off your shoulders – as you will have freedom to spray your other pests and diseases without stressing too much about your predatory mites. You’ll have few predators left and next to no spider mites, so you will see the results in a much better-quality crop, without it suffering greatly from miticide sprays. Release few predators, here and there, and now and then, in accordance with your scouting results.

“We have benefited significantly from the improvement in the information and analysis provided by this technology”, explains John Ngugi, technical manager of Equinox Horticulture near Mt. Kenya in East Africa. “Once we had the structure and control measures in place, we reduced our requirements for Phytoseiulus persimilis by 60-90%, depending on the season.”

It’s a win-win

This is a triple win. You as a grower benefit from improved crop quality and lower long-term costs of pest control. The predator supplier will have grown their market share in terms of hectares – perhaps selling less per hectare but they will sell to a greater number of hectares. And of course, the environment benefits from reduced pesticide usage.

By Lisbeth Riis, CEO of Scarab Solutions


[1] Count data collected daily over 15 years in 2500 hectares of industrial greenhouse roses

[2] Henceforth referred to as spidermite

Scarab Solutions announces enhanced scouting, tracking and mapping solution to help Kenyan Rose Farms combat the threat of the False Codling Moth (FCM) Wed, 15 Jan 2020 16:34:07 +0000 Scarab Solutions announces enhanced scouting, tracking and mapping solution to help Kenyan Rose Farms combat the threat of the False Codling Moth (FCM)
  • Kenya Flower Council (KFC) member Scarab Solutions offers unmatched scouting, tracking and mapping methodology to pinpoint and manage False Codling Moth (FCM) proliferation
  • Increased threat of FCM occurrences in Netherlands rose imports triggers potential check increases from Dutch National Plant Protection Organisation (NPPO) and European Union (EU
  • Click here for digital map example

January, Kenya – Scarab Solutions, the crop pest and disease mapping experts, today pledged its assistance to combat the proliferation of Thaumatotibia leucotreta or False Codling Moth in Kenyan rose exports. Scarab has announced consultation, knowledge and mapping solutions designed to help Kenyan rose growers address this severe threat and reduce the likelihood of 100 percent import inspections from the Dutch National Plant Protection Organisation and the EU by 2021.

With caterpillar season in full flow, the Kenya Flower Council has called for its members and non-members to share information on FCM. This call follows Dutch NPPO and EU findings that the number of FCM interceptions on Kenyan roses remained over 30+ during 2019. If Kenya cannot bring this figure down, there could be increased checks to either 50 or 100 percent of all imports by 2021.

Scarab Solutions, a member of the KFC, has amassed vital experience from mapping of pheromone traps which confirm the likelihood of FCM being present on farm. This includes digital maps of FCM captured in these traps with a colour-coded display.

As a crop pest and disease mapping specialist company, Scarab Solutions goes beyond just confirming the presence of FCM. It also strongly recommends directly scouting the crop for both the pest itself and its damage symptoms. Direct crop scouting can be carried out at a much higher sampling density in order to provide a quantified insight into the spatial distribution of the pest and the risk zones.

“Time is of the essence to get on top of FCM in Kenyan rose growing, which poses a serious industry threat at this point. But expecting scouts to differentiate damage symptoms from FCM caterpillars from other caterpillars in flower crops is wishful thinking,” explains Dr Lisbeth Riis, founder and CEO, Scarab Solutions (UK). “FCM-specific pheromone traps remain the key to accurate identification, but the number of sampling points is limited due to the cost of pheromone traps. Our advice to the growers is to combine pheromone traps with direct crop scouting for caterpillars, eggs, moths and treat any damage symptoms from these as a potential FCM threat.”

To discuss how to combat FCM in your rose farm, contact the Scarab Solutions team.

About Scarab Solutions

Scarab Solutions is the global leader in crop pest and disease management software for protected crops. Scarab offers a software-based service that keeps your team on top of your crop scouting information with high precision pest and disease maps, charts and tables, and accompanies you in the implementation and follow-up processes.

Media contacts:
Geoffrey Macharia
Managing Director of Scarab Solutions (Kenya)

Jamie Kightley
IBA International – PR for Scarab Solutions
Tel: +44 1572 757932

Scarab Makes a Difference in Global IPM Mon, 29 May 2017 12:22:59 +0000 Scarab Makes a Difference in Global IPM


This press release formed the basis of an article in HortiDaily: Smart software and portable device takes pest scouting to the next level

Since 2005, SCARAB Solutions has worked with the flower industry to increase their profits, lower their use of pesticides, and improve product quality, using SCARAB’s state of the art crop scouting system for precision horticulture. SCARAB’s initial market was the flower industry in Kenya, Tanzania, Ecuador and Colombia. Last year SCARAB entered the precision horticulture market in Mexico supporting local IPM strategies in Tomato, Bell Pepper, Cucumber and Eggplant crops. With their technology and strong on-site support, SCARAB has strengthened IPM processes and generated more profit for its customers.

“We want to give our customers the opportunity to be more efficient on their current production surface with reductions in the use of chemical products and greater quality production, taking into account the new environmental and social conditions they face. We are becoming a close partner with our new customers in Mexico, supporting them on the best use of information applied to precision horticulture,” says Luis Trujillo, Business Development Manager of SCARAB Mexico.

“SCARAB works very well for us in Bell Peppers and Eggplants. It has enabled us to improve our detection and contain the pests and diseases. With SCARAB we have been more efficient in the use of pesticides and we are now able to evaluate quickly and precisely and follow-up on our IPM processes.”  Roberto Figueroa E., Grupo Doble RR, Sinaloa, Mexico.

SCARAB will continue its process of changing how the world targets crop pests and diseases.

Time to Zero-In on Zero Residues Tue, 26 Apr 2016 11:08:48 +0000

Time to Zero-In on Zero Residues


Louise Labuschagne reports:

When politicians need to negotiate safe passage through a minefield of difficult issues – they make a Road Map. Real IPM Kenya is putting its money where its mouth is and making its Road Map to Zero Residues a very public affair. Progress reports are published on social media (#zeroresidues) and include step-by- step progress reports and YouTube videos. The greenhouse, in Thika (Kenya) is open to rose growers to see for themselves and even take samples to test for chemical residues. The programme started two weeks ago and is already showing very encouraging results. By the time the Nairobi IFTEX Show is running there may be even more to shout about.
They are attempting to demonstrate that even in a very highly infested rose crop, with a highly susceptible variety, on the Equator with all year round growing conditions and during the rainy season – that it is possible to use biological controls curatively for all pests and diseases in roses. If it is possible to get out of the quagmire just using biological controls – they hope to encourage growers to be more confident about using a bio-intensive IPM programme as the front line way for all growers protect their crops in the New Age of Rose Farming. A prophylactic, preventive programme with high application rates and short spray intervals for biopesticides and predatory mites is claimed to be the most sustainable and reliable way to improve yield and quality – is this true? Their challenge to rose growers everywhere is SEE IT – BELIEVE IT – DO IT

When retailers task their suppliers to reduce chemical pesticide residues, growers hear alarm bells ringing. The immediately envisage huge crop losses, irate buyers on the phone and foresee a fast scramble back to the safe bunker of programmes that rely on chemical pesticides.

Measuring risk and progress

It is not unusual for growers trying bio-intensive IPM to jump ship when they are not sure about achievements or risks. The #zeroresidues rose greenhouse is being scouted using the Scarab Solutions state of the art GPS scouting system. Hand-held smart phones are used by trained scouts to enter information on the presence and severity of the pests and diseases at about 13 observation pints in a 40-meter row. This data is even separated into three strata inthe crop (base, middle and top).

Within three minutes of pressing ‘send’ to have the data analysed by Scarab Solutions – a very detailed contour greenhouse map of the individual pests are displayed either on the phone or on a number of computers anywhere in the world.

Managers with passwords can immediately see the progress of powdery mildew control or mealybug control etc. – even if they have not been able to visit the greenhouse. Not all farm managers would want the owners breathing down their necks from another country. But eventually with a successful bio-intensive programme, the farm manager will have less to worry about. Ethan Chege, Technical Manager at NIRP Show-house in Kenya says “ I sleep at night now – knowing that I am in control, having successfully implemented the bio-intensive spray programmes”.
Scarab is a very useful tool because it is impossible to ‘cheat’ with the scouting – since the week-on- week comparison of hot spots and spread of disease or pests takes a biologically logical route. Access to this technology and the immediate reports – replace piles and piles of un-read scouting data from the old fashion scouting methods! The Real IPM #zeroresidues rose greenhouse will be publishing key comparisons of ‘before’ and ‘after’ the bio-intensive spray programme.

Powdery mildew history
Rose growers around the world have serious problems with powdery mildew and may have to spray up to 50 times per year for this disease. If growers could replace fungicides with biological controls – they could make a serious dent in their performance targets for #zeroresidues. Already after only two weeks, the Real IPM programme has made powdery mildew ‘history’. Powdery mildew on the stems and leaves were at seriously high levels. The Scarab powdery mildew maps show how this turnaround has happened.

Fig 1 : Scarab map BEFORE the Real Bacillus subtilis programme started. Circles indicate where live powdery mildew was observed on the stems near flower heads.


Fig 2: Scarab map AFTER 40 days of the Real Bacillus subtilis programme. This has been achieved without any chemical fungicides.

Therefore a prophylactic preventative programme is a reliable substitution for fungicides and runs no risk of resistance developing.

Over the next few weeks, similar results are expected on downy mildew, mealybugs and thrips. These are all difficult targets, even for chemical fungicides and insecticides. But even after two weeks – the Scarab maps are showing significant improvements using higher rates of biopesticides and shorter spray intervals for curative programmes.

Lower spray volumes of water are key to the success of biopesticides. They must not be sprayed to ‘run-off’. Successful bio-intensive growers have had excellent results with just 800 litres of water volumes per hectare for pest and disease control.

Predators to tackle agricultural pests Thu, 07 Apr 2016 11:05:01 +0000 Predators to tackle agricultural pests

Kenya is helping to lead biological pest control development due to the importance of agricultural exports for the Kenyan economy.

BBC has the story of the founding of Dudutech and Real IPM, the two major Kenyan producers of biological control agents:

Scarab is proud to collaborate with both companies (as well as Koppert Biological Systems whose products are pictured in the article) to enhance the effectiveness of biological control.