Foliar feeding with fully water‑soluble fertilizers at these critical stages can dramatically increase yields and improve quality. Because nutrient uptake through foliage is considerably faster than through roots, foliar sprays are also the method of choice when rapid correction of nutrient deficiencies is required.

When to Foliar Spray

The best time to spray is late in the afternoon or early in the morning, when temperatures are mild and wind is minimal. When wind is low, finely atomized sprays drift readily — this is ideal. Absorption is further enhanced when weather conditions are humid and moist. The presence of dew on leaves also facilitates foliar feeding.  Absorption is maximized when sprays coat the underside of leaves, where the majority of stomata are located. Avoid spraying when temperatures exceed 30°C or onto wilted plants, as this can reduce uptake and damage the plants.

For detailed foliar feeding programmes on all crops, contact your local Hygrotech representative. (Adapted from an article on: drearth.com/learning-center/projects/foliar-feeding)

ColourUp

ColourUp is a proprietary translaminar liquid Calcium Complex which works with the plant’s natural ripening and colouring stages on various fruit and vegetable types. The product is manufactured by Miller® Chemical & Fertilizer, LLC in Hanover, Pennsylvania,17331, United States of America. ColourUp is imported to South Africa by Hygrotech South Africa (Pty) Ltd. The name ColourUp is used only in South Africa and is registered as a Group 2 Fertilizer (Reg. No. B3386 of Act 36 of 1947). Internationally the product is known, marketed, and sold as Calexin® in countries such as the USA, Peru, Chile, Costa Rica and Australia, and CalXpress in New Zealand. ColourUp is applied as a foliar spray and is totally systemic. Being part of the Miller® patented Nutrient Express® technology products, ColourUp focuses mainly on plant energy production and contains no hormonal substances. During periods of rapid growth, fruit development and ripening, plants require energy for proper physiological development and high levels of calcium for fruit quality. Physiological and environmental crop stress slows down plant metabolism and the movement of calcium within plant tissue. Consequently, plants may suffer, crop development may weaken, and fruit may lack necessary nutrients (including calcium) required for optimum harvest quality. International documented benefits from ColourUp applications include calcium mobilization to fruit and supporting natural colour development. Known commercial crop uses of ColourUp in South Africa include table grapes, mangoes, and citrus.

Trials

Locations and apple varieties

• Trials were conducted in 5 different areas (Koue Bokkeveld, Elgin, Helderstroom, Greyton and Riviersonderend). As many as possible bicolor apple varieties were evaluated. These were Gala, Pink Lady, Sundowner, Rosy Glo and Fuji. 

ColourUp rate and application timings

• ColourUp was applied 3 times at 10 – 14-day intervals at 2 L/ ha by means of tractor mounted commercial spray equipment. Applications commenced when at least 80% of the apples in the orchard had developed or had started developing colour.

Commercial harvesting practices

The general commercial harvesting practices in the Western Cape may be as follow:

• First pick: Quick process during which fruit that are mature (adequate colour development) ahead of the bulk fruit load are harvested and placed in cool storage. This fruit are packed after two weeks in cool storage. 
• Second pick: This is the main harvesting stage. Harvested apples are kept “fresh” in controlled-atmosphere storage often for months. During these months of storage, the objective is to sort, pack and deliver these apples during optimal marketing (economical) opportunities.
• Third pick: This process is similar to the first pick, but in this case, it is late maturing fruit or fruit from a later fruit set.

These practices do however vary among growers and apple varieties. While some varieties go through all three harvesting stages, other varieties are only harvested once (with the aim of having as many fully coloured fruit as possible at that time). These various harvesting procedures had an obvious effect on the assessments of these commercial trials.

Assessments

Randomly tagged apples from randomly chosen trees within ColourUp treated and untreated orchards were frequently monitored for colour development during the trial period. The tagged fruit were sampled as close to commercial harvest as possible. This depended on whether the grower harvested over three picks or only once.  Fruit sampled from orchards harvested three times often showed less colour development compared to fruit harvested once only, as the objective of a single harvest is to maximize the presence of fully coloured fruit at picking. In contrast, fruit from trees destined for multiple picks had to be sampled earlier to avoid losing tagged fruit, which affected colour development and final data.

Results

In most of the trial locations the increase in fruit colour development from ColourUp treated trees compared to untreated trees were visible in the orchard (example Photo 2) and also in the commercial picking bins (Photo 3).  The extent of the ColourUp treatments are however better visually illustrated by comparing the sampled fruit next to each other (Pictures 4 to 8).

Photos 4 – 8:

Sampled apples of various varieties (as indicated) from ColourUp treated (left) and untreated trees (right) from various trial locations.

(Written by Herman Walters – Hygrotech Technical Manager: Southern Region)

How do different adjuvants react at different spray volumes when applied with either Spirotetramat or Pyriproxyfen containing insecticides for the control of California red scale on citrus?

Introduction

It has been well documented that the South African citrus industry relies heavily on medium to high-volume cover crop sprays, especially when managing pests such as red scale and mealybug or diseases such as Alternaria brown spot (ABS) and Citrus black spot (CBS) (Van Zyl et al., 2013). According to Beatie et al (1989) a medium-volume cover spray is defined as 2000-7000 L water/ ha and a high-volume spray as more than 7000 L water/ ha. These defined volumes compare readily with the volumes of 6000 L water to an extremely high 16000 L water/ ha currently reported from South Africa (Fourie, 2013). Although these high volumes have become the market standard and are known to be effective in managing these target pests (Grout, 1997, 2003), conventional airblast sprayers and oscillating boom sprayers capable of achieving them are known to be more wasteful and costly to operate (Furness and Piczewski, 1985). 

Currently the standard spraying volumes in citrus production is indiscriminately determined without taking tree characteristics into consideration (Scapin et al., 2015). However, several studies over the years have focussed on the optimisation of agricultural sprays using quantifiable approaches based on tree characteristics such as tree row volume (TRV), leaf area index (LAI) and surface area index (SAI) (Bataglia, 1999). Of these, TRV has shown definite promise as spray volumes have been established in Brazil for the control of several citrus diseases such as citrus bacterial canker (Scapin et al., 2015), citrus black spot (Silva Junior et al., 2016) and post bloom fruit drop (Soares, 2015), as well as certain pests including the Asian citrus psyllid (Scardelato, 2013) and leprosis virus-transmitting mite (Scihieri, 2018). In which the case of citrus canker management resulted in a 73% reduction in water usage as well as a 40% in savings. 

From the mentioned research it has become apparent that an improved deposition uniformity led to higher levels of control of not only citrus diseases, but also certain pests requiring medium to high-volume cover sprays as well. Unfortunately, this coincided with higher spraying volumes.

Therefore, the challenge is to improve uniformity without the coinciding increase in spraying volume to eventually achieve more efficient spraying volumes without a decrease in efficacy.

Previous studies by Van Zyl et al. (2019), found that certain adjuvants increase the deposition uniformity of spraying applications. Thus, the aim of the research was to determine if TRV, when used in conjunction with several different types of adjuvants, could realise similar levels of biological efficacy against the different target pests at lower spraying volumes compared to standard high volumes as well as the effect that different production formulations would have on this.

Image 2: Citrus foliage sprayed at 6080 L TRV containing EntréeTM.

Image 4: Citrus foliage sprayed at 6080 L TRV containing Super Wetter.

Materials and Methods

A Nadorcott citrus cultivar on Carrizo Citrange rootstock with a history of Californian red scale infestation was selected in the Porterville area of the Western Cape Province of South Africa for the trial site. The TRV of the experimental site was estimated on two occasions. Firstly in September before any spraying occurred and then secondly, in the middle of the spraying season late November. The area of 1 ha (10 000m2) was divided

by the tree spacing (2 m between trees and 6 m between tree rows) and then multiplied by the average tree height and width in accordance with the concept developed by Sutton and Unrath (1988). The average values were calculated by measuring the width and height of 10 randomly selected trees throughout each of the experimental sites. The density factor currently standardised by the pome and stone fruit industry as indicated on several registered strobilurin fungicide labels (l water /ha = (Tree height x Tree width x 937) /Row width) of 93.7 litre/1000 m3 TRV was used throughout the study.

Figure 1: The effect of spirotetramat (Spirot) – A, and pyriproxyfen (Pyripr) – B containing insecticides in water, with and without Nu-Film 17 (NF17), at various tree row volume (TRV) applications on the percentage presence of red scale on Nadorcott citrus fruit (inside and outside the canopy) 176 days after last application.

Figure 2: The effect of spirotetramat (Spirot) – A, and pyriproxyfen (Pyripr) – B containing insecticides in water, with and without Entrée, at various tree row volume (TRV) applications on the percentage presence of red scale on Nadorcott citrus fruit (inside and outside the canopy) 176 days after last application.

Trial Layout

At the trial site, the grower’s spray equipment was calibrated using tractor speed and water pressure to achieve 1: 1728 L water/ ha, 2: 3835 L water/ ha and 3: 6080 L water/ ha calculated TRV based volumes. At the time of the investigation the commercial standard spray volume on the farm for the specific target pest was 6080 L water/ ha. 

Each of the spraying volumes were used to apply either a systemic insecticide: Movento® (from Bayer (Pty) Ltd.; active ingredient: 240 g/ L spirotetramat; Reg. No. L8559 of Act 36 of 1947) at 10 ml/ 100 L water and a contact insecticide: Nemesis® 100 EC (from Philagro South Africa (Pty) Ltd.; active ingredient: 100g/ L pyriproxyfen; Reg. No. L6378 of Act 36 of 1947) at 30 ml/ 100 L water registered to control Californian red scale. Label instructions regarding the recommended programme were followed. This entailed both product programmes to start either between 80% and 100% petal fall or at the first sign of crawler movement with follow up applications of the Movento and Nemesis 100 EC programmes respectively 4 and 6 weeks later. 

The first sign of crawler movement ended up being the determining event to initiate sprays. Two sprays were conducted. One on 7 November 2022 and another on 12 December 2022.

Figure 3. The effect of spirotetramat (Spirot) – A, and pyriproxyfen (Pyripr) – B containing insecticides in water, with and without mineral spraying oil (Oil), at various tree row volume (TRV) applications on the percentage presence of red scale on Nadorcott citrus fruit (inside and outside the canopy) 176 days after last application.

Furthermore, each of the TRV based spray volume systemic/contact insecticide combination programmes have been amended by adding one of the following Act 36 of 1947 registered adjuvants:

• • Nu-Film 17 (extender sticker-spreader from Miller® Chemical & Fertilizer, LLC; active ingredient: 905 g/L di-1-p-Menthene; Reg. No. L 2981) at 600 ml/ ha.
  • Entrée (non-ionic activator enhancer from Miller® Chemical & Fertilizer, LLC; active ingredient: 819 g/L vegetable oil; Reg. No. L 8055) at 1200 ml/ ha.
  • Super wetter at 100 ml/ 100 L water.
  • Mineral oil at 300 ml/ 100 L water.

The objective was to determine the effect of the different adjuvants on the efficacy of the insecticides at the different Calculated TRV’s. The untreated in this regard was left unsprayed while a treated control received a TRV 1, 2 and 3 TRV and 3 with a systemic or contact insecticide programme without the addition of an adjuvant (water only). Each treatment consisted of 3 randomly selected five tree plots of which the three centre trees served as data trees. An untreated buffer row was left between each treated row.

Figure 4. The effect of spirotetramat (Spirot) – A, and pyriproxyfen (Pyripr) – B containing insecticides in water, with and without a super wetter (SW), at various tree row volume (TRV) applications on the percentage presence of red scale on Nadorcott citrus fruit (inside and outside the canopy) 176 days after last application.

Assessment of Insect Pests

On 5 June 2023 (176 days after last application) 10 fruit per tree position (inside and outside of the canopy) on each of the 3 data trees per plot were inspected for the presence of red scale according to an infestation scale of 1 being infested and 0 not infested.

Results and Discussion

From Figures 1 to 4 it can be clearly observed that all the treatments numerically reduced the percentage of red scale infected fruit compared to the untreated control. With both Entrée and Nu-Film 17 (Fig 1b and 2b) there was an increased efficacy from the 1728L/ha volume to the 3835L/ha application when applied with the contact insecticide pyriproxyfen. There was however a slight reduction in efficacy at the highest spraying volume of 6080L/ha. This can be due to Entrée and Nu-Film 17 having a per hectare dosage. However, when in combination with the systemic insecticide, spirotetramat, the efficacy increased with an increase in spraying volume when applied with Nu-Film 17 (Fig 1a), while Entrée (Fig 2a) had a similar effect as with the pyriproxyfen. Mineral oil (Fig 3) in both cases had an increased effect on efficacy with an increase in spraying volume when applied with both insecticides. The super wetter (Fig 4) on the other hand had a reduced effect on red scale control with both registered insecticides as the spraying volume increased. This can be attributed to spray run-off. In both cases where Entrée and Nu-Film 17 were applied with either the systemic or the contact insecticide it gave numerical similar results as the market standard of mineral oil. The addition of Entrée, Nu-Film 17 and mineral oil to both insecticides in water (at all spray volumes) managed to improve control when compared to the insecticides in water only (Figures 1 to 3).

The results from these investigations indicate that Entrée and Nu-Film 17 have the ability to improve the control of California Red Scale on citrus at various application volumes when applied with two types of insecticides respectively. The results were as favourable when applying the insecticides with mineral oil. Control was however compromised when the super wetter was applied to the insecticide solutions as the application volume increased.

(Written by Charl Kotze and Herman Walters – FertAgChem Division of Hygrotech South Africa)

References

• Beattie, G.A.C, Broadbent, P., Baker, H. & Kaldor, C.J. 1989. Comparison of conventional medium to high-volume sprayers with a low-volume sprayer for the control of Black Spot, Guignardia citricarpa Kiely, on Valencia orange. Plant Protection Quarterly 4(4) 146-148.
• Fourie, P.H., van Zyl, J.G., Schutte, G.C. & Grout, T.G. 2013. Optimisation of spray application in South African citrus orchards: challenges and progress. Suprofruit 2013. 54–56.
• Grout, T.G. 1997. Spray volumes and coverage requirements for citrus in South Africa. Citrus Journal 31: 19e20.
• Grout, T.G. 2003. Use of plant protection products. Section 2.7. In: Grout, T.G. (Ed.), Citrus Production Guidelines, Integrated Pest Management, vol. III. Citrus Research International, Nelspruit, South Africa.
• Furness, G.O. & Pinczewski, W.V. 1985. A comparison of the spray distribution obtained from sprayers with converging and diverging air jets with low volume air assisted spraying on citrus and grapevines. Journal of Agricultural Engineering Research 32: 291-310.
• Scapin, M., Behlau, F., Scandelai, L.H.M., Fernandes, R.S., Silva Junior, G.S. & Ramos, H.H. 2015. Tree-row-volume-based sprays of copper bactericide for control of citrus canker. Crop Protection 77: 119-126.
• Scardelato, D. A. 2013. Adequação do volume de calda no controle de Diaphorina citri Kuwayama (Hemiptera: Liviidae) em pomar de laranja, no munic ́ıpio de Colˆombia. Fundo de Defesa da Citricultura – Fundecitrus, Araraquara, SP, Brasil.
• Sichieri, C. E. 2018. Volumes de calda acaricida para controle do  ́acaro da leprose dos citros (Brevipalpus yothersi) utilizando turbo pulverizador convencionale electrostático. Fundo de Defesa da Citricultura – Fundecitrus, Araraquara, SP, Brasil.
• Silva, G., Scapin, M., Silva, F.P., Silva, A.R.P., Behlau, F.& Ramos, H.H. 2016. Spray volume and fungicide rates for citrus black spot control based on tree canopy volume. Crop Protection. 85:38–45.
• Soares, M. A. 2015. Eficiˆencia de volumes de calda fungicida e da adição deadjuvantes no controle da podridão floral dos citros em pomares de laranjadoce. Fundo de Defesa da Citricultura, Araraquara, SP, Brasil.
• Sutton, T.B. & Unrath, C.R. 1988. Evaluation of the tree-row-volume model for full-season pesticide application on apples. Plant Disease 72: 629-632.
• van Zyl, J.G., Fourie, P.H., & G.C. Schutte. 2013. Spray deposition assessment and benchmarks for control of Alternaria brown spot on mandarin leaves with copper oxychloride. Crop Protection 46: 80-87.
• Van Zyl, J.G. 2019. Evaluation of adjuvants in fungicide spray application for the control of Alternaria brown spot in South African citrus orchards. PhD thesis. University of Stellenbosch.

A tomato cultivar fertigation program and foliar spray program combined Hygrotech and Miller products during the production of greenhouse tomatoes in the Ermelo district in the Mpumalanga Province of South Africa. The combined treatments were allocated to a greenhouse of 300 m2 and was compared with the standard treatment used in the other greenhouses. Below is a summary of the tomato variety and products used.

Millerplex is a proprietary liquid fertilizer containing macro nutrients and sea plant extracts from seaweed (Ascophyllum nodosum) for increasing plant biomass and/ or yield on crops (maize, sweetcorn, sorghum, millet, potato and sweet potato). The product is formulated by Miller® Chemical & Fertilizer, LLC in the USA. In South Africa the product is registered as a Fertilizer Group 3 (Reg. No. M351 of Act 36 of 1947) – biostimulant. Internationally crop usage also includes almond, table grape, cotton, sweet pepper and nectarine. 

Millerplex contains Miller’s Transcuticular Delivery System to secure absorption and translocation of all materials. Millerplex has proven to strengthen cell walls, plant stems and increase nutrient response, especially during periods of abiotic stress. For additional Millerplex attributes, visit Miller’s webpage at: www.millerchemical.com or your nearest Hygrotech branch.

MAIZE

Since the publication of the Hygrotech Forum article (in Volume 2 of 2021) on the successful use of Millerplex during corn seed production under center pivot irrigation, several growers and distribution agents have been keen to investigate the effect of Millerplex for themselves. Especially when used during the production of commercial maize under dryland conditions. One of these trials and its results were as follow:

MILLERPLEX TRIAL

Objectives

To determine the effect of the foliar application of Millerplex in comparison to a biostimulant used as a commercial standard during corn production.

Materials and Methods

• The trial was conducted near Danielsrus in the Free State Province of South Africa in a field containing sandy loam soil. A commercial maize corn variety, DKC 73-72, was used for the trial at a planting density of 36000 plants per hectare.
• A 2:2:1 fertilizer was applied at the plant (sowing) at 250 kg/ ha. In the corn field of 80 ha, 15 ha was treated with Millerplex and 65 ha with the standard commercial biostimulant of the farmer. Except for Millerplex and the standard bio stimulant in the tank mixtures, the rest of the tank mixture was similar, as indicated in the table below. Both tank mixtures were applied at V6 growth stage (21 December 2022) using a boom sprayer with an application volume of 200 L water/ ha.

RESULTS

Discussion

The results from the paired sampling evaluation indicate that corn plants treated with Millerplex had a seed weight of 10.00 T per hectare in comparison to corn plants treated with farmer’s standard which had a seed weight of 9.14 T per hectare. Thus, an increase of 0.86 T per hectare. Taking into consideration the August 2023 sales price for yellow maize of R3850/T the paired sampling evaluation calculated that Millerplex contributed R3311.00 more per hectare when compared to the farmer’s standard.

In the 500 m combined strip, seed weight from corn plants treated with Millerplex was 12.36 T per hectare in comparison to 11.99 T per hectare of seed from the corn plants treated with the farmer’s standard. Thus, an increase of 0.37 T per hectare. Compared to the farmer’s standard, Millerplex contributed to an increased remuneration of R1425.00 per hectare.

Research Results

Nitrospray Plus was applied as follows:

• Sugarcane – 3L/ha – 30cm plant height and 14 days later.
• Banana – 1L/200L water and 250ml/plant soil drench.
• Wheat – 2L/ha – at stool stage and 14 days later.
• Carrot – 2 ml/L water at true leaf stage and 14 days later.

What are cytokinins?

Cytokinins are one of the 5 major classes of plant hormones. In general, plant hormones control every aspect of plant growth and development. Plant hormones are produced in very small concentrations, but even a minute amount can have a profound effect. Reactions to plant hormones always depend on their relative concentrations compared to other hormones present. It is the hormonal balance that controls the growth and development of each plant.

Cytokinins and auxins were the first plant hormones detected. Cytokinins is the key plant hormone as it not only initiates different effects, but also controls the action of all other plant hormones like auxins and gibberellin. Cytokinins prevent aging of plant tissue. It prevents chlorophyll bleaching and maintaining of protein, RNA, DNA and nucleic acid synthesis, therefore the plant does not deteriorate.

The improved root system also makes the plant more resistant to stresses such as drought, waterlogging, soil nutrient deficiency and salinity, nematode infestations and soil borne diseases.

Nitrospray Plus applied to plants also produces plants with a stronger root system, showing enhanced resistance. Nitrospray Plus efficiency as a cost effective agricultural fertilizer has been proven in numerous programmes under differing climatic conditions and on a wide variety of crops. Nitrospray Plus has a broad application base, is easy to apply and is compatible with most crop protection chemicals and foliar feeds. Its consistency in result and cost efficiency has led to its position in the market.

Written by: Pieter Vorster – Fertagchem Technical Manager, Gauteng.

Introduction

Onions (Allium cepa) are herbaceous biennial plants and can be propagated anywhere in South Africa. However, the main production areas are located in the Northern and Western Cape, Free State, North West, Limpopo and Mpumalanga Provinces mostly under pivot irrigation.

An annual watering requirement of about 400 – 600 mm is needed during the growing season. Due to this type of irrigation, coverage and retention of the agricultural chemicals during spray application are of the utmost importance. The moist conditions not only make the plants susceptible to fungal and bacterial infections, but harder to cover the plant surface as well.

In relation to the latter the trial was conducted to confirm the ability of Nu-Film P to improve the deposition of agri-chemicals during sprays on onion leaves.For evaluation purposes a fluorescent pigment and a newly developed mobile phone application called Dropsight (www.dropsight.ag) was used.

Materials and Methods

Application

The site used during the trial is located in the Swartwater area of Limpopo. It consisted of a 10 ha onion field at three leaf developmental stage propagated under pivot irrigation. A boom sprayer with a 2000 L tank was calibrated to 500 L water/ha and used to apply the spray mixture. The spray mixture consisted of 1 L iprodione fungicide/ ha iprodione and 4 L foliar feed/ ha. To determine deposition, a fluorescent pigment (UView) was added to the spray mixture at a rate of 2%. The untreated control consisted of the spray mixture and fluorescent pigment without Nu-Film P and was applied first (Figure 1). Thereafter, 300 ml Nu-Film P/ ha was added to the spray mixture and fluorescent pigment and applied (Figure 2). The untreated and Nu-Film P treated plot consisted of approximately 2 ha each.

Evaluation

After the sprays dried off, 15 onion plants were randomly sampled from each plot and the middle leaf of each plant used for analysis. The analysis consisted of placing each leaf in a black photographic box (LeafLab) lined with UV lights. Using a cell phone, images were taken of the fluorescence on the onion leaves in the photographic box (Image 3A & B). Each of the 15 leaves per treatment were pictured separately and using the DropSight mobile application the %FPC was determined for each leaf. The %FPC relates to the amount of leaf surface covered with fluorescent pigment.

Results and discussions

The results received from the DropSight application indicated that when Nu-Film P was added to the spraying mix the average %FPC was 1.86% compared to 0.95% of the standard treatment without Nu-Film P. This either suggests a higher retention of active due to the waxy nature of onion leaves or a better deposition of active. Either way, the results do show that when Nu-Film P is added to a spraying mix there is almost a doubling of active available on each leaf, when you accept that the pigment observed relates to the amount of active deposited.

Currently available online

Written by: Charl Kotze

Introduction

Recent editions of Hygrotech Forum (Volume 1 2019 and Volume 2 2020) reported on the successful inclusion of Asco-Gro (Reg. no. K6714 of Act 36 of 1947) during the reproductive growth stage of soybean production. Asco-Gro consists of kelp extracts (with amino acids and carbohydrates) which is combined with macro nutrients (N, P and K) as well as chelated secondary nutrients (Mn, Ca, Mo, Ca and Fe). The product is manufactured in the USA by MillerTM Chemical & Fertilizer, LLC and has been reported to have the following benefits:

• Enhancing fruit set.
• Increasing fruit size.
• Enhancing plant physiological activities.
• Assisting plants against environmental stress factors.

In recent years South African citrus producers also reported the successful inclusion of Asco-Gro as part of their total fertigation practices during production. Due to these various successful commentaries Miller and Hygrotech decided to investigate the use of Asco-Gro during citrus production and especially during growth stages known to be physiologically challenging, namely flowering and fruit drop. This research is reported below.

Trial information

Treatments

• The trial consisted of 4 treatments (Table 1). The control treatment refers to commercial fertilization of the grower. The other 3 treatments are in addition to the commercial fertilization.
• Each treatment had 10 replicated plots. A replicated plot consisted of 3 adjacent trees. The middle tree was used as a data tree, with a buffer tree on each side.
• Applications were conducted with a trailer-mounted, high-volume, high-pressure (2500 – 3000 kPa) sprayer with a hand-held spray gun (Figure 2). The application volume was the equivalent of 5000 L water/ ha.

Assessments

• At commercial maturity (3 August 2021), all fruit from each data tree from each treatment was harvested and counted.
• A mechanical trailer mounted fruit sizer (Figure 4; supplied by Citrus Research International) was used to divide the fruit from each tree into the following size categories: less than 48, 48, 56, 72, 88 and 105. Size categories represent the average number of fruit to fill a 15 kg export carton. Thus, the lower the number of the size category, the bigger the fruit.
• Average yield per tree (for each treatment) was calculated by multiplying standardized weight factors (in kilogram) with each of the fruit within the various size categories per tree (Table 2). The calculated average yield per tree was multiplied with 349 (trees per hectare) to calculate the average yield per hectare for each treatment.

Conclusion

The results from this trial indicate that the Asco-Gro treatments applied contributed to an increase in the average number of fruit per tree by increasing the number of fruit within the various fruit size categories. The increased average number of fruit calculated to an increased average yield per hectare where the Asco-Gro treatments were applied.

Currently available online

Written by: Johann van der Vyver (MillerTM Technical Sales Director: Africa Region)

Laeveld Agrochem focuses on Tuta absoluta

Tuta absoluta has been a constant thorn in the side of many growers across South Africa, costing them millions of Rands worth of revenue. One of the crops affected is tomatoes. In the Brits-area, Anna van der Merwe, from Laeveld Agrochem, Brits was supported by a team of experts that undertook to design a spray programme to control the Tuta absoluta to the advantage of the grower. The past season they achieved success with this programme amongst many growers in Gauteng. Hygrotech is honoured to have permission and support from Anna to publish this programme in the Hygrotech Forum, as it can benefit everybody in the tomato industry. We are also very proud that we could contribute in a small way and have one of our flagship products playing an integral part in the programme. Nu Film P® is synonymous with Hygrotech the past 50 years and once again this product has delivered on what it was designed to do.

Leafminers that attack solanaceous crops

(note: limitless variations of damage symptoms may be encountered)

Tuta absoluta has caused serious damage and economic losses since 2016, particularly on tomatoes. The plague has since also been observed on other crops of the Solanaceae like brinjals, potatoes and tobacco. The insect is a moth and resorts under the order: Lepidoptera. After the moth has laid her eggs, it takes 3 to 5 days to hatch. The wandering phase of the newly hatched larva? takes 10 – 30 minutes before they start to gorge through the cuticula to tunnel into the leaf. Fruit and stems are also prone for the same damage. The larva stage is usually completed in 8 -14 days, whilst all the larva-instars enjoy the security of a leaf cuticula or fruit mesocarp. This impedes the control of Tuta absoluta.

It is further important to take note of the specific process of nutrition of the insect, as the time of exposure to any chemical product on the leaf surface is very short. As a consequence, it is therefore essential to deposit as much as possible of any registered Tuta-chemical product for as long as possible and on the biggest surface area of the plant possible.

The use of a wetting-, sticking- and spreading product like Nu Film P® is recommended for this purpose in conjunction with an insecticide. Nu Film P® also protects the insecticide against UV degradation and enhances rain fastness. Lengthened control is therefore obtained and the effectiveness of all the so-called ‘worm’ remedies is promoted.

Anti Resistane Management Programme for the control of Tuta Absoluta in tomatoes

(2nd Edition, February 2022)

Tomato leafminer

Currently available online

Written by: Henry van der Voort & Anna van der Merwe, BSc Agric (Hons) Horticulture.