Alpha Naphthyl Acetic Acid 4.5% SL Plant Growth Regulator Uses

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    Alpha Naphthyl Acetic Acid (NAA) 4.5% SL is a CIB-registered plant growth regulator (PGR) used as a low-concentration spray to improve fruit set, control fruit/flower drop, regulate fruit size and manage flowering in a range of fruit and cash crops. Unlike most PGRs it is applied as a very dilute ppm (parts per million) solution mixed fresh before spraying, not as a simple per-acre rate. This page lists its mode of action, key benefits and the complete crop-wise recommended usage as per the CIB-approved label.

    Which Growth Problem Is This For?

    NAA 4.5% SL sprays are reached for at specific fruiting or flowering bottlenecks rather than used as a routine input. The table below maps common growth problems in the crops covered on this page to when an NAA spray is generally used to address them.

    Crop Growth Problem What You'll See / When to Use
    Tomato Poor fruit set, flower drop Flowers opening but not setting into fruit, or dropping off before fruit forms; sprayed at flowering
    Chillies Poor fruit set Low fruit numbers despite good flowering; sprayed at flowering, with a follow-up spray 20–30 days later
    Mango Small fruit size / mango malformation (deformed panicles) Fruit staying small through development, or panicles/vegetative growth showing a bunched, deformed “malformation” look instead of normal flowering; sprayed at pea-size and marble-size fruit stage for size, or before flower bud differentiation for malformation
    Grapes Small berries / berry drop before harvest Berries not sizing up well, or matured bunches shedding berries in the run-up to harvest; sprayed at pruning/flowering for berry size, or 10–15 days before harvest for drop control
    Pineapple Delayed/uneven flowering, small fruit Plants flowering unevenly across the plot or fruit staying small; treated at planting/vegetative stage to induce uniform flowering, or later to size up the fruit
    Cotton Shedding of flower squares and bolls Flower squares and young bolls dropping off before maturing, cutting into yield; sprayed at 15-day intervals starting from square formation

    Mode of Action

    Alpha Naphthyl Acetic Acid is a synthetic auxin – a plant growth hormone analogue that mimics the natural auxin indole-3-acetic acid (IAA). At the very low ppm concentrations used in field sprays, it strengthens the hormonal signal that holds flowers and young fruit attached to the plant, reducing the formation of the abscission (separation) layer that causes flower and fruit drop. At the same time it influences cell division and cell enlargement in developing fruit tissue, which is why higher-ppm sprays at later fruit stages help increase fruit/berry size. Because the effective dose window is narrow, NAA is always applied as a precisely diluted ppm solution rather than a flat per-acre rate.

    Features & Benefits

    • Reduces flower and fruit drop by strengthening fruit attachment at the pedicel, improving effective fruit set
    • Increases fruit/berry size when applied at the recommended fruit-development stage
    • Helps induce more uniform flowering in pineapple and supports better crop scheduling
    • Can delay fruit maturity by a short window when applied close to harvest, useful for staggering picking/marketing
    • Used at extremely low ppm doses, keeping per-acre input cost minimal despite the precise mixing required

    Recommended Usage of Alpha Naphthyl Acetic Acid 4.5% SL Plant Growth Regulator

    NAA doses are given as a spray concentration in ppm (parts per million), each with its own dilution instructions, rather than a simple per-acre gram/litre rate – follow the exact dilution method given for each crop and purpose below.

    Crop Purpose Concentration Dilution / How to Prepare Timing
    Tomato Improve fruit set 45 ppm As per label 2 sprays at flowering
    Chillies Improve fruit set 10 ppm As per label 1st spray during flowering; 2nd spray 20–30 days after the first
    Mango Increase fruit size (1st spray – pea-size fruit) 20 ppm 2 ml in 4.5 litres of water At pea-size fruit stage
    Mango Increase fruit size (2nd spray – marble-size fruit) 200 ppm 20 ml in 4.5 litres of water At marble-size fruit stage (≈2 cm diameter)
    Mango Control mango malformation As per general practice† Consult current product label for exact rate Approx. 3 months before flowering, before fruit bud differentiation
    Grapes Increase berry size & weight 10 ppm 2 ml in 49 litres of water At pruning time and again when the flowering shoot appears
    Grapes Control berry drop 100 ppm 20 ml in 49 litres of water On matured bunches, 10–15 days before harvest
    Pineapple Induce flowering & uniform growth 10 ppm (use 5 ppm/half-strength in dry weather) 1 ml in 4.5 litres of water; pour 30–50 ml of solution into the head of each plant At the recommended vegetative stage
    Pineapple Increase fruit size 199 ppm 10 ml in 4.5 litres of water, spray to wet the whole plant At the recommended fruiting stage
    Pineapple Delay maturity 100 ppm 10 ml in 4.5 litres of water, spray to wet the whole fruit Two weeks before harvest
    Cotton Prevent shedding of flower squares & bolls 10–20 ppm 222–444 ml formulation in 1000 litres of water 3 sprays at 15-day intervals starting from square formation stage

    All doses above are given exactly as per the CIB-approved label, as a spray concentration in ppm with its own dilution instructions – this formulation is not sold on a flat per-acre basis like most other PGRs, so always prepare the solution using the dilution method given for your crop and purpose rather than converting it to a per-acre figure. †The CIB table does not list a separate ppm figure for mango malformation control; apply as per general orchard practice before flower bud differentiation and confirm the exact rate on the current product label. Always confirm against the product label before spraying, and follow your local agricultural extension advice.

    How to Use

    1. Identify your crop, purpose and the exact ppm concentration and dilution instructions from the table above.
    2. Prepare the spray solution freshly at the time of use, measuring the formulation quantity precisely into the specified volume of water – do not estimate, as NAA is effective within a narrow concentration window.
    3. Spray as a fine, uniform mist covering the flowers, young fruit or foliage as specified for your crop and purpose, using a knapsack or power sprayer.
    4. For pineapple flower induction, pour the prepared solution directly into the crown/head of each plant as described, rather than an overhead spray.
    5. Apply during the cooler hours of early morning or late evening, and avoid spraying in strong wind or if rain is expected within a few hours, as this can wash off the spray and reduce effectiveness.
    6. Where the crop calls for more than one spray, repeat at the interval/stage given in the table – do not bunch sprays closer together than recommended.

    Precautions & Safety

    • Wear appropriate personal protective equipment (gloves, mask, full-sleeve clothing) while mixing and spraying.
    • Measure quantities precisely – because NAA is used at very low ppm concentrations, even small errors in mixing can under- or over-dose the crop.
    • Check compatibility before tank-mixing with other pesticides, fertilisers or micronutrients; do a small jar test first if unsure.
    • Store in a cool, dry place away from direct sunlight, heat and out of reach of children and animals; keep the container tightly closed.
    • Do not exceed the recommended concentration or spray frequency – over-application can cause abnormal fruit drop, poor fruit quality or other adverse effects rather than an improvement.
    • Wash hands, face and exposed skin thoroughly with soap after handling, and avoid contaminating ponds, wells or other water sources with spray residue or rinse water.

    Brand names mentioned on this page are registered trademarks of their respective owners and are referenced here for identification purposes only; FarmMate is not affiliated with or endorsed by these brands. This page is for general information only – always consult your local agricultural extension office and confirm the current product label before use.

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