Revitalizing Old Cashew Plantations: Techniques and Best Practices

Across India’s cashew-growing regions, a significant portion of plantations consists of old, unproductive trees of seedling origin. Research from the ICAR-Directorate of Cashew indicates that approximately one-third of plantations owned by cashew development corporations are old and senile, directly contributing to the country’s persistently low cashew productivity. Replacing these trees with fresh planting is time-consuming, expensive, and involves years of waiting before any harvest. Fortunately, a well-established horticultural technique called top working offers a faster, more practical path to revival – one that uses the old tree’s own root system to power a productive new canopy.

What makes a cashew plantation “senile”? 🔗

A cashew tree doesn’t suddenly stop producing. The decline is gradual. Trees of seedling origin – grown from seed rather than grafted planting material – are genetically variable and often inherit low-yielding traits. Over time, the canopy becomes dense and overcrowded, light penetration drops, and the flowering-to-fruiting ratio deteriorates. Add years of poor canopy management, minimal nutrition, and pest pressure, and the plantation slowly becomes economically unviable.

The core problem with seedling-origin trees is genetic unpredictability. Because cashew is a highly cross-pollinated crop, seedling progenies show tremendous variation in yield potential, nut size, and tree habit. Many trees in older plantations simply never had the genetics to be high performers. According to researchers at IARI New Delhi, better management practices alone can only marginally improve yields in such trees – a more decisive intervention is needed to transform the genetic potential of the existing plantation.

Top working: the core rejuvenation technique 🔗

Top working is a method of genetic transformation in situ – meaning the existing tree is retained, but its aerial portion is replaced with material from high-yielding varieties. The deep, established root system of the old tree continues to function, supplying water and nutrients to support rapid regrowth. This is the key advantage over replanting: the root infrastructure is already in place, so new growth is vigorous and fast.

Studies show that top working can effectively rejuvenate poor-yielding cashew trees in the age group of 5 to 20 years. Beyond this window, the success rate declines. Trees that are too old may have compromised root systems or weakened sprouting ability, reducing the technique’s effectiveness.

Which trees qualify for top working? 🔗

Not every old tree in a plantation is a suitable candidate. Selection should prioritize trees that are:

• Structurally sound with no major root or trunk damage
• Within the productive age window of 5-20 years
• Free from active stem and root borer infestation
• Located in areas with adequate soil moisture for post-operative recovery

Trees already severely weakened by pest damage or disease should be removed entirely rather than subjected to top working, as they are unlikely to regenerate adequately.

Step-by-step procedure for top working 🔗

Step 1: Beheading the tree 🔗

The unproductive tree is beheaded at a height of 0.75 to 1.0 m from ground level. This height is deliberate – cutting too close to the ground limits the number of usable sprouting points, while cutting too high can lead to structural instability in the new canopy. A clean saw cut is essential; a splitting or crushing cut damages the stump and can impair sprout emergence. The recommended season for beheading is May to June, timed to coincide with the onset of the southwest monsoon, which supports both wound recovery and vigorous sprouting.

Step 2: Wound treatment 🔗

Immediately after cutting, the exposed stump and cut surface must be treated to prevent infection and pest entry. A swabbing mixture of copper oxychloride and carbaryl 50 WP (50 g each per litre of water) is applied to the cut surface and around the base of the stump. This dual-action treatment targets both fungal pathogens and insects – particularly the cashew stem and root borer – that are attracted to freshly wounded wood. Skipping this step significantly increases the risk of post-beheading pest loss.

Step 3: Sprouting and shoot selection 🔗

Sprouts begin to emerge from the stump within 30 to 45 days of beheading. Sprouting tends to be more prolific in younger trees. Once sprouts appear, the shoots are allowed to grow until they reach approximately 20 to 25 days of age – at this young, actively growing stage, the tissue is ideal for softwood grafting. To ensure at least six or seven successful grafts per tree, it is recommended to perform 10 to 15 grafting operations per tree, accounting for the natural rate of graft failure.

Step 4: Grafting with high-yielding scions 🔗

Grafting is carried out using the softwood grafting technique, with scions procured from certified high-yielding cashew varieties. The best window for grafting is July to November. Scions should be taken from healthy, disease-free mother trees of known performance. The graft union is secured with a polythene strip, which is later removed once the union is confirmed successful. Excess sprouts arising from the stump below the graft union must be regularly removed, as they compete with the grafted shoots for resources and can dominate if left unchecked.

Step 5: Post-grafting canopy management 🔗

Once grafts are established, thinning of extra shoots from the stump is necessary to channel growth energy into the selected grafted branches. Research published in the Journal of Horticultural Sciences notes that top working, combined with good post-operative management, can offer a 3 to 4-fold increase in cashew production within a short period. Top-worked trees have been observed to develop a canopy of 3-4 m in diameter and 5-6 m in height within two years – comparable to naturally grown trees 8 to 10 years old.

Yield recovery timeline 🔗

One of the most compelling advantages of top working is the speed of yield recovery. Top-worked trees typically begin bearing from as early as the second year after the operation, with initial yields of 3 to 5 kg of nuts per tree in the first bearing season. This precocity – the ability to fruit early – is a major advantage over replanting, which requires 5 to 7 years before any economic return. The established root system accelerates everything: nutrient uptake, canopy development, and flowering.

Over the medium term, sustained yields of 5 to 10 kg per tree per year are achievable with good post-working management, compared to near-zero yields in the old senile trees. For farmers managing large areas of unproductive plantation, this turnaround can be financially significant.

The biggest risk: stem and root borer attack 🔗

Top working creates a vulnerable window. The freshly beheaded stump and the emerging tender shoots are highly attractive to the cashew stem and root borer (Plocaederus ferrugineus) – the most destructive pest in cashew cultivation. According to ICAR’s Directorate of Cashew Research, this pest remains concealed within the bark and hardwood interface, making early detection difficult. Infested trees show gum oozing, frass accumulation at the base, yellowing foliage, and eventual death if unchecked.

The stem borer problem is serious enough that researchers have identified it as the major disadvantage of top working, responsible for significant tree losses when management is inadequate. This is also the primary reason why large-scale adoption of top working has been challenging despite its clear productivity benefits.

Managing the stem and root borer in top-worked trees 🔗

Controlling stem borer after top working requires a proactive, integrated approach. Key management steps include:

• Immediate wound treatment with carbaryl and copper oxychloride paste at the time of beheading, as described above.
• Regular stump inspection for early signs of borer entry – gum oozing, frass, or entry holes at the collar region.
• Scraping and swabbing affected bark areas with a carbaryl 0.2% suspension where early-stage damage is found.
• Carbaryl 50 WP swabbing (2 g/litre) on exposed trunk surfaces up to one metre height as a preventive measure, as recommended by agronomists.
• Biological control options: Studies have shown that soil application of the entomopathogenic fungus Metarhizium anisopliae at 250 g/tree can significantly reduce borer infestation, offering a more sustainable management option.
• Phytosanitation: Removing and destroying severely infested stumps to reduce pest inoculum in the orchard.

Additional management practices after top working 🔗

Nutrition and irrigation 🔗

Top-worked trees are in active recovery and require targeted nutrition to support rapid canopy rebuild. Fertilizer applications should be timed to support flush emergence and early flowering. Organic matter inputs help sustain soil health in older plantation soils. Where irrigation infrastructure allows, supplemental watering during summer months significantly supports graft establishment and early canopy growth, particularly in regions with a long dry season.

Inter-cropping during the recovery period 🔗

Since top-worked trees take one to two years to re-establish a productive canopy, the inter-row spaces become available for short-duration crops. Crops such as groundnut, ginger, turmeric, chilli, cucurbits, pineapple, and papaya can be grown during this period, maintaining income flow for the farmer while the cashew canopy recovers. This inter-cropping window is an important economic buffer, especially for smallholders who depend on annual cash flow.

Pruning of regenerated canopy 🔗

Once the top-worked canopy is established, it must be managed just like any productive cashew tree. Removing dead wood and crisscross branches alone can increase cashew yield by 30 to 40 per cent. Periodic canopy pruning every two to three years helps maintain light penetration, reduces disease pressure, and keeps the tree at a manageable height for harvesting operations. Heavy pruning should be avoided as it promotes excessive vegetative growth at the expense of flowering.

Is top working worth it? 🔗

When properly executed and followed up with attentive management – especially for stem borer control – top working delivers a compelling return. It converts an economically dead tree into a productive asset within two years, using the existing root infrastructure to drive rapid recovery. The technique is relatively low-cost compared to replanting, doesn’t require fresh land preparation or new plant material, and delivers high-yielding genetics into trees that already occupy productive land.

The main barriers to wider adoption are the stem borer risk and the skill requirement for grafting. Farmers who have received proper training and who commit to post-operative pest monitoring consistently achieve better outcomes. Government extension services and agencies like ICAR’s Directorate of Cashew Research provide technical guidance and training programs specifically to support farmers in adopting rejuvenation techniques at the field level.

What do you think? If you manage or have observed an aging cashew plantation, what has been the most practical barrier to implementing top working – skill availability, pest pressure, or the income gap during tree recovery? And do you think biological control measures like Metarhizium anisopliae could realistically replace chemical treatments for stem borer management in smallholder settings?

References

1. https://www.redalyc.org/journal/5770/577074696002/html/
2. https://www.biotecharticles.com/Agriculture-Article/Top-Working-in-Cashew-3279.html
3. https://www.farmatma.in/cashew-nut-plantation/
4. https://jhs.iihr.res.in/index.php/jhs/article/view/905
5. https://cashew.icar.gov.in/pestsite/cashew-stem-root-borer/
6. https://mapmycrop.com/cashew-crop-guideindia/
7. https://www.researchgate.net/publication/237714964_Management_of_cashew_stem_and_root_borer_Plocaederus_ferrugineus_L_by_microbial_and_plant_products
8. https://cashew.icar.gov.in/