Custard Apple Climate Resilience: Managing Heat Stress, Drought, and Erratic Monsoon

Climate vulnerability assessments published by ICAR-Central Research Institute for Dryland Agriculture Hyderabad and the National Innovations in Climate Resilient Agriculture project document that the primary custard apple growing districts of Nashik, Aurangabad, Solapur, Kurnool, and Chittoor experienced a 23 percent increase in erratic monsoon distribution events between 2010 and 2023 compared to the preceding decade, characterised by longer dry spells within the monsoon period, more intense but shorter rainfall events causing runoff rather than infiltration, and increased frequency of temperature anomalies above 42 degrees Celsius during the critical flowering and fruit set period from April to July. NICRA demonstration trials across Maharashtra and Andhra Pradesh testing climate-adaptive management practices including rainwater harvesting, modified pruning schedules, heat stress mitigation, and drought-tolerant rootstock use documented yield loss reduction of 35 to 45 percent in climate-adapted plots compared to conventionally managed control plots during stress years, validating the economic importance of proactive climate adaptation in custard apple orchards.

Heat Stress During Flowering: The Most Critical Climate Risk

Research from IIHR Bangalore and Anand Agricultural University identifies temperature stress during the flowering period as the single most economically damaging climate risk for custard apple in India. Custard apple flower viability research documents that temperatures above 40 degrees Celsius for more than 3 consecutive days during the female stage of flower receptivity cause stigma desiccation and loss of receptivity within 12 to 18 hours instead of the normal 24 to 36 hour receptive window, directly reducing fruit set rates even when hand pollination is performed. Pollen viability is similarly reduced by high temperatures, with germination rates falling from above 70 percent at 30 degrees Celsius to below 25 percent at 42 degrees Celsius in laboratory germination trials at IIHR. Field data from Maharashtra orchards during the anomalously hot pre-monsoon season of 2022 documented fruit set rates of only 2 to 4 percent in unprotected orchards during the April to June heat wave period compared to normal fruit set of 8 to 15 percent in the same orchards during the preceding cooler season. Research-validated heat stress mitigation practices include kaolin particle film application at 3 percent concentration as foliar spray on tree canopies during heat wave periods, which ICAR trials show reduces leaf and flower surface temperature by 2 to 4 degrees Celsius through reflectance, and scheduling hand pollination operations between 5 AM and 7 AM before peak daytime temperatures rather than during afternoon hours.

Rainwater Harvesting for Drought Resilience

CRIDA Hyderabad watershed management research for dryland custard apple growing regions documents that in-situ rainwater harvesting structures constructed within and around orchards capture 40 to 60 percent of runoff from intense monsoon rain events that would otherwise leave the field without infiltrating into the soil profile. Continuous contour trenches of 30 cm width, 45 cm depth, and 60 cm spacing dug along orchard slope contours at a cost of ₹8,000 to ₹12,000 per acre using MGNREGS labour have been shown in CRIDA trials to increase effective soil moisture storage by 35 to 50 mm of water equivalent per season in shallow to medium soils. Farm ponds constructed in the lowest corner of custard apple orchards at a cost of ₹80,000 to ₹1.5 lakh for 100 to 200 cubic metre capacity with 50 percent subsidy available under Pradhan Mantri Krishi Sinchai Yojana Har Khet Ko Pani component store monsoon runoff for supplemental irrigation during dry spells that CRIDA research shows occur on average 3 to 4 times per monsoon season in Marathwada and Rayalaseema regions. NICRA trial data shows custard apple orchards with farm pond based supplemental irrigation capacity suffered 38 percent less yield loss during the drought-within-monsoon conditions of 2018 and 2019 compared to entirely rainfed orchards in the same village.

Modified Pruning to Manage Climate-Induced Phenology Shifts

Climate change phenology research from ICAR-IIHR documents measurable shifts in custard apple flowering timing across Maharashtra and Andhra Pradesh, with average first flower appearance advancing by 8 to 12 days over the period 2000 to 2022 due to rising winter temperatures reducing the depth of dormancy. This earlier flowering increasingly exposes flowers to late cold spells in February and March in higher altitude orchards above 600 metres and to extended heat stress in April and May in low altitude orchards. Research from MPKV Rahuri documents that modified pruning timing, specifically delaying post-harvest pruning from the traditional January-February window to March, delays the onset of new flush and flowering by 15 to 20 days, effectively shifting the peak flowering period from April to May-June when monsoon onset provides temperature relief. In high altitude Nashik and Satara district orchards, this flowering delay has been shown to improve fruit set rates by 18 to 25 percent by avoiding late frost events in February and March that directly damage open flowers. Climate-adaptive pruning scheduling tailored to local altitude and historical temperature patterns is therefore an effective zero-cost adaptation strategy for custard apple farmers experiencing climate-induced phenology disruption.

Drought Tolerant Rootstocks for Water Stress Adaptation

Rootstock research published by ICAR-NRCAH Bikaner and Anand Agricultural University evaluates the drought tolerance of different Annona species rootstocks and their influence on grafted custard apple performance under water stress conditions. Annona reticulata, the standard rootstock used across India, shows moderate drought tolerance but susceptibility to prolonged dry spells exceeding 45 days. Annona glabra, a wild species native to coastal and riparian areas, has been identified in ICAR rootstock screening trials as significantly more drought tolerant than A. reticulata, maintaining turgor pressure and stomatal conductance at soil water potentials 30 to 40 percent lower than the point at which A. reticulata grafts show wilting symptoms. Trees grafted on A. glabra rootstock in ICAR-NRCAH trials at Bikaner and Hisar showed 22 percent higher fruit retention during simulated drought stress compared to A. reticulata grafted trees of the same Arka Sahan variety. Commercial availability of A. glabra rootstock plants is currently limited to a few research stations and progressive nurseries in Maharashtra and Gujarat, but ICAR has identified this rootstock as a priority for commercial multiplication and distribution in drought-prone custard apple growing areas under the NICRA climate adaptation program.

Managing Erratic Rainfall and Waterlogging Risk

While drought within the monsoon season is increasing, CRIDA climate analysis also documents that rainfall intensity when rain does occur has increased significantly across custard apple growing regions, with 24-hour rainfall events above 100 mm becoming more frequent in Marathwada, Telangana, and Rayalaseema. Custard apple's extreme sensitivity to waterlogging, where even 48 to 72 hours of root zone inundation can cause fatal Phytophthora root rot infection, means that intense but erratic monsoon rain events create both drought stress between events and waterlogging stress during events within the same season. Research from CRIDA and ICAR documents that raised bed planting where custard apple trees are established on mounds 30 to 45 cm above surrounding field level created using soil from between-row channels provides effective protection against even 48 to 72 hour waterlogging events by elevating the critical root collar and upper root zone above the water table that forms during intense rainfall. Installation of field drainage channels of 30 cm depth at 5 to 6 metre intervals across the orchard slope is an additional waterlogging risk management measure documented by CRIDA as reducing Phytophthora root rot incidence by 55 to 65 percent in high-intensity rainfall years compared to undrained flat-planted orchards.