Expert Talk: Microbial Preparations for Onion Storage in Maharashtra

Expert perspective: Alexander Samsonov, Agricultural Storage Engineer. View LinkedIn profile.

Editorial note: This article describes a pilot-testing concept, not a universal treatment prescription. Any microbial product, concentration or application method must be locally registered, tested against local isolates and validated with a qualified plant pathologist.

Black mold can cause material storage losses in warm, humid regions such as Maharashtra. Microbial protection is being studied as one possible part of an integrated storage programme, alongside curing, handling discipline and uniform ventilation. Here’s how biocontrol works in real storage systems.

Microbial Protection for Onions in Maharashtra: Why It Matters and How It Works

Warm, humid weather at harvest makes Maharashtra one of the world’s most challenging environments for onion storage. These conditions are ideal for Aspergillus niger, the black mold responsible for rapid rot, weight loss, and high post-harvest losses.

With chemical fungicides becoming less desirable or restricted, growers are turning toward microbial biocontrol - biological-control approaches that must be validated for the local pathogen population, onion variety and permitted products.

Why Onions in Maharashtra Need Microbial Protection

The combination of:

high temperature,
high humidity,
dense harvest season,
traditional open curing,
and warm-storage systems (27–31 °C)

creates perfect conditions for A. niger to colonize bulbs.

Black mold can develop on the outer scales and enter through damaged or poorly cured tissue. Moisture, condensation, handling damage and uneven drying all increase the risk.

Biological-control candidates may compete with the pathogen or influence the bulb surface, but their effect must be demonstrated under local conditions.

Which Microorganisms Can Be Screened?

Depending on local registration and laboratory advice, a research programme may screen candidates from groups such as Bacillus species, Trichoderma species, Aureobasidium pullulans, antagonistic yeasts and Clonostachys rosea. Inclusion on this list does not establish efficacy for a particular onion variety, pathogen isolate or commercial product.

How Application Methods Should Be Developed

There is no universal concentration or application recipe for every commercial product. A qualified plant pathologist should select locally permitted candidates, test them against local A. niger isolates, confirm compatibility with the onion variety and determine whether spray, dip or another application route is appropriate. Treated onions must still enter storage properly cured and dry.

What Does a Pilot Project Look Like?

A typical field trial includes:

Selecting 2–3 candidates (e.g., Bacillus, Trichoderma, a yeast).
Running lab tests against local A. niger isolates.
Small-scale trials with 1,000–2,000 bulbs.
Comparing treated vs. untreated onions for 30–60 days.
Measuring:
- visible mold,
- weight loss,
- rot progression,
- sprouting behavior.

This approach identifies the best strain for local climate and bulb type.

How Results Should Be Evaluated

Compare treated and untreated lots under the same curing, airflow and climate conditions. Track visible mold, total weight loss, rot, sprouting and marketable yield over a defined period. A pilot is successful only when the measured improvement is repeatable and economically relevant.

Microbial protection cannot compensate for wet, immature or badly damaged onions, or for a storage room with uncontrolled condensation and poor airflow.