Farmers use traders because of the loans and transport they offer, said Yudi Firmansyah, a chilli trader in Sukabumi who supplies vegetables to three regional markets on a rented truck.
About 15 percent of chillies reach their destination spoilt or too dry for Indonesian tastes, said Dadi Sudiana, chairman of the Association of Indonesian Chilli Agribusiness. Spoilage rises to almost 40 percent of fresh fruit and vegetables, according to industry estimates.
President Widodo took office in October with promises to solve such problems with a massive infrastructure push, but so far his administration has failed to spend the $22 billion budgeted for such projects this year due to a lack of coordination among ministries.
Widodo, whose approval rating has slumped from 72 percent to just 41 percent in July, had promised to build more dams, modernise irrigation systems, increase planting areas for foods and provide easier access to credit for smallholder farmers.
Read MoreWidodo seeks to tame bureaucrats blocking infrastructure drive
To water Rahmat's plants, he relies on rain or fills buckets and small plastic bottles at a nearby stream. It can take up to a week of one worker's labour to water a hectare of crops.
He said he had yet to see any government help under Widodo.
"The government must boost irrigation infrastructure," said the association's Sudiana. "When the rainy season comes we plant chillies, but when the dry season comes we have no other option than to reduce our plants."
Agriculture Minister Amran Sulaiman said 2 trillion rupiah ($145 million) had been allocated this year for dam building in dry areas and the work was ongoing.
Indonesia was once self-sufficient in rice and sugar, but like many other food crops, output has fallen due to competition for farmland from either cash crops like palm oil or from industry and housing.
Since coming to power, Widodo has pursued ambitious self-sufficiency goals to protect domestic farmers. This has included curbing or delaying imports of raw sugar, beef and cattle, corn and rice, which has resulted in shortages and price rises.
The government blames dry weather, food hoarding and speculators for the price swings, and has increasingly turned to state food buyer Bulog to limit price increases, buying from farmers and selling below market price.
"Bulog was involved to stabilise chilli prices temporarily during Ramadan and Lebaran," the agency's chief Djarot Kusumayakti said. "We're like a fire extinguisher."
Read MoreRupiah plunge: It's not just commodities
Instead of ad hoc imports to help control food prices, Widodo has signed a decree letting government cap prices of staples.
Regional auctions and markets that aim to reduce traders' involvement are also being planned by the government, but that won't address supply constraints.
"Red chilli production is sufficient to cover household demand, which is 400,000 tonnes," Suryamin, head of Indonesia's statistics bureau, told reporters last month. "But there is demand from industries, such as for chilli sauces. So in total, we are still in deficit."
At Jakarta's big Kramat Jati market, chilli sellers said prices can change by the hour, and the produce easily spoils without cold storage.
"The chillies became very expensive after Hari Raya. Everything changed," said David Emma, a restaurant owner buying chillies at a market. "My customers won't eat at my restaurant if I don't make the food spicy. No matter what the sellers tell me about price, I must buy because I don't have an option."