Organic farmer Steve Mann wears mosquito netting while surveying the grounds on his Old Ways Farm in Captain Cook, Hawaii. Hawaii's strong anti-pesticide sentiment and tropical conditions present challenges in the fight against dengue fever.

HONOLULU — On a farm in the heart of Hawaii’s ongoing dengue outbreak, coffee grows wild among the ferns, and vanilla vines climb guava trees. It’s hard to know where nature ends and the farm begins, and that’s the way organic farmers there like it.

But state efforts to combat the outbreak — and prevent the related Zika virus from making inroads on the island — could put these farmers out of business. Posting “no spray” signs on their properties, they’re pushing back on the use of pesticides to kill the mosquitoes that transmit both infections.

Global health officials have identified mosquito eradication as the key to curtailing the Zika outbreak that has taken hold in Latin America and been linked to birth defects in Brazil, as well as preventing it from taking hold in other areas where the Aedes aegypti mosquito is prevalent, including the southern U.S.

“Any place a dengue outbreak can occur, a Zika outbreak could occur,” Lyle Peterson, director of CDC’s division of vector-borne diseases, said in an interview with The Associated Press. “Given the fact that many affected travelers could be coming to Hawaii as outbreaks occur around the Pacific, there is always the possibility of infecting local mosquitoes.”

But mosquito control is highly variable around the U.S., and a chunk of the $1.8 billion in emergency funding the Obama administration is seeking for Zika would go to shoring up those capabilities, Dr. Anne Schuchat, CDC’s principle deputy director, told a Senate committee Wednesday.

Plus, this mosquito species is particularly hard to deal with, an aggressive daytime biter that can live not just in the yard but inside the house. A little water left in a flower pot is enough for its eggs to hatch; they even can survive drought until rain returns.

Hawaii has had four cases of Zika, all in travelers to countries with ongoing transmission, according to the Centers for Disease Control and Prevention. But local mosquitoes have infected 260 on the Big Island with dengue fever. And the CDC reported active local Zika transmissions in Pacific islands that have a fair amount of traffic to Hawaii, including Samoa, American Samoa, the Marshall Islands and Tonga.

In a report, Peterson said staff shortages in the state Health Department and conditions on the island make it difficult to fight mosquito-borne diseases. The report cited abundant mosquito breeding grounds, dense vegetation, unoccupied homes and widespread use of cisterns for water.

Organic farmers aren’t the only ones pushing back. Hundreds of residents flock to the Legislature annually decrying pesticide use.