FAIRFIELD -- Before walnuts get to the snacking stage, they grow in the fields of family farmers like Lisa Howard.
She's one of many now battling a tiny enemy that could have a giant impact on their plans for harvest.
"It is very scary. It's just concerning that a small pest like this could do such big damage to our livelihood," she said.
The scare in the fields in Fairfield these days is the Mediterranean fruit fly.
It can lay eggs in and then have its larvae burrow through 250 different host plants.
The trouble spot for walnuts is not the nut itself, but the green husks that initially grow around it.
Five adult flies have been found since the end of August, prompting an 84 mile quarantine around the Tolenas neighborhood.
"We are on the boundary for one of our largest crops which is walnuts, so we'll be keeping a close eye on that," said Howard.
For her olives inside the quarantine zone that are a week away from harvest, she's able to process in the zone.
As a result, the mandatory spraying regimen the Solano County Agricultural Commission and California Department of Food and Agriculture were teaching farmers about tonight won't hold her up.
For others, the scenario could be very different.
"Unfortunately in some instances there may not be an option...depending on where you are, how close you are to harvest...because it's a minimum of four treatments within 30 days to be able to harvest," explained Vince Arellano with the California Department of Food and Agriculture or CDFA.
The CDFA met individually with farmers up against deadlines for trying to get out of their fields all that they put in, so treating for these pests doesn't put product headed to market in jeopardy.
Derrick Lum's glad he went with his gut and did some proactive treatment when he heard about the discovery of the very first fly.
"This Friday coming I will have my fourth spray of Spinosad applied to my persimmons and the walnuts and also too I do olive oil," he said.
That means he's in compliance with quarantine rules just now put into place that could have delayed his harvest if he was just starting.
It's not yet known how this threat came to the fields in and around Fairfield, but its suspected someone in the area might have just received a package with a few pieces of infected fruit mailed in from the backyard of a loved one.
"It was probably an innocent mistake, but it really needs to be known that you cannot take a risk like this," said Howard.
In the next week, the CDFA plans to roll out another containment measure along with the pesticide treatments.
Thousands of sterilized, male medflies will be air-dropped over the quarantine area per week so any mating that happens won't produce new flies.
So far field teams have only found the five adult flies and no larvae, which experts say is a good sign.
The quarantine is expected to last until July of next year.