How We Grow

2022 Spring How We Grow

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ALMOND ORCHARD 2025 GOAL 3 More information about leaffooted bugs is available at embryo to abort and drop to the ground. Growers can monitor their orchards for leaffooted bug feeding by looking for the telltale sign of strings of clear gum oozing from the hull. Even after the shell hardens, the bugs can probe through it, leaving a brown spot on the kernel – damage nearly identical to that caused by the green stink bug. Wolter noted that drier conditions, and warmer winter and springs, have led to an increase of damage from the pest. "One leaffooted bug can lay more than 200 eggs in the first two months of spring," Wolter said. "With our changing climate, we're seeing more favorable conditions for the bug because we're not getting that winter die-off." Brown spot damage caused by the leaffooted bug – and true bugs such as stink bug – is also leading to increased rejection rates by handlers. "I've been watching this for several years and the trend is growing as a percentage of damage of the total rejects," said Mel Machado, vice president of member relations at Blue Diamond Growers. "We're seeing up to 30% of the total rejects caused due to brown spot. So, if you have 1 to 2% overall rejects, then about a third could be caused by leaffooted bugs and the brown spot they leave. There's been cases where if a grower didn't have brown spot, they wouldn't have a reject problem. I'm watching this trend grow and it scares me." According to Machado, the leaffooted bug prefers several other almond varieties over Nonpareils, so he recommends that growers monitor Price, Fritz, Aldrich and Sonora varieties first in the spring. As for the brown spot caused by true bugs – green stink bug and brown marmorated stink bug for example – that damage usually occurs in the summer months from June to July, seemingly without a preference for a particular almond variety exhibited by the leaffooted bug. Monitoring for leaffooted bugs has had two major hurdles to clear – the lack of a pheromone to attract the bug and a viable trap to catch it. However, thanks to recent ABC-funded research, scientists at UC Riverside and Berkeley have identified pheromone blends for the two common species of leaffooted bugs found in California almond orchards. The pheromone will be tested in field trials this fall, and if proven effective, will eventually be commercially available. With the prospect of an effective pheromone and trap on the horizon, Wolter noted that an action threshold for growers can be identified. However, more research is necessary to create a sound IPM program that offers growers various treatments to minimize damage from leaffooted bug. More information about management of leaffooted bug is available at the UC Statewide IPM website. 3 "There's been cases where if a grower didn't have brown spot, they wouldn't have a reject problem. I'm watching this trend grow and it scares me." — Mel Machado Brown Marmorated Stink Bug Almond Board of California 4

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