Posts Tagged: pheromone
Nissa Coit Seminar on Honey Bee Research
Nissa Coit, a master's graduate student in the laboratory of Extension...
An inside look at a honey bee colony. (Photo by Kathy Keatley Garvey)
The scent that could save California’s avocados
Scientists search for pheromone to disrupt insect mating
UC Riverside scientists are on the hunt for a chemical that disrupts “evil” weevils' mating and could prevent them from destroying California's supply of avocados.
Avocado weevils, small beetles with long snouts, drill through fruit to lay eggs. The weevil grubs or larvae bore into avocado seeds to feed, rendering everyone's favorite toast topping inedible.
“They're extremely hard to control because they spend most of their time deep inside the fruit, where they're very well protected from insecticides and natural enemies,” said UCR researcher Mark Hoddle, a UC Cooperative Extension entomology specialist.
Not only are the insects reclusive, they are also understudied, making information about them hard to come by. “All books on avocado pest management will tell you these weevils are bad. They're well recognized, serious pests of avocados, but we know practically nothing about them,” Hoddle said.
One strategy for controlling pests is to introduce other insects that feed on them. However, that is unlikely to work in this case. “Natural enemies of these weevils seem to be extremely rare in areas where this pest is native,” Hoddle said.
To combat avocado weevils in Mexico, an area where they are native, and to prevent them from being accidentally introduced into California, Hoddle is working with Jocelyn Millar, a UCR insect pheromone expert. They are leading an effort to find the weevil's pheromone, with the goal of using it to monitor these pests and prevent them from mating in avocado orchards.
Pheromones are chemicals produced and released into the environment by an insect that can be “smelled” by others of its species, and affect their behavior.
“We could flood avocado orchards with so much pheromone that males and females can't find each other, and therefore can't reproduce,” Hoddle said. “This would reduce damage to fruit and enable growers to use less insecticides.”
Alternative control strategies could include mass trapping, using the pheromone as a lure, or an “attract-and-kill” approach, where the pheromone attracts the weevils to small sources of insecticide.
The work to identify, synthesize and test this pheromone in the field is supported by grants from the California Department of Food and Agriculture, as well as the California Avocado Commission.
An initial phase of the project sent Hoddle to a base of operations three hours south of Mexico City, an area with large weevil populations. Using a special permit issued by the USDA, Hoddle brought weevils back to UCR's Insectary and Quarantine facility.
Hoddle and Sean Halloran, a UCR entomology researcher, captured the chemicals that avocado weevils release into the air. Possible pheromone compound formulas were identified from these crude extracts and are now being synthesized in Millar's laboratory.
“Weevil pheromones have complicated structures. When they're made in a lab, they can have left- or right-handed forms,” said Hoddle. Initially, Millar's group made a mixture of both forms to see if the blend would work as an attractant, as it is far cheaper to make the blend than the individual left- or right-handed forms.
Field work in Mexico with the pheromone cocktail by Hoddle, his wife Christina Hoddle, an associate specialist in entomology, and Mexican collaborators did not get a big response from the weevils, suggesting that one of the forms in the blend could be antagonizing the response to the other.
As the next step, the researchers plan to synthesize the individual forms of the chemicals and test the insects' response to each in Mexican avocado orchards.
Because the levels of avocado imports from Mexico are increasing, the risk of an accidental weevil invasion is rising as well. Hoddle is hopeful that the pheromone will be successfully identified and used to lower the risk this pest presents to California's avocado growers.
“We've been fortunate enough to be awarded these grants, so our work can be implemented in Mexico and benefit California at the same time,” Hoddle said. “The tools we develop now can be used to make sure crops from any exporting country are much safer to import into California.”
/h3>Our research on Argentine ant IPM
Our research on Argentine ant IPM was published in August 2021 issue of Journal of Economic...
Status of diamondback moth population dynamics
Diamondback moth adults have been actively flying across the Salinas Valley these winter months, based on our area-wide monitoring program. There were a couple of locations where we recorded 'zero' captures during January. It looks like low temperatures in the Valley just slowed down this moth development. At this point, it will be difficult to propose that there was an overwintering generation this past winter. Specially in the Castroville area, where there has never been a 'zero' capture from our two traps. Having an overwintering generation would have represented 'zero' captures from all or most of our pheromone traps across the Valley.
We continue the effort to validate automated pheromone traps. In partnership with AgCeleration and TrapView, we are testing in the field a new prototype (Fig. 1). So far, there is no significant difference on the weekly captures between this new automated trap when compared to a typical cardboard pheromone trap. These automated traps provide real-time information on the number of diamondback moth males captured in a daily based. This type of information could ultimately help to understand the trends of the adults moving across the farmscape, strengthening an IPM program in cole crops.
Daily captures of diamondback moth male adults indicate that the highest populations are currently located in the Castroville area. On average, we have captured 12 males per day since February 11th (Fig. 2.). Most of the fluctuation on number of captured adults might have been mediated by air temperatures. The current trend shows that adult captures are going down. It is likely that large populations of this pest were able to go through a generation in the Castroville area using crop, weed host plants, and crop residues. It is important to recognize that:
1) Castroville area continues to be a hot spot with the largest diamondback moth population across the Salinas Valley.
2) Promptly scouting of blocks with cole crops will help to early detect the presence of economically relevant numbers of caterpillars.
3) Manage weeds, specially at the surrounding areas of established blocks, will reduce the overall population.
4) Promptly elimination of cole crop residues from previous plantings will reduce the overall population.
5) Rotate the use of insecticides will reduce the possibility to develop insecticide resistance.
6) Use of adjuvants/stickers will reduce the possibility of washing away any insecticide spray onto waxy cole crop leaves.
If you would like to learn more about the current status of diamondback moth in the Salinas Valley, please contact Alejandro Del-Pozo at adelpozo@ucanr.edu or call 831-759-7359.
Update on diamondback moth area-wide monitoring program
Last year, this pest was present in large numbers during August and September. The idea is to have additional data from the pheromone traps to inform the IPM decision making process. Below is a table showing the number of moths per day and per trap since February.
Table 1. Male diamondback moth captures by pheromone traps across the Salinas Valley. There are two type of traps deployed in the fields. We have the cardboard traps labeled as 'Regular' and also the automated traps labeled as 'Automated' and shown in Fig. 1.
Fig. 1. Automated trap (provided by AgCeleration and manufactured by TrapView) in a broccoli field. This type of trap has four cameras on top of the sticky liner. Cameras will take daily pictures. Pictures are analyzed to recognize the adult of diamondback moth. This trap uses a cellular connection to transmit the pictures daily to a centralized computer. The computer will use machine learning to recognize and count new moths getting stuck onto the liner.
To put these captures on a time perspective, the below time series graph shows the fluctuation of the diamondback moth captures since we set up the traps. The below graph does not include the data from the automated traps. Capture data is broken into a series labeled 'Castroville' (dotted line) indicating the moth captures from that specific location, and a second series labeled 'Other' (solid line) where the average captures among the other locations are presented.
If you are interested in learning more about this monitoring program, please contact Alejandro Del-Pozo at adelpozo@ucanr.edu or 831-759-7359.