- Author: Sandipa Gautam
Monitoring California red scale populations by using pheromone traps and degree days
California red scale is an armored scale that attacks all citrus varieties. It attacks all aerial parts of the tree including leaves, fruits, twigs, and branches by sucking on plant tissue with its long filamentous stylet. Heavy infestations cause leaf yellowing and drop, dieback of twigs, and occasional death of the infested tree. Heavily infested fruits with patches of California red scale may be downgraded in the packinghouse. Growers use monitoring methods, i.e., pheromone trapping, examining fruit, and bin counts (at harvest) for making treatment decisions.
In the San Joaquin Valley, many citrus growers rely on the use of pheromone traps to monitor male-scale flights. Following the biofix (first male flight) degree day units (DD) are used to predict when the next crawler emergence or next-generation flights is occurring. Degree days are heat units accumulated above the lower developmental threshold of an insect and have been long used to monitor the seasonal activity of California red scale populations. Knowing when the most vulnerable life stage of the insect is present helps growers make timed insecticide applications.
Citrus IPM research group led by Dr. Sandipa Gautam at Lindcove Research and Extension Center updates degree day accumulation in the San Joaquin Valley counties. Information for different counties can be found here.
Pheromone traps are used to monitor either weekly changes in male flights or to track densities during flights, especially the fourth flight.
The squares represent 20% of the card – you count what is inside the squares on both sides and multiply by 5 to estimate the total number.
How to use pheromone traps for weekly monitoring male flights?
- Monitor 5 to 6 orchards that have a known population of California red scales every week,so thatyou can determine when flights are occurring and time sprays.
- Change the sticky cards weekly and the pheromone lure caps monthly through October.
- Use two to four pheromone traps per10-acre block;add two traps for each additional10 acres.
How to use trap card information to make management decisions?
- Hang pheromone traps with a fresh lure in early March to detect the biofix (first male flight). Historically, biofix for Kern County occurs around the 1st of March, and biofix for Tulare, Fresno, and Madera Counties occurs around March 15.
- Use the biofix and degree-days to predict when crawler emergence or next flight is occurring. Degree days are accumulated heat units over the lower developmental threshold of California red scale.
- Crawler emergence for first-generation will occur 550 degrees days after biofix.
- Subsequent flights will occur at intervals of 1,100-degree days after the biofix of the first male flight (1,100 DD for 2nd flight; 2,200 DD for 3rd flight; 3,300 DD for 4th flight and 4,400 DD for 5th flight). Subsequent crawler emergence for the 1st, 2nd, and 3rd generation occurs at 550 DD, 1650 DD, and 2750 DD after the biofix.
- Check the Lindcove Research and Extension Center Website for updated information on accumulated degree day
How to use pheromone traps to determine areas of heavy infestation?
- Use 2 to 4 pheromone traps per10-acre block;add 2 traps for each additional10 acres.
- Time placement of traps at the beginning of the biofix for the flight and remove them at the end of each flight and count scales and record the numbers.
In the past, when an average of more than 1,000 scales are trapped during the 4th flight and fruit is infested with scale at harvest, a pesticide application is planned for the next season. However, this threshold of 1,000 scales per flight developed in the 1980s is no longer a stand-alone tool for determining when treatments are necessary. It is critical to use other tactics, such as fruit and twig examination.
Note that pheromone cards are not reliable predictors of scale populations on their own. In all orchards in all growing regions,whether Aphytis wasps are released or not, conduct visual inspections of citrus fruit once a month during August, September, and October to confirm that fruit is free of scale.
Situation 1: Scale densities on traps may be high, but the fruit is free of scale:
- When Movento or Admire (and generics) are used because they remove scale from leaves and fruit but not the wood of the tree.
- Aphytis prefer to attack virgin female scales and the males may escape parasitization, resulting in a high number of male scales on traps.
Situation 2: Very few male scales on traps, but the scale is found on fruit
- When insect growth regulators (buprofezin and pyriproxyfen) are used, the frequently molting male scales are more affected than female scales.
- When mating disruption is used, males cannot find the trap cards so their densities on traps can be very low. A threshold of 50 scales per flight is helpful in determining if mating disruption is effective.
Consult UCIPM guidelines for management options.
And Read more from Citrus IPM News: https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=52294
- Author: Ben Faber
We were recently bird watching on one of the sky islands in southern Arizona. It was pretty impressive, the diversity of birds and BRIGHT colors compared to those in the Ventura area. Arizona locals, though, were saying numbers were way down. Why? Less and fewer berries and insects to feed on.
Fewer berries, because of drought has really hit the area. But fewer insects? Recent research indicates we have lost more than 40% of our insects in the past 20 years. This decline may have been first noted by some Germans who realized that they didn't need to clean their windshields any longer. This would be a sign of rejoicing, yes? But there are severe consequences, such as less food for birds.
Entomologists estimate that the services insects provide exceed some lots of billions of dollars a year. Other factors in their performance besides bird food, is pest control, pollination and manure management. Insects provide a lot more services than these, like improved soil fertility, nutrient cycling and decomposition. That billions of dollar estimate is probably way under estimated. Way under.
In Worldwide Decline of the Entomofauna: A Review of its Drivers, Sanchez-Bayo and Wyckhuys highlight some of the issues:
*Over 40% of insect species are threatened with extinction.
*Lepidoptera, Hymenoptera and dung beetles (Coleoptera) are the taxa most affected.
*Four aquatic taxa are imperiled and have already lost a large proportion of species
*Habitat loss by conversion to intensive agriculture is the main driver of the declines.
*Agro-chemical pollutants, invasive species and climate change are additional causes
And they have these conclusions:
The main drivers of species declines appear to be in order of importance: i) habitat loss and conversion to intensive agriculture and urbanisation; ii) pollution, mainly that by synthetic pesticides and fertilisers; iii) biological factors, including pathogens and introduced species; and iv) climate change. The latter factor is particularly important in tropical regions, but only affects a minority of species in colder climes and mountain settings of temperate zones. A rethinking of current agricultural practices, in particular a serious reduction in pesticide usage and its substitution with more sustainable, ecologically-based practices, is urgently needed to slow or reverse current trends, allow the recovery of declining insect populations and safeguard the vital ecosystem services they provide. In addition, effective remediation technologies should be applied to clean polluted waters in both agricultural and urban environments.
Now what are the solutions?
- Author: Ben Faber
Are you interested in learning more about Nitrogen Management?
Are you ready for the big time?
Are you a Certified Crop Adviser seeking Continuing Education Units and/or preparing for the new California Nitrogen Specialty Exam?
Has your grower clientele asked if you are eligible to sign off on a Nitrogen Management Plan?
Registration for the brand new UC Nitrogen Management course is now open at:
http://ucanr.edu/NitrogenCourse
The UC Nitrogen Course is taught online through a video series delivered by UC Researchers and Extension Specialists. Each module is eligible for Certified Crop Adviser (CCA) continuing education units (CEUs).
The course is open to anyone interested in learning more about N management in California. The curriculum addresses all the learning objectives set forth by the American Society of Agronomy (ASA) for the new California Nitrogen Management Specialty Exam.
The 7-part video series starts Monday May 9th.
Register at http://ucanr.edu/NitrogenCourse
You may join the course at any time up until July 31st.
For more information contact Sat Darshan Khalsa at sdskhalsa@ucdavis.edu or visit the FAQ page.
map of groundwater management areas of Ventura county
- Author: Ben Faber
There are all kinds of pollinators in an avocado orchard, not just honeybees. In fact, there is a whole range of native bees that also pollinate the trees. There are nearly 1,600 native bee species in California, and over 30 have been identified in avocado orchards in Ventura County alone .
Another pollinator group is comprised of the Diptera order – flies. This order includes hoverflies and houseflies. Flies can be better at cross-pollinating avocado than honeybees because they move randomly through an orchard between different cultivars, visiting male and female flowers. The effectiveness of flies as pollinators varies between species, but there can often be more than 20 types in an orchard. This means it is likely that some good pollinators will be present, and that pollination can occur whenever the female flowers are open.
In the aforementioned Ventura avocado study, hoverflies are the most common flower visitor.
Housefly
Hoverfly
- Author: Ben Faber
Terrestrial laser scanning data show that trees move their branches in a diurnal pattern, settling down for the night – as if falling asleep. So far, however, researchers have been uncertain as to why this happens.
A new study utilising time-series of terrestrial laser scanning measurements shows that changes in the water status of leaves and branches causes branches to move downward at night, up to 20 cm depending on the tree species. Leaves and branches replenish their water storage during the night, increasing their weight and causing them to droop down. Terrestrial laser scanning is a remote sensing technique that can produce a 3D representation of the surroundings with millimetre accuracy. With repeated measurements, it is possible to study small structural changes in the environment, such as the movement of branches.
“By monitoring the movement of tree branches, we can gain insight into how water moves inside the tree. Climate change reduces the availability of water and increases drought stress, so it is important to understand the movement of water in trees in order to understand changes in forest health,” Postdoctoral Researcher and the lead author of the article Samuli Junttila from the University of Eastern Finland says.
In the laboratory, the researchers found that tree branch position followed changes in tree water status also over a longer time period. These findings also have practical applications. For example, laser scanning could be used to monitor plant water status in a greenhouse to automate watering regimes and save valuable resources.
The study was conducted at the University of Eastern Finland in collaboration with the Finnish Geospatial Research Institute and the University of Helsinki. The study was conducted within the UNITE Flagship Programme funded by the Academy of Finland.
https://www.mdpi.com/1999-4907/13/5/728
