Posts Tagged: m

Avocado Pollination Workshop

bees pinned 2

Rats!!!!

Rodents, particularly rats, have wreaked havoc in California orchards and vineyards this year. Some growers have reported yield losses, damage to trees and destruction of irrigation lines, electrical wiring and other infrastructure.

Farmers face soaring costs to replace what has been destroyed or damaged, but also to control populations of the pests.

The rodent problem was initially reported in San Joaquin Valley nut orchards. But Roger Baldwin, a wildlife specialist and expert in rodent management at the University of California, Davis, said the problem is more widespread. He has heard about rodent damage on the west side of the Sacramento Valley and along the Central Coast, particularly in citrus orchards.

One reason for increased rodent activities this year could be abandoned orchards, which provide plenty of food and shelter for rodents to proliferate, Baldwin said.

“Rodent damage, if ignored, can lead to substantial losses,” Baldwin said.

Rats and other rodents can damage trees by removing the bark, which can cause disease and, if severe enough, kill the tree. The animals also chew through drip hoses.

Baldwin has studied different rodenticides for controlling roof rats in almond orchards. He found that using 0.005% diphacinone-treated oats inside elevated bait stations resulted in more than 90% reduction in rat activity.

Baldwin recommended constructing a bait station from PVC pipe and placing it roughly 4 feet above ground by attaching the stations to branches. He placed stations either 98 feet or 165 feet from each other throughout the orchard. Using 165-feet spacing reduces the cost, but efficacy drops to about 75%, he said. “The closer the stations are, the more likely it is that it's going to work,” he said.

After knocking down much of the rat population using bait, Baldwin placed trapping tunnels, or snap traps, 250 feet apart throughout the orchard. During a five-month period, the tunnels further reduced rat activity by 90% to 95%, he said.

After trapping, growers should still do periodic monitoring, Baldwin said, as some rats will evade the traps over time, and populations may start to rebound.

Using a diphacinone application remains a good strategy for initial knockdown of rodents, Baldwin said. He added there are other tools for keeping populations down for a longer period. One is burrow fumigation, with aluminum phosphide being the most effective, he said.

Other control measures include pressurized exhaust machines that inject carbon monoxide into burrows. But there's not much data on their effectiveness on rats, Baldwin said. He thinks they probably don't work as well as aluminum phosphide but could provide some relief.

Source: California Farm Bureau

Photo: rat damage to lemon tree

rat damage citrus bark

Flower Visitation Technique

An Australian Curtin University study has revealed a new method of capturing DNA could provide farmers with a valuable tool for boosting crop production — while also benefiting the environment.

Researchers from the School of Molecular and Life Sciences used an emerging scientific method known as ‘eDNA metabarcoding', to track which insects interacted with avocado flowers at two orchards in Western Australia.

Led by Dr Joshua Kestel and Associate Professor Paul Nevill, the team took bunches of flowers from avocado trees, which were then frozen and ground up before being taken through the DNA extraction process.

“We use eDNA metabarcoding to effectively amplify the DNA from whatever interacts with that flower and that lets us work out who was there,” Dr Kestel said.

“We are literally able to detect the footprints of a bee.”

eDNA metabarcoding was found to detect five times the number of unique pest species than filming plants with digital cameras, which is another cutting-edge method currently used.

“Digital video recording is advanced, but eDNA metabarcoding is Star Trek level – we are talking about a different universe,” he said.

Dr Kestel said eDNA metabarcoding could help improve yields and make agricultural operations more efficient.

Many farmers hire honeybee hives at significant expense to encourage pollination and grow more fruit, however Dr Kestel said native pollinators aren't currently part of the bigger picture and their role remains unknown for many types of trees and crops.

“Honeybees aren't big fans of avocado pollen and nectar: an avocado tree has about a million flowers, but less than 200 will be pollenated and mature into fruit,” Dr Kestel said.

“Using eDNA metabarcoding allows us to detect pollinators, pests, and — quite conveniently — predator species which can help protect crops by eating these pests.”

Dr Kestel said there was immense benefit to knowing which pests were occurring in a crop or orchard and where on the trees they were.

He said it would give farmers the option to introduce natural predators or, if they were to use pesticides, to use them more efficiently and in a more targeted way.

“At the moment we manage these pests with very generalised methods, which comes at a huge cost as the pesticides kill the wild pollinators and the natural predators, not just the pests you want to be rid of.

Dr Kestel said while the application of eDNA metabarcoding was still in its infancy, it could have a large impact.

“While it's not yet widely adopted, there's growing interest in this technology because there's a recognition of how powerful it is.”

‘Spatio-temporal variation in arthropod-plant interactions: A direct comparison of eDNA metabarcoding of tree crop flowers and digital video recordings' was published in Ecological Indicators. https://www.sciencedirect.com/science/article/pii/S1470160X24012846?via%3Dihub

flower visits

Eat More Plants! Eat Local, Live Balanced: Tips for a Healthier Planet and You

Eating more plants and sourcing food locally are two of the simplest ways to improve personal health, protect the environment, and even save money. By making small adjustments to our diets, such as incorporating more fruits and vegetables and reducing...

Avocado Leaves Last and Last

Avocados come from a wet environment. The Guatemalan and Mexican races come from cloud forest environments that are dripping much of the year from if not rain, a high humidity that creates a cloud-like condition. These are conditions that leaf fungi love, so in order to protect from leaf fungi, they have developed a waxy cuticle so that water runs off. This also protects the leaf from water that would dissolve nutrients in the leaf. This is one reason that foliar nutrient sprays don't work well with avocado. They can get into flowers, so floral sprays can work. But then you might mess up pollination.

 

Greg Alder photo

Another consequence of this cuticle is that the leaves are resistant to decay. One reason for the thick leaf duff/mulch/layer found in avocado orchards.

I tagged leaves that had newly fallen with different colored propylene string at time different times of the year. Leaves were 1 month, 6 months and one year old. The leaf on the right is one year old. That waxy layer is really resistant.

 

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