- Author: Ben A Faber
- Posted by: Gale Perez
Sterile Pollen Technique Shows Promise for Palmer Amaranth Weed Control
Newly published research provides a novel and sustainable weed-management strategy
WESTMINSTER, Colorado – 22 May2024 – Recently published research in the journal Weed Science shows that a sterilization technique commonly used to control insect pests can be modified to control weeds that require pollination to reproduce. More specifically, the researchers determined that employing a sterile pollen technique (SPT) could effectively disrupt Palmer amaranth (Amaranthus palmeri S.) reproduction.
Palmer amaranth remains among the most detrimental weeds in North American agriculture, and its resistance to several herbicide groups makes its control a serious challenge. Yet, researchers in this study were able to find a promising new control method for Palmer amaranth and possibly for many other difficult-to-control weeds.
“Our results indicate that SPT, using irradiated pollen, can be a valuable approach for reducing weed-seed production,” says Mohsen B. Mesgaran, Ph.D., a plant sciences assistant professor at the University of California Davis, and the article's corresponding author. “SPT also holds potential for broad-spectrum weed control by mixing sterile pollen from multiple weed species in a single application.”
Additionally, the researchers found that SPT shows promise for managing troublesome herbicide-resistant weeds that have survived in-season control efforts.“We observed the greatest reduction in seed set when irradiated pollen was introduced to the stigma through artificial pollination prior to open pollination,” notes Mesgaran. “It appears that irradiated pollen exerts a preventive effect on naturally occurring pollen that arrives later.”
While the researchers determined that a dose of 300 units of ionizing radiation (Gy) strikes the optimal balance to achieve both efficient Palmer amaranth pollination and seed sterility, challenges still remain. For example, irradiated pollen is currently less competitive than naturally occurring pollen. Thus, field managers may need to employ additional measures to successfully control Palmer amaranth with SPT, such as dispersing irradiated pollen in the field before male anthesis and releasing it multiple times.
More information about SPT and Palmer amaranth control can be found in the article (by Wenzhuo Wu and Mohsen B. Mesgaran), “Exploring sterile pollen technique as a novel tool for management of Palmer amaranth (Amaranthus palmeri).” The research is featured in Volume 72, Issue 3 of Weed Science, a Weed Science Society of America journal, published online by Cambridge University Press.
Original source: Weed Science Society of America (https://wssa.net/2024/05/sterile-pollen-technique-shows-promise-for-palmer-amaranth-weed-control/)
- Author: Ben Faber
With all the rain last year, even extending into August and now with the rains since December there is a lot of natural ground cover growing, When it gets out of hand, we call it weedy. It might still serve the purpose of protecting the ground from erosion, but it can become an impenetrable mess and if allowed to go into summer, a major fire hazard. In the case of some young orchard, the malva and mustard is bigger than the trees themselves. Getting control of them before they get woody and go to seed is easier earlier than later. So it's time to do something about them if you haven't done so already.
A common practice on flat ground is to mow the middles and then weed whack/whip the tree row up to and around the tree trunk. In the case of trees that have their canopies down to the ground or near the ground or that have created a thick leaf mulch, there's not usually much weedy growth near the trunk. Then weed whacking around the canopy is not much of a problem. If on a slope like most avocados, it's a big, expensive, laborious, hot, sweaty, arduous process of weed whacking. Just waiting long enough for the leaf mulch to create a barrier to weed growth and for the canopies to grow out to rob the sun from the surface undergrowth.
In young trees without a large canopy, it can be a really difficult process of getting those weeds near the trunk. Care must be taken to avoid damage to the trunk. In a couple of recent examples, weed whacking got right up and on the trunks and significant damage was done to the trees. When a wound occurs in any tree, a process kicks in to generate tissue to cover the wound, much like what happens with humans and wound cuts. There's a scar left, but it heals over. If the wound is too large, many trees cant cover the woody tissue fast enough. The wood beneath the cambium ( the green tissue below the bark) is prone to fungal infection and eventually the fungus eats away at the interior of the tree. If the wound is large enough and girdles the tree, all the nutrients from the leaves feeding the roots is cut off. The photosynthate sugars that keep the roots functioning, and the roots stop doing what roots do. This is absolutely true is citrus and most other orchard tree crops. But not avocado.
When making a cross section of most trees, it's possible to see the growth rings – the growth increments that appear each year. The tree starts and stops growth each year and it's possible to clearly identified in what year there was more or less growth. In long lived trees like redwood, it's possible to identify years when certain events happened – the year of Lincoln's Gettysburg Address, for example. This growth habit is called ring porous.
In the case of avocado, it has a growth habit called diffuse porous. There is growth throughout the year and the rings are nor clearly delineated, if at all. It's because of this possible active growth occurring, that the avocado can often cover over damage that is quite extensive. After a fire, given time, mature avocado trees can summon up energy to recover to a great extent. It's not so true of young trees, however. Avocados still have a greater regenerative capacity than a lemon tree, and if the damage is to just one side of the tree, there's a very good chance of recovery.
But these young tree are severely impaired. They do have a chance of recovery, but the damage is extensive and the trunk is fully girdled. Only time will tell if they do recover. If the tree were only a year old, it would be a good idea to pull them and start over. But a number of these trees are three years old and have had a lot of investment in them besides their initial nursery cost – pruning, weeding, irrigation, fertilization, etc. It is heart breaking to see damage like this after so much attention has been paid to them.
And the best thing is to let the tree recover on its own. Use of pruning paint actually impairs tissue regeneration. The grower asked if a kaolin protectant like Surround might be used to provide some sun protection. Since that breathes, it might be a good idea. It might also be a good idea to apply some trunk wraps. These were taken off in order to prevent earwig and snail harbor which can cause significant damage to young trees. But they also provide protection from overly aggressive weed whackers. It is always a compromise when making these decisions.
- Author: Ben Faber
So I've gotten a few calls lately about this vine with a big green pod that is growing in lemon trees. What is done with it and how do you get rid of it?
Araujia sericifera, cruel vine, moth plant, bladderflower is an escaped ornamental that has become an invasive weed in California. Yes, a pretty vine brought into the garden – “poor man's stephanotis” - and it's gotten out of the garden into southern California. It's in the hills, in abandoned orchards, on backyard fences and when it gets into a lemon tree, it takes some effort to remove it before the seeds spread to other trees and beyond.
Bladderflower is a perennial vine that is very vigorous where it gets summer water. It is a common weed in citrus groves, where it would enshroud & smother entire trees if not controlled. Stems are tough and ropy, leaves thick & slightly spongy. Sap is milky white, moderately poisonous & causes skin irritation. It flowers Aug-Oct and the seed pods are obvious later in the fall. The flowers have a pleasant fragrance like jasmine. The reason for gardeners planting it. Plus it grows fast in our environment.
The plump pods produce copious seeds when ripe. The fruit splits down one side and turns itself inside out. The numerous, loosely attached seeds parachute away on silky hairs, dispersed by the wind – on to the next tree or fence.
So the vine is entrained in the tree canopy so you cant spray an herbicide. To get rid of it, it's important to get down to the base of the tree and cut it out at ground level, removing as much of the root as possible. It still can regenerate, so it will be necessary to monitor the site, removing new growth as it might happen. Be sure to use hand protection because many people are allergic to the sap. Just cutting the vine at its base is sufficient to kill it. Removing the rest of the vine is necessary if there are pods, in order to prevent them going to seed.
The upside of the plant aside from the fragrant flowers is that it is an alternative food source for monarch butterfly caterpillars.
Calfflora shows cruel vine spread mostly along the coast south of San Luis Obispo, but it has the potential to spread thoguhout much of California. Currently, in the US, it is only found in California and Georgia. It is in New Zealand and Australia.
Calflora Description and Distribution of Bladderflower
USDA Description of Plant as attachment below:
Araujia sericifera WRA
- Author: Ben Faber
Who says you can't know all those wild things growing in the field you didn't put there? Here's a chance to learn what they are for cheap. UC Publications is having a book sale and they are a deal until February 14.
Weed Control in Natural Areas in the Western United States
This is the first comprehensive book to focus on control options for invasive plants in natural areas. Covers control methods for 340 species in 13 western states, covering rangelands, grasslands, pastures, riparian and aquatic areas.
Publication Number:: 3547
Availability:
Available
$37.00
$27.75
Weed Pest Identification and Monitoring Cards
Based on the bestselling Weeds of California and Other Western States; this is the perfect pocket-sized companion for anyone working in the field.
Publication Number:: 3541
Availability:
Available
$25.00
$18.75
Weeds of California and Other Western States
This easy-to-use 2-volume set is the most comprehensive guide available. Includes a CD of every photograph in the book; perfect for presentations.
Publication Number:: 3488
Availability:
Available
$65.00
$45.50
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- Author: Cheryl Wilen
IPM Natural Resources Extension Coordinator
Endemic and Invasive Pests and Diseases Strategic Initiative Leader
UC Statewide IPM Program & UCCE- You need to get a Remote Pilot Airman Certificate (FAA Part 107) if you are going to do anything commercial with it. That includes even if you are using it on a job where you will not be paid.
- You can use it for scouting but you can't fly it over people (unless you get a waiver). You also always have to have it in your or an assistant's (the spotter with radio communication) line of sight.
- Even if you have a drone that is capable of doing a spray application, the Dept. of Pesticide Regulation currently requires that the drone pilot have an Airman's Certificate (Pilot's license). This is addition to the Pest Control Aircraft Pilot Certificate from DPR. However, things may change in 2018. See pages 3-47 to 3-52 in http://www.cdpr.ca.gov/docs/enforce/compend/vol_1/entirerep.pdf
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