- Author: Oleg Daugovish
When Richard Smith tells you that he is impressed with efficacy of an organic herbicide you better take notice. Richard shared his results on this blog site last year and showed good weed control with 'Suppress' from Westbridge. This OMRI approved herbicide is a mix of caprylic and capric acids and is a contact material that interferes with plant cells membranes causing leakage and desiccation.
It looked like a good fit for organic plasticulture systems such as strawberry that have wet weedy furrows which are difficult to access with mechanical tools because of proximity to plastic. We placed a trial in a very weedy field that also had one of the SoCal classics–yellow nutsedge. 'Suppress' at 6 and 9% by volume was applied to well-established weeds just before strawberry planting.
The effects of application were noticeable in minutes. We learned that:
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Both 6 and 9% rates provided nearly 100% control of common lambsquarter (predominant species) and other occasional broadleaved weeds.
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About 10-15% of common purslane plants survived and yellow nutsedge seemed unaffected by application. However, biomass of both purslane and nutsedge were significantly reduced, suggesting that production of seed and tubers for the two weed species, respectively, may be delayed.
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Good coverage was important and some of the horizontally–inclined leaves of broadleaf weeds likely intercepted the herbicide deposition to vertically inclined nutsedge shoots.
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When we simulated drift by over-spraying strawberry, it responded just like any broadleaf perennial plant—the canopy wilted and dried but in 3 weeks the new leaves developed from the crown. This was also true for the neighboring bindweed that lost above ground canopy but had new growth within a month after 'Suppress' application.
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Since perennial weeds or those in soil seedbank are not controlled, repeated applications are needed with obvious caution of avoiding the spray drift to the crop.
- Author: Ben Faber
http://apsjournals.apsnet.org/doi/pdfplus/10.1094/PDIS-11-12-1026-RE
But here's the abstract:
The polyphagous shot hole borer (PSHB) is an invasive ambrosia bee-tle that forms a symbiosis with a new, Fusarium sp., together causing Fusarium dieback on avocado and other host plants in California and Israel. In California, PSHB was first reported on black locust in 2003 but there were no records of fungal damage until 2012, when a Fusarium sp.was recovered from the tissues of several backyard avocado trees infested with PSHB in Los Angeles County. The aim of this study was to determine the plant host range of the beetle–fungus complex in two heavily infested botanical gardens in Los Angeles County. Of the 335 tree species observed, 207 (62%), representing 58 plant families, showed signs and symptoms consistent with attack by PSHB. The Fusarium sp. was recovered from 54% of the plant species attacked by PSHB, indicated by the presence of the Fusarium sp. at least at the site of the entry hole. Trees attacked by PSHB included 11 species of California natives, 13 agriculturally important species, and many common street trees. Survey results also revealed 19 tree species that function as reproductive hosts for PSHB., approximately a quarter of all tree individuals planted along the streets of southern California belong to a species classified as a reproductive host. These data suggest the beetle–disease complex potentially may establish in a variety of plant communities locally and worldwide.
A PSHB conference is set for February 18 at the Huntington Library in San Marino. For registration contact:
http://ucanr.edu/sites/pshb/Events/
The damage
- Author: Ben Faber
It's that time of year when grower's think about pruning their avocado trees. What scars many growers is the regrowth that occurs. If the cut is to the middle of a branch, there is all kinds of wild growth that results. The best cuts are back to a crotch or a subtending branch. Then there is little regrowth. Sometimes those cuts cannot be made and a mid-branch cut needs to be made.
Tre-Hold, naphthalene acetic acid was registered on avocado several years ago to retard that regrowth. The growth hormone is mixed with white latex paint so it is possible to see where it has been applied. We recommended that the paint be hand applied to a distance two times the width of the cut. So if the cut is 2 inches in diameter, paint back 4 inches around the base of the cut. It works.
Many growers don't use the material, but recently I saw a neatly pruned grove that has been using NAA for a number of years and in order to avoid any confusion about how much paint to put on, they just apply a 2 inch width of paint to all the cuts. This is easier for the pruners and speeds up the process. Try it, you may like it. It certainly saves time in maintenance over the long haul after pruning.
- Author: Ben Faber
You come on a leaf with the margins munched on. It's got to be a beetle or a looper or some insect doing the damage, right? Not necessarily. It's not time to drag out the Raid. Look at the damage closely. In the photos below you can see the dead leaf margins caused by either salt damage or more likely leaf blight. Leaf blight is a disease that shows up with water stress and is caused by a fungus, one of the Botryoshpaerias. It causes an uneven marginal necrosis that goes along the margin in a somewhat irregular pattern and often not at the leaf tip. In this case it does affect the leaf tip, and since salt burn and leaf blight are caused by the same conditions of water stress, it's probably a bit of both.
Lepidopteran larvae will more commonly feed in a smooth pattern, not the rough pattern seen here. Now with this dead tissue, the wind blows it out, and what's left is the uneven margin. No it's not time to spray an insecticide. It's time to reflect on irrigation. There's a lot of this damage out there now. On avocados, citrus, landscape plants. It's going away until the leaves drop and are replaced with new ones, that will hopefully be well hydrated by rain and proper irrigation.
Top photo is salt/leaf blight damage
Bottom is necrotic tissue that the wind has blown out
- Author: Ben Faber
It ain't over yet, and this last week we had a wonderful 2 day meeting with folks who have dealt with drought in many different ways. Here are presentations made by people from Israel, Australia and California. Soon the actual videos will be available, but now see the powerpoints.
http://www.droughtmgt.com/#!presentations-and-documents/niui7
The grower panels are wonderful, but are not uploaded at this point
DAY I: UNDERSTANDING IRRIGATION WATER MANAGEMENT
Session I: California Response to Drought
9:15am // Overview of California Drought Response
9:30am // El Nino Forecast for California and Possible Impacts on Irrigated Agriculture
Session II: Technology of Water Management
9:45am // Soil Water Sensing
10:15am // ETc Estimates - Weather Stations (CIMIS), surface renewal
11:00am // Salinity Measurement
11:30am // Consideration In Selecting Water Stress Indicators
12:00pm // Precision Water and Fertility Management During Deficit Irrigation
Session III: Alternative Water Supplies
1:30pm // Irrigation With Recycled and Desalinated Water
2:00pm // Effects of Irrigation With Poor Quality Water on the Soil - California Experience
2:30pm // Effects of Irrigation With Poor Quality Water on the Soil - Israeli Experience
3:00pm // The Challenge of Sustainable Irrigation with Water High in Salts: Lessons from Dates, Olives and Grapevines
Session IV: Water Management Strategies During Drought
3:45pm // Water Management Strategies during Drought - Australian Experience
4:45pm // Cultivation Under Protective Structures to Save Water
Day II: WATER MANAGEMENT FOR INDIVIDUAL CROPS & GROWER EXPERIENCES
Session V: Technology Demonstrations​
8:00am // Irrigation Scheduling - Australian Experience - IrriSAT Approach (IrriSAT Supporting Materials)
8:30am // Using the Pressure Chamber for Drought Mangagement Decisions
9:00am // Irrigation System Evaluation
9:30am // Salinity Mapping for Water Management
Session VI: Conncurrent Breakout Groups
10:30am // Citrus - Israeli Experience: Long Term Effects of Deficit Irrigation, Salinity, and Rootstocks on Orchard Productivity
10:30am // Grapes - Table and Wine Grape Irrigation Scheduling
10:30 // Deciduous Nut Crops - Irrigation and Crop Load Interactions
10:30// Almond Irrigation, the Israeli Experience
11:15am // Olives - Israeli Experience: Cultivation Under Limited Water Availability
11:15am // Grapes - Wine Grapes Irrigation - Coastal Vineyards
11:15am // Deciduous Nut Crops - Almond Irrigation - Israeli Experience
1:00pm // Avocado - Israeli Experience
1:00pm // Grapes - Wine Grapes Irrigation: San Joaqin Valley
1:00pm // Deciduous Nut Crops - California Experience
1:30pm // Deciduous Nut Crops - Pistachios Irrigation
1:45 // Subtropical Crops - California Experience
1:45 // Grapes - Irrigation, the San Joaquin Valley
2:00pm // Deciduous Nut Crops - Walnut Irrigation
2:30pm // Grower Panels
3:15pm // Concluding Remarks