Monday, May 29, 2017

A Red Flag Goes Up When Cotton Fields Develop Bare Spots & Plants Start to Wilt

With a month or more under their belts, Valley cotton growers are starting to survey their young crop for early signs of trouble.

This is the time to survey the fields and record areas that they suspect suffering from Race 4 Fusarium wilt. They need to act quickly to confirm that soil-borne fungus is the culprit and then consider management options.
Bare spots will start to develop due to Race 4 Fusarium issues.
First, let’s describe technical aspects of the soil condition called Fusarium, which causes plants to wilt. There are four types, or races, of Fusarium oxysporum f. sp. Vasinfectum in California soil. Three are rather mild and don’t cause major problems with cotton plants, unless they are also infected with root knot nematodes, according to UC IPM.
Early sign of wilting leaves on a cotton plant.
The most insidious is Race 4 Fursarium.  It can be quite nasty because it moves within fields through the soil or water. Your boots or a shovel can spread it around easily.  Also, the Race 4 Fusarium survives indefinitely in the soil.
For many years, Northern San Joaquin Valley growers didn’t have to worry about it. The problem was confined mostly to the south.
But increasingly, north area growers have been discovering the presence of Fusarium wilt in their fields, according to Dan Munk, cotton specialist with the University of California Cooperative Extension for Fresno County.
What makes matters worse is the fungus increases when infected plants are plowed down after harvest. Certain Pima and Acala varieties are susceptible.
Here’s how UC IPM describes the symptoms:
There is evidence of “a general wilt, which is especially evident on warm days, and yellowing and necrosis of lower leaf margins. The vascular system of infected plants is discolored brown in affected portions of the tissue. This is most apparent in the lower stem and upper taproot. The discoloration starts in the taproot, spreads into the stem, and is generally continuous in contrast to the speckling nature of the discoloration in plants affected by Verticillium wilt.”
Plant starting to die from the soil-borne disease.

“In seedlings and young plants, cotyledons and leaves wilt, may turn necrotic, and even fall off the plant, resulting in bare stems. Seedlings of susceptible Pima varieties often die and resemble plant losses caused by damping-off fungi. In mildly affected plants, lower leaves develop symptoms but plants survive, but with reduced vigor and noticeable stunting. Certain strains of the causal fungus only cause symptoms when plants are also infected with the root knot nematode. In those cases, galls are usually prevalent on lateral roots.”

Field scout Damien Jelen hasn’t seen evidence of bare spots in the fledgling cotton fields – so far. In the coming week, he will be visiting more fields to assess stand development and give us a better idea how the crop is faring so far this season.
Dig up the entire plant to take a sample.

For those growers who suspect aRace 4 Fusariumtrouble spot should collect a soil sample and contact their local farm advisor about testing it. Here are some tips for taking a sample:

·         Use a shovel to dig out the entire plant without disturbing the entire root
·         Rinse soil from roots and place the plants in a plastic bag
·         Select plants that show symptoms but are not dead. Try to get plants at different growth stages
If there is a problem, UC IPM suggests a number of management strategies:

·         “Rotations to any crop other than cotton prevents an increase in the soil population of Fusarium but may not significantly reduce the number of spores in the soil. The fungus will sustain itself on the roots of most plants, including weeds (without causing any symptoms), and cannot be eliminated by crop rotation alone.”

·         “Always use Fusarium-free seed produced in disease-free fields at all times. Avoid moving gin trash that originated in infested cotton fields to noninfested fields. Any field operation that moves soil from one location to another can spread spores of the fungus and introduce it to other fields. Washing soil from equipment with pressurized water will help limit the spread of Fusarium and should be considered in sites where race 4 has been confirmed.”

·         “Other containment options for Race 4 Fusarium include restricting traffic in affected patches, especially when the soil is wet, destroying affected plants and surrounding nonsymptomatic plants, and stopping irrigation of affected patches in order to prevent movement of infested soil. Soil solarization under clear plastic for a minimum of 5 to 6 weeks may reduce fungal populations, but will not eradicate all spores of the pathogen.”
Avoid growing seed cotton in infested field.

·         “Cotton seed intended for planting should never be produced in infested fields. This is especially true in fields infested with Race 4, which can cause devastating yield losses in certain susceptible Acala, non-Acala Upland, and Pima varieties.”

Let’s hope only kind of Race 4 growers saw over the weekend was Sunday’s iconic Indianapolis 500 auto race.




Monday, May 22, 2017

It’s Not a Good Agricultural Practice If You Get My Drift

Pests, diseases and weeds – they’re a fact of life for farmers.

When they get out of hand and threaten the crops, growers often have to resort to chemical treatments. It has been especially true this season due to the wet winter.

For almond growers, for instance, weeds have been literally growing like weeds in their orchard. Fungus issues have been a constant threat. And pest issues are starting to crop up.

“We have had a lot of applications,” almond field scout Jenna Mayfield observes. “People who are making all the money this season are probably the applicators.”

Pesticide drift impacts crops, workers and the environrnment.
Jenna is reminding everyone about being mindful of drift when applying herbicides and pesticides.

Drift can be an issue that not only impacts the grower’s farm, but the neighbor’s operations as well. It also can affect the health of workers and water quality.  “Almonds are a high value crop. You don’t want  drift from a nearby field to damage the almond crop,” Jenna says.

 State and local regulators continue to toughen rules on pesticide drift. This year, the state is developing new rules about applications near schools – regulations that will become effective on January 1, 2018.

In recent years, the Almond Board of California has funded research that has demonstrated how improving the accuracy and efficiency of spray applications can generate better returns to growers while reducing drift onto the orchard floor and off site. Simple changes such as slowing sprayer speeds and volumes and modifying nozzles can bring better results.
Growers can take some basic steps to minimize drift.

In an Almond Doctor column, UC Cooperative Extension (Fresno County) adviser Kurt Hembree offered these tips to minimize drift from a ground sprayer:

1. Don’t spray when it’s windy: Do not spray in winds above 6 – 10 mph.

2. Be cautious on calm days: Do not spray under dead calm conditions in early morning, evening or the night. Calm conditions are often associated with temperature inversions which can result in long-distance spray drift (1 mile or more).

3. Check the buffer zones: Refer to the product label to determine adequate buffer zones outside of the field treated. Do not spray if the wind is blowing towards a nearby sensitive crop, garden, waterway, or other sensitive area.

4. Use a shield: Consider equipping your sprayer with a protective shield. A number of designs are available that can reduce drift between 35 and 75 percent. Avoid spraying trunk-to-trunk with unshielded spray booms.

5. Use a spray drift retardant: Spray drift retardants are available that can be added to many products to help reduce off-target drift.

6. Check the formulation: Use amine formulations of 2, 4-D when possible. Use special care when using ester or other volatile herbicides. Avoid spraying these products on or immediately before hot days.

7. Sprayer type: Sprayers designed to apply herbicides at low volumes (<10 gpa), such as controlled droplet applicators, produce extremely fine droplets which can drift long distances. Advances in sprayer technology allow for certain post emergence herbicides (like glyphosate) to be applied through low volume, shielded equipment or in low doses based on weed populations present at the time of treatment.

  8. Watch the nozzle pressure: Avoid nozzle pressures above 45 psi for conventional flat fan tips. Excessive pressure can create fine droplets that are prone to drift. Use a minimum of 10 gallon/acre, unless otherwise specified on the label.

 9. Nozzle height: Operate nozzles at their lowest recommended height. For 80 degree tips, this is 18 inches, and for 110 degree tips, this is 12 inches. Orienting nozzles forward also allows for further height reductions. 10. Nozzle selection: Special nozzles are available by various manufacturers that create coarse, low-drift sprays. These nozzles can reduce drift by 50 to 95 percent.

Monday, May 15, 2017

It’s Time to Assess the Best Time to Irrigate Cotton

Young cotton plants are basking in the warm, sunny weather.

Field scout Damien Jelen reports everything is progressing well as growers prepare for the first irrigation after planting. But UC experts caution growers about opening the water spout earlier than usual. 

Bob Hutmacher, a local UC Cooperative Extension specialist, says it’s tempting to do so because of the increased availability of water following the drought-busting winter. Resist the temptation, though, he says.
UCCE's Bob Hutmacher.
His reasoning: If growers had pretty good moisture for planting and early root development in the upper 18 to 24 inches of the soil, it is better to wait because you will end up cooling the soil. That could slow growth.

Hutmacher also says early irrigation also can heighten the risk of plant loss because of seedling diseases. The time to water is before planting, which leachesout the salt built up. Growers that didn’t do that can make it up by adding more water and making an earlier first in-season irrigation this month or in June.

Cotton plants are quite salt tolerant. Salt accumulation can wind up affecting plant growth and yields.

The first post-planting cotton irrigation will be soon.
If well water with mild to moderate salinity levels was used to irrigate on previous crops in the area where cotton was planted this season, then growers should consider collecting soil samples to determine salinity levels in the upper root zone.

This season’sheavy rains are likely to prompt growers to do more weed management in the fields, Hutmacher says. The increase in weeds coupled with fewer fallow fields may translate into more complicated pest management issues. Early season thrips and lygus could lead to increased crop damage in 2017.

Almonds are getting big.
Meanwhile in almonds, field scout Jenna Mayfield reports no significant pest concerns orchards. She says almonds are larger than normal for this time of year. That’s a good sign so far. Of course, there’s still a long way to go before harvest.

Monday, May 8, 2017

Almond Season and Pests Are Right on Schedule in Valley

 It’s always nice to hear that the almond season is progressing well.

Trees are chock full of nuts. Weather has been warm. And, of course, pests are out in the orchards.
“Everything is on schedule for almonds, including the pests,” says field scout Jenna Mayfield.
Gumming occurring on the outside of the hull
Those bugs, she says, include leaffooted bugs and stink bugs. They are gumming things up onthe developing fruit. “It’s pretty widespread and extensive.”

On the technical side, the condition is called gummosis. 

Usually stink bugs and leaffooted bugs are considered infrequent pests in almonds. But the two pests do surface when weather and other conditions are right.

Stink bugs feed on almonds from early spring through July and can cause the kernel to abort. The pestwill migrate into the orchards when weeds or other host habitat start to dry up.
Stink bug feeds on almond. (UC IPM photo)
Both bugs will bore a pinhole in the hull and young kernel.  The gumming is clear oozing-like substance that can be found on various locations on the nuts.

Even if the pest doesn’t reach the kernel, too much feeding activity can trigger crop loss, fungi and bacterial infections and discoloration of the kernel. 

Jenna points out you need to split open a nut to determine if the bug penetrated the kernel. Damage is evident by finding a small pinhole caused from the pest’s feeding mouth part.

A leaffooted bug is on the prowl in this almond tree.
UC Integrated Pest Management says there are no treatment thresholds for stink bugs. Growers should base their treatment decision on the amount of damage. The decision to treat should be based on the appearance of damage and the extent of the damage. Stink bugs aren’t very mobile so sprays can be quite effective, according to UC IPM. Studies indicate one application cuts down the population enough that another treatment may not be necessary for three years.

Here’s what UC IPM says about the leaffooted plant bug pest: “The leaffooted bug overwinters in the adult stage in orchards or near orchards on native host plants, from which it migrates into orchards in March or early April in search of nuts on which to feed. Feeding by adult leaffooted bugs on young nuts before the shell hardens can cause the embryo to wither and abort, or may cause the nut to gum internally, resulting in a bump or gumming on the shell. It can also cause nut drop. After the shell hardens, leaffooted bug feeding can still cause black spots on the kernel or wrinkled, misshapen nutmeats. Varieties with softer shells such as Fritz, Sonora, Aldrich, Livingston, Monterey, and Peerless are more susceptible to plant bug damage for a longer period during the season.”

Slicing open an almond to look for bug damage.
Growers can be confused about what pest is creating the damage to their nuts since both the stink bug and leaffooted bug cause gumming on the hull. Gumming also can be caused by other factors.
Because the symptoms are similar, advisers recommend finding the actual pests or their egg masses. Check out UC IPM online for more information about monitoring and treating for stink bugs and leaffooted bugs in almonds.

Alfalfa field after harvest
Meanwhile, field scout Damien Jelen says alfalfa growers have wrapped up another cutting for the season. He expects many growers to start irrigating the fields this week. So far, there aren’t any significant pest issues.

In cotton, the young plants are moving into the true leaf development stage at many farms. Some growers are preparing for the first irrigation of the season.