Monday, August 27, 2012

Valley Ag, Pests Really Cooking with Hot August Nights & Days

In some fields, cotton bolls are opening early this season.
It has been a weird week in the Valley. Perhaps Mother Nature has concocted a little weird science with these blistering triple-digit temperatures we’ve been having here.

Tomatoes and melons are ripening at a meteoric pace, forcing growers to accelerate their harvesting plans. Alfalfa plants are turning to seed. Cotton bolls are starting to open earlier than normal. And crop-threatening pests are exploding on the scene.

What started as a fairly calm, normal season earlier this summer could be turning a little weird for cotton growers as we approach the fall equinox.

Let me put my weather cap on and give everyone a recap: Despite a few record-breaking high temperatures in early June, the overall weather was fairly normal for the month and provided ideal growing conditions for cotton; July remained routine with no surprises; and then there is August with 18-straight days of triple-digit temperatures before finally dropping into the 90s on Saturday. In fact, just five days have been under 100 degrees this month, according to the National Weather Service. We could be back to triple digits Tuesday.  W 

The result: I’ve seen the first bolls already open up. That’s a little early. Usually, bolls open sometime in the first week of September. If this keeps up, we could be in for an early harvest.

To ease the heat-induced stress on the plants, some growers have started to add an extra dose of water to their crop. This extra irrigation is aimed at slowing the down boll opening.
First open boll.

In the meantime, aphid and whitefly counts are on the rise. The pests are migrating from nearby fields due to the accelerated tomato and melon harvests. Also, the heat wave also is causing some alfalfa to dry out fast and go to seed, prompting pests to seek more lush habitats such as nearby cotton fields.

Meanwhile, a few anxious growers are moving ahead and treating their cotton fields. I suggest growers hold off a few days before spraying, especially if the bolls are still closed.  By being patient and monitoring the fields, the aphid counts could drop few in a few days – beneficial insects may come in and help keep pests under control. In addition, growers should run the numbers, comparing the percentage of open bolls and pest counts to help them determine threshold for treatment. Go online and check out UC IPM’s monitoring aphids and whiteflies guidelines covering the first open boll to preharvest.
The alfalfa season is starting to wind down in the Valley.

Right now, I’m generally seeing 15 to 20 percent infestation in fields. The treatment threshold is about 30 to 40 percent infestation.

In the alfalfa, some plants are flowering and ready to turn to seed. In that case, growers may lose out on getting one more cutting. Other growers are hoping for two more cuttings before closing out the season. On the pest front, I’m seeing an uptick in beet armyworms. UC IPM also offers tips about monitoring for armyworms in alfalfa.
Almonds are approaching hullsplit in this orchard.
Almond field scout Jenna Horine reports an explosion of spider mites in some orchards. Some areas are hit harder than others. Harvest timing still varies, with some growers still waiting for hullsplit while others are well into their nut harvest. In dealing with mites, long-time entomologist and almond expert Walt Bentley tells us that growers they can’t do anything about mites if harvest has started.

Some growers are still  waiting for the harvest.

If they haven’t started to harvest, growers may be able to treat with a short pre-harvest interval miticide. This would have to be done by air. Growers should consult their pest control advisors. For the most part, he says, “We will probably have to sit through this and get the harvest done. This shouldn’t hurt this year’s crop and won’t hurt next year’s.” Thanks for the tips Walt.Th 

Monday, August 20, 2012

It's Time for Cotton Growers to Bid Farewell to Lygus Worries, Say Hello to Aphid Concerns

 Hello Houston, we’re at cut-out.

More than four months since the seeds were planted, growers are getting a good indication about how much cotton they can bank on at harvest time. Cut-out is the final stage of plant growth before the bolls open. You have mostly mature fruit on the plants and new terminal growth stops taking place.

So, we can pretty much scratch lygus off our list of pests to watch. Of course, we’re far from out of the woods. Now, growers are on aphid watch and their concern (what farmer doesn’t worry) turns to risk of sticky cotton.

Cotton plants are at their final stage of plant growth.
To a lesser extent, Mother Nature has added another thing to worry about – plants stressed by the recent heat wave. In one plot that I’ve scouted, I found cracked bolls. It’s too early for bolls to normally open up. But in this field, the last irrigation came a little early – before the recent parade of triple-digit temperatures, which accelerated the timetable for bolls to open. There’s an interesting article about boll shed and high temperatures in this month’s UC Cooperative Extension Cotton Field Check newsletter.

We can live with more seasonal temperatures in the uppers 90s to 100-degrees. Forget the scorching 110-plus weather. Let’s hope we can stay a little cooler this month.
Growers turn their attention to aphids.
Aphid numbers are up in the fields. I’ve seen some fields treated. Usually, you see higher populations in cotton planted later in the season – around late April. To enhance biological controls, I’ve been releasing beneficial insects – green lacewings – in various fields. They have held back the aphids for a few days. Since the bolls are still closed, I believe growers can be a little more patient and wait a little longer before applying materials. Check UC IPM for more information about aphids in cotton and treatment thresholds.

Green lacewings are released to help control aphids.
Meanwhile, alfalfa growers are finished with their fifth cutting and preparing for the next harvest. They should have two to three more cuttings before wrapping up the season. There have been some worm issues, prompting a few growers to apply treatments. Overall, though, pests have been pretty light.

Our almond field scout Jenna Horine reports pests have been light in the almond orchards in the past week. “That’s good,” she remarked.

Some almond growers already are shaking nuts off the trees.
The harvest varies greatly around here. Some growers are shaking the nuts from the trees. Others are still irrigating their trees with no signs of hullsplit yet. The crop on the westside seems to be maturing faster than the eastside. Soon, she’ll be picking up samples for crack-out to check for pests and help growers develop pest management plans for next season.

Monday, August 13, 2012

When Hot Weather Is Real Hot Even for Valley Cotton Plants

As a Central Valley native, you grow accustom to hot summer days and learn to adapt to triple-digit temperatures.  But I must admit the 111-degree weather we had last Saturday (it was just 109 degrees today and last Friday) was a bit excessive even for long-time farmers. It was sooo hot that weather forecasters issued an excessive heat warning over the weekend. I’ll be drinking lots of water this week with triple-digit temperatures expected to last until the weekend.

A cotton plant showing signs of heat stress.
-  Science Daily photo by Stephen Amus 
This heat wave has farmers and others who work outdoors (myself included) getting started really early and heading for cooler environs by mid-afternoon. While hot weather normally provides ideal growing conditions for cotton (the average July and August temperatures around the Valley is the mid- to upper 90s), this excessive heat could turn out to be a little troublesome, especially if these near-record high temperatures last for a spell.

Plants could become stressed; especially for growers who got an early jump on their final crop irrigation of the season. The result could be some bolls opening up early or some fruit dropping – all resulting in a lower yield at harvest time. Check out an interesting article about heat and water stress in cotton by UC cotton expert Bob Hutmacher in the UC Cooperative Extension’s California Cotton Review published in 2004.

Another concern is the super-hot weather could ripen melons or tomatoes faster and prompt farmers to harvest earlier. That could send pests into nearby cotton fields sooner than usual. As Dr. Pete Goodell of UC IPM says, farming is a community as a whole – no matter what crop you grow – and what happens in one field can affect what happens in another. Let’s hope the dominoes don’t start falling. Too bad Mother Nature doesn’t offer air conditioning in the Valley.

Here's the back of a cotton leaf dotted with lots of aphids.
Speaking of pests, we’re almost past the lygus danger zone for cotton. Fields are pretty much at cut-out. But growers still need to monitor for lygus to ensure the smaller bolls at the top of the plant won’t drop. At this time, however, you can allow for a higher pest threshold for possible treatment – five nymphs vs. three for every 50 passes of your sweep net.
I saw aphids on the rise in the past week. But the rate of increase varies from field to field. In general, growers that treated their fields early for the pest or used stronger materials that can impact beneficial insects are experiencing higher counts (a 25 to 40 percent increase) than those farmers who didn’t treat or used softer materials (an 8 to 12 percent increase).  While aphids aren’t a threat right now, we still need to monitor these pests to keep them from becoming a major problem when bolls start to open. That’s when you have to worry about sticky cotton.

A bean plant  habitat next to cotton.
It’s hard to tell when most bolls will start opening. A lot depends on the weather and the timing of the last irrigation.  Conditions are ideal for growers to wrap up or stop irrigating their plants. My guest is we’re around three weeks away for bolls to start opening up.

The alfalfa crop continues to move along without any significant issues. Growers are approaching their fifth cutting. After that they’ll have two or three more before calling it a season in September or October.

On the almond front, our field scout Jenna Horine reports the crop is shaping up nicely with no major pest concerns. Some orchards are experiencing a few more mites than others but there aren’t signs of a potential mite explosion. Dust kicked up from roads around nearby fields remains the major source for mites. Also, the pests are coming from nearby fields where grains and tomatoes are being harvested.

Hullsplit varies. Some nuts are in the early stages of splitting while other nuts are ready to be shaken from the trees. Some growers are still irrigating their orchards while a few already have nuts on the ground. Overall the harvest is following the normal schedule, although growers are saying this is an early season (primarily because the harvest season has been later than usual in recent years).

An almond orchard still getting irrigated.
 Soon, we’ll be collecting nut samples before the crop is sent to the huller. The rule of thumb is to take 500 samples per block and then crack the nuts to check for pests. This practice helps almond growers prepare next year’s management plan as well as helps them compare the grade assigned by the huller. UC IPM has more information online about harvest sampling.

Monday, August 6, 2012

It’s All About Timing When It Comes Time to Stop Worrying About Lygus in Cotton

 As we approach the start of August, I am beginning to see evidence of cut-out in cotton fields around the Valley. The timing couldn’t be better.

I’m finding during my field sweeps a general increase in lygus counts – anywhere from a 25 to 50 percent pick up from the week before. Dr. Pete Goodell of UC IPM provided these charts about lygus counts and fruiting branches from information gathered from fields in our San Joaquin Sustainable Farming Project

There is a large upswing lygus nymphs in these fields.
Retention is still good, but these numbers should give
some pause, especially the number of immobile nymphs.
 Cut-out is the final stage of cotton plant growth before the boll opens. This means you see mostly mature fruit on the plant with an absence of squares and blooms. Generally the plant has set more than 95 percent of its yield. UC IPM says you can stop monitoring for lygus about 10 days after cut-out. Check the UC site for more about how to time the count date.

Fruiting branches from all fields. Have we reached cut-out?
For now, growers need to continue with their plant mapping and monitoring for lygus in the field. Mapping helps you determine when to stop watching out for lygus. For the most part, I’m seeing four nodes above white flower. I’m reminding growers that lygus still can cause damage to small bolls. Remember, every boll counts. It’s money in your pocket at harvest time.
In the meantime, aphids are showing up here and there. But I’m spotting an increase of ladybugs and green lacewings, which at the moment can keep aphids in check. Growers are wrapping up their last irrigation. Before you know it, we’ll be on the backstretch of the harvest time finish line.

Everything is moving along with alfalfa. Growers have wrapped up their fourth cutting and are preparing for the fifth harvest. I’m noticing a little more aphids and worms in the fields. But I haven’t seen any growers treating their fields.

For almond growers, Merced County UC Cooperative Extension farm advisor David Doll, author of the popular Almond Doctor blog, spoke at our recent field day and offered some tips about pre- and post-harvest task:

As we approach harvest we want to cut that water back. But we don’t necessarily want to eliminate the application of water. We want to dry trees down so they can be shaken without much damage. But we want to make sure we are applying some water. We don’t want to go two weeks with no water. The other thing to keep in mind is as we approach the post-harvest period it’s a good time to make the consideration for foliar sprays. That includes boron.

 If you are battling with rust disease, knock the leaves off tree to reduce overburdening inoculation. In late October, apply 25 to 35 pounds of zinc sulfate to trees to knock off leaves. When applied in the fall, this nutrient can help break the rust and shot hole disease cycle. It’s important to remember when you knock the leaves off with that zinc spray you’re not going to get any uptake of any that zinc. So if you have a zinc deficit, you need to make that application earlier in the post-harvest period, probably with the boron.