Monday, June 24, 2013

In the Long Haul, Hull Split Timing is Critical in Almonds

 Tick tock, tick tock. Tick tock, tick tock.

While almond growers aren’t sitting idly by the clock, they certainly are playing a waiting game trying to figure out the timing of hull split, says our almond field scout Jenna Horine. So far, she hasn’t seen it arrive yet in various orchards in the northern San Joaquin Valley.
Almonds are experiencing rapid growth this season.

However, almond experts say the rapid growing season has accelerated the process and the start of hull split is likely to come this week for some growers, especially those with the early varieties. Normally, growers start checking for hull split in early to mid-July.

So how hard can it be to identify hull split initiation? The green hull starts to split, exposing the brown shell inside. Soon, it will be time for harvest.

Here is an unsplit almond.
It’s a little trickier than that. Says UC IPM: The exact timing of hull split initiation is complicated. Ripening does not occur simultaneously. It begins in the upper and outer most parts of the tree, in the southwest quadrant, later extending through the lower and inner sections (nuts at eye level will be less mature than those at the tree tops.) Almonds should be harvested when the hulls on 95 to 100 % of the nuts on the tree nuts on the tree have split.”

This photograph shows the initiation of hull split.
-  UC IPM photos
Of course, growers have to deal with those pesky pests. Determining the beginning of hull split is critical for integrated pest management and if a summer treatment for the dreaded navel orangeworm is needed. Applications are timed with start of hull split and NOW egg laying. Hull split also leaves the almonds vulnerable to peach twig borer and hull rot fungi.

These almonds are  at hull split.
Years of field trials have demonstrated the importance of timing sprays for nonpareils during the first 10 percent of hulls splitting, according to Walt Bentley, retired entomologist and UC IPM emeritus.  The later the spray timing, the poorer the insect control.  Over the past two years there has only been one orchard with greater than 2 percent damage.  Walt says your history of damage and this year’s mummy load is an indicator for the need of an insecticide application.  These sprays serve to reduce NOW numbers in the next generation (August to September).  The third generation is the one that produces significant levels of infestation.
Read more about how to identify hull split  at UC IPM online. You also get more information online about managing navel orangeworm.

Growers need to monitor for navel orangeworm.
During her field scouting rounds last week, Jenna found only one orchard dealing with mite issues, which could have been related to water stress. While the grower flood irrigated a week earlier, the water apparently didn’t go deep into the ground. The grower and his pest control advisor dug into the ground and found hard pan only five feet down. The recent hot weather contributed to the water stress, she says.

Meanwhile, field scout Carlos Silva says most alfalfa growers have completed their third cutting and left border strips to create a habitat for pests to stay out of nearby cotton fields. Cotton continues to progress well with no major lygus concerns at the moment.

This week, Carlos may start taking petiole samples to determine nitrogen levels in cotton plants. Nitrogen is an important nutrient for cotton production.


Monday, June 17, 2013

Alfalfa Pest Control: Celebrate the 50th Anniversary of a BPM That’s Still Good as Gold

With summer around the corner, alfalfa farmers are already in the middle of their third cutting of the season. This is an important pest management milestone for cotton.
A grower leaves a strip of uncut alfalfa to create a habitat
 for pests and help keep them out of a nearby cotton field.

That’s right. And if alfalfa growers have listened to their neighboring cotton growers and University of California IPM advisors as well as our field scout Carlos Silva, they will be leaving strips of uncut alfalfa in the fields.

Lygus is a big threat to cotton plants.
We talked about the importance this practice three weeks ago. If you forgot, here’s a quick summary: Leaving strips of alfalfa creates a habit to attract natural predators as well as pests, including lygus, a serious pest threat in cotton.

Here’s what other UC ag experts say:

“Lygus can re­produce on a variety of wild and culti­vated plant species. However, in many areas alfalfa is the key breeding place and overwintering habitat. During favorable periods, lygus populations increase to great numbers in this crop.

“An important feature of the lygus prob­lem is that they are very rarely a pest of alfalfa hay. However, when the alfalfa is cut, the adults fly to adjoining crops and to prevent crop loss, chemical treat­ments are often necessary to suppress the invading pest.

“Since alfalfa is a key crop in California agriculture, it would be impossible to eliminate alfalfa as a means of reducing lygus populations. The problem then is how to stabilize the alfalfa hay environ­ment to prevent or lower the probability of lygus adults leaving the alfalfa habitat where they do little or no damage.”  

“Lygus bug control is possible by strip cut­ting alfalfa to keep the bugs in the alfalfa where they do little harm, and allow sur­vival of natural enemies. The end result could well be a very considerable saving to California farmers, and perhaps even more importantly, a significant reduc­tion in pesticide hazard problems.”

Insightful words – from a 1964 article published in a UC publication called California Agriculture.
Indeed, pictured above are a strip cutting diagrams pulled from a 1963 field study called “Alfalfa Control.” That research by trio of UC Berkeley, Davis and Riverside entomologists      a half century ago is certainly paying dividends today. Happy Golden Anniversary.

Carlos will keep us updated on the how well the alfalfa strips are doing to keep the bad bugs out of cotton.
So far, he has found only one field with concerns about lygus during his recent sample taking. In that field, he netted four lygus bugs per 50 sweeps along one row of the field. The grower pulled six to eight pests per 50. UC IPM thresholds are less than two lygus per 50 until June 15 and more than 2 from June 15 to 30. After consulting with his pest control advisor, they decided to hold off with any treatment and continue monitoring the field.

For the most part, cotton plant development is faring well. Carlos says plants have three to six fruiting branches. We’ll talk more about plant mapping next time.

Monday, June 10, 2013

Central Valley Alfalfa a Haven for Good and Bad Bugs

We talk about bugs a lot, especially those pests that can cause heavy damage to crops. It is basic economics: Damaged crops equal loss income.

One place where you can find lots of bugs is an alfalfa field. These fields are home to more than 1,000 species of bugs, according to University of California ag researchers.
Carlos uses his sweep net to catch bugs in a local alfalfa field.

In fact, alfalfa fields are dubbed the “insectary of the Central Valley” because they host many predators and parasites that travel to nearby fields. At the same time, alfalfa plays an important role in biological controls of pests in diversity of crops, including alfalfa. Of course, out of the hundreds of bugs that call alfalfa fields home, there are only a handful of bugs that can do serious damage to alfalfa. These pests are worrisome at different times of the season.
Right now, we’re at the tail end of the threat from alfalfa weevils. Our field scout Carlos Silva found some potential problems in a couple alfalfa fields last week. His sweep net snagged 18 weevils per sweep – near the threshold for treatment. However, these growers are likely to avoid spraying because the alfalfa is ready for the third cutting of the season. Harvesting would take away the food source for alfalfa weevils.

This week, Carlos will be keeping an eye out for beet armyworms, which are usually active from June to September. Here is a UC list that highlights the seasonal period for other major pests:
  •           Leafhooper – now until August.
  •           Alfalfa caterpillars – now until August
  •           Cowpea aphid – July to August
  •           Spotted alfalfa aphid – July to September

We can’t stress enough the importance of weekly monitoring because pest populations can explode with little notice. Monitoring is key for an effective integrated pest management program.

To get started, you simply need a sweep net. Here’s a quick field scout guide on sweep net sampling: Pick three or four different locations of the cotton field to perform the sweeps. Picture a big “X” overlaid on top of your field and take your pest samples at each leg of the X. This ensures your locations are equally spaces out to give you a good overview or sample from your entire acreage. You also can follow a “V” pattern. 

Net sampling should be done weekly. Also be sure to rotate the sample locations to ensure you cover all areas of the field.

Lygus is starting to show
up in a few cotton fields.
- UC IPM photo
The technique is pretty straight forward. As you walk down a row, you move in a sweeping motion back and forth or right to left (left to right if you’re a lefty). Image the sweep net as a tennis racket. One sweep is a forehand move and the second sweep is a smooth backhand motion – just like last Saturday’s French Open champ Serena Williams.

The same sweep net monitoring technique applies to cotton. Carlos is seeing some early concerns with lygus in cotton. One grower has already treated for the pest.

During one field visit last week, Carlos found four lygus after 50 sweeps. UC guidelines put the treatment threshold during June at two lygus bugs per 50 sweeps. Growers can learn more about lygus in cotton from UC IPM online.

Monday, June 3, 2013

When It Comes to Bugs in the Orchard, Some Like It Hot

 Put on the hat and slap on the sunscreen. Hot, hot  weather has arrived in the Valley.

 While summer is still some three weeks away, weather forecasters say we’re in for more triple-digit temperatures and plenty of 90-degree days. For almond growers, this late-spring mini-heat wave could trigger a population explosion of web spinning spider mites.
Now is the time for the spider mite population to increase.
- UC IPM photo

Almond field scout Jenna Horine says she is bracing for these pests this week and will be keeping a close eye for them as she makes her rounds scouting almond orchards across the Valley. What a difference a week makes when temperatures were in the 80s and pests were in check.

Here’s what University of California Integrated Pest Management has to say about webspinning spider mites: “The mites reproduce rapidly during warm weather between June and September. During favorable conditions, mites develop within seven days, with eight to 10 generations per season.”

Spider mite damage will  impact crops the following year.
- UC IPM photo
On damage: “Mites damage foliage by sucking cell contents from leaves. The damage begins with leaf stippling. Leaves can turn yellow and drop off. High populations cover tree terminals with webbing. Crop reduction and reduced vegetative tree growth shows up the year after damage occurs.”

Jenna says most growers added a miticide in their May spray. We’ll keep you updated to see how effective the treatment was and what Mother Nature cooks up during this hot spell.

Meanwhile, cotton field scout Carlos Silva says cotton plants are developing nicely and should thrive in this hot weather. Growth is good with the advanced plants having two to three fruiting branches and eight to 10 main stem nodes.
- University of Florida agriculture extension diagram

Growers are wrapping up the first irrigation of the growing season.
During his field visits, he’s been finding a beneficials in his sweep net – bigeyed bugs, minute pirate bugs and lady bugs. That’s good.

In alfalfa fields, Carlos has caught some weevils but it’s nothing to worry about for the moment. 

Growers should be starting the third cutting in a couple weeks. He expects to see growers leaving strips of uncut alfalfa to keep pests from migrating to nearby fields, especially cotton.

Speaking of cotton, don’t forget this Wednesday’s Cotton Field Day from 10 a.m. to noon at the McCurdy Farm along Highway 33 in Fresno County. Go to the Sustainable Cotton Project website for directions

Headlining this impressive line-up of UC experts are: Dr. Pete Goodell, who will offer a cotton pest management update; Steve Wright of UCCE in Tulare on herbicide resistance; Dan Munk of UCCE Fresno on cotton production risks in low water years; and UC cotton extension specialist Dr. Bob Hutmacher Race 4 fusarium.  See you there.