Bug Counts Up: Time for Border Strips in Alfalfa fields

There’s one way I can tell when the spring will begin getting warmer and sunnier. The bugs start coming out.

With daytime temperatures now in the upper 70s and low 80s, I’m starting to see more pests in the alfalfa fields. Specifically, looper worms and alfalfa caterpillars are showing up in greater numbers as I scout various fields around the San Joaquin Valley. I’m also noticing lygus counts are on the way up.

Monitor  for  looper  worms.      Photos by  Jack Kelly Clark

Last week, my sweep net collected an average of 5 to 7 worms for every 50 sweeps in the alfalfa. That’s up from an average of 1 to 3 worms the previous week. So far, the sampling indicates were in a safe mode, which means the pest pressure isn’t great enough to warrant pesticide treatment. As the days grow warmer, I expect the pest numbers will increase.

Right now, most growers are preparing for the second cut of alfalfa. A few are even poised for their third cut. The recent rains had growers on edge and mulling the timing of their next harvest.

It’s never too early to think about creating border strips. It’s good to have small strips of uncut alfalfa this time of the year. I recommend a leaving quarter swath – roughly a 2 to 3 feet wide strip – at the end of the field. These strips will retain loopers, alfalfa caterpillars and lygus, preventing them from migrating to nearby fields and damaging those crops, especially cotton. Alfalfa strips also will attract natural enemies such parasitic wasps.

Keep an eye out for alfalfa caterpillars in the fields.

This farm management practice can save time and money because you’re holding off spraying pesticides until absolutely necessary. That’s where field monitoring and pest sampling comes in. Here’s a rule of thumb: Consider treatment when after 50 sweeps per stop, you collect 10 or more alfalfa caterpillars, or 15 armyworms, or a combination of 10 alfalfa caterpillars and armyworms. I usually make 3 to 4 stops in each field.

In early summer start sweeping fields with adequate plant height 2 to 3 times per week to monitor for caterpillars and continue through fall.  Early cutting will give satisfactory control if the infestation appears late in the cutting cycle.
Combine monitoring of armyworms with monitoring for alfalfa caterpillar as described in Alfalfa Caterpillar and Armyworm Monitoring. Count and record the number of healthy and parasitized caterpillars caught in your sweep net on a monitoring form (68 KB, PDF).
If cutting is not practical or not scheduled soon after monitoring, treat if there is an average of 10 or more nonparasitized alfalfa caterpillars (those not infected by parasites) per sweep, 15 or more nonparasitized armyworms per sweep, or 10 or more nonparasitized alfalfa caterpillars and armyworms combined per sweep.

When you need to spray, consider selecting from a variety soft pesticide materials on the market. They’re effective and good for the environment. Talk to your pest control advisor about the available materials, especially those that won’t harm beneficial insects.

There are great resources available from the University of California Statewide Integrated Pest Management program. Check out UC IPM’s website for more tips about pests and alfalfa.

Making Dollars and Cents out of Applying Miticides

 Want to keep a few thousand dollars in your pocket? Here’s my money saving tip of the week: Hold off spraying miticides in your cotton fields.

Every year, I see a number of growers trying to get “free ride” by adding miticides to their weed control applications. They figure “why not control weeds and spider mites at one time.” By my estimation, you spend $5,000 to $7,000 for a miticide to cover a 150-acre block of cotton. Save the money.

 

In the past three years, I haven’t seen any significant spider mite outbreaks. Biological controls – meaning natural predators such as six-spotted thrips and big-eyed bugs – can take care of any small threats by mites.

Newly planted habitat of corn, mustard and sunflowers.

Spraying to control weeds takes place during the development of the first node and sixth node on a cotton plant. The most common weeds are crab grass, nut sage and morning glory. To save on labor costs, growers will add a miticide to their weed control spray – thus getting that free ride or a “two-fer” you might say.

Spider mites feed on the leaf surface of a cotton plant, causing the leaves to fall and ultimately affecting yield. There are alternatives to control mites without spending thousands on a miticide application.

Around the borders of the fields, you can water the roads to keep dust down and lessen the disturbance of over wintering mites, which emerge from the soil. We’ve encouraged growers to plant a natural habitat to attract more beneficial insects. I’ve included a list detailing the plants and the corresponding beneficial insects they attract below.                                                                                                    

                                                                   

My message is simple: Why spray if you don’t need to. It makes a lot of dollars and cents.

Extra notes:

Final call to almond growers: Don’t forget our San Joaquin Sustainable Farming Project’s field day Friday from 10 a.m. to noon at Del Bosque Farms on the west side of Firebaugh. The “Almond Doctor,” also known as UCCE Merced farm advisor David Doll, and UC IPM bug expert Walt Bentley will talk about “Almond Practices for Late Spring and Summer.”  Check our SCP website for directions and additional details. See you there.

Planting the Seeds for Biological Pest Management

Plants	Prey	Beneficial Insects
Dill	Aphid, spider mite and many other insects	Aphid midge, aphid parasites, braconid wasp, lacewing, tachinid fly, chalchid wasps, ladybird beetles, mealybug destroyer, spiders, spider mite destroyer, syrphid fly, whitefly, parasitic wasp (Encarsia Formosa)
Mustard	Aphid, armyworm, cabbageworm, codling moth, gypsy moth, European corn, borer, beetle larvae, flies, aphid, caterpillars and other insects	Braconid wasp, aphid midge, aphid parasistes (Aphidius Matricariae and others).
Sweet clover	Aphid	Aphid midge.
White clover	Aphid (see mustard)	Aphid parasites, braconid wasp and chalcid wasps
Yarrow	Aphid, thrips, leafhopper, treehopper, small caterpillars, fall armyworms, sawfly, Colorado potato beetle and Mexican bean beetle.	Spined soldier bug, mealybug destroyer, ladybug, chalcid wasps, damsel bug, braconid wasp and aphid parasites.
Sunflower	Soft-bodied insects, including aphid, thrips, mealybug, scale, caterpillars and mites.	Braconid wasp, damsel bug, lacewing (Chrysopa spp.), ladybug, mealybug destroyer, minute pirate bug, spined soldier bug and whitefly parasitic wasp (Encarsia Formosa).
Buckwheat	Aphid, mealybug, spider mites and soft scales.	Ladybug, minute pirate bug (Orius spp), tachinid fly, chalcid wasps, lacewing (Chrysopa spp), and Braconid wasp.
Corn	Thrips, spider mites, leafhopper, corn earworm, small caterpillars and many other insects	Lacewing (Chrysopa spp), minute pirate bug (Orius spp.)
Fennel	Cutworm, armyworm, tent caterpillar, cabbage looper, gypsy moth,’ some attack sawfly, Japanese beetle, May beetle, squash bug, green stink bug and sow bug.	Braconid wasp, chalcid wasps (many families, including Trichogrammatidae). Ladybird bettle or ladybug, mealybug destroyer, spider, spider mite destroyer, syrphid fly, whitefly and parasitic wasp (Encarsia Formosa).
Sweet alyssum	Spider mites	Spider mite destroyer, tachinid fly, syrphid fly or hover flies.
Alfalfa	Many insects, including other bugs, flea beetles, spite mites, insect eggs and small caterpillars.	Big eye bug (Geocoris spp.), damsel bug and minute pirate bug.
Sorghum	Nematodes.	Parasitic nematodes and buffer zone (insect trap zone).
Black eye beans	A number of insects.	Parasitic wasps.
Valvet beans	A number of insects.	Parasitic wasps.
Suddan grass		Buffer zone (Trap zone)
Cilantro	Aphids, thrips and small caterpillars.	Hover flies, parasitic wasps and tachinid fly.
Radish	Aphids, thrips and worm eggs.	Hover flies and parasitic wasps.

Sustainable Irrigation Blossoming in Cotton

As you drive around the San Joaquin Valley this summer, you might notice something different going on in some of the cotton fields. You might ask, “Where’s the water?”

Well, the answer is simple: It’s underground.

More cotton growers are using subsurface drip irrigation.

I’m seeing more growers turn to subsurface drip irrigation this season – even with the wet winter and spring and the U.S. Bureau of Reclamation boosting water allocations to 80 percent of normal. Still, everyone around here is still conscious of the devastating drought. That’s one reason why a small group of growers see drip as a sustainable way to irrigate.

This year, almost a third of our Cleaner Cotton growers are using drip irrigation in their cotton fields. In 2010, we had only one grower use drip.

Cotton is a good rotation crop for tomatoes, which are irrigated by drip systems. With the buried drip tape already in place, cotton growers don’t have to spend money to install a new system for their cotton crop.

Drip has an advantage over conventional furrow irrigation. It’s more efficient because you can apply water uniformly to all the plants in the field. In the end, you get better boll retention and higher yields while saving on water. With cotton prices still high, growers are looking for every opportunity to increase their profit margins. Expect to see more cotton growers using drip irrigation.

Checking out first true leaf of a cotton seedling.

As I traveled around the Valley last week, I saw cotton plants at first true leaf for about 80 percent of the growers. Expect to see the first nodes in about 10 days. 

 I still haven’t seen any major signs of pest or disease problems. Plants are growing pretty uniformly. This season, growers have planted about 16 to 18 pounds of cottonseed per acre.

 For the coming week, growers should continue to monitor any signs of armyworms migrating from neighboring alfalfa fields into cotton. The pests are easy to spot. Battalions of armyworms will cross ditches and roads any time of the day, moving in a rainbow shape. I’ve seen these pests gobble up plants, leaving a rainbow-shaped path of destruction in a field.

Field Day Alert: Almond growers will want to attend our San Joaquin Sustainable Farming Project’s spring almond field day next week at the Del Bosque Farms on the west side of Firebaugh. “Almond Practices for Late Spring and Summer” will be discussed 10 a.m. to noon on Friday, May 20, and feature UCCE Merced farm advisor David Doll, UC IPM entomologist Walt Bentley and Kevin Parkinson, SJSFP field scout. We have applied for 1.5 hours of CE credits.

 I will join our SCP staff at the event to learn about orchard monitoring and management tips from some of the state’s leading almond experts. Check our SCP website for directions and additional details.

Around the Cotton Growing Season in 180 Days

For the next six months during the cotton-growing season, I’ll be giving you my view from the ground around the San Joaquin Valley.

First True leaf of cotton seedling.

Well, it’s nice to see cotton plants finally emerging. I’ve seen seedlings of 1 to 2 inches. The crop emergence is good all around with stands uniform with few skips. I expect to start seeing plants entering the first true leaf stage this week.

 To determine if your crops is growing satisfactory, check out the University of California Statewide Integrated Pest Management website about assessing stand development.

 In the past week, a number of growers turned their attention to making sure the cotton beds retain moisture.

The windy weather late last week – with gusts of up to 35 mph – had growers concerned about the ground drying and causing surface cracks.  I saw growers rolling their cotton beds to seal any cracks and create a moisture barrier.  Water is always a precious commodity around here. With diesel prices hovering around $4.50 a gallon in the Valley, some growers are monitoring their fields for the time being and waiting before the right time to roll their beds.

UC IPM photo by Jack Kelly Clark

At this time, everyone is keeping an eye out for any signs of seedling diseases such as Pythium disease. UC IPM also offers information about  seedling diseases.

 On the bug front, I haven’t seen signs of worm pressure in the cotton fields after the first cutting of alfalfa this season. This week, growers should keep an eye out for worms and mites. So far, so good.