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Agronomist Update: Planning for 2019 CA Vegetable Production

October 24, 2018
This agronomic image shows watermelon.

Recognizing, understanding and managing potential yield threats is crucial to maximizing marketability. At this year’s CAPCA Conference, we brought in our agronomists Garrett Gilcrease and Christine May to provide insights on key insect and disease pests from the 2018 season and how to manage them during the 2019 season.

Leafy Vegetables

What were the most damaging insects in leafy vegetables this year?

Thrips, aphids, and lepidopteran pests are always top of mind for Pest Control Advisers (PCAs).

What products stood out the most to control these pests?

For lepidopteran pests, a good choice would be Besiege® or Proclaim® insecticide. If you have thrips pressure, Minecto® Pro insecticide is a rotational option with other commonly used thrips products, especially when there are other pests present, such as lepidopterans and leafminers. It’s also a best practice to rotate chemistries for resistance management purposes. 

What practices do you recommend for controlling thrips?

Using Minecto Pro in rotation with other commonly used thrips products will help you manage thrips and resistance threats. Minecto Pro has a good fit early in the season when thrips are present at low populations and when other insects, including leps, leafminers and whiteflies, are also present.

Have you seen downy mildew in leafy fields this season?

Downy mildew is always top of mind for PCAs when scouting. But, downy mildew pressure has been intermittent over the past year. There were times when it was heavy and times when it wasn’t. Weather and changes in cultural practices can be factors. PCAs are always scouting and applying products preventively in a program throughout the season.

How can growers manage this disease?

They should use a preventive approach whenever possible and stay on a program. Always scout for downy mildew in case it breaks early or weather conditions cause pressure to build. There are many good products available for downy control, such as Revus® and Orondis® Ultra fungicides, which are a mixture of oxathiapiprolin and mandipropamid, the active ingredient in Revus. Both products can be used in the same spray program. Another product that is used early in some leafy and spinach crops is Actigard® plant activator, as it can help protect the plant from downy pressure.

Are there other disease issues growers should monitor for?

Yes, other diseases of importance in leafy vegetables are Sclerotinia (or lettuce drop), Pythium, and powdery mildew, which is rarely an issue but has become more of an interest lately. Sclerotinia can be controlled by our product Cannonball® fungicide, and when we get registration of Miravis® Prime fungicide in CA, it looks like it will be a good choice for Sclerotinia control. Pythium (or damping off) can be prevented with a Ridomil Gold® SL fungicide application early and preventively. Other difficult diseases to watch for that don’t currently have a crop protection solution are: Fusarium wilt, Verticillium wilt, black root rot, and INSV (Impatiens Necrotic Spot Virus) which is vectored by thrips.


Cucurbit Vegetables

Has drought affected which insects were present in CA cucurbits this year?

Yes and no. In one sense, surrounding weeds and brush will dry down faster, thus moving the insects into fields. But on the other hand, the fact that we had less water this year made the amount of brush and surrounding vegetation much less than in previous years. The later rains we had were the most impactful. We came in at around 7” inches of rainfall, which is about 2 below normal, but most of it came later in the year. This allowed for the existing brush to be there longer, and we ended up having high but irregular pressure.

What diseases should growers be scouting for?

Throughout the year it really depends on the crop, but primary concerns are powdery mildew, downy mildew and late blight.

How do they identify each one?

All of these are really timing dependent, with downy coming in early if planted during the spring, when wet, warm temps are present. Then powdery comes in when temps rise, but relative humidity drops. Later on when temps go down and dew becomes more present, downy and late blight come in and can be real issues.


Fruiting Vegetables

There was high thrips pressure in CA tomatoes this year. Do you see them being an issue in 2019, too?

If it’s anything like this past year, I would say yes. We had a weird spring, in that it was warm but still had cooling periods throughout, with short stretches of heat. This was long enough to dry up the surrounding vegetation and wake up the thrips, but was not hot enough to knock back some of the numbers. We then had this prolonged hatch that just kept coming.

What products do you recommend for controlling thrips?

Minecto Pro for suppression.

Brown marmorated stink bug populations are increasing in CA and can cause damage to tomato crops. What are your recommendations to manage this pest?

This is a real issue in some areas, and can really devastate tomatoes and cucurbits. I would say coverage is really key here. There are many chemistries which are very efficacious, but getting the active ingredients to the pest is very tough; more so when you have a large canopy. It really takes getting the numbers low for you to get coverage, and then using combinations of high gallonage, air shear technology sprayers and hollow cone nozzles to get the best control.

What diseases posed issues for fruiting veg this year?

Same as cucurbits (powdery mildew, downy mildew and late blight, with the addition of black mold. Black mold really targets tomatoes in the later season, especially late season tomatoes. They are just so tough to keep clean for all of the above reasons, such as temperature changes, dew and the chance of rain.

Has this changed over time?

Yes, it really has in terms of black mold. Chlorothalonil was the main active ingredient used, but it has been in such short supply over the past 5 years that it is tough to get. So seeking alternative chemistries such as Azoxystrobin are going to be key to keeping black mold under control.

The above reflects several key considerations as you look to build your management plan for next year’s vegetable crops. For more insights, reach out to your Syngenta agronomist.

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