Kern County Vegetable Crops

September 2020

UCCE Kern Vegetable Crops Program during COVID 19

Over the past several months COVID-19 has impacted a lot of people in the United States and globally

and led to an unprecedented social, economic, and public health crisis. Although agriculture is an

essential industry and we need it more than ever to maintain the food supply chain, it is also coping with

the challenges posed by COVID-19. Like many other agriculture sectors, University of California

Cooperative Extension, Kern County has continued research and extension activities with safety

guidelines in place

Our team has been busier than ever supporting over 15 projects while keeping all safety measures in

place. Several spring projects such as the potato variety trial, carrot variety trial, potato southern blight

fungicide trial, Melon nematicide screening trial were harvested for data collection and several other

studies such as the carrot herbicide trial, carrot, and tomato nematicide screening trials, garlic fusarium

trial, studies are on-going. In addition to that, we have also continued the diagnostic services for growers

and stakeholders in Kern County. Unfortunately, we had to forego the traditional field days and local

meetings this year but we are still committed to sharing our research and reaching out to our

stakeholders. Here is some brief information about the trials this year and I will be sharing the research

findings in the upcoming months.

1. Potato Variety trial: The potato variety trial is

conducted every year on a grower’s field and this

year the trial was harvested in June. Usually, the

trial is followed by a field day that showcases the

tubers of potential new varieties, how they

performed this year, and how they performed

compared to standard varieties. For a full report

and details on the trial, please click on the link

below.

https://ucanr.edu/sites/Kern22/files/330232.pdf

2. Potato southern blight fungicide trial: Southern blight caused by Sclerotium rolfsii (recently

renamed as Athelia rolfsii), has been causing increasing problems for vegetables, including

potatoes. There are no California registrations for potato fungicides which include control of

southern blight on the label. Some California potato fungicides such as azoxystrobin or others

may provide some benefit, but do not seem to be

highly effective. Information is lacking about the

efficacy of these fungicides for control of southern

blight under California conditions. This project

evaluates fungicides for efficacy in southern blight

control in a field trial and to optimize the timing of

fungicide application.

3. Garlic Fusarium fungicide screening trial:

Clove rot caused by Fusarium proliferatum is an

emerging post-harvest disease on garlic. The

occurrence of clove rot during drying, conditioning,

and storage can result in losses of up to 30% in

harvested bulbs. The bulbs may show no visible

disease symptoms in the field but rot can progress

on harvested bulbs in storage. Management of garlic

clove rot is challenging due to lack of garlic

varieties with resistance to clove rot and limited

information on the efficacy and timing of chemical

treatments. The purpose of this field trial is to screen

fungicide for their efficacy against F. proliferatum

in garlic and to optimize the fungicide application

timings.

4. Nematicide screening trial; Carrots, tomatoes,

and melons

Root knot nematodes (RKN), Meloidogyne spp. are

the most important plant-parasitic nematodes

affecting several crops such as melons, carrots, and

tomatoes in California. In the past, RKN

management has mainly relied on the use of pre-

plant soil fumigants and soil-applied nematicides.

Management with these products is expensive and

involves safety and environmental risks.

Alternative control options that have high efficacy,

are economically viable and environmentally safe

are evaluated under field situations. It is imperative

to have alternative chemistries available to avoid

the development of nematicide resistance. An over-

reliance on any one particular nematicide product

would likely lead to a loss of that product. In 2020

we are evaluating various products such as Nimitz,

Salibro, and Velum for conventional agriculture

and several products for organic production

systems.

5. Carrot variety trial: The Kern County carrot variety

trial is conducted every year at a grower’s field in

Kern County. Common standard carrot varieties

used by the California carrot industry are grown

alongside the newly released carrot varieties and

potential new carrot varieties for release. For a full

report please click on the link below.

https://ucanr.edu/sites/Kern22/files/330849.pdf

6. Biological fungicide screening in cavity spot in

carrots: We continue to maintain the cavity spot

nursery at the Shafter Research Farm to screen for

cavity spot resistance and fungicides. We are

screening biological products like AGN, DN, and

Serenade in 2020 to help address the needs in

organic production of carrots.

7. Herbicide screening in carrots: Weeds are a

persistent problem for carrot production. Carrots

are sensitive to weeds and are poor competitors.

Herbicides are essential for carrot production as

high-density planting limits the use of mechanical

options. Therefore, carrot growers have long relied

on herbicides like trifluralin and linuron.

New regulatory restrictions along with loss of crop

tolerances and costly environmental monitoring

studies may lead to the loss of some really good

herbicides. Weed control in carrots will require

control options if some of these herbicides are

phased out. We are evaluating ten pre-emergence

and post-emergence herbicides in this trial for

safety and weed control in carrots.

8. Stop-the-rot: Combating onion bacterial diseases

with pathogenic tools and enhances management

strategies

This is a USDA project to research onion bacterial

bulb diseases in collaboration with 3 researchers

from California and a larger group of researchers

from 11 other states. This past onion season, we

surveyed some commercial onion fields for

diseased samples, and this coming season, we’ll

establish field trials to evaluate management

methods. I will be looking for affected onion fields

again in the spring/early summer of 2021.

Diagnostic highlights: Some of the issues that I encountered frequently this year included Phytophthora

in watermelons, Southern blight in several crops, Fusarium spp. in several crops, bacterial rots in

onions, soft rot and Scab in potatoes, etc.

Jaspreet Sidhu, Farm Advisor

Vegetable Crops jaksidhu@ucanr.edu

Cell 661-304-8870 Office 661-868-6222

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