Drought May Cause Pest Migration To California Cucurbit Crops

The drought may stop the spread of some plant diseases in California this year, but what some growers and researchers are finding is the insects that typically feed in weedy areas and pastures moved to cropping areas earlier in the season as the weedy areas have dried up.

Looking for new places to feed, these insects migrate from the non-crop areas to crops, transmitting viruses and disease along the way.

To mitigate losses, as shown here and above with the deformed squash and  yellowed leaves, scout your fields so you can take action to reduce pest populations.   Photo courtesy of Steve Koike
To mitigate losses, as shown here and above with the deformed squash and yellowed leaves, scout your fields so you can take action to reduce pest populations.
Photo courtesy of Steve Koike
“Everyone knows that California dries up this time of year anyway, but this has happened earlier with the drought,” says Steve Koike, plant pathology farm advisor, with University of California Cooperative Extension, Monterey County. “I think with the early drying of the whole state of California, all the insects that sometimes have the viruses in them are fleeing the dry areas early and going to the crops. As a result, we are seeing some early virus issues.”

Viruses Of Cucurbits
Viruses that typically impact cucurbit crops such as watermelon, squash, pumpkin, and cucumbers include cucumber mosaic virus, papaya ringspot virus, watermelon mosaic virus, and zucchini yellow mosaic virus. All of these are aphid vectored viruses. California also gets some squash mosaic virus which is spread by the spotted cucumber beetle, Koike adds.

The final malady seen periodically out West is the curly top virus, which is vectored by leafhoppers. This disease impacts cucurbits and a host of other crops.

Koike points out that it is very difficult to distinguish the symptoms of the different viruses. He adds, however, that in most cases, growers know that on all cucurbits, these viruses cause leaf deformities and discoloring of the foliage. Plus the fruit, although edible, is completely unmarketable.

“The fruit have bumps and are misshapen,” he says. “They are very much edible but not marketable because of how they look. Unfortunately, once the plant is infected, the grower can’t do anything to correct the problem.”

Infected But Productive
All is not lost, though. In some cases, the plant can be productive, and the fruit can be marketable, depending on when the insects fed on the plant.

“You may have a virus that causes the leaves to become yellow and deformed but you still get zucchini fruit, for example, that look pretty normal,” Koike says. “You have to observe what is happening with the crop because you may be able to still get fruit off the plants.”

It is a timing issue, he says, as growers can continue to harvest until they see that the fruit are no longer usable.

“These viruses are all systemic so they eventually move to all parts of the plants,” Koike explains. “Once that happens, and if it is a fruit deformity type virus, all the fruit will start showing deformities.”

Employ IPM Tactics
Koike advises growers to keep up with a sound IPM spray program keeping the viruses in mind, but warns that even though you have sprayed for the insect, whether it is aphid, beetle, or thrips, it doesn’t mean your plants are completely protected from the virus.

“It takes the insect anywhere from 30 seconds to 5 minutes to inject the virus,” he explains. “So the insect pest can feed for a brief amount of time, inject the virus, infecting the plant, but the insect then dies because you sprayed it. We know from research that vector control does not prevent diseases. However, the grower should still manage the vector.”

To further reduce the incidence of disease and virus pressure, Koike encourages growers to manage weeds and vegetation around cucurbit fields. He also says for growers who have the luxury of site selection, and are in an area that is at high-risk for viruses, to consider moving the cucurbits to another field. “Put your radishes in that field and put your squash someplace else where it is less of a risk,” he adds.

In the end, however, by paying close attention to what is occurring in your fields, you will be able to mitigate losses by keeping up with an IPM program and correctly identifying the insects and symptoms of viruses.

Topics: ,

Leave a Reply

Cucurbits Stories
Belmont watermelon from Sakata
Cucurbits
October 27, 2016
9 Melon Varieties To Keep In Mind
View some of the latest watermelon and cantaloupe varieties making an impact on the market. Read More
This worker is in the process of grafting watermelon. 
Photo credit: Tri-Histil
Crop Protection
October 25, 2016
Vegetable Grafting Facility Gears Up For Increased Production
The Tri-Hishtil vegetable grafting facility in North Carolina hopes to double grafted plant production by next year. Read More
Adult whitefly is feeding on a tomato leaf. Photo credit: Saioa Legarrea, University of Georgia.
Cucurbits
October 8, 2016
Georgia Whitefly Populations Explode, Troubling Vegetable Growers
Researcher says growers must be up-to-date on spray programs. Read More
CBP officers working at the Otay Mesa cargo
port of entry Oct. 2 discovered almost
3,100 pounds of marijuana hidden inside a shipment of cucumbers.
Photo courtesy of  U.S. Customs and Border Protection
Cucurbits
October 8, 2016
3,100 Pounds Of Marijuana Hidden In Cucumbers Confiscated
U.S. Customs and Border Protection made the discovery at the Otay Mesa cargo port in California. Read More
The striped cucumber beetle is a vector of the bacterial wilt pathogen.     
Photo credit: Gerald Holmes
Crop Protection
October 3, 2016
Take Control Of Cucumber Beetles
Tactics to manage the pest of cucurbits include proper scouting, trap cropping, plus cultural and chemical controls. Read More
34-749-rz
Cucurbits
September 25, 2016
10 Cantaloupe And Melon Varieties You Need To Know
Browse this slideshow for more information on 10 cantaloupe and melon varieties you need to know about from the nation’s leading Read More
white grubs
Cucurbits
September 21, 2016
Don’t Let White Grubs Gobble Up Your Vegetable Crop
Learn how to identify, the survival and spread, as well as management methods for this pest. Read More
The Latest
Crop Protection
November 30, 2016
The Effect Of Soil Fertility On Fusarium…
Ongoing research sheds light on the role soil health plays in the severity of the deadly pathogen. Read More
Crop Protection
November 8, 2016
The Effect Of Soil Fertility On Fusarium…
Ongoing research sheds light on the role soil health plays in the severity of the deadly pathogen in watermelon crops. Read More
Cucurbits
October 31, 2016
7 Squash And Cucumber Cultivars To Consi…
Get the lowdown on several of the latest varieties making a name for themselves in the marketplace. Read More
Cucurbits
October 27, 2016
9 Melon Varieties To Keep In Mind
View some of the latest watermelon and cantaloupe varieties making an impact on the market. Read More
Crop Protection
October 25, 2016
Vegetable Grafting Facility Gears Up For…
The Tri-Hishtil vegetable grafting facility in North Carolina hopes to double grafted plant production by next year. Read More
Cucurbits
October 8, 2016
Georgia Whitefly Populations Explode, Tr…
Researcher says growers must be up-to-date on spray programs. Read More
Cucurbits
October 8, 2016
3,100 Pounds Of Marijuana Hidden In Cucu…
U.S. Customs and Border Protection made the discovery at the Otay Mesa cargo port in California. Read More
Crop Protection
October 3, 2016
Take Control Of Cucumber Beetles
Tactics to manage the pest of cucurbits include proper scouting, trap cropping, plus cultural and chemical controls. Read More
Cucurbits
September 25, 2016
10 Cantaloupe And Melon Varieties You Ne…
Browse this slideshow for more information on 10 cantaloupe and melon varieties you need to know about from the nation’s leading Read More
Cucurbits
September 21, 2016
Don’t Let White Grubs Gobble Up Yo…
Learn how to identify, the survival and spread, as well as management methods for this pest. Read More
Crop Protection
September 6, 2016
Purdue Entomologist Receives USDA Grant …
The goal of the research team is to help growers of cucurbits achieve effective pest control while protecting honeybees and other beneficial pollinating insects. Read More
Cucurbits
July 22, 2016
California Cantaloupe Growers To Celebra…
The Golden State’s cantaloupes are now in peak production from major areas in the San Joaquin Valley. Read More
Cucurbits
July 21, 2016
Study Shows Buckwheat Can Help Stifle Sq…
Unique cover crop choice attracts beneficial bugs, increasing pollination prospects and reducing insect threats. Read More
Crop Protection
July 18, 2016
Early Infection Of Downy Mildew Confirme…
The pathogen has been confirmed in Michigan cucumbers in Bay County for the 2016 season. Read More
Cucurbits
July 18, 2016
21 Pumpkin Varieties You Need To Know
Leading seed breeders and distributors highlight some of the latest pumpkin varieties available.   Read More
Cucurbits
June 14, 2016
Worry Spreading In Florida Over Exotic W…
UF/IFAS expert warns species likely to cause problems for growers. Read More
Cucurbits
June 2, 2016
23 Top-Notch Watermelon Varieties
Take a look at this slideshow for more details on watermelon varieties from the nation’s leading seed breeders and distributors. Read More
Cucurbits
May 25, 2016
Whitefly Threat Has Florida Growers On H…
Researchers, state agencies working together to prevent a potential outbreak. Read More