Plants Act As Crop Protectants

Cover Crops

One of the reasons growers use Brassica cover crops is to help defend vegetables against abiotic stress, such as flooding, as well as biotic stress, which includes attacks from insects and disease.

Drilling down to the technical aspects, these cover crops produce glucosinolates (sulphur containing substrates), which are secondary metabolites used by plants to guard against biotic and abiotic stress. Glucosinolates are broken down by thioglucosidase (myrosinase) enzymes, which are the enzymes that catalyze the chemical reaction.

These cover crops, which include oilseed radish, brown mustard, oriental mustard, yellow mustard, turnip, and rapeseed, release enzymes when tissue is damaged or there is an attack from insects or pathogens, triggering the breakdown reaction that is sometimes referred to as the “mustard bomb.” Because of the ability of Brassica species to produce these volatile toxic compounds, Brassica cover crops are referred to as biofumigants.

When managed properly, biofumigants can help reduce the populations of nematodes, weeds, and diseases. Some tips presented here will help maximize the benefits of biofumigants. Also included are some pointers on practices to avoid during biofumigation.

Tips For Efficient Biofumigation

1. Species and cultivar selection. Use a species or cultivar with high glucosinolate content, and be aware that mustard cover crops vary in their glucosinolate content.  

2. Biomass production. Maximize biomass production by using appropriate seeding rate, method, and timing. Note that high seeding rates may actually result in low biomass production due to plants competing for the same resources.  

3. Tissue break- down. Break down plant tissue to trigger the chemical reaction. A flail mower will do an excellent job.

4. Soil moisture. Adequate soil moisture is critical during cover crop incorporation. Efficacy of biofumigation is reduced significantly when the cover crops are incorporated into dry soil. If necessary use overhead irrigation about 12 hours before integrating the cover crop.

5. Residue incorporation. Be sure to add the residue immediately as most of the breakdown products are volatile.

Depending on soil conditions, a roto-tiller or multiple passes of a disk can be used to incorporate residue.

6. Soil surface sealing. Seal the soil surface (with irrigation or a packer if possible). In plasticulture systems, lay the plastic immediately after cover crop has been added. The combined effects of biofumigation and anaerobic soil disinfestation may be achieved with the use of plastic mulch.

7. Plant-back period. Brassica cover crop residue is toxic. Avoid planting susceptible crops shortly after Brassica cover crop incorporation. This is especially important for small seeded crops that are direct seeded. It is important to note that severe injury has been reported on transplants. Observe a cash crop plant-back period of at least two to three weeks (depending on the crop).

What To Avoid During Biofumigation

1. Avoid rotation with other Brassica species. There are several reasons to avoid this practice:

Brassica species do not form mycchorizae. Therefore, monoculture practices could reduce mycchorizae in the soil.

An increase in cabbage maggot populations has been observed in some growing conditions after Brassica cover crops. This could negatively affect Brassica cash crops.

Flea beetles are attracted by Brassica cover crops and may increase the risk of crop injury if Brassica cash crops are a component of the cropping system. It is noted that yellow mustards with hair-like structures, Ida Gold being one, are less attractive to flea beetles than Oriental mustards or oilseed radish.

2. Avoid volunteer cover crops. Viable seed formation by the cover crops could result in serious weed problems with volunteers. Drilling the cover crops (as opposed to broadcast and incorporation) will also reduce the risk of volunteers. 

Disponible en español aqui.

Leave a Reply

Featured Stories

IrrigationCalifornia Growers Sue State Over Drought
October 30, 2014
They claim the State Water Resources Control Board illegally denied water deliveries. Read More
CucurbitsNew Watermelon Planting Program For The Southeast U.S.
October 30, 2014
Sakata seeking to make regional impact by providing in-demand material through several local producers. Read More
Leafy Vegetables3 Can’t-Miss Cabbage Varieties For Florida Growers
October 30, 2014
Reed's Seeds highlights a trio of high-performance selections for Sunshine State producers. Read More
Insect ControlTake Control Of Thrips In Your Greenhouse
October 30, 2014
Why such a foreboding title? Thrips, one of the tiniest pests of greenhouse crops, are the carrier of one of Read More
BerriesManage Black Root Rot Of Strawberry
October 30, 2014
Controls include preplant nematode analysis, three-to-five year crop rotations, and more. Read More
FruitsSexual Evolution May Bear More Fruit In The Orchard
October 30, 2014
Scientists take a closer look at genes and find new plant breeding possibilities. Read More
Apples & PearsWashington Apples To Restart Shipments To China
October 29, 2014
Agreement reached between U.S. and Chinese governments to reinstate market access after two-year absence. Read More
EquipmentEnter To Win A Kubota At The Washington State Horticultural Association Annual Meeting
October 29, 2014
Attendees have a chance to take home a new utility vehicle courtesy of Wilbur-Ellis and Western Fruit Grower. Read More
CitrusUSDA To Provide $4 Million For Honey Bee Habitat
October 29, 2014
The funds will go toward helping growers implement conservation practices to improve honey bee health. Read More
FruitsHuge California Drought Meeting Planned
October 29, 2014
State, federal officials to meet as forecasts for the coming year look bleak. Read More

The Latest

IrrigationCalifornia Growers Sue State Over Drought
October 30, 2014
They claim the State Water Resources Control Board illegally denied water deliveries. Read More
CucurbitsNew Watermelon Planting Program For The Southeast U.S.
October 30, 2014
Sakata seeking to make regional impact by providing in-demand material through several local producers. Read More
Leafy Vegetables3 Can’t-Miss Cabbage Varieties For Florida Grower…
October 30, 2014
Reed's Seeds highlights a trio of high-performance selections for Sunshine State producers. Read More
Insect ControlTake Control Of Thrips In Your Greenhouse
October 30, 2014
Why such a foreboding title? Thrips, one of the tiniest pests of greenhouse crops, are the carrier of one of Read More
BerriesManage Black Root Rot Of Strawberry
October 30, 2014
Controls include preplant nematode analysis, three-to-five year crop rotations, and more. Read More
FruitsSexual Evolution May Bear More Fruit In The Orchard
October 30, 2014
Scientists take a closer look at genes and find new plant breeding possibilities. Read More
Apples & PearsWashington Apples To Restart Shipments To China
October 29, 2014
Agreement reached between U.S. and Chinese governments to reinstate market access after two-year absence. Read More
EquipmentEnter To Win A Kubota At The Washington State Horticult…
October 29, 2014
Attendees have a chance to take home a new utility vehicle courtesy of Wilbur-Ellis and Western Fruit Grower. Read More
CitrusUSDA To Provide $4 Million For Honey Bee Habitat
October 29, 2014
The funds will go toward helping growers implement conservation practices to improve honey bee health. Read More
FruitsHuge California Drought Meeting Planned
October 29, 2014
State, federal officials to meet as forecasts for the coming year look bleak. Read More
PotatoesNew CEO At Black Gold Farms, A Top 100 Grower
October 28, 2014
Eric Halverson takes the reins at the potato operation, while his father Gregg will remain president of the farm’s board of directors. Read More
FruitsValent U.S.A., MGK Enter Into Marketing Agreement
October 28, 2014
Valent U.S.A. to manage the marketing and sales of MGK’s crop protection line of insect control products beginning in April 2015. Read More
VegetablesMultistate Land-Grant University Research Project Contr…
October 28, 2014
The project began in the 1970s as a Regional Initiative and has since expanded Internationally. Read More
FruitsMichigan State Offers Online Database Of Tree Fruit Dis…
October 28, 2014
Search engine helps growers identify several issues in the orchard. Read More
Stone FruitStudy Examines How To Keep Sweet Cherries Fresh
October 28, 2014
Canadian researcher says cooling of sweet cherries is key to delivering a quality product. Read More
Protected AgricultureLED Lighting Symposium To Be Held At University Of Ariz…
October 27, 2014
Event to focus on LED lighting technologies for specialty crop production. Read More
Cucurbits11 Cool Cucurbits For Florida’s Climate
October 27, 2014
Leading vegetable seed companies highlight high-performance selections for growers in the Sunshine State. Read More
CitrusModern Agriculture Is A True Centerpiece Of Thanksgivin…
October 27, 2014
FFAA's Mary Hartney says take time during this holiday season to give thanks where thanks is due. Read More