Beneficial Of The Month: Bt

Beneficial Of The Month: Bt

Classification And Utility

Bt is one of the most common microorganisms used in biological control of certain insects. Bt is a rod-shaped bacterium that produces protein toxins lethal to many pest species, including caterpillars, beetles, and mosquito larvae. These toxins are harmless to humans, birds, and other beneficial wildlife.

Biological Specs

Various Bacillus thuringiensis (Bt) strains occur naturally in soil and on plant leaves. Literally thousands of Bt strains exist within the various Bt subspecies. Each individual strain produces its own insecticidal protein toxin mix targeting specific groups of pests. There are more than 80 different subspecies of Bt, but the following are used commercially:
Bt kurstaki — caterpillar control
Bt aizawai — caterpillar control with specific activity on armyworms
Bt tenebrionis — beetle larva control
Bt israelensis — mosquito, black fly, and fungus gnat control

Commercial Bt products contain endotoxin crystals or a mixture of crystals and Bt spores. In insects, the toxin acts as a selective stomach poison. Spores contribute to their toxicity by causing blood poisoning and providing environmental persistence.

When an insect pest ingests Bt toxins from treated leaves, feeding stops within minutes after the crystals are solubilized in the gut and gut cells are damaged. After toxin damage to the gut occurs, spores enter through the gut wall and germinate rapidly in the body cavity causing blood poisoning. Larvae stop feeding within minutes and die in one to three days. Smaller larvae die more quickly, so precise timing can measurably improve the performance of the application.

Beneficial Activity

Traditional chemicals and Bts both have a place in a grower’s toolbox for worm control. Bts can control lepidopteran pests just as traditional chemicals, but also provide added benefits. Some benefits of Bt insecticides include:

- Low impact on beneficial insects
– Not toxic to bees, predatory mites
– Avoidance of secondary pest issues
– No preharvest interval required after application
– No restrictions on use
– Resistance is slower to develop than resistance to chemicals.

Grower Options

Rotating formulations will help in warding off resistance problems. Through proper scouting and application of the appropriate Bt insecticides at strategic points in the crop season growers can reduce reliance on traditional chemicals and often improve their control program.

Some pest species are difficult to control with toxin alone. Germinating Bt spores provide an additional control mechanism. Spores germinate in the midgut and spread throughout, ultimately causing death of the target insect.

This effect is especially apparent in armyworm larvae, which can be difficult to control with toxin alone.

Since different species have different susceptibilities to Bt toxins and different Bt products have different profiles of these toxins, it is important to match the Bt insecticide to the pest being targeted.

Leave a Reply

Featured Stories
Biocontrols 2015 Conference
CitrusGrowers Go In-Depth At Biocontrols 2015 Conference & Tradeshow
March 9, 2015
The first-of-its-kind event brought growers, researchers, regulators, and suppliers together for a two-day discussion on the latest biocontrols tools and technologies. Read More
Crop ProtectionAt Paramount Farming, Mating Disruption Pays Off
February 10, 2015
To say Brad Higbee is an expert in mating disruption, the use of pheromones to confuse target pests and reduce Read More
Crop ProtectionGrower Experienced In Biocontrols Says: Be Patient
February 4, 2015
The use of biocontrols in all aspects of agriculture is becoming more widespread. But incorporating biocontrols in a vegetable farming Read More
FruitsSounding Off On GMOs: The Arctic Apple Decision
March 27, 2015
Industry leaders share their feelings on the recently approved genetically modified apples. Read More
BerriesBuilding A Better Black Raspberry
March 27, 2015
Studies focusing on consumer preference, aphid resistance, heat tolerance, and genetics aim to capitalize on an expanding market. Read More
CitrusMore California Citrus Placed Under Psyllid Quarantine
March 27, 2015
Asian citrus psyllid is found in Madera County – the heart of the San Joaquin Valley. Read More
FruitsAhead Of The Curve, Part 2
March 27, 2015
Get educated with great resources in the tree fruit industry available at your fingertips. Read More
Apples & PearsMeet USApple’s Class of 2015 Young Apple Leaders
March 27, 2015
Young decision-makers see trip as an opportunity make sure the voice of the apple industry is heard by representatives. Read More
GrapesGlassy-Winged Sharpshooter Found In Marin County
March 26, 2015
This pest, known to spread Pierce’s Disease, could devastate California winegrapes. Read More
GrapesFirst Raisin Grape That Dries Naturally On Vine Developed
March 26, 2015
The new Sunpreme variety eliminates the need for growers to cut into woody canes before harvest. Read More
Fresh From Florida Strawberry Parfait recipe
BerriesNew Partnership Sends Florida Strawberries To Puerto Rico
March 26, 2015
Latest addition extends Sunshine State’s agricultural export reach in the Caribbean. Read More
drought management; irrigation; water management
FruitsHow To Become A Soil Sleuth
March 26, 2015
To correctly apply the proper nutrients at the right rates, you need to know where your fields are deficient and how to correctly diagnose a disorder. Read More
NutsWhy You Should Use Low-Rate Applications Of Potassium
March 26, 2015
These rates provide growers a low-cost method comparable to conventional applications. Read More
The Latest
FruitsSounding Off On GMOs: The Arctic Apple Decision
March 27, 2015
Industry leaders share their feelings on the recently approved genetically modified apples. Read More
BerriesBuilding A Better Black Raspberry
March 27, 2015
Studies focusing on consumer preference, aphid resistance, heat tolerance, and genetics aim to capitalize on an expanding market. Read More
CitrusMore California Citrus Placed Under Psyllid Quarantine
March 27, 2015
Asian citrus psyllid is found in Madera County – the heart of the San Joaquin Valley. Read More
FruitsAhead Of The Curve, Part 2
March 27, 2015
Get educated with great resources in the tree fruit industry available at your fingertips. Read More
Apples & PearsMeet USApple’s Class of 2015 Young Apple Leaders
March 27, 2015
Young decision-makers see trip as an opportunity make sure the voice of the apple industry is heard by representatives. Read More
GrapesGlassy-Winged Sharpshooter Found In Marin County
March 26, 2015
This pest, known to spread Pierce’s Disease, could devastate California winegrapes. Read More
GrapesFirst Raisin Grape That Dries Naturally On Vine Develop…
March 26, 2015
The new Sunpreme variety eliminates the need for growers to cut into woody canes before harvest. Read More
Fresh From Florida Strawberry Parfait recipe
BerriesNew Partnership Sends Florida Strawberries To Puerto Ri…
March 26, 2015
Latest addition extends Sunshine State’s agricultural export reach in the Caribbean. Read More
drought management; irrigation; water management
FruitsHow To Become A Soil Sleuth
March 26, 2015
To correctly apply the proper nutrients at the right rates, you need to know where your fields are deficient and how to correctly diagnose a disorder. Read More
NutsWhy You Should Use Low-Rate Applications Of Potassium
March 26, 2015
These rates provide growers a low-cost method comparable to conventional applications. Read More
Cold ProtectionWind Machine, Electric Pruners Donated To MSU Research …
March 25, 2015
New equipment to help protect research blocks from frost damage and provide center with latest technology. Read More
CitrusProposed Farm Bill Provision To Limit Payments To Non-F…
March 25, 2015
USDA has proposed a new rule which would limit payment to those who are only actively engaged in farming. Read More
Pennsylvania hard cider guild logo
Apples & PearsPennsylvania Hard Cider Producers Founded Independent T…
March 25, 2015
The Pennsylvania Cider Guild is designed to help promote and educate members and consumers. Read More
FruitsHow To Get Started With Partnerships And Sponsorships
March 25, 2015
Mark Saunders of Saunders Farm says your business is never too small or too big to get more value for what you do on your farm. Read More
FruitsValue Through Partnerships And Sponsorships [Opinion]
March 25, 2015
Mark Saunders of Saunders Farms says admission is one way to get value for what you do, but sponsorships and partnerships are the next level. Read More
chateau hough urban vineyard Cleveland Ohio
GrapesFrom Riots To Vineyard — A Story of Urban Revival
March 25, 2015
Ex-convict’s inner-city vineyard in the Hough neighborhood in Cleveland an opportunity for those leaving incarceration for a bright future in viticulture. Read More
FruitsWorld Ag Expo 2015: New Tools For Fruit Growers
March 24, 2015
From wind machines to solar-powered pumps, here is some of the new equipment on display this year's edition of the nation's largest farm show. Read More
Apples & PearsNeedles Found In Honeycrisp Sold At Grocery Store
March 24, 2015
Apples were believed to be tampered with; initial surveillance footage was inconclusive. Read More