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Greenbug

CROPS IMPACTED: wheatgrass, oats, barley, rice, wheat, maize, sorghum

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Family: Aphididae

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About Greenbug

Reproduction and Life Cycle

If the greenbug is present in mild or warm climates, they are capable of reproducing without the need to mate. In this case, the female will directly produce the nymphs, skipping the egg stage of development. In areas that have cold winters, males and females will mate, at which time the female will overwinter her eggs so that they can hatch into nymphs when it warms up in the spring. A female can produce up to 5 nymphs each day for up to 2 weeks. The nymphs go through 3 instars. This will take anywhere from 7 to 9 days to complete, as long as temperatures from 60 to 80 degrees Fahrenheit are reached.

Greenbug Identification and Habitat

Identification

Adult greenbugs can be yellow or a bright green colour. They are small, usually between 1.3mm and 2.1mm, and are elongated oval shapes. They are an aphid type, with its head and thorax a light green and a slightly greener abdomen. The adults have a dark green stripe located on its abdomen in the center. Greenbugs have cornicles that are also light in colour, and are somewhat flared with black tips; their legs also have these dark tips. There antennae are often a longer length than their body; however, sometimes they can be the same length. Female adults can have wings, but have also been found to be wingless. Usually when host plants begin to die off, greenbugs will develop wings so that they can disperse themselves and find more viable food.

Habitat

The greenbug has been an identified pest in Central, South, and North America, Africa, Europe, Asia, and the Middle East. For more than 150 years this pest has caused grievances for small grain farmers. These small grain plants can handle a sizable amount of greenbugs at one time without causing a significant effect on its yield if the plant is already fairly mature. However, if the greenbug infests young plants, there can be a considerable amount of damage. Therefore, damage will often occur in the spring or later in the fall. This pest will often eat the lower leaves and will sit on the underside of the leaf. While this aphid feeds off of the plant, it will transfer its saliva to the plant. This saliva is toxic, especially to sorghum, and will destroy the leaves chlorophyll. This will lead to the leaves turning yellow, red and then a rusty brown in colour, which is when the leaf will die. First signs to look for would be small red spots or patches on the plant. It is important to implement control measures as soon as you notice this symptom or else the greenbug can quickly infest your entire field.

Greenbug Management and Control Methods

Management

Treatment methods are advised to be done in the beginning of fall if you have a greenbug infestation (as soon as the proper threshold is reached). Greenbug population almost always will naturally decline in the months of December and January, in which case, treatment at this time in unnecessary. The only time you may need to treat for greenbugs during these months is if the weather is significantly mild. If greenbugs overwinter in the ground, they can cause damage when it begins to warm up in February and March, so always make sure you are keeping a close eye on your fields to make sure you avoid a bad infestation. When there is an infestation, having satisfactory control on this pest is dependent on using an integrated management system that includes the use of cultural and chemical methods.

Cultural Control

The greenbug does have some natural enemies, which includes ladybeetles, lacewings, hoverflies and parasitic wasps. These beneficial insects can have a large impact on the greenbug population, especially in the middle of April. When the parasitism level reaches around 10 to 15 percent, you will start to see a big decrease in the amount of greenbugs present in your crops. When these other insects are not present, other cultural control methods may be necessary, especially for small grain crops in cool, but above freezing, weather. There are several wheat varieties available that can help in the resistance of the greenbug. Do not plant you small grains too early or late in the season as this can help keep their population to a minimum. Additionally, the greater amount of plant residue on the surface of your fields can help, so try no-till wheat. You should refrain from applying pesticides when the beneficial insects are present, as they are a much less costly and a natural method for controlling the greenbug.

Chemical Control

One chemical control method for greenbugs is the use of treated seeds. This can help early in the season to protect your crops form this pest. You can use Cruiser (usually also applied with a fungicide treatment), Poncho, and Gaucho seed treatments. You can also apply soil treatment when you are planting, such as Terbufos (Counter 15G). This would be a wise decision for farmers in areas that tend to have greenbug infestations soon after crop emerge. It is always important to read all product labels before use, as some products are for commercial application, some are for end-use seed treatment, and some warn that animals should not graze on the treated area, along with other restrictions. It is important to note that greenbugs have been known to develop a resistance to numerous insecticides throughout their existence. This is usually attested to high insecticide application, meaning that the decision to spray your crops should be carefully considered as the greater the application, the more likely they will grow immune to it. In order to avoid this from happening when spraying is absolutely necessary, change the materials you use and also use them in different ways if possible; only apply the amount the chemical label recommends, and only spot treat when this is an option. *Always make sure the greenbug is at its economic threshold before any chemical control methods are used.

Latin / Alternative Greenbug Names

  • -Schizaphis Graminum
  • -Green Bug Aphid

Sources

http://bugguide.net/node/view/371013

http://entomology.k-state.edu/extension/insect-information/crop-pests/sorghum/greenbug.html