Insect Management

Wheat is considered a winter crop. As a result, the insects that attack wheat are oriented primarily to the fall and spring time periods. In the fall, the primary insects of concern are aphids, fall armyworms and the initial infestation of the Hessian fly.

S.No

Insect name

Insect Description

Infection Time

Causes

Remedy

1.

Armyworms

armyworms

Fall armyworms feed on the young plants and eat the plants to the ground, causing a loss of stand.

During the warmer part of the day; most of the recommended materials have limited activity below 60 degrees F. In the spring, true armyworms are a threat about the time heading starts to occur.

Wheat is very attractive to the armyworm and thick, vigorously growing fields can attract high infestations.

The armyworm may be controlled using registered insecticides. The best time to apply an insecticide would be late afternoon since the armyworm feeds primarily at night.

2.

Greenbugs

greemworms

The greenbug is a pale green aphid. When the young aphids become about half grown, they have a dark line down the middle of the back. This is an internal marking, not a surface stripe. The dark green marking or line on the back is a reliable identification characteristic for non-winged forms.

Field scouting for greenbug infestations should occur weekly from emergence until cold weather (temperatures below 45 degrees F) is occurring regularly. As spring temperatures start to go above 45 degrees F, weekly scouting should resume.

Greenbugs can damage wheat during this period of time and potentially cause yield reduction. Greenbug injects toxin into the plant leaves as it feeds. Feeding on wheat causes distinct damage that is easily recognized by yellowing of leaves and the occurrence of chlorotic spots, plants may turn brown and die when infestations are high. It is quite typical for greenbugs to be higher in number on sandy knolls or higher places in the field.

When treatment is required, treat during warmer periods (above 50 degrees F) to receive the greatest activity from the insecticide.

Treatment levels for greenbugs in wheat.

Number  Plant Height    Time of

Per Linear                    foot season

 

50           4 - 6 inches      Fall & early

springs

200         6 - 10 inches    Mid-March

300         18 - 20 inches  Mid- April

800         30 + inches      Mid-May

3.

Bird Cherry-Oat Aphid

wordcherry

The bird cherry-oat aphid is probably one of the most common aphids. This aphid is relatively easy to identify in the field. The bird cherry-oat aphid is about 1/16 inch long. The body is usually olive green but may vary from nearly black to a pale green. A reddish-orange patch occurs at the tail of the insect between and at the base of the cornicles. This dark spot, reddish in color, is probably the most distinguishing field character that can be used for identification purposes. The legs and cornicles are pale green with black tips.

Throughout the year

The bird cherry-oat aphid does not inject a toxin into the plant and thus does not cause injury to the plant. Damage seldom occurs from this insect and plants tolerate high populations without losses.

Treatment is seldom required.

4.

Corn Leaf Aphid

cornleaf

The corn leaf aphid is about 1/16 inch long. The body is greenish-blue with darker spots surrounding the base of the cornicles. The cornicles are short and broad with a dark spot at the base. The legs and cornicles are black. Winged and wingless forms are found, especially when high populations occur.

The corn leaf aphid reproduces rapidly and large numbers are common in some years.

The insects feed until they are killed by a heavy frost or until their food plants dry up. Large numbers may be tolerated on small grains and grain sorghum without loss in yield.

Growers are often concerned about this aphid but it seldom requires any treatment.

5.

Grasshoppers

grasshopper

Locusts are several species of short-horned grasshoppers of the family Acridities that sometimes form very large groups(swarms). Grasshoppers have antennae that are almost always shorter than their body), and short ovipositors.

Grasshoppers mainly infect the wheat crop during the summer season and are also highly active in the rainy season.

Grasshoppers can be highly destructive and migrate in a more or less coordinated way. Thus, these grasshoppers have solitary and gregarious (swarm) phases. Locust swarms can cause massive damage to crops.

Carolyn, grasshoppers are one of the more difficult pests to control. There are chemicals such as maliathon and Sevin which are fairly effective. Organic controls include pyrethrum and rotenone. A long-term organic control is Semaspore Bait, which contains nosema locustae, a disease specific only to grasshoppers. This product can only be purchased through organic gardening companies such as Planet Natural or Gardens Alive.

6.

Hessian Fly

fly

The Hessian fly, also called Mayetiola destructor. Adult Hessian flies are small black flies about the size of a mosquito. Adults live for about two days, during which time they mate. Females lay about 200 eggs in the grooves of the upper side of wheat leaves. The entire life cycle requires about 3

The Hessian fly is a cool season insect that can function normally at temperatures as low as 38 ° F. The insect spends the summer months as puparia (flaxseed) in wheat stubble; therefore, burying stubble can reduce fall populations. The number of generations during the year is governed largely by temperature. 5 days at 70 ° F.

Newly hatched larvae are exposed on the leaf surface and are susceptible to disease and adverse weather conditions, but once larvae move to the stem base they are protected from natural enemies and the environment.

The most effective method for controlling the Hessian fly is use of a resistant variety. Unfortunately, few wheat varieties grown in the South are resistant to the biotype (Biotype L) of Hessian fly. Crop rotation, destruction of volunteer wheat and tillage that buries wheat stubble will help reduce Hessian fly infestations in susceptible varieties.

The best method to reduce injury and damage by the Hessian fly is to delay planting as late as is reasonably possible. In Hessian fly research, early-planted wheat had a 21 percent infestation compared to less than 1 percent in the later planting date. Dissulfoton granules also reduced Hessian fly infestations. Studies have shown that foliar applications of insecticides in the winter and spring for Hessian fly control are not effective.

7.

Cereal Leaf Beetle

cerealleaf

The cereal leaf beetle is a native to Europe. The adult beetle is about 3/16-inch long, metallic blue-black in color with red legs and a red pronotum (neck). The female is generally larger than the male. Adults begin to emerge in late March to early April from overwintering habitats, which include crop remnants, field trash, grain stubble and corn plants.

The cereal leaf beetle overwinters in fields of wild grasses, and as the weather warms in the spring it enters cultivated fields and deposits eggs. The larvae emerge and cover themselves with their own excreta in order to mimic the droppings of birds or other insects. They usually appear as shiny, wet lumps adhered to the surface of leaves. They gorge on the plants, then drop off and pupate in the soil for about 3 weeks, emerging full-grown to continue feeding on the plants.

Adults and larvae feed on the leaves of the plant, removing long narrow strips of tissue between the veins similar to the rice water weevil except the strip is slightly larger. Fields with heavy damage have a white frosted appearance. Adults and larvae are easily detected in the field by visual examination. Damage from cereal leaf beetle is apparent when the tips of leaves turn white and the leaves develop white stripes or slits where the beetle has consumed a strip. A field with extensive damage will look frosted or whitewashed.

Parasitoids successfully employed against the cereal leaf beetle as agents of biological control include the parasitic wasps Diaparsis carinifer, Lemophagus curtus, and Tetrastichus julis, which attack larvae, and Anaphes flavipes, which is an egg parasitoid. Lady beetles eat the eggs and larvae.