Several aphid species feed on the leaves and grain heads of wheat. Adult aphids are only about 1/8 inch long, and may or may not have two pairs of nearly transparent wings. These pests are significant in that they are capable of transmitting diseases, such as barley yellow dwarf (BYD) virus, in addition to the damage inflicted by their feeding habits.
The bird cherry-oat aphid is dark green and the primary species that transmits BYD. It is usually the most common species observed in wheat.
The English grain aphid is pale green with black antennae and cornicles (‘tailpipes’), which are longer than the antennae and cornicles of other aphid species normally observed in wheat.
The greenbug is pale green with a dark green stripe down the back of the wingless form. The tips of the legs and cornicles are black, and the antennae are mostly black.
The corn leaf aphid is bluish-green with black legs, cornicles and antennae.
The rice root aphid occurs on the roots of wheat and is also known to transmit BYD.
A good sampling plan is to scout 1 row foot of wheat at 10 locations throughout the field. Aphids are typically found on the stems and underside of leaf blades. Examine each plant within the row foot for number of aphids and determine the aphid species present. Samples should be taken during the fall (e.g., approximately 30 days after planting) or late winter (prior to March).
Bird cherry-oat, English grain, corn leaf, and rice root aphids. With the exception of greenbug (below), treatment for high numbers of aphids is generally not recommended unless they are causing leaves to dry up and die in several portions of the field. However, more aggressive management is needed to prevent BYD. Insecticide seed treatment such as Gaucho, Cruiser, and NipsIt Inside can be used to reduce transmission of BYD. Data suggests that early planted wheat is most likely to benefit from the use of a seed treatment. If a seed treatment is not used, a foliar insecticide application during the fall or late winter (prior to March) can also reduce transmission of BYD. These applications should be made when aphids are present but before populations exceed 6-8 aphids per row foot, otherwise transmission of BYD may have already occurred.
Greenbug. This aphid injects a toxin while feeding. Treatment should me made when aphids are killing three or more leaves per plant. For wheat less than 6 inches tall, treatment should also be considered if greenbugs number 50 or more per linear foot. Treatment should also be made if greenbugs number 200 or more per foot in wheat 6-10 inches tall.
|Insecticide (Trade Names) for APHIDS||Lb Active Ingredient per Acre||Amount Formulation per Acre||Performance Rating|
|clothianidin (NipsIt Inside 5)||0.75 - 1.79 oz per 100 lb seed||8|
|imidacloprid (Gaucho 600)||0.8 - 2.4 oz per 100 lb seed||8|
|thiamethoxam (Cruiser 5)||0.75 - 1.33 oz per 100 lb seed||8|
|dimethoate 4||0.25 - 0.375||8 - 12 oz||7|
|methomyl (Lannate LV 2.4)||0.225 - 0.45||12 - 24 oz||7|
|β-cyfluthrin (Baythroid XL 1)||0.014 - 0.019||1.8 - 2.4 oz||8|
|γ-cyhalothrin (Declare 1.25)||0.015||1.54 oz||8|
|λ-cyhalothrin (Warrior II 2.08)||0.02 - 0.03||1.28 - 1.92 oz||8|
|Z-cypermethrin (Mustang Max 0.8)||0.02 - 0.025||3.2 - 4 oz||8|
*See label for suggested insecticide rates for different species
- Early planted wheat is more likely to be infested by aphids during the fall and often results in higher infection with BYD. Thus, planting is not recommended until October 15 or later, which also helps avoid infestations from Hessian fly.