BIRDCHERRY OAT APHID: Rhopalosiphum padi, Aphidae

ADULT: A small to medium sized (3/32 in.), elliptical- to pear-shaped aphid. Wingless females are medium green with reddish areas toward end of abdomen and area around bases of cornicles. Winged females have a black head and thorax, and green abdomen.

NYMPH: Winged or wingless adult females deposit live nymphs, skipping the external egg stage in Florida.  Nymphs are similar in color and shape to adults, only smaller.  They molt several times to adult in 7 to 10 d.  There is no pupal stage in aphids.

GENERATION TIME: 7 to 10 d.

HOSTS: In Florida, these aphids feed on corn and other wild and cultivated grasses.

DAMAGE: Birdcherry oat aphids have become a greater problem for sweet corn during the last several years. Their preference for feeding down in the canopy on or around corn husks makes chemical control difficult. Honeydew makes ears and husks sticky and encourages sooty mold growth which can result in husk discoloration and grade reduction.

CONTROL: Many types of natural enemies may control these aphids under low pesticide input situations, such as in field or sileage corn.  However, these aphids appear in sweet corn at a time when pesticide use increases for armyworm, thereby greatly reducing the potential impact of their predators and parasitoids.  Pathogens kill many winged adults before they begin producing nymphs.  Aphids feeding on husks are somewhat protected from chemical control strategies by the corn canopy and silks.   Pesticides are available for post-emergence foliar treatments. They are less susceptible than corn leaf aphids to pesticides frequently used for armyworm control.  Formulations, rates, and pre-harvest intervals of insecticides for birdcherry oat aphid control are listed below for sweet corn (Table 1) and field corn (Table 2).