SOUTHERN CORNSTALK BORER: Diatraea crambidoides, Pyralidae

ADULT: The moths have tan wings and a 1 1/4 in. wingspan.  The rear margin of the fore wings form a straight perpendicular line across the axis of the body when at rest. Some of the mouthparts extend outward in front of the head to almost the length of the first pair of legs.

EGG: Flat, oval, creamy white eggs are deposited 2 to 25 per group in an overlapping fashion like fish scales on leaves and stems. Eggs develop three thin orange stripes near maturity.  larvae emerge in 7 to 10 d.

LARVA: Ivory colored larvae have two large, round, dark spots (tubercles) and four smaller dark spots on the second thoracic through last visible abdominal segments.  Larvae have three pairs of true legs and five pairs of prolegs.  Larvae complete development in 20 to 35 d.  Second generation larvae overwinter within corn stalks.

PUPA: They pupate within the corn stalks. Adults emerge through exit holes precut in the stalk by the larvae. Adults emerge in about 10 d.

GENERATION TIME: 37 to 55 d.

DAMAGE: Southern cornstalk borer is an occasional pest in north Florida.  Larvae begin feeding on leaves in the whorl before entering and tunneling within leaf midribs and stalks. Second generation larvae feed entirely within stalks. Frass accumulates outside entrance holes. Feeding results in broken tassels or stalks and reduced yields. Rows of irregular holes may be present on young emerging leaves from early first instar damage.  Damage by stem-boring instars is often not observed until severe stalk damage has occurred.

CONTROL: Control involves foliar sprays directed at first instar nymphs or adults. Disking and covering stalks of the previous crop prevents weak adults from emerging from stalks.  Larvae do not overwinter well in uprooted, exposed stalks.  Crop rotation is also important.  None of the pesticides registered for corn specifically mention this insect. Formulations, rates, and pre-harvest intervals of insecticides labeled for stalk borer control in Florida are listed below for sweet corn (Table 1) and field corn (Table 2).