Field Crops News

Native Predators Reduce Armyworm Damage to Corn

Naturally occurring predatory insects and spiders may be important in reducing armyworm damage in corn. Laboratory studies showed that individuals of several ground beetle species, a rove beetle and a wolf spider consumed 5-10 second or fourth instar armyworm larvae in a 24 hour period. A field study used pitfall traps to reduce the density of ground dwelling generalist predators in corn. Based on densities removed and known feeding habits, the most important predators in the field study included ground beetles, rove beetles, wolf spiders and possibly ants. Percentage of damaged plants was increased from 10% to almost 40% where predators were reduced with pitfall traps.

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Convergent Lady Beetle Partially Tolerant of Permethrin

When female convergent lady beetles were exposed to permethrin (Ambush, Pounce) residues on alfalfa, 95.6% experienced initial knockdown symptoms (difficulty in movement, paralysis) within 12 hours. However, 61% of females recovered when removed from exposure. Those recovering showed no reduction in longevity, number of eggs laid or length of egg laying period compared to those not exposed to permethrin. These data indicate that if covergent lady beetles survive field exposure to permethrin there are no long term effects on life span or egg laying.

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