Timing Insecticide Applications for Pink Bollworm (Lepidoptera: Gelechiidae) Management: Comparison of Egg and Larva Treatment Thresholds

Sampling of pink bollworm, Pectinophora gossypiella (Saunders), eggs was evaluated during 1987 as an alternative to conventional sampling of larvae for making insecticide treatment decisions. Eight cotton, Gossypium hirsutum L., fields, ≈16 ha each, were managed using a treatment threshold of 4-6% egg-infested bolls. The remaining eight fields were managed by pest control advisers and treated when 5% of susceptible green bolls were infested with one or more larvae. Total insecticide applications in the egg and larva threshold fields averaged 6.26 and 8.13 per field, respectively. Despite the significant 23% reduction ( P ≤ 0.05) in insecticide use and significantly higher larval infestations in the egg threshold fields (8.8 compared with 4.6% in larva threshold fields) ( P ≤ 0.05), there were no significant differences in yield ( P = 0.49 for lint weight) between the fields assigned to each management scheme. Results are discussed in light of previous studies on pink bollworm treatment thresholds.