Integrating novel technologies for cabbage IPM in the USA: value of on-farm research

Integrated pest management (IPM), particularly for high-value crops, is often viewed by growers as a more risky approach compared to their current (conventional) pest control practices. In this article we present the results of a 3-year on-farm trial, which documents the expected benefits, and risks of IPM and a conventional pest management system for cabbage. In Minnesota, USA, ca. 500 ha of cabbage and cole crops are produced each year. Despite relatively few hectares, the high value of the crop ( 9,000 US$/ha), and high insecticide use (5-9 sprays/season), continues to create a demand for alternative pest management programs. Throughout the Midwestern states, cabbage is attacked by three important lepidopteran pests: Pieris rapae, Plutella xylostella and the cabbage looper, Trichoplusia ni. In the absence of insecticide resistance, as well as high parasitism rates of P. xylostella (80-90%), T. ni is often the most common, and most difficult insect pest to control. Much of our focus over the past 8 years, has been to: a) evaluate rapid presence/absence (binomial) thresholds that account primarily for T. ni, b) validate thresholds for use with “reduced-risk” insecticides such as SpinTor (spinosad) and Proclaim, with pyrethroid use as needed (e.g., lambda-cyhalothrin; Warrior), and c) measure and communicate the value of IPM in on-farm trials. Use of a 10% action threshold and the reduced-risk insecticides, consistently provided a lower proportion of plants infested with late-instar T. ni larvae and a higher percentage of marketable heads for the 3-year study (1998-2000), compared with a conventional system. The conventional system used by the grower included pest scouting only to determine the first spray. Thereafter, sprays were applied approximately every 10 days or when convenient. The IPM program resulted in the highest percentage of marketable heads, while reducing the number of insecticide applications in 1998 and 1999 (43-66%). Despite a slight increase in sprays in 2000 (3.0 vs. 2.6) for the IPM program, net profits were still highest for the IPM program in each of the three years, ranging from 16 to 107% over the conventional program. Expected utility analysis also revealed that the IPM program provided the highest expected net revenue ($973/ha) with the least risk, compared with the conventional strategy and untreated check. In summary, these results confirmed the economic benefit of an IPM approach by careful measurement of the benefits and risks of IPM and has been well-received by Minnesota growers.