- Author: Peter B Goodell
- Monitoring Lygus in cotton
- Stripping alfalfa hay
- Movement of Lygus in the Landscape
- Natural enemies in cotton
With growing conditions continuing to look favorable for cotton growth and development, fruiting is beginning or well underway in some locations. Fruiting is being noticed in Firebaugh area at 6th main stem node, which is line with early season temperatures we have experienced and good planting dates.
Setting the early fruit sets the plant up for the rest of the season. With a shortage of the irrigation deliveries this year, the season must be as compact as possible. Protecting early fruit is critical in these water short conditions.
Lygus will be a localized problem. Movement will occur from neighboring sources, most likely other cultivated crops. Key sources for Lygus include safflower, forage alfalfa and seed alfalfa. Within safflower and alfalfa forage, the Lygus population can be managed to prevent mass movement into surrounding cotton fields. Lygus is closely managed in seed alfalfa can still acts as a major source.
Safflower is currently being treated for Lygus to prevent the first generation from
Alfalfa forage is the most common crop which Lygus prefers. It is a unique crop in our cotton landscape because it is harvested frequently for its vegetative biomass, not its reproductive parts, e.g. fruit, lint, seed. Providing even a limited habitat during cutting can have a substantial effect on mitigating Lygus movement into cotton. During the June and July cuttings, if uncut strips of alfalfa are left in the field, Lygus will move to them and stay until the next irrigation cycle, when they return to the larger alfalfa field.
Limiting the movement of Lygus into cotton not only protects the fruit during this critical early stage but can reduce the need for insecticide applications. This allows additional natural enemies to build and helps reduce pressure for the development of insecticide resistance.
Early intervention through the cultural control of Lygus source management will help set the cotton up for high fruit retention, shorter season and fewer secondary insect and mite problems, as well as reduce costs in early insecticide treatments.
- Author: Peter B Goodell
Preventing Lygus bugs from coming into a cotton field is the next best thing to not having the pest at all. Since cotton is embedded in a complex cropping mosaic, bugs building in neighboring fields can move to cotton. While cotton is not a preferred crop for this insect to set up a household, it will, nonetheless, settle in if nothing else is available.
Since there is no indication from the plant that harvest is imminent, there is no urge to leave the alfalfa field. Our studies have shown Lygus will remain in a harvested alfalfa field for up to 24 hours before leaving.
However, if given a choice, such as an uncut strip of alfalfa, Lygus will stay longer in the alfalfa field and may not leave at all. Additional trials at Kearney Ag Center demonstrated that the population density within a strip can triple compared to density prior to harvest. In other words, they will stay on their familiar host as long it is available.
Throughout the San Joaquin Valley, alfalfa strips have become common and according to farmer testimonials, resulted in substantial savings in cotton treatment costs. These green islands provide a refuge for a reluctant pest and have been incorporated into the cotton IPM programs of thoughtful and progressive farmers.
For more information, see:
The IPM website page on managing Lygus in alfalfa
An impact statement on management of forage quality in strip-cut alfalfa