- Author: Richard Smith
- Author: Steven Koike
During this time of year, there are various weather issues that affect lettuce. Frost damage can often occur during the cold, clear nights in the winter and spring. Interestingly, frost damage on lettuce causes some classic symptoms that are easily recognizable and some that are a bit surprising. Different types of symptoms can be caused due to differences in the severity and duration of low temperatures, as well as the age and location of the leaf tissue. One of the more common symptoms of frost damage on lettuce is when the outer leaf cuticle separates from the underlying cell tissue; this can result in a bronzed look to the leaf, which is probably due to the death or damage of the surface epidermal cells (Photo 1). More severe frost conditions may cause necrotic interveinal lesions as well as necrotic spotting on the leaves (Photos 2 and 3); such symptoms could resemble those caused by heat damage or pesticide burn. Occasionally the tips of young leaves are killed, and as the leaf continues to grow, the leaf may curl around this dead area (Photo 4). Sublethal frost damage tends to occur towards the edges of the leaves and causes thickening and roughening of the texture of the leaf tissue (Photos 5 and 6). Lettuce is mostly tolerant of temperatures near freezing for a short period of time, though plants will grow more slowly. Freeze damaged leaves that are not removed from heads may break down, decay, and cause post harvest issues.
Growers and others in the field should be aware of how very low temperatures can also damage other crops, such as cauliflower transplants (Photo 7), that are present during this time of year.
- Author: Steven T. Koike
View new year-round IPM program video & year-round IPM program to protect cole crops from agricultural pests
Got pests and want to use integrated pest management? Use a year-round IPM program. If you’re not familiar with what a year-round IPM program is, think of it as a checklist for the agricultural pest management activities you should be doing throughout the season. Take the new video tour “Using Year-Round IPM Programs” to explore the benefits and uses of IPM in vegetable, field, orchard, and vineyard crops. Managing pests in Cole Crops? View this new year-round IPM program.
Monitoring the most important pests, making management decisions, and planning for the following season are all activities in the year-round IPM programs. Even better are how they connect to the Pest Management Guidelines so you can read about the details…how to monitor, what the treatment thresholds are, or the best pesticide to use.
One of the basic IPM principles is to choose the best pesticide for the situation. The year-round IPM programs help you do this by ensuring you’re applying pesticides only when you need to, and providing you with information so you can choose the most effective pesticide with the least harm to water quality, air quality, natural enemies, and honey bees.
The checklist, photo ID pages, and monitoring forms are easily printable for use in the field. Interested in other crops? We have 25 year-round IPM programs:
- Alfalfa
- Almond
- Apricot
- Asparagus
- Avocado
- Cherry
- Citrus
- Corn
- Cole crops
- Cotton
- Cucurbits
- Dry Bean
- Grape
- Lettuce
- Nectarine
- Peach
- Pear
- Pepper
- Pistachio
- Plum
- Potato
- Prune
- Strawberry
- Tomato
- Walnut
Let us know how year-round IPM programs are benefiting you. Thank you.
Tunyalee Martin, tlamartin@ucanr.edu
Jodi Azulai, jlazulai@ucanr.edu
Romy Basler, rbasler@ucanr.edu
www.ipm.ucdavis.edu
- Author: Lennis Arriaga
CropManage Workshop Announcement
- Author: Shimat Villanassery Joseph
- Author: Richard Smith
Removing weeds from the seedline is the most difficult part of weed control for many of the vegetable crops that are grown on the Central Coast. Standard cultivation removes weeds in about 80% of the bed, but leaves a band 4 inches wide around the seedline. In conventional production the seedline is treated with preemergent herbicides which can significantly reduce weed pressure; however, uncontrolled weeds are removed by hand and weeding costs vary depending on the density of weeds and the time needed to remove them. Finger weeders are a tool that can reach into the seedline and kill small weeds. They are most useful for transplanted or large seeded (e.g. corn, beans, squash) vegetables. They take advantage of the fact that the vegetable is firmly rooted and that the weeds are small and less well rooted; as such, timing is critical for the effectiveness of the finger weeders. In our trials, they were most effective when used 7-14 days after the first germination water when the weeds were in the white thread stage. However some weed species, such as malva, grew very quickly and were too tough for the finger weeder to remove them, while other weeds such as nettle, shepherd’s purse and others were highly susceptible. Finger weeders are available from the Buddingh company in Michigan (http://www.buddinghweeder.com/products.html) and three companies in Europe. Of the European companies, we have mostly worked with the Kress Company, Germany (www.kress-landtechnik.de). To date they have not had a distributor in the US, but now Washington Tractor in Quincy Washingon is importing Kress Finger weeders (http://www.washingtontractor.com/locations/store/quincy ). For more information on finger weeders view the video that we put together at: http://www.youtube.com/watch?v=I4kzebMG6rE.
 Uncultivated band left around Broccoli seedline |
 Finger weeders cultivating celery transplants |
 Seedline on right cultivated with finger weeder (note disrupted soil surface) |
 Young pigweed seedling under cut by finger weeder |
