Identifying nontarget crop and ornamental plant damage from herbicides has become much easier with the launch of a new online photo repository by the Statewide IPM Program, University of California Division of Agriculture and Natural Resources.
Herbicides applied to manage weeds may move from the site where it was applied in the air or by attaching to soil particles and traveling as herbicide-contaminated soil. When an herbicide contacts a nontarget plant, a plant it was not intended to contact, it can cause slight to serious injury. Herbicide injury also occurs when the sprayer is not properly cleaned after a previous herbicide application. Herbicide residue can be found in the spray tank, spray lines, pumps, filters and nozzles so a sprayer must be thoroughly cleaned after an application. Dry herbicide particles can be redissolved months later and cause herbicide damage to plants. Economic damage includes reduced yield, poor fruit quality, distorted ornamental or nursery plants, and occasionally plant death.
Accurately diagnosing plants that may have herbicide injuries is difficult. In many cases, herbicide symptoms look very similar to symptoms caused by diseases, nutrient deficiencies, environmental stress and soil compaction. Plant disease symptoms such as mottled foliage, brown spots or stem death and plant pests such as insects or nematodes cause foliage to yellow and reduce plant growth similar to herbicide injury.
Dr. Kassim Al-Khatib, weed science professor at UC Davis and director of the UC Statewide Integrated Pest Management Program (UC IPM), has gathered nearly a thousand photos of herbicide-damaged plants, drawn from his own and others' research. The images are cataloged to show damage that can occur from 81 herbicides in more than 14 specific herbicide modes of action, applied in the field to demonstrate the symptoms or when known herbicide spray has drifted onto the plant.
Each image is characterized with the name of the plant, mode of action of the herbicide, and notes the specific symptoms of damage. Together these photos provide a comprehensive archive of damage to over 120 different crops and ornamental plants by known herbicides, which users can easily compare with what they see in the field.
Also included in the repository is information about the modes of action of various herbicides and an index of example herbicide trade names and active ingredients. Users can learn how unintended injury from herbicide occurs from misapplication and carryover from previous crops in addition to drift and herbicide-contaminated tanks.
The repository can be found at http://herbicidesymptoms.ipm.ucanr.edu. Increased knowledge about what causes herbicide damage and how it occurs can lead to fewer cases of herbicide injury occurring through drift or herbicide-contaminated tanks. Using the repository can increase the skill to correctly identify plant damage. Correctly identifying damage as herbicide injury and not from a plant pest or nutrient deficiency can prevent unnecessary applications of pesticides or fertilizers. Fewer applications can lessen the risk of harm of pesticides and fertilizers to people and the environment.
The brown stink bug (Euschistus servus) has arrived in the Palo Verde Valley on the Arizona-California border. This pest has caused damage from Georgia to Arizona.
In addition, brown marmorated stink bug is in Sacramento Valley, Consperse stink bug has caused damage to tomato growers in the westside of Fresno County, and bagrada bug continues to expand its range.
To better aid in identifying stink bugs, the national IPM Centers have revised the Guide to Stink Bugs, from Virginia Cooperative Extension. This illustrated guide covers a wide range of stink and plant bugs and provides an excellent overview of stink bug biology.
- UC Pest Management Guidelines for Cotton
- Whitefly Management Guide
- Whitefly Webinars, Plant Management Network
August is the typical time for change in managing cotton pests in the San Joaquin Valley. As the plant is shifting from setting fruit to maturing fruit and our attention is shifting from protecting yield to protecting quality. Lygus becomes much less of a concern as bolls mature beyond 10 days after flowering and our attention focuses on preventing excessive honeydew from drifting down onto open bolls and exposed lint.
Minimizing the occurrence of sticky cotton remains a critical goal for San Joaquin Valley cotton. Close attention to fields
In the past several years, a resurgence in sweetpotato whitefly biotype B (formerly silverleaf) has been experience in the San Joaquin Valley. I am noting a very preventative approach in managing whitefly with treatments being applied at very low population densities. The concern for sticky cotton is real and the response to prevent it is understandable.
PCAs and growers should consult regularly to review their individual situations, determine a course with the remainder of the season in mind, and select insecticides based on the threat, the population composition and insecticide resistance principles.
There is a good collection of information available and the interested pest manager is directed to these list above for more details.
- Plant Management Network - Focus on Cotton Webinars
- CA Cotton Growers and Ginners Association - Slides for viewing from Whitefly-Aphid Workshops
- UC IPM - Pest Management Guidelines for Cotton
Producing the highest quality cotton lint is paramount for cotton growers, PCAs, ginners and merchants. Honeydew produced by sweetpotato whitefly, Biotype B (Bemisia tabaci) and cotton aphid (Aphis gossypii) can settle on open bolls and create sticky cotton. The contamination of cotton lint with sugary honeydew creates major problems with the spinning mills
UC IPM and California Cotton and Ginners Associations (CCGGA) recently hosted three workshops to remind the cotton community of the importance of managing these pests to prevent the development of sticky cotton.
The slides presented by IPM Advisor Pete Goodell and UC Davis Extension Entomologist Larry Godfrey are available through CCGGA link by clicking here.
In addition, a series of webinars on the subject has been produced by Cotton Incorporated and Plant Management Network. It is available through my website.
Detailed information on aphid and whitefly management can always be found at UC IPM Pest Management Guides.
There have been numerous reports of pale striped flea beetle in cotton around the Five Points area of Fresno County. Population densities of 20-30/50 sweeps have been found, causing some concern among PCAs. The most common species is the pale striped flea beetle, Systena blanda.
In most cases, flea beetle is usually a problem on seedling cotton, not on blooming cotton according to IPM Manual for Cotton in the Western US.
The manual states: "Flea beetles, small beetles with enlarge hind legs that enable them to jump, chew small round holes or pits in cotyledons and young leaves. They
However, given enough beetles moving into a cotton field at one time, damage can occur. One field I observed in late July had over 500 beetles for 50 sweeps and caused considerable leaf damage in the lower canopy. The source of beetles were neighboring alfalfa fields which were recently cut and water stressed.
Damage to the leaves was mainly superficial feeding. Leaves were not tattered nor did they display
While not normally a damaging pest to mature cotton, high population densities of pale striped beetle can potentially cause damage at any stage of growth.