In the past week there have been a large number of lettuce samples from diverse parts of Monterey County submitted to our office with damage to the roots that looks like wind whip. Wind whip is an issue that we normally see to a small extent each year at certain times of the season in the Salinas Valley. However, the level of damage that growers and PCAs are reporting right now is higher than we normally see (e.g. 10 to 30%).
Wind whip is usually a short lived phenomenon in lettuce production fields. It typically is initiated during thinning when divots are cut to remove unwanted plants. If the divot is too deep or too close to the lettuce plant, it can lean excessively to one side or the other or actually twist. In either case the hypocotyl between the soil level and the base of the plant can get pinched which can be either lethal or have sub lethal effects on the plant. Given the high winds that we experience in the Salinas Valley, it is quite amazing that we do not see more damage to lettuce fields from wind whip.
According to the King City CIMIS weather station there were particularly strong winds on January 30 and February 9, 11 and 24. Many of the fields that were affected were thinned around or before these dates. It is interesting that most of the samples that we received came into the office between February 25 and March 1 indicating when the symptoms became obvious to the growers and PCAs. It appears that symptoms developed slower on this “winter” grown lettuce than it normally develops during summer months.
The wind whip samples that we saw in the field looked a bit like fertilizer burn or ammonium toxicity due to stunting, yellowing and wilting of the plants (Photos 1 – 5) (see Table 1). Upon close examination of the plants, they all had roots that were impaired by the constriction at the crown of the plant. The herbicide Goal can cause damage to the crown of the plant (Photo 6), but there was no Goal used on any of the beds with the wind whip issue that we have received to date.
Wind whip also shares some symptoms in common with soilborne diseases of lettuce. The closest match is probably Fusarium wilt, which likewise causes lettuce to be stunted, chlorotic, and wilted in late stages of disease development. Both wind whip and Fusarium wilt cause the inner core of crown/taproot to become discolored. However, Fusarium wilt in our county is a mid- to late-summer disease; it is very unusual to have Fusarium wilt of lettuce in February. Early development of Sclerotinia lettuce drop can also cause lettuce to fall behind in development, turn yellow, and collapse. Lettuce drop, however, always causes the crown to be soft and decayed, with white mycelium and black sclerotia present. See Table 1 for a summary and comparison of these symptoms.
Table 1. Comparison of wind whip and soilborne disease symptoms
Wind whip symptoms varied from slight (Photo 7) to increasingly severe to severe (Photos 8-11). The functioning of the roots is impaired by the constriction and damage to the phloem. As a result the roots often are stunted and have discolored cores indicating stress (Photos 12-13). As the roots lose their ability to function, the plant cannot grow normally and is stunted.
Wind whip appeared to be worse on east-west fields, and appeared to be worse on romaine vs head lettuce. One question that we were not able to settle was if wind whip was less severe on auto thinned fields due to the lack of disturbance of the beds in the thinning process.
The widespread occurrence of wind whip in the last few weeks appears to be literally a perfect storm of high winds and susceptible lettuce. Hopefully the rest of the year will not have as severe of conditions.
- Author: Shimat Villanassery Joseph
- Author: Mark Bolda
Two spotted spider mite (Fig. 1A) is a major pest of strawberry and caneberries. The spider mites lay 0.14 mm eggs (in diameter) on the undersides of strawberry leaves. Once the eggs hatch and the larvae go through three stages and molt into adult males, and reproductive females. As the name suggests, they are called two spotted spider mite because of one or more dark spots on the bottom half of each side of the body. They are typically dull or yellow colored organism but during the winter months, they undergo diapause (a resting stage) and appear as reddish or orange color (Fig. 1B) which often is confused and misidentified as carmine mite or presumably a new mite never seen before. Carmine spider mite is a bright red colored mite (Fig. 1C) but do not have spots on the either side of the body. They rarely cause economic injury to strawberry. They occurring during the winter and spring months in the Salinas/Watsonville strawberry fields. Predatory mites are also greyish, pale reddish or orange colored in general but they are shiny and moves very fast on the leaves (Video).
For further reading click the Pest Management Guidelines for mites in strawberry (http://www.ipm.ucdavis.edu/PMG/r734400111.html)
- Author: Shimat Villanassery Joseph
- Author: Shimat Villanassery Joseph
The soil-dwelling springtail (Protaphorura fimata) is a serious pest of lettuce in the Salinas Valley of California. This springtail is ~ 2.5 mm long and white and has no jumping organ (furcula) and eyes. They feed primarily on the radicle of the germinating lettuce and broccoli seeds causing stunted seedling growth, and their high densities at planting is associated with poor lettuce stands. Most springtails are saprophytic feeders considered as beneficial organisms because they aid in the decomposition of decaying plant material, thereby contributing to the cycling of carbon and nitrogen, which in turn improves soil health and structure. These springtails typically known to feed on fungi in the soil.
There is no grower-friendly monitoring method to determine incidence and abundance of springtails in the lettuce and broccoli fields of California's central coast. Garden symphylan another soil-borne arthropod pest that occurs in vegetable fields, is commonly monitored using a potato slice bait. Potato slices are typically deployed on the soil surface, and they attract garden symphylan. The utility of potato slices for captures of springtail has not been investigated. Because potato slices are off-white in color, it might be difficult to quickly quantify lightly-colored arthropods such as springtail and garden symphylan on the potato surface. Beets are dark red in color and may provide background contrast and to help quantify lightly-colored organisms on it.
Recent research suggest that beet and potato attract springtail when placed in lettuce fields and these baits could be used to monitor in commercial field settings. It could only provide the presence or absence information, which might be still important to avoid unnecessary insecticide application with no or low captures on baits. Capture of springtails on the baits suggests that their populations are likely developing in the upper soil profile especially near the root system. Also, the incidence and abundance of springtail is subjected to soil moisture and their captures likely decline sharply as the upper soil layer loses moisture. It is likely that springtail populations multiply as the pre-plant irrigation is initiated. Monitoring the field using baits before or during the initial irrigation may provide an indication of active springtail population in the upper soil profile. Study also show that greater numbers of springtails were collected on beet one day after deployment than extended days of exposure. Perhaps deployment of baits for extended periods of time in soil may cause desiccation and make them less attractive to springtails.
Therefore, beet and potato can attract springtail in the soil and could be used for monitoring springtail.
If you are interested to read further on the published article, click the link below.
- Author: Tunyalee A. Martin
Wildlife and people have been in the news lately. Perhaps you've heard of coyotes wandering in your neighborhood. You might have also read about how you shouldn't feed wildlife. Did you know they are connected? It's a problem when people feed coyotes either intentionally or unintentionally through uncovered garbage and outdoor pet food. Available food may encourage coyotes to associate closely with humans and to lose their natural fear of us. These interactions will be discussed during a special symposium on urban coyotes at the 27th Vertebrate Pest Conference.
The Vertebrate Pest Conference is held every two years, mostly in California. This year, the meeting will be Monday through Thursday, March 7to 10 in Newport Beach. Meetings are held in cooperation with the Pesticide Applicators Professional Association (PAPA). The leading authorities with vertebrate management expertise from around the world congregate to present the latest research and extension information. Are you an animal control official, wildlife manager, agricultural producer, pest control adviser, consultant, educator, researcher, or natural resource manager? Then this meeting is for you. California Department of Pesticide Regulation and California Department of Public Health continuing education units are available for participants.
Special symposia include bird management, wild pig management, and urban coyotes. In Cooperative Extension Advisor Niamh Quinn's backyard of extremely urban Southern California, these coyote-human conflicts occur. With over 3 million people in Orange County, 8 state parks and beaches, countless city parks and 19 county parks and wilderness areas, conflicts with urban coyotes are bound to happen. Managing coyotes includes managing people's behavior too.