Useful resources:

• Year round IPM Program for Cotton: Early Squaring Activities:
• Monitor Cotton Growth – Early Squaring
• Monitoring to Make Lygus Decisions
• Calculate Expected Square Retention
• Cotton Field Check (June 2011) - Why the Cotton plant is the Great Indicator for Lygus Management

 

For San Joaquin Valley cotton growers, one of the most important production decisions is to get the plant into a vigorous fruiting cycle and to hold the early fruit so the plant is manageable for the remainder of the season.

During the earliest fruiting period, retention of fruit on the first 10 fruiting branches is top priority and the most difficult to interpret. We understand the Acala Upland retention very well but are stretching the data for Pima. However, using the Acala data developed over 20 years ago provides valuable guidelines in evaluating fruit loss and retention.

There are many factors which can cause squares to drop including weather, management factors, and insects. In the 2012 season, the early development has promoted rapid growth and fruit set, favoring the plant over thrips. Lygus will be the primary insect pest to monitor by frequent field inspections (twice weekly is recommended) and monitoring retention. Low populations densities of Lygus need to be monitored closely to ensure that loss of early fruit set meets the expected retention for the age and fruit load of that field.

June is a critical month to manage Lygus but once the initial fruit is set and bloom occurs, greater densities of Lygus can be tolerated. If June treatments are required remember to:

• Make sure the fruit loss can be related to Lygus;
• Lygus are present
• Selective products are utilize to preserve the natural enemies already in the field
• Practice good insecticide resistance management practices and take care to not over use any particular active ingredient

Much of cotton pest management involves sweeping a field for insects, inspecting fruit for damage or inspecting leaves for mites, aphids or whiteflies. However, quietly in the soil may be one of the most threatening pest situations.

  Useful resources:

• Information leaflet
• Identification videos
• General Fusarium information 
• UC IPM Cotton Pest Management Guidelines

Fusarium Wilt, caused by Fusarium oxysporum f. sp. vasinfectum, is a widespread disease causing damage to a wide host of crops. Until recently,  cotton was affected only through the association with root knot nematode. However with the emergence of Race 4, its presence has been felt throughout the San Joaquin Valley.

Current research efforts by USDA-Ag Research Service  and University of California Agricultural Experiment Station and Cooperative Extension  is working hard to find ways to manage this disease. Thus far, breeding for resistance and tolerance to the fungus is the most promising approach.

In order to use the variety best suited for your situation, knowledge of the infestation is required. This early period of plant development (emergence to first fruit) is a good time to watch for symptoms in the field. In seedlings and young plants, cotyledons and leaves wilt and drop, resulting in bare stems. In severe cases, plants die. In mildly affected plants, lower leaves develop symptoms but plants survive, but with reduced vigor. Look for breaks in the plant stand with associated dead or drying plants. Other symptoms include a general wilt, which is especially evident on warm days, and yellowing and necrosis of lower leaf margins. The vascular system of infected plants is brown. This is most apparent in the lower stem and upper taproot.

The UC CE Cotton Team has developed valuable information for identification and management of Fusarium Wilt Race 4. The UC CottonInfo website  provides current information including UCcottoninfo Channel on YouTube.  Bob Hutmacher and Brian Marsh have developed a video about “how to” look for disease symptoms, including which plant to sample which is very helpful.

COMMENTS ON THE DISEASE - From UC IPM Cotton Pest Management Guidelines

Four genotypes (called races) of Fusarium oxysporum f. sp. vasinfectum presently occur in California. Races 1, 3, and 8 are mildly virulent and cause few, if any, symptoms on cotton unless the plants are also infected with root knot nematodes. Race 1 is widely distributed in the San Joaquin Valley; races 3 and 8 are found in a limited number of fields in Tulare and Fresno counties. Race 4 is significantly more virulent and can cause severe symptoms on certain Pima varieties and mild to moderate symptoms on most Acala varieties. Seedlings of susceptible Pima varieties often die and resemble plant losses caused by damping-off fungi. Stand establishment in some fields is markedly reduced. The distribution of race 4 is not fully known, but it is becoming more common in Fresno, Tulare, Kings, and Kern counties.

     The fungus sustains itself on the outer surface of roots of many crops and weeds and survives indefinitely in soil. In addition, the pathogen is seed-borne in cotton, which accounts for long-distance spread, and is also spread whenever infested soil is transported on boots, farm equipment, in flood irrigation, etc.

As cotton seedlings develop, western flower thrips (WFT) can occur in great numbers.  As winter grain fields  dried up for harvest or alfalfa fields are cut for hay, large numbers can descend on a cotton field causing growers and PCAs to pause and wonder, who goes there, friend or foe?

FOE: Western Flower Thrips feed on young leaf tissue causing the leaves to distort and curl. If present in sufficient populations, they can feed and destroy the growing meristem region, setting back the development of the plant. Such damage occurs during extended of cool temperatures during the seedling stage. In most years, the growth rate of cotton will outpace the damage caused by thrips to the leaves.

FRIEND: Western Flower Thrips is a key natural enemy to spider mites. Seeking mite eggs, WFT will move through mite webbing and consume many mite eggs in a day. In addition, they became an important prey base for general predators such as minute-pirate or big-eye bugs.

Under current conditions, it is unlikely that WFT will present any threat to developing cotton seedlings and will provide valuable ecological services to your farm. Early treatments are mostly unnecessary and interfere with the annual development of the cotton food web that is developing within your fields.


For more information, go to UC IPM Website by clicking here.  

Cotton planting is well underway in the past 3 weeks now that the weather turned warm. While the initial planting was cool and intermittently wet, temperatures since April 16^th in the San Joaquin Valley have been excellent for planting cotton. Looking at temperature conditions from March 1 to April 26, 2012 according to accumulated degree-days > 60◦ F five days after planting, Shafter and Five Points had 47% and 37% of those days in the Adequate to Ideal categories (Figure 1). 

Figure 1 (click to enlarge)

Since April 15^th, all dates have had ideal heat accumulation five days after planting (Figure 2A). These data are based on actual temperatures rather than forecasted data. While the forecasted (predicted) degree day accumulation 5 days post planting varied from actual temperature recordings, this year it under-estimated the degree day total (e.g. more conservative) more than it over-estimated (Figure 2B). Some of the the difference can be attributed to inaccuracy in predicting temperatures five days out and the generalized nature of forecast as compared to actual site recording. 

     

The cotton is germinating and emerging from the soil very nicely. In the warm days since April 15^th, most cotton should have germinated 10-14 days after planting. Getting a good, vigorous stand is a fundamental step in developing a season long IPM plan. Assessing your stand to determine the number of plants/acre is a useful indicator to address replant concerns and future management decisions. Guidelines for assessing your stand can be found by clicking here on Cotton Year Round IPM site.