European corn borer numbers are up |
The number of European corn borer moths captured in pheromone traps throughout the state increased during the week of June 17 to 24 (See figures). In some locations, traps caught high numbers of moths (e.g., an average of 79 per trap in Ingham County, and over 250 per trap in Monroe County). All of Lower Michigan has experienced the necessary heat (GDD50 - see degree day table in the back of this issue of the CAT Alerts) for European corn borer moths to fly and lay eggs (450 GDD50). Egg laying peaks about 650 GDD, but continues until about 900 GDD. The tallest corn is most attractive for egg laying. In many areas corn is small because of cool May temperatures. If suitable corn is not available, female moths will lay their eggs on other plants, including potatoes. Sweet corn can tolerate more corn borers when young. Larvae generally do not survive on corn at less than the 6-leaf stage. Prior to tassel emergence, treatment is only required if the pressure is very high, to prevent lodging as a result of the larvae boring into the stem. Just before tassel emergence, treatment is recommended if 10 to 15 percent of the whorls are infested with corn borers. Application of a granular insecticide (such as Capture, Pounce or Avaunt - see Extension bulletin E-312 for insecticides registered for this type of application) directly into the whorl will prevent the corn borers from migrating to the newly forming ears as the tassel emerges. |
More aster leafhoppers |
Increasing numbers
of aster leafhoppers are being found in carrot fields in several Michigan
counties. Recent warmer weather most likely brought in migrating leafhoppers
from the southern United States. During the week of June 9, six aster
leafhoppers were captured in 100 sweeps in carrot fields in Oceana
County. The following week (June 16), the number of aster leafhoppers
captured in 100 sweeps ranged from 6 to 35. The infectivity rate (proportion
of leafhoppers carrying aster yellows) was tested using PCR and was
3.2 percent. Using this infectivity rate, treatment thresholds (number
of aster leafhoppers per 100 sweeps) would be:
These estimates are for the Oceana County area only and for mid-June only. We are currently investigating how variable the infectivity rate is from one location to another and over the season. |
Pollination of vine crops |
Vine crops are starting to bloom or are already in bloom. All of the vine crops (cucurbit family) such as cucumber, squash, zucchini, gourd, pumpkin, watermelon and muskmelon require insect pollination. The majority of these crops have male and female flowers as separate flowers, but usually on the same plant. Some have complete flowers (both female and male parts are in the same flower), such as honeydew melons, but even then insects are needed to transfer the pollen, because all vine crops have sticky and heavy pollen grains that would not move without the aid of insects. Move in bees early Hive density To use the numbers in the table, you must observe 10 flowers for 10 minutes in three different locations (30 flowers/30 minutes) and compare your findings to the table for the particular time of day you do your counts. If your bee counts are less than those found in the table you need more colonies.
Irrigation and pollination Update on varroa mites |
Scouting for Cercospora and Alternaria blights on carrots |
Disease scouting can be an effective method for timing the first fungicide spray to control Cercospora and Alternaria blights on carrots. In 2001 and 2002, prolonging the initial fungicide spray until disease symptoms appeared saved one to three sprays without compromising disease control. The first fungicide spray was applied when the first blight symptom, even if it was just one lesion, was detected on leaves or petioles in the field. Fields should be scouted for disease symptoms on a weekly or biweekly schedule when the carrots are large enough to touch within the rows or when insect monitoring commences. Cercospora blight generally appears earlier in the season than Alternaria, although both blight fungi overwinter in carrot debris and can be seed-borne. For Cercospora, look for light silver to tan-colored lesions on leaves partially or fully enclosed in the crop canopy. The lesions will often appear as pinpoint necrotic spots surrounded by a faint yellow or chlorotic halo. Alternaria lesions do not have a distinct shape like those of Cercospora. Alternaria symptoms appear along leaf margins as dark brown or black irregularly shaped lesions and look like typical blighting or burning of the leaf edges. These symptoms should not be confused with herbicide burn, which are often light brown in color. |
Recommendations
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Potato late blight was confirmed in Montcalm County on June 22, 2002. Further reports in 2002 were limited and sparse. However, the risk of potato late blight is always foremost in crop protection programs. The primary source of the infection may have been from infected seed. Previous versions of the full recommendations for late blight control, which still apply, may be viewed at http://potato.msu.edu In this note, only a summary of the recommendations is presented. In 2002, other diseases and disorders making news were increasing levels of early blight and white mold. Stem canker, caused by Rhizoctonia solani is also becoming prominent and common scab is becoming more of a problem every year. Updated recommendations are being developed for these diseases in 2003. Storage problems caused by what has been described as "pink-eye" is also on the increase, but no pathogenic cause has been shown to be responsible for this disease. Careful fertility and irrigation management may help reduce the disorder but a cause and a cure have yet to be found. Applications of disinfestants (such as Oxidate or Ozone) at storage may help reduce losses but at processing temperatures, which are conducive to the development of the disorder (and other diseases such as Pythium leak, pink rot and bacterial breakdown) losses have occurred even with applications of disinfestant programs. Studies at MSU have shown that the varieties currently grown commercially are highly susceptible to late blight. Snowden and Pike are moderately susceptible but require an intensive fungicide application program. Computer programs are available that calculate disease severity values for both late blight and early blight based on weather data obtained within the crop. Michigan State University Late Blight Project maintains a web site (http://potato.msu.edu) where weather data and severity values are reported through the season from potato growing areas in Michigan. Recommendations for fungicides use rates and frequency of applications are given for all regions of Michigan. These (and other) trials form the basis of the recommendations for late blight control programs for 2003. In situations where disease is present, recommendations for the control of disease in combination with crop destruction practices are shown in Table 1. MSU Extension recommends that disease loci in crops be destroyed with Reglone and treated with fungicide (Supertin or Agritin [TPTH] 80WP) until the loci are completely dead. Recommendations In seasons when the severity of weather conditions would not favor severe late blight development, programs based on chlorothalonil [e.g. Bravo WS 6SC, Echo 6SC, Equus 6SC (registered July 2000) or other formulations], EBDC (e.g. Dithane 75DF, Manzate 75DF, Manex 4FL, Penncozeb 75DF, Polyram 80WP) will reduce the risk of the establishment of the disease. The addition of TPTH 80WP to any of the protectant programs would enhance disease control particularly towards the end of the growing season. (TPTH 80WP has a 14-day pre-harvest interval, also note maximum use rate for 2001 is 11.25 oz per season.) Fixed copper-based products (such as Champ and Kocide) can also be used in protectant programs. These products are best used early in programs or immediate post-harvest for killing spores perhaps from adjacent crops and should always be applied at the full recommended rate of application. The observations of individuals responsible for implementing programs should determine when best to change from one product to another. The appropriate placement of translaminar and other systemic products within programs is determined by the mode of action of the product in relation to host and disease development, but all products are best used within a preventative protectant program. For example, Previcur, Acrobat, Quadris or Curzate may be applied to protect new growth early in development, Curzate and Previcur may be applied while the canopy is expanding but before senescence and Acrobat is most effective as a post-senescence product and can be applied up to late crop senescence. Recommended programs for late blight control are again not straightforward. The product of choice may well depend on how and from where the disease has developed. Some possible scenarios are shown in Table 1 where a range of containment procedures is described for different variety types and different levels of disease in the field. Acknowledgments to MPIC, Robert Schafer and Ron Gnagey. Also to all sponsors of the late blight research program at MSU. |
Strategies to improve color and quality of tomato fruit |
Quality in vegetables often extends beyond flavor to appearance and nutritional quality. Because the pigments that make tomato fruit red are pro-vitamin A and lycopene, poor color translates into less nutritious fruit. Color disorders can affect as much as 50 percent of the tomato crop. Yellow and white shoulder disorders are common color problems. The severity of symptoms ranges from internal white tissue to distinct yellow or green sectors. Thus, quality defects are sometimes called different names, from yellow eye, green shoulder, yellow tag, internal white tissue, to yellow shoulder. Yellow shoulder is a disorder that involves modified development with reduced cell size, random orientation and the green chloroplasts fail to develop red pigments. These alterations occur very early in fruit development and are not reversed even if harvest is delayed. Delaying harvest to let colored sectors catch up is ineffective and will reduce the quality of unaffected fruit. Many factors interact to cause fruit color and quality disorders. Tomato variety, soil, weather and the interaction of weather with the plant and the soil all play a role. Although environmental conditions that lead to color disorders are difficult to control, some nutritional and growth management factors can be managed. Soil quality can influence color quality. Soil pH, available potassium, magnesium, calcium and soil organic matter are all important factors in tomato fertility management and optimizing fruit quality. Uniform color requires more available potassium than is necessary for yield alone. In California, recent research suggests that soil application of either potassium or gypsum, to increase the ratio of available potassium to magnesium, can reduce color disorders, if the soil does not have a high potassium fixation capacity. Research conducted at Ohio State University documents the important role for soil organic matter and pH. Tomatoes grown on soils containing greater than 3.4 percent organic matter produce fruit with a low incidence of yellow shoulder disorder while tomatoes grown on soils with organic matter below 2.4 percent produce fruit with a high incidence of yellow shoulder disorder. Tomatoes produced on soil at a pH of 6.4 have a low incidence of yellow shoulder while tomatoes grown on soil in excess of 6.7 have a high incidence. Recent experiments in Southwest Michigan indicate that improved K fertility may be a key component to good nutrition under Michigan conditions, to support high quality, marketable fresh tomato yield. One field experiment in 2002 found that increasing late fertigation to a 1N: 3K fertilizer regime (instead of 1N:1K and 1N:2K) and application of boron foliar sprays after fruit developed both improved yields and quality. Note: Do not apply more than 0.25 lb/acre of actual boron per foliar spray and be very cautious of multiple applications of boron. Late season calcium foliar sprays were also beneficial in some cases, but not in all. These were a modest reduction in shoulder check defect associated with calcium, boron or calcium plus boron foliar sprays. Nutrition is the foundation of improving fruit appearance but there are other cultural practices to consider. Following recommended pruning practices will enhance air circulation and promote uniform growth. A much more expensive but effective means to optimize fresh market tomato fruit quality is to erect "micro" high tunnels that protect fruit from rain splash and provide some frost protection. |
Regional reports |
1 - SW Michigan Research and Extension Center |
Weather Commodity reports Asparagus harvest is complete and growers are applying herbicides and fertilizer. Cucumber harvest began last week from tunnel-applied fields. Direct seeded fields are at tip over. Cantaloupe under tunnels has softball-size fruit. Harvest volume is increasing from summer squash/zucchini grown under tunnels. Early direct seeded fields will bloom next week. No squash vine borers have been trapped. Early, non-tunneled tomato plants have 1-inch diameter fruit. Staking, pruning and tying continues. Earliest tomatoes are at their third tie. Colorado potato beetle eggs can be found. Potatoes are in bloom. Peppers are at early flower. Final plantings will go in this week. Most pumpkin fields have been planted over the past two weeks. Biggest problem appears to be thirteen-striped ground squirrel activity digging up the seeds. Sweet corn growth has improved providing they have adequate moisture. European corn borers averaged one per trap, down from two per trap last week. |
3 - Oceana County |
Weather Commodity reports In carrots, growth continues to be very slow and some growers have begun to irrigate. Aster leafhopper numbers are up in many fields. In winter squash, plantings of this crop have emerged, but will not do much without some rain. In summer squash, most of the early planting is in the ground, but some of it may need irrigation to emerge. Planting of snap beans has begun, but again most of the seed is going into dry soil. |
6 - Presque Isle County |
Weather Commodity reports |
7 - Southeast |
Weather Commodity reports Tomatoes are being staked. Septoria leaf spot and possibly bacterial canker is appearing on lower leaves of older plants. Red beets and bunching carrots are now added to the list of early crops being offered at farmers markets. Aphids are appearing on a number of crops, including the tassels of early transplanted corn. European corn borers are averaging about 14 per trap, down from last week. Corn flea beetle feeding can be found on the leaves of corn, but no Stewart's wilt is apparent. Zucchini harvest for the wholesale market should begin in three weeks. |
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Japanese beetle survey: Help us help you |
As many growers, gardeners and homeowners in the Lower Peninsula know, Michigan faces a prolific pest in the Japanese beetle. This iridescent beetle has moved from the eastern coast of the United States, where it was introduced, and is now a significant pest of turfgrass, small fruit and some field crops. In 2002, the National Agricultural Pest Information System (NAPIS) reported Japanese beetles within the southern most counties of the Lower Peninsula (Figure 1). However, we anticipate its spread to continue to the north and west across Michigan. Effective management of this pest requires a proactive approach. To better inform the public and assist researchers and state extension agents, our colleagues at the University of Illinois have designed a website to help us track this pests' spread across Michigan: http://www.pmcenters.org/northcentral/jbeetle/ At this website, you can click on the reporting beetles link, and follow the subsequent instructions to report the location and level of Japanese beetle infestation. We invite all who have encountered this beetle in their home or commercial fields to report them to this website. This information will be reported back on the website as regional maps, illustrating the current range of Japanese beetle. Reporting Japanese beetle infestations will help us better understand the landscape and climate factors that may impact this invasive species' ability to spread across the US. In return, there are several pages describing the biology of the beetle and management options for the adults and grubs. By helping us to identify the current range and population level, we can better help you to manage this destructive pest. Figure 1. 2002 reported range of Japanese Beetle (JB) in US. Data from National Agricultural Pest Information System. Figure from National Agricultural Pest Information System web site: |