European corn borer and corn earworm season summary
Beth Bishop
Entomology

Sweet corn growers in Michigan experienced moderate “worm” pressure this season. In many locations the first flight of European corn borer moths was high, and early-maturing varieties had to be treated at tassel emergence to prevent larvae from entering the ear (see graphs below). In most locations the second flight was lower, but by then growers were protecting their corn from corn earworm (see graphs below). The second flight of European corn borer moths was pretty much over by late August, and we did not have a warm enough summer to produce a third flight.

As usual, it was an unusual season for corn earworm. This is a migratory pest, and its appearance in the state and its abundance is dictated by weather patterns. Weather fronts brought a moderate number of corn earworms into the state much earlier than normal, in mid-June, and low numbers of corn earworms were present for most of the growing season (see PestWatch for seasonal summary: http://www.pestwatch.psu.edu/sweetcorn/tool/tool.html). Not until late August were weather conditions again favorable for corn earworm migration and the remnants of hurricanes Gustav and Ike brought more moths into the state. Pheromone trap numbers increased over the past weekend in those areas still trapping (Ingham and Oceana counties) averaging between five and eight moths per night.

I want to take the time to publicly thank all the cooperators throughout the state that set up, maintained, and collected European corn borer and corn earworm traps in 2008 and in previous years. Your efforts have helped provide essential information for Michigan vegetable growers.

A corn earworm, European corn borer, and fall armyworm.	A corn earworm trap pheromone trap.	A European corn borer larva in an ear of sweet corn.

1. Soil sample. Many of the vegetable crops utilize large amounts of nutrients, especially potassium. Soil sampling and testing in the fall provides the opportunity to apply lime where needed and to determine fertilizer needs for the next year, and possibly fertilizer purchases prior to the end of the year. 
   
2. Remember and locate the areas in fields where plant growth was not as good as the rest of the field. Soil sample and test those areas separate from the rest of the field. This will let you know if the poor plant growth was related to an improper soil pH or lack of one of the nutrients. Special application to these areas may be necessary.
   
3. Chisel or subsoil fields or areas of fields where compaction may be suspected. There is no benefit from subsoiling more than two inches below the zone of compaction. The zone or depth of compaction may be identified by using a tile rod or soil probe when there is good soil moisture. Compaction is indicated by resistance in pushing the rod into the ground. Probe the soil in several different spots in a field to determine whether the concern is compaction, or the depth of compaction. Also, check the soil moisture at the depth of subsoiling. The soil should break apart when handled and not stick together in a clump when squeezed. If the soil is too wet, subsoiling will not be of benefit. The shanks should shatter the soil and not create a smeared channel.
   
4. Seed a winter cover crop. At this time of year seeding the winter cereal grains, barley, wheat or rye, will give good vegetative cover to minimize wind and water erosion during the winter and early spring months.  
   
5. Fall nutrient application. Some farmers apply nutrients, particularly potassium and nitrogen, in the fall in preparation for next year’s crops.Fall application is satisfactory on loam and clay loam soils, but on sandy soils with a cation exchange capacity (CEC) less than six me/100 gram significant loss of potassium by leaching can occur. Therefore, on soils with a CEC of less than six, fall potassium application is discouraged. Fall application of nitrogen is generally not encouraged. If fall nitrogen is applied, it should be done after the soil temperature at two inches is below 50°F and a nitrification inhibitor should be added to the nitrogen fertilizer. Anhydrous ammonia is the preferred material to apply in the fall. Fall nitrogen application on sandy soils with a CEC less than six is discouraged because of the greater risk of nitrogen leaching loss. Much of the potassium and nitrogen leaching loss occurs in late winter and early spring when saturated soils are draining from snow melt and spring rains.
   
6. Bed formation in the fall. Some growers prefer to form their beds in the fall because soil moisture is usually favorable and it saves time in the spring. When plastic is laid over beds in the fall, nitrogen and potassium in the bed will be much less subject to leaching loss because water will not be moving down through the bedded soil. This is a management system which could enable fall application of potassium and nitrogen on low CEC sandy soils with minimal concern for loss. 

Pumpkins and squash are warm-season crops, and require a relatively long, warm, sunny growing season to reach maximum size and yield. In a cool summer such as we have just experienced, the rate of growth is reduced and fruit require extra time to reach full maturity.

Pumpkins and winter squash are mature when the color of the skin turns from shiny green to their mature color. When the fruit is mature, it may be wise to cut the fruit from the vines and let the curing process begin. Curing of pumpkins and squash is a very important part of the post harvest process and should always be included in the crop plan.

Curing allows the fruit to shrink about 10 percent in weight, which results from loss of some water. During the process, cuts and bruises heal, and fruit infected with pathogens rot. If shipped immediately off the field, these infected fruits often rot at retail outlets, and growers have to retrieve them or pay for removal. Fruit should be kept above 70°F for about two weeks for optimum curing. At the very least, fruitshould be cut from the vines and allowed to cure in the field for two weeks before shipping.

Pumpkins and squash are very susceptible to cold temperatures, and exposure to temperatures below 40°F will shorten shelf life. Never place pumpkins or winter squash in refrigerated storage below 40°F. A cool night or two in the field normally won’t hurt the fruit, but a frost will cause fruit damage and rapid rots. “Frost on the pumpkin” is a phrase we often use to remind us of the approaching fall, but it causes rot in pumpkins.

As harvest season winds down, take a moment to get familiar with resources at Enviro-weather. (www.enviroweather.msu.edu) There you will find current weather conditions and forecasts, potential evapotranspiration and irrigation planning, and pest prediction tools like TomCast and Pestwatch for corn earworm.

Click on the image to go to the Enviro-weather site.