Monroe County MSU Extension

Vegetable Scouting report archives:  During the 2005-7 growing season, Paul Marks made weekly reports as he helped area vegetable growers scout and troubleshoot their crops. The latest report is at the top of the list for the 2007 report below. For the 2008 season click here. For statewide reports and other current information relating to vegetable production, see http://www.ipm.msu.edu/vegetable.htm

For current pesticide recommendations for any of these crop problems, please refer to MSU bulletin E-312, "Control of Insects, Diseases and Nematodes in Commercial Vegetables", available at county MSU Extension offices or online. Go to http://web2.msue.msu.edu/bulletins/ to purchase, or http://web4.msue.msu.edu/veginfo/index.cfm?doIntro=1 to search the bulletin.

To review information or diagnostic photos from prior year's reports, you can go to http://web1.msue.msu.edu/monroe/vegetable%20reports/vegetable_report06.htm or http://web1.msue.msu.edu/monroe/vegetable%20reports/vegetable_report05.htm

September 7: Specialist contacts: Chris Long - potato variety plots, Beth Bishop - Corn earworms

For the week ending on Friday, September 7th, please note last week's information on corn earworms and be aware that this week the trap counts have declined by almost one half, but still remain very high and continue to be of concern for any sweet corn still to be harvested, as well as peppers and tomatoes.

Many growers have asked this week about the continued decline of plants, especially peppers and tomatoes, by general wilting of the entire plant. In the absence of any obvious pathogens, I have dug and pulled a number of these plants from several fields and find the root system has at least partially collapsed. I suspect that this problem developed several weeks ago when we had the heavy rains and soils were saturated to a point that adequate oxygen was not available in the soil for the plant roots. Then why has it taken this long to show visual symptoms above ground? In my opinion, this last week soils have become more dry, air temperatures have increased again and the plants are heavily loaded with fruit. Potential evapotranspiration has again approached the two tenths of an inch per day. The combination of these factors has been more than the plants can sustain with this reduced root system, and daily wilting of the plants in fields that did not show symptoms last week is now evident. In many of the plants that I have dug this week, new roots are now attempting to grow and replace the collapsed portion, but it cannot happen fast enough to keep the plants growing normally. The fact that these new roots are growing helps to confirm the problem is environmental and not pathogen related. Cooler temperatures and some additional moisture will help to reduce the stress on these plants.

August 31: Attention growers of sweet corn, tomatoes and peppers! This last weekend there was a very heavy flight of corn earworm moths. During my professional years in Extension I may have seen corn earworm pheromone trap catches with as many as 10 to 15 moths, but never more. This last week I had nearly 100 in my trap and many other Extension Agents across Michigan had numbers that approached 1000. This was also true for both Ohio and Indiana.

So what is the significance of this information this late in the growing season? If you are growing sweet corn, please remember that this insect lays its eggs directly in the silks. If you are growing non-Bt sweet corn, you should be on a three day insecticide application schedule as long as soft silks are present in your field. Once the silks are completely dry this insect will no longer deposit eggs in the crop. Don't be caught thinking that since you are growing Bt sweet corn that this pest cannot infest your crop. There is a short window of time, beginning as the silks start to turn color until they are dry and brown, that the Bt is no longer effectively protecting the silks and that the insect may still be attracted to your crop. Therefore, Beth Bishop, MSU Extension Vegetable Entomologist, is recommending that at least one properly timed insecticide must be applied to all sweet corn just as the silks begin to dry, in order to keep from having very wormy corn. Celeste Welty from Ohio State Extension makes the following recommendation, "When moth density is this high (>90 moths per trap per week), and air temperatures are high (>80F), then ears can be protected from earworm damage by a 2-day schedule of insecticide sprays during silking. If moth density remains high but temperatures drop below 80F, then a 3-day schedule will be adequate." Don't miss this one!

Another name for the corn earworm is the tomato fruitworm. Tomato growers who have removed insecticides from the late season schedules may want to add one back as we go through this heavy moth flight. Eggs are laid either on the tomato foliage or the fruit and larvae may enter the fruits within two days of hatching, where they will be impossible to eliminate.

Pepper growers should also be aware that this insect can infest their crop as well. I have never seen this problem, but I have also never seen this insect as heavy as it is this last week. In one pepper field I saw two moths for every step I took. That's a lot! Look at this photo of the moth in a pepper plant (photo 07-M1) to get an idea of what you should be watching for in your fields. As you can see, they are larger than the corn borer moth, so you should not be easily confused. Also, please note that Orthene is not a very effective control for this insect. Beth Bishop is recommending we consider Asana or Warrior as the materials that will give the best control. Be sure to check the labels and observe both the re-entry and pre-harvest intervals of these materials as you continue with crop harvest.

August 17. Specialist contacts: Mary Hausbeck - downy mildew, Beth Bishop - Corn earworms, Jan Byrne - Pepper samples, Ron Goldy - peppers, sent MSU samples w/ Brian Webster from Mary Hausbeck's staff

Topics of phone conversations and field visits with growers: downy mildew, tomato diseases, muskmelon and zucchini downy mildew, tomato and pepper disorders, cucumber and muskmelons diseases, sweet corn insects, pumpkin diseases, the potato plot and potato beetles

For the week ending Friday, August 17, the most significant vegetable crop information I can provide is that we now have confirmed the presence of downy mildew on a number of additional vine crops in Monroe County. In addition to home gardens, this disease has now also been found in several commercial fields of muskmelons. If you are searching for symptoms in your melon field look for leaves with the yellow spots similar to those in cucumbers (photo 07-L1) and then examine the back of the leaf. One thing I have learned this week about downy mildew is that on leaves other than cucumber, the underside of the leaf does not have the typical black color when this disease is present. Look at this photo (photo 07-L2) and compare to your field. We have also found downy on gourds and zucchini in home gardens this week. Again, look for the typical yellow spots on the upper surface (photo 07-L3) which may appear rather slight as in this photo when the disease first begins and then progress to more serious symptoms later in the infection. Regardless of the stage of development you should also be able to see symptoms on the leaf underside (photo 07-L4) at the same time.

While these new finds of downy on squash and gourds have been in home gardens, including my own, they do indicate that the disease has potential to move into commercial fields as well. Given the current weather pattern of extended periods of morning leaf wetness, I would caution that all cucurbits should be on a very good spray program for the control of downy mildew. Follow the link in last week's message below for the current MSU recommendations for downy mildew controls and current information on its spread in Michigan.

Sweet corn growers should continue to monitor for corn earworms and corn borers. We are currently in the middle of second generation corn borer moth activity, though flight numbers are very low, and also in the corn earworm season with somewhat higher numbers than the corn borers, but still at relatively low pressure.

Potato growers should be alert for late season infestations of potato beetles. This week I have seen several fields heavily infested (photo 07-L5) with this insect. Watch closely as this late season infestation can become a problem with tuber feeding as the vines mature or are killed in preparation for harvest. Also, according to the MSU information for late blight forecasting we have a very serious threat for potato late blight. Fungicide applications should be made at intervals of 7 days or less. Use the highest rate labeled of the protectant fungicide plus Supertin at 2 oz/acre if near the end of the season at early senescence. We have some later maturing potato fields this season which have now responded to recent rains with a lot of new, soft growth that could certainly be susceptible to blight.

Always read and follow pesticide labels!

August 10: Specialist contacts: Jan Byrne - re:samples to diagnostic lab at MSU, Mathieu Ngouajio - pepper problems

Topics of phone conversations and field visits with growers: Peppers, sweet corn, corn borers, cabbage insects, cucumbers and melons

For the week ending Friday, August 10th, we now have accumulated 1998 degreedays base 50 which compares with a long term normal for this date of 2064, putting us about three calendar days behind this normal level.

Downy mildew should be a very serious concern for growers of any of the cucurbits, especially cucumbers and melons. Since our dry weather ended nearly two weeks ago the trap counts of downy mildew spore releases rose from 10 per day to almost 15,000 per day. For more information on this, or to continue to watch the trap numbers and view current control recommendations, go to Dr. Mary Hausbeck's web site for growers at http://plantpathology.msu.edu/labs/hausbeck/Hausbeck%20Lab%20For%20Growers.html Here you will find information from Monroe County as well as four other locations in Michigan. With the rains coming on almost a daily basis, the timing for application of recommended fungicides must be at a maximum of five day intervals and even shorter intervals following a heavy rainfall.

Sweet corn and pepper growers should be watching closely for corn borer activity in this crop. Even though adult catches of European Corn Borer adults continue to be low, adult activity can be observed when walking fields this week and I have found several egg masses in peppers. Read labels carefully for applications and pre harvest intervals. Also remember in peppers that only two applications of Orthene are allowed per growing season. This last week I have also seen the first winged aphids of this season in several pepper fields, but no colonies have yet been established. Combining the ECB egg find and the winged aphids, one would think that within a week the first Orthene application might be justified; however, check your pepper field closely to be sure your timing is correct for maximum effective control.

Sweet corn growers should also note that this week I have caught the first significant number (10 in one night) of adult corn earworms in pheromone traps. Any sweet corn from silks emerging (photo 07-K1), up until dry silks (photo 07-K2), needs to be protected on a tight schedule of 4-5 days with this heavy CEW pressure as this is where CEW eggs are laid. I have not seen CEW moth numbers this high in traps for several years!

Last but not least, we have just experienced a five day period of weather that could not have been more favorable for the development of fungal pathogens in any crop. Extended periods of wetness combined with very warm nights and lots of soft plant tissue are the most ideal conditions we could provide for fungal diseases. This week I have seen diseases such as Phytophthora (photo 07-K3) in local fields. This, as well as alternaria and botrytis, need to be looked for carefully. Do not delay in applications of crop protectants, even if your calendar schedule indicates you are good for another three of four days. Your crop is definitely at risk! Check MSU Extension bulletin EB-312 for specific listing of crops and controls. Check it out on the web at http://web4.msue.msu.edu/veginfo/index.cfm?doIntro=1

August 3 This week I spoke with Beth Bishop re: ECB numbers and beetle identification

Topics of phone conversations and field visits with growers: powdery mildew and downy mildew in vine crops, bacterial canker in tomatoes and other tomato and pepper problems.

As of Friday, August 3rd, we have now accumulated 1818 degreedays, base 50. This compares with a long term normal for this date of 1902, putting us about three calendar days behind the long-term average. Potential evapotranspiration for this last week has averaged about .20 per day, much less than one might think. During the daily high temperatures, many plants basically "shut down" and do not transpire as they normally would for plant growth and development. This may also help explain why crops such as tomatoes have not been ripening as fast as we might think they should.

Corn borer numbers continue to be very low with my traps averaging less than one moth per trap again this week. This is consistent with all other areas of Michigan, with the exception of Macomb County where numbers have continued to run much higher for the last several weeks.

This week a number of vegetable problems have created management challenges in local fields. Again downy mildew of cucurbits has been a topic for discussion. As of Friday, August 3, there are now eight counties in Michigan with confirmed cases of downy mildew on cucumbers. So far Monroe County is the only one with confirmation on muskmelons. There have not been any confirmed cases of this disease on pumpkins in Michigan, although both Ohio and Indiana have made this identification. Locally the downy mildew continues to ravage cucumbers with these symptoms on upper leaf surface (photo 07-J1) and then the black development on the lower leaf surface (photo 07-J2). Compare these symptoms with powdery mildew which has also appeared in many fields this week. With powdery mildew you will see this white development, first on the upper surface of the leaf (photo 07-J3) and then also on the lower surface as it becomes better established. Don't confuse the normal plant leaf with powdery mildew. In this photo (photo 07-J4) I am pointing to the leaf on the left with powdery mildew, while the leaf on the right has a normal uneven appearance which develops as pumpkin leaves are growing rapidly.

Tomatoes have continued to become infected with bacterial diseases. Both bacterial speck and bacterial canker are in many fields of both market tomatoes and processing tomatoes. Bacterial speck generally shows as small dark lesions on the leaf (photo 07-J5) and then brown to black specks (photo 07-J6) on the fruits. Bacterial canker usually causes a "burning" of the leaf margins (photo 07-J7) and then the symptoms of the white halo spots (photo 07-J8) show up on the fruits.

Control of all of these diseases requires proper selection and timing of pesticide applications. Refer to MSU Extension bulletin E 312, Control of Insects, Diseases and Nematodes in Commercial Vegetables, for current recommendations. Also, remember we currently recommend a five day spray schedule for downy mildew in cucurbits. This interval must be reduced if any rain event occurs.

High temperatures this last week have increased the amount of sunscald in many fields. Both peppers (photo 07-J9) and tomatoes are prone to this problem if foliage is not covering the fruits. One day this week I placed a thermometer into a tomato that was exposed to the sun. It had an internal temperature of 135 degrees. No wonder the fruits "cook" in their own skins!

July 27 This week I spoke with the following specialists: Mathieu Ngouajio - Tomato plants ,Steve Gower - Tomatoes, Chris Long - potato plots, Mary Hausbeck - Alternaria on pumpkins, Downy mildew

Topics of phone conversations and field visits with growers: pumpkins, cucumbers, tomato plants, pumpkins and honeybees, downy mildew on pumpkins and cucumbers

Downy mildew is again the main topic for this week. Locally several additional fields of cucumbers and melons have been identified with the disease present. Given the change in weather, from the dry conditions of the last month, to one now with abundant moisture on plant leaves the probability of more infestations has dramatically increased! Growers must also be aware that the normal five day schedule must be shortened following the heavy rains of Thursday night, which no doubt removed much of the protectant fungicide from the plants. Reapplication as soon as machinery can get in the field is a must! Do this in less than your normal five day schedule! Pumpkin growers need to know that downy mildew has been confirmed on pumpkins (photo 07-I1) in both central Ohio and Indiana. While we have not had a field of pumpkins identified in Michigan with downy mildew, it is just a matter of time before this happens, given the now very favorable weather, and the presence of the spores in our area. Click on this link to get a quick overview from the Ohio State people with some additional pumpkin photos of downy mildew to help you scout your fields. http://vegnet.osu.edu/news/currentvn22-07.htm

Squash and pumpkin growers need to continue to watch for the squash vine borer (photo 07-I2) in their fields. The blooming of the chicory is an indication it is time to protect your winter and summer squash from squash vine borer. The adult moth is a day-flying moth and looks and behaves very much like a wasp. I have seen this insect a number of times this week in local fields so you need to protect the plants before the larvae bore into the stems and there is no control.

Alternaria is also present in a number of squash and pumpkin fields this week. Look for the target shaped lesions (photo 07-I3) on leaves and remember that the fungicides being recommended specifically for down mildew will not prevent this disease, nor does it protect from powdery mildew which will most likely begin to show up in the next week or two. Be sure to include one of the protectant fungicides in your spray program such as mancozeb or chlorothalonil to improve the effectiveness of the downy mildew products and increase the control of these other diseases.

Sweet corn growers should be aware that trap counts of corn borer and corn earworm moths continue to be very very low. We have now moved past the 1600 degreedays where we would have expected the second generation of this insect to become active. Perhaps the abundant moisture will bring on a new population of this pest. Check back next week to get an update on these pests.

July 13  This week I spoke with the following specialists: Beth Bishop - ECB data, variegated cutworms and Japanese beetles, and Mathieu Ngouajio on Tomatoes and pumpkins. He also visited the county to help solve a dying tomato problem

Topics of phone conversations and field visits with growers: Tomatoes, Pumpkins, Aphids, Sweet corn rust, Market tomatoes and cabbage, Processing tomatoes, Muskmelons, Cucumbers and downy mildew

For the week ending Friday, July 13th, weather continues to be a water management issue on many local vegetable farms. Potential evapotranspiration the last seven days now totals 2.25 inches. This means that on a daily basis, crops that have the soil surface completely covered have needed 0.32 of an inch of moisture from the soil. If you are in a position to irrigate, have you been adding this much??? Accumulated degreedays, base 50, now total 1416 for the season. This compares with a long term normal for this date of 1382, putting us about one calendar day ahead.

Sweet corn growers should be happy to know that as of this week no corn borer moths or corn earworm moths have been captured in my local traps. As we approach the 1500 degreeday mark we certainly expect the second generation to emerge so keep watch as you travel at night. Seeing this moth in the car headlights is a sign that your field may be at risk. Any precipitation will no doubt move this second generation along rapidly. While corn borers are few and far between at this time and insecticide use is low, continue to monitor fields closely as another pest is now active in sweet corn. The Japanese beetle (photo 07-H1) has emerged in large numbers and loves to feed on sweet corn silks. If left unchecked this pest will dramatically reduce pollination and could lower market quality.

Downy mildew has not changed this last week other than one more new discovery in Gratiot County. Locally there has been no change, and spore traps monitored here by Dr. Mary Hausbeck's staff have been all zeros, which is a good sign. This disease can change very quickly if we get into any period of precipitation. Pumpkin growers should be reminded that powdery mildew is not yet present. Recommendations would be to monitor for this disease and begin to apply materials for powdery mildew after it has been seen in the field. These two diseases have very different management requirements in pumpkins! Please note, there have been no identifications of downy mildew in pumpkins so far this year, only cucumbers and muskmelons; however, since muskmelons appear to be less likely infected with this disease, and they now are infected, recommendations are to protect hard squash and pumpkins as well as the other cucurbits.

Variegated cutworms have appeared this week in both potatoes and tomatoes. Look for the small feeding holes in leaves (photo 07-H2) and then search under the plants for the small larva (photo 07-H3) which this week range in size from one quarter of an inch up to three quarters of an inch. If left unchecked, this pest can damage both tubers in potatoes and fruits in tomatoes. Check fields closely!

Several pumpkin growers have asked about the damage on leaf margins (photo 07-H4) and are concerned about a new disease. This is a physiological disorder and was most likely caused by the extreme dehydration of the new soft tissue as a result of high temperature, low humidity and the wind of this last week. These leaves were giving off more moisture through evapotranspiration than the plant was able to replace through the root system. Do not attempt to apply a pesticide to correct this disorder. In all cases where I have seen this, it is in the newest, most fully developed leaf.

July 6: This week I spoke with the following specialists: Mathieu Ngouajio and Darryl Warncke - Molybdenum deficiency in cauliflower, Beth Bishop - ECB data, Chris Long - Potato plots, Adam (plant pathology technician) - Downy mildew spore traps,  Shantee (plant pathology grad student) - Downy mildew sample

Topics of phone conversations and field visits with growers: Molybdenum deficiency in cauliflower and potato plot, downy mildew and pickle pollination, ECB traps, tomato problems, phytophthora, downy mildew on melons and manganese deficiency.

For the week ending July 6th the most significant update is the identification of downy mildew on muskmelons in a local home garden. This should bring attention to the need to be also protecting this crop from infestation by the downy mildew organism. Check below for recommendations of fungicides, and also with Mary Hausbeck's web page for growers for new information. There you will find that this week the spore trap count for Monroe County was "0"; however, we still found this new infection in a home garden, which of course was not protected with the recommended fungicides. So far there have been no additional confirmations of downy mildew in commercial fields of any of the cucurbits following the first one of several weeks ago!

Sweet corn growers should begin to watch for second generation corn borer activity. My traps were all empty this week indicating that the flight of second generation moths has not yet begun; however, we are now at 1247 degreedays, base 50, and would expect them to become active in the next 7-10 days. Check back next week for an update on this pest.

Tomatoes in several fields have begun to show the symptoms of bacterial canker (photo 07-G1). Recommendations for control generally include copper materials and might include a biological product, Serenade. However, please note that there is no eradication of this disease and all that can be done is to attempt to prevent the spread of the infection to new growth, including fruits. Notice in the photo the "burned" edges of the leaf and the white target lesions on the fruit, telltale symptoms of this disease.

I have been in two cauliflower fields this week that are showing signs of Molybdenum deficiency (photo 07-G2). At this point in the growth of the plant, as it nears harvest, there is very little that can be done. However, younger plants may be treated to insure this does not show up in fall crops. Cauliflower is one crop that is quite sensitive to molybdenum availability, even though the amount required is very small. Some varieties are more sensitive than others. If you have seen this problem, then a standard practice for growing cauliflower should include spraying the foliage with 2 ounces of sodium molybdate per acre every 2 to 3 weeks.

June 29:This week I spoke with the following specialists: Mary Hausbeck - Downy mildew, Beth Bishop - Corn earworm and ECB, Darryl Warncke - Cardy meter readings

Topics of phone conversations and field visits with growers: Cucumbers and Downy mildew, Tomato transplants, strawberries and pumpkins

For the week ending Friday, June 29th the accumulated degreedays using a base of 50 now total 1136 for the year. This is about five calendar days ahead of a long term normal for this time of the year. Use this information to help predict what insects it is time to watch for in your crops. For instance, we have now begun to see the adult squash bug (photo 07-F1) active in squash and pumpkins. Egg laying has begun and this week small masses (photo 07-F2) are beginning to appear in fields. It is important to get control of this pest early in the season before entire plants are colonized. Another insect that has appeared this last week is the squash vine borer, (adult photo); click on the link above to the MSU Vegetable CAT Alert for this week to see more photos of this pest.

This week as the small grains and grasses are maturing, thrips have begun moving to better feeding and I have found them in two fields of cabbage feeding just under the outer wrapper leaves. Check closely for this pest and remember that the Bt products do not give any control.

Corn borer traps were empty again this week, but several fields still have larva of this first generation in the plants. These larvae are between one inch and one and one half inch in size. Pupation will begin soon and second generation will begin to appear in two to three weeks. Check back for this information.

The HOT topic this week has been the appearance of downy mildew in cucumbers here in Monroe County. Check out the information just below this message, dated June 26th, for photos and links to sources of up to the minute information, as well as recommendations for control strategies from Dr. Mary Hausbeck at MSU.

June 26 URGENT INFORMATION ABOUT DOWNY MILDEW IN CUCUMBERS IN MONROE COUNTY!
There have been two confirmed cases of downy mildew identified in Monroe County this week!  These are more than 15 miles apart and neither had been protected by fungicides prior to the infection.  For the most up to date information, including recommendations, please click on this link http://plantpathology.msu.edu/labs/hausbeck/Hausbeck%20Lab%20For%20Growers.html and then select the 6-26-07 URGENT! SPRAYS RECOMMENDED: Downy mildew confirmed in 2 sites in Monroe Co.

For photos of the symptoms on one of the above cases, click here: Yellowish spots on upper leaf surface, dirty look of lower leaf surface in those spots where spores are being produced, overall appearance of infected plant.

June 22 This week I spoke with the following specialists: Chris Long - potato plots, Beth Bishop - ECB and CEW numbers, Mary Hausbeck - downy mildew

Topics of phone conversations and field visits with growers: downy mildew, Pepper problems, tomato diseases, nitrogen and irrigation management, aphids and injury in peppers, cucumbers, Pumpkin nutrition, pollination, leafhoppers, nitrate testing and the MSU variety plot.

For the week ending June 22 accumulated degreedays base 50 now total 992. This compares with a long term normal for this date of 896, putting us about five calendar days ahead of the normal. Potential evapotranspiration for this last seven days now totals 1.89 inches or about .27 pr day.

Downy mildew update The most important topic this week for local growers is that on Wednesday, June 20th, downy mildew was confirmed in a cucumber field in northeast Ohio, Medina County, just south of Cleveland. This should be an extreme caution to anyone who has cucumbers in the field. Dr. Mary Hausbeck has a very good website for growers at http://plantpathology.msu.edu/labs/hausbeck/Hausbeck%20Lab%20For%20Growers.html where you can get up to date information on the spread of this disease, local (Monroe County) spore trap information to help with predictions of infections, and updated recommendations for fungicide applications. Check out this information and bookmark the site so you can check on it regularly as this disease has now established field infestation in the midwest for 2007. Another very good source of up to the minute information on downy mildew is at the North Carolina website http://www.ces.ncsu.edu/depts/pp/cucurbit/

I am listing below Dr. Hausbeck's fungicide recommendations as a reminder for anyone who is not able to view these at her website listed above. If you see any symptoms in your cucurbits that you think might be the start of downy mildew please call Paul Marks at 734-735-7299 or marksp@msu.edu and request a field visit to confirm the disease.

Recommended products for managing downy mildew on cucumbers, from Dr. Mary Hausbeck:

Fungicide trials: Chemical control must be focused on using the most effective products, alternating the products and applying fungicides at short intervals. Results from our downy mildew research in 2005, indicate that an effective spray program includes the following: Previcur Flex (propamocarb hydrochloride) plus Bravo (chlorothalonil) alternated with Tanos 50DF (cymoxanil + famoxadone) plus mancozeb.

The initial sprays for the 2006 trials were applied when plants had one true leaf and no disease symptoms were apparent. Ten applications were made on August 1, 7, 11, 15, 21, 26 and 31; September 6, 13 and 20 following a five to seven day spray schedule. Plots were visually evaluated for necrotic leaves on September 11. Fruits were hand-harvested four times from the entire 15 ft of all treatment rows on 5, 11, 18, and 25 Sep. Products that looked favorable in our 2006 field studies include Ranman 3.6SC (cyazofamid), Gavel 75WG (mancozeb + zoxamide), V-10161 4FL (fluopicolide), Tanos 50WG and Previcur Flex 6SC. Each of these products should be mixed with either Dithane or Bravo.

This week I have had several growers ask about insecticide applications to peppers in an effort to keep the soybean aphids from spreading viruses into the pepper crop. This is not a good management strategy! I have found aphids in several fields of peppers this week, but in all cases these have most likely been green peach aphids and have not had wings. Soybean aphids do not live on vegetable crops. Any aphids you find on your vegetables are not likely to be soybean aphids. Any alate (wingless) aphids on vegetables are definitely not soybean aphids, since soybean aphids cannot reproduce on vegetables. Soybean aphids may land on melons, beans and peppers in an attempt to find their host plant (soybean), but they will not stay. Instead, they will “taste” the plant to determine if it is a soybean plant, and if it does not “taste right” they will fly off again. During the few seconds it tastes the plant, any viruses that it is carrying can be transferred. No insecticide works fast enough to prevent this transmission. Insecticides do not prevent virus transmission in most vegetables and any application of insecticides to prevent viruses does more harm than good by killing natural enemies.

Now that cucumbers are developing we are beginning to see the impact of low honeybee numbers. Remember, it takes at least ten visits to a viable female cucumber flower to completely pollinate the ovule. If less than ten visits are made, then the cucumber will not develop into a straight fruit. Look at this picture (photo 07-E1) and compare the two fruits. The top fruit was completely pollinated while the bottom did not get ten or more bee visits. Cut them open (photo 07-E2) and look at the lack of seeds in part of the bottom fruit, which has caused this misshapen growth. Review the information below in the June 8th report for a method of estimating adequate pollination in your fields.

June 15, 2007 This week I spoke with the following specialists: Chris Long - MSU potato variety plots, Beth Bishop - ECB trap counts and  Shantee (Mary Hausbeck staff) - Spore trap counts for downy mildew.

Topics of phone conversations and field visits with growers:Cucumber beetles, pollination, Irrigation, irrigation reporting, Tomato fruitworm, Cucumber burn, Corn borer control and Downy mildew

For the week ending June 15 the accumulated degreedays, base 50, now total 840. This compares with a 30 year normal for this date of 747 putting us about 7 calendar days ahead of normal in terms of anticipated insect development. This week we also have experienced one of the highest potential evapotranspiration water losses that I can remember in a seven day period, totaling 2.065 inches. This is an average of .29 per day. If you are calculating a water balance sheet this information is available on line from the Petersburg site of the Michigan Ag Weather Network at http://www.agweather.geo.msu.edu/mawn/report.asp?fileid=ptrd Numbers are generally updated by 7:30 each morning.

Downy mildew of cucumbers has appeared again this year within 30 miles of Monroe. It has been confirmed on greenhouse cucumbers in Essex County in Canada. These are not plug plants for field production but are “hothouse” cucumbers. Dr Mary Hausbeck recommends that Monroe County growers "should spray fields preventively now. If the growers in the areas of the Midwest closest to Essex County spray diligently, perhaps a 2007 epidemic can be averted. Spore trapping for downy mildew in Michigan began last week with some stations still to be set up this week.

Sprays can be banded for fields that are young and newly emerged. Cucumbers that have been growing under tunnels will be larger and will need to be covered completely with spray to be protected.

A spray interval of 10 days is currently recommended. The following fungicides are recommended:

-Gavel

-Previcur Flex

-Ranman

-Tanos

Alternate these products and mix each with either mancozeb or chlorothalonil (i.e. Bravo)."

In last week's report I showed the photo (07-C3) of Dr Hausbeck's staff setting up the spore trap to monitor downy mildew (DM) here in Monroe County. This week we have had a lot of east wind which has concerned me regarding the potential for the movement of this disease into our area. This trap in Monroe County as of Wednesday, June 13, has caught no DM spores. This is very good news; however, I would suggest that you diligently watch all cucumbers for signs of the disease. Check back in this message next Friday for an update on the development of DM. Just in case you may have forgotten what this looked like last season, here is a photo from last year of the first signs you may notice in the field (07-D1) and a closer look at the lower surface of the leaf (07-D2) showing how you can make a more positive identification. Contact Paul Marks at 734-735-7299 or marksp@msu.edu if you would like help evaluating a problem in your cucumber field. I would also suggest the you watch the movement of this disease on the North Carolina website at http://www.ces.ncsu.edu/depts/pp/cucurbit/

Another problem that has developed this last week is the European Corm Borer. Trap counts this last week have fallen to just under 4 per trap compared with 23 last week. However, this week the larvae are here in large numbers. Several sweet corn fields that I visited this week have infestations as high as 75% of the plants. In most fields I have been able to find egg masses (07-03), shot hole feeding on the leaves (07-04) and many small larva (07-05). While the weather this last 12 days has been great for crop development, it also has been great for corn borers. There has been very little in nature to reduce their numbers. Very little wind and no rain, both of which normally help reduce the survival rate of the small larvae. Check your fields closely. Any sweet corn with tassels forming in the whorl, or more advanced, no doubt needs your attention. Chemical controls will be most effective if applied from above the plants since the larvae are already in the whorls.

Sweet corn also has begun to show Stewart's Bacterial Wilt in many local fields. There seem to be two levels of infection in most of the fields. When infected early (07-D6) this disease will kill the sweet corn plant. If infected later in the development of the plant (07-D7) the impact will be less, but some yield loss will most likely occur (this is what I have seen the most this week). The internal portion of the stem of the plant is actually destroyed by the bacterium Erwinia stewartii. This disease was spread by the feeding of the flea beetle earlier this summer and is now showing up in the corn. Very little can be done now! Seed treatments and resistant varieties apparently did not completely solve this problem this season. For a better illustration of this damage, check out this photo (07-D8) which I took to help compare the normal stalk at the top, late infection in the middle and early infection at the bottom. See in the middle photo how the bacterium collects in the nodes first, and then completely destroys the tissue, (lower photo) while the upper photo shows the stalk as it should appear if healthy. For more on this disease check out the Illinois information at http://www.ipm.uiuc.edu/diseases/series900/rpd907/#table1 Also, keep in mind that flea beetles feeding on later sweet corn this season will be more likely to spread this disease since the inoculum is now present.

June 8, 2007 I conferred with the following specialists on these subjects: Mary Hausbeck - Downy mildew of cucurbits and spore trap, Beth Bishop - Corn Borer traps, phenology for cabbage root maggots, Chris Long - MSU potato variety plots
 
Topics of phone conversations and field visits with growers: hosting of spore trap for downy mildew, petiole nitrate test on cucumbers, cucumbers, pollination,
potato leafhoppers, corn borers, ECB traps, potato variety plot data

For the week ending June 8 there have been several questions that keep "popping up" as I have visited with local vegetable growers. The first of these is "Do I have enough bees to pollinate my vine crops?" This question can be difficult to answer, but merely looking at the hive entrances (photo 07-C1) is not the best method as the activity here will change by the time of the day and the source of their food supply. Once the cucurbits have begun to flower (photo 07-C2) , female on the left and male on the right, there is a very easy field estimation method that you can use that was developed a number of years ago, but is still very valid. In a year when bees are less available for pollination this might be a management tool to use. It requires spending some time in the field and makes no difference when doing the count whether the bees are visiting the male or female flowers. Consider the following:

Estimating honeybee density as reported by
Zachary Huang, MSU Entomology

For squash and melons, at least one colony per acre should be used. For pickles, we recommend at least one colony per acre for hand-harvested fields and two to three colonies per acre for machine-harvested fields. Hand-harvested fields require fewer colonies because of the lower number of flowers open in the field at any given time and that the field is harvested several times. More honeybee colonies are required for a machine-harvested field because there is a limited time for pollination to occur to ensure that the fruit is of a uniform size when harvested. If you are not sure whether there are enough bees in your field providing pollination, use the following table. This table was developed specifically for pickle cucumbers but should also be applicable for squash and melons.

To use the numbers in the table, you must observe 10 flowers for 10 minutes in three different locations (30 flowers per 30 minutes) and compare your findings to the table below 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 bee colonies.
 

A second very common question this week has been concern about the potential for nitrogen loss from the soil by leaching in view of the recent heavy rains. This potential changes according to the soil type in your field. Refer to the Monroe County Soil Survey Book and look at Table number 16 to estimate the available water holding capacity and the permeability of your soil. Many soils were well below "field capacity" just prior to the rains, perhaps at about 50% field capacity. In soil such as Selfridge this means the two-inch rain moved water approximately 20 inches into the soil profile if it was at 50% prior to the rain. In a soil such as the Pewamo this movement into the soil profile would have been much less, approximately 12 inches. In an effort to help estimate the need for additional nitrogen applications consider a pre-sidedress soil test for nitrogen, available at the Monroe Extension office, or give Paul Marks a call at 734-735-7299 or marksp@msu.edu and ask to have the petiole sap in your vegetable fields tested for nitrate levels. Now is the time to do these tests as corrections can be made in time to have direct impact on your crop.

A third question this week has been relative to downy mildew on cucumbers. I would like report that as of today there has been no downy mildew identified in Michigan. I can also report that Dr. Mary Hausbeck is diligently monitoring the potential for this disease. This week her staff has placed a spore trap (photo 07-C3) in a Monroe County cucumber field to help predict the arrival of the disease even before we see foliar symptoms and to help you schedule fungicide applications as needed and with an economically wise plan. More information on this will be reported in the next several weeks. Please check back!

The fourth question this week has concerned corn borers.  Should we begin insecticide applications now?  My pheromone traps this week averaged 23 moths per trap, compared with only 6 per trap last week.  Should you spray?  The answer to this question is, "It depends".  If your sweet corn is larger than any nearby field corn then "probably".  If your sweet corn has tassels developing in the whorl  (several fields I have seen this week meet this qualification) or is more advanced, then the answer is definitely YES!  If your sweet corn is smaller than surrounding field corn then the answer is "probably not yet".

June 1, 2007 Topics of phone conversations and field visits with growers included: Leafhoppers in potatoes, MSU potato variety plot, vegetable culture, leafhoppers in greens, cucumber beetles, cole crops, melon diseases, corn borers, leafhoppers, irrigation, bean leaf beetles, sweet potato culture, cabbage

I conferred with the following specialists on these subjects: Dr. Darryl Warncke - Cardy Meter for testing plant petiole sap for nitrogen, and Jan Byrne - Cabbage sample to diagnostic clinic at MSU

For the week ending June 1, 2007 we have now reached 552 degreedays, base 50, which puts us about four calendar days ahead of a long term normal for this time of the year as we anticipate insect and disease development in our vegetable crops. As a result of reaching the 500 degreeday level we are now in the flight of the first generation of European Corn Borer (ECB). My traps averaged only 6 moths per trap this week, but others around Michigan had much larger numbers. There is not much sweet corn in Monroe County large enough to be of concern with this insect; however, if your sweet corn is larger than any surrounding field corn, I would suggest you monitor closely for ECB eggs in your crop beginning this next week.

Several other problems have appeared this week for the first time of the season. Bean leaf beetles are on everyone's snap beans. This insect feeds by chewing holes (photo 07-B1) in leaves. Snap beans are very attractive to this insect which somewhat resembles a ladybug in size and color. Look more closely (photo 07-B2) and you will notice they are a bit smaller, more elongated and come in color variations from dark red to green to yellow. They always have the double row of six black dots on their back, which should help you differentiate them from ladybugs. If you are growing snap beans, they may need control for this pest. If you are choosing an insecticide, I would suggest using one which not only controls this pest, but also the potato leafhopper.

Potato leafhoppers (photo 07-B3) have appeared in much larger numbers this week. Potato fields that I have checked show about half of the fields are above the action threshold of 10 or more adults per 20 sweeps with the insect net. I am including this photo from my net to help you identify the pest in case you are not familiar with it. With many local alfalfa fields nearing the first harvest I would suggest that you watch potato fields and snap bean plantings closely for even greater populations this next week. As the alfalfa is harvested, the leafhoppers will quickly move to another feeding area, perhaps your potatoes or snap beans. If you would like help evaluating this insect population in your crop please contact Paul Marks at marksp@msu.edu or his cell phone at 734-735-7299.

The cole crops have made tremendous growth in the last two weeks and are now showing stress where roots are less than normal. Drier soils combined with higher temperatures develop the symptoms in fields where either root maggots or Rhizoctonia Stem Rot

have reduced the plants’ root systems. Look for signs such as slow development of a head (photo 07-B4) among otherwise normal plants, or dying plants (photo 07-B5) and pull one or more of these plants to see the actual maggot (photo 07-B6) feeding on what once was the root system or the dying root (photo 07-B7) as a result of the Rhizoctonia Stem Rot. In either case there is little that can be done for control in this crop. Treatment of the transplants in the greenhouse next time is the best way to prevent the root rot, while soil application of an insecticide will be the best strategy for maggot control. However, this season, even fields which were treated with an insecticide have some damage from maggots. We had several conditions that favored infestation early as the cabbage plants established in the field; mainly long lasting periods of moist, cool soil.

Also in the cabbage field the diamondback moth continues to infest plants. Look at this photo (photo 07-B8) of one of my pheromone traps to see why it is not easily spotted in the field. It flies very quickly from plant to plant as we walk among them and is quite small. In fields this week I have seen all life stages including the small larva (photo 07-B9) and pupae (photo 07-B10) on cabbage leaves. Remember, this is one of the most resistant insects to our chemical insecticides and you may want to use one of the Bt products which seems to offer better control.

May 18, 2007 Topics of phone conversations and field visits with growers included Corn borer trap placement, Tomato and pepper planting, Cabbage diseases, Frost damage on peppers and potatoes, Cucumber disease control and potassium applications on tomatoes.

I conferred with the following specialists on these subjects:  Mary Hausbeck - Cucumber and cabbage diseases, Darry Warncke - Cardy meter calibration, Beth Bishop - ECB traps and lures, Jan Byrne - Rhizoctonia of cabbage and  Ed Grafius - Insect egg identification 

For the week of May 18th there has been a lot of weather activity that either did, or could, impact vegetable crops in our area.  The low temperatures of Sunday morning, May 13, and again Friday morning, May 18, have damaged some sensitive crops.  I have seen damage on tomatoes, peppers, potatoes and vine crops.  If your crops have not been affected, you are fortunate.  Look at this photo of a potato plant (07-A1) which has already begun to regrow, five days after the damage of the frost.  Compare with this tomato photo (07-A2)  which was taken the day after the frost, and now look at the same plant (07-A3) six days later, with the new buds just now emerging in the leaf axil. Don't make management decisions from frost damage too hastily! 

Cabbage growers, as well as growers of all cole crops, need to be watching fields closely for signs of Rhizoctonia.  Check out photo (07-A4) I took this week to show the damage being done in a number of cabbage fields in Monroe County.  See how the stem looks normal above the ground, is dying below ground and is very constricted at the soil line.  Infected plants in fields at this point show only the symptom of slower growth.  Pull some plants and look at the stems.  New roots may be trying to grow above the infection, but the plant will likely die when we return to high temperatures and drier soils. Samples have been submitted to the MSU Diagnostic Clinic for confirmation, but from the symptoms, I am confident Rhizoctonia will be the answer.  This disease organism is generally present in soils and just needs the right conditions for infestation to occur.  Continuously wet conditions favor its development.  Treatment to protect from this disease must be done in the seedling stage.  There is no effective treatment in the field.

  Monroe County MSU Extension welcomes inquiries at 963 S Raisinville Rd, Monroe, MI, 48161 and by phone (734) 240-3170, FAX (734) 240-3183 or e-mail msue58@msu.edu Hours 8:30am-5:00pm weekdays