Vegetable Crops - Weekly update

Wayne County IPM weekly vegetable crop report -06/30/2009

• Commercial vegetable crop pesticide recommendations can be found at http://ohioline.osu.edu/b672/index.html

• Cole Crops - Cabbage worms and flea beetles are going over threshold. Some plantings have also had problems with zebra caterpillars, which can be controlled with the same sprays as the cabbage worms.  Control is recommended if there is an average of 5 or more flea beetles per plant.  Cabbage worm control is recommended when there is an average of .5 worms per plant.

• Eggplant - Aphids - spray if more than 30% of the plants have clusters.  Spider mites are also becoming a problem.  Spider mites can be found by looking for leaves that have stippling (tiny yellow spots and a dull color) and examining the back of the leaf with a hand lens. Colorado potato beetles and leafhoppers are also reaching threshold numbers.

• Green beans -   Potato leafhoppers are causing most of the damage.  Use a 15 inch sweep net to check for leafhoppers and spray when there are more than 2 leafhoppers per sweep.

• Onions- Thrip populations are increaseing with some fields goning over the threshold of  10-15 thrips per plant.  If you notice tiny mites feeding on the thrips, do not spray!  They have controlled the thrips in several fields the past few years.  Please let me know if you have these mites in your onions.  Make sure to use high pressure if you spray for thrips.  Botrytis is also being found on onions.  Bravo, Maneb or Quadris can be used for control of botrytis.  We have also found fusarium basal rot in some fields.  There is no spray program that can be used for this, but it is best to remove and destroy infested plants and plan on a 4 year rotation out of onions.

• Peppers - Aphids are being found on peppers in the fields, but still below the threshold of 30% of the plants with aphid clusters.  If bacterial spot is present, a copper spray should be applied on a 7-10 day schedule.

• Sweet Corn -    Corn borer numbers have gone down, both in the traps and in the fields.  Trap numbers as of 6/29 are 0 in all location around the county.  The threshold for corn in the whorl stage is when 30% of the plants show the shot hole damage and worms are present.  For corn that is starting to tassle, spray when 10% of the plants are infested.   Silking corn should now be on a 5-7 day spray schedule to prevent damage to the ear.

• Potatoes - Early blight is being found in the area and Late Blight has been found in Ohio! Potato beetle eggs are starting to hatch in large numbers.  Spray for control if there is 20% or more defoliation.  Bt type insecticides can be used if they are applied as soon as the eggs hatch.  Potato leafhoppers may need to be sprayed for if there are more than 1 per sweep of a 15 inch sweep net.    All potato fields should be on a preventative spray schedule with chlorothalonil or mancozeb.

• Tomato - Early blight is being found in the area and Late Blight has been found in Ohio!    Growers should use a  7-10 day spray schedule as a protective spray for both blights  (Bravo, Quadris or Mancozeb).  If bacterial diseases are also a concern, add copper to the fungicides suggested above.    Actigard can also be used as a preventitive if planting  in an area where there is a history of bacterial diseases.

• Vine Crops - Cucumber beetles are being found.  Spray for control if there is more than 1 beetle per plant.  This is the only way to prevent bacterial wilt disease. 

•  ****Downy Mildew has now been found in Sandusky County in Ohio (6/30).  Therefore it is suggested to apply Bravo, Maneb or Manzate to Cucumbers and Muskmelons as a protectant on a 7-10 schedule.  Though it has not yet been found in our area, you may want to consider adding a curative type fungicide to the spray mix.  The spray schedule should not be required on squash, pumpkins or watermelons at this time.****  A  fact sheet about Downy Mildew can be found at http://ohioline.osu.edu/hyg-fact/3000/pdf/3127.pdf