Vegetables

Vegetable Crop Insects - Joanne Whalen, Extension  IPM Specialist;   jwhalen@udel.edu

 

Cabbage.
Be sure to sample fall planted fields for diamondback and cabbage looper larvae. We can find both insects in recently planted fields. If both species are present, Avaunt, a Bt, Proclaim or  Spintor  will provide control. If cabbage looper is the predominant species, a pyrethroid, Intrepid, or Confirm  will also provide control.

Lima Beans.
Continue to scout for lygus bugs and stinkbugs as soon as pin pods are present. Treatment should be considered if you find 15 adults and/or nymphs per 50 sweeps. You should also start scouting fields with pin pods for corn earworm. A treatment will be needed if you find one corn earworm larvae per 6 ft of row from late flat pod stage until harvest.  Capture, Mustang, Lannate or Warrior will provide corn earworm control.

Melons.
Continue to scout all melons for aphids, cucumber beetles, and spider mites. Be sure to watch for bees foraging in the area and avoid insecticide applications on blooming crops. 
 

Peppers.
Be sure to maintain a 5-7 day spray schedule for corn borer control. Since corn earworm populations are starting to increase in many locations, you will also need to consider treating for corn earworm.  Continue to scout for beet armyworm, especially if fields are weedy.  Avaunt, Intrepid and Spintor will provide the best beet armyworm control.

Snap Beans.
At this time, all fresh market and processing snap beans will need to be sprayed for corn borer from the bud stage through harvest. With the increase in corn earworm trap catches, you will also need to consider this pest when making your chemical selection. Remember, Orthene provides poor corn earworm control. So if Orthene is used at the pin stage, a pyrethroid should be added to the mix. Since moth catches can change quickly, be sure to check our website for the most recent trap catches and information on how to use this information to make a treatment decision in processing snap beans. (http://www.udel.edu/IPM/traps/latestblt.html and http://www.udel.edu/IPM/thresh/snapbeanecbthresh.html). 

 Sweet Corn.
All fresh market silking sweet corn should be sprayed on a 2-3 day schedule.  Since corn earworm populations have increased quickly in some locations, be sure to check trap catches frequently. You can check trap catches and treatment decision guidelines on our website (http://www.udel.edu/IPM/traps/latestblt.html and http://www.udel.edu/IPM/thresh/silkspraythresh.html). Continue to watch for fall armyworm feeding in the whorls. A treatment is needed if you find 12-15% of the plants infested. Generally, 2-3 whorl sprays are needed to achieve control. In whorl stage corn, Avaunt, Lannate, Larvin and the high rate of Warrior have provided the best control in recent years. In addition, we also have a 24C SLN label for Lorsban 4E for armyworm control in sweet corn. With all products, the best control will be achieved if worms are small at treatment time.  Also be sure to check all labels for grazing restrictions and feeding restrictions for corn silage, forage or fodder.  In addition, if fall armyworm pressure is heavy in your whorl stage fields (above 30% infested plants), you should consider a combination of a pyrethroid plus Lannate, Larvin or Lorsban for the first 1-2 silk sprays.  Be sure to check labels for days between last application and harvest for all materials.

Lima Bean Fields Are Being Sprayed for Downy Mildew Prevention – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

 

With conditions favorable for the development of Downy mildew (Phytophthora phaseoli)  on lima beans, many processors, consultants, and growers are taking steps to prevent Downy mildew on lima beans.  While no outbreaks have been reported in commercial fields, we have seen some Downy mildew on home garden pole lima beans.  Typically, preventative applications of a fixed copper (Champ DP or Kocide 2000) are being applied, often in conjunction with insect sprays, but not necessarily. 

 

If Downy mildew is suspected or found on lima beans, please contact your county agent, an Extension plant pathologist, or me.  We are interested in determining what races of Downy are present.

 

This Downy mildew is a different species of fungus from the Downy mildew fungus that attacks cucurbits (Pseudopersonospora cubensis).

 

Please refer to Issue 19 for specific spray recommendations.

 

 

 

Downy Mildew on Pickling Cucumbers – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

 

This Downy mildew (Pseudopersonospora cubensis) is still plaguing all cucurbit crops, including watermelons, cantaloupes, pumpkins, squash, and cucumbers.  Yields of pickling cucumbers are reduced from the inability of the plant’s foliage to support fruit growth and from the interruption of pollination due to the adverse impact on the pollinator varieties.  The latter situation is especially true with varieties that use older, less resistant pollinators, and results in a high percentage of unusable fruit.

 

Early reports from North Carolina on the Downy mildew infection on the fall crop are discouraging.   Even with a rigorous fungicide program, many fields are showing Downy mildew infection.

 

If there is any good news in all of this, it is that this organism does not over winter in our region.  The source of primary innoculum for our region is considered to be wind-borne sporangia from infected cucurbits grown in areas to the south of us.  Historically, the conventional wisdom has identified Florida as the primary source, with the sporangia moving up the coast as the season progresses.  Typically, we don’t see Downy mildew on cucurbits until mid-August or September.

 

As a reminder, this fungus infects only members of the Cucurbitacae family. 

 

 

 

Spinach Planting Will Begin Soon – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

 

Spinach plantings for fall harvest will begin soon.  Successful weed control programs in the past have utilized Ro-Neet used as a pre-plant incorporated material, and Dual as a pre-emergence material.  Ro-Neet can be applied at 3-4 pints/acre and incorporated into the soil at 2-4 inches.  This should be done 7 to 10 days in advance of planting to reduce potential injury.  Ro-Neet will do a good job of controlling most grasses and the broadleaf weeds pigweed and purslane.  It will do a fair job on common lambsquarter.

 

Dual Magnum has a 24c special local needs label for pre-emergence control of weeds in spinach.  This label is in place for Delaware, Maryland, Virginia, and New Jersey.  Dual will provide control of the same weeds, but also have good activity on yellow nutsedge, hairy galinsoga,  and eastern nightshade.  The labeled rate is 0.33 to 0.67 pints per acre.  Sandy, or coarse textured soils should receive the lower rate.

 

If Ro-Neet and Dual are going to be used, consideration should be given to reducing the Ro-Neet rate to the 2-3 pint range, again to help avoid potential injury.

 

Post-emergence herbicides such as Poast 1.5 EC and Select 2EC are available for grass control later in the season if necessary.  Spin-aid is available for post-emergence control of chickweed and other broadleaf weeds in the fall months only.

 

 

 

Vegetable Crop Diseases - Bob Mulrooney, Extension Plant Pathologist, bobmul@udel.edu

 

Late Blight Advisory.

 

Disease Severity Value (DSV) Accumulation as of August 4, 2004 is as follows:

Location: Joe Jackewicz Farm, Magnolia, DE. Greenrow: April 25, 2004

Date	Daily DSV	Total DSV	Spray Recommendation
6/26-30	0	87	10-day
7/1-7/11	7	94	10-day
7/12	5	99	7-day
7/13	2	101	7-day
7/14	2	103	7-day
7/17	10	113	5-day
7/19	1	114	5-day
7/22	2	116	7-day
7/23	2	118	7-day
7/24	9	127	7-day
7/26	5	132	7-day
7/27	11	143	5-day
7/29	2	145	7-day
7/30	10	155	7-day
8/2	4	159	7-day
8/3	2	161	7-day

 

Application rates for protectant fungicides (Dithane, Bravo, etc.) should be at the high end of the rate with the amount of foliage present. For specific fungicide recommendations, see pages F132-33, 2004 Delaware Commercial Vegetable Production Recommendations Book. EB 137.

 

No late blight has been seen in DE-MD area on potatoes.

 

Note:  Late blight has been confirmed on tomato in Burlington County, NJ and is present in southeast PA on tomato as well. Conditions have been very favorable for it to appear if the fungus is present. Growers with late potatoes and those that may have tomatoes nearby should continue to spray and scout for symptoms.

 

                                                                                    Photo by Bob Mulrooney

 

Late blight on tomato leaf.

 

Note the white ring of the late blight fungus sporulating on the edge of the lesion.

 

 

 

 

 

Field Crops

 

Field Crop Insects - Joanne Whalen, Extension  IPM Specialist; jwhalen@udel.edu

 

Soybeans.
We continue to find low levels of soybeans aphids in all three counties.  You will need to look at the entire plant when sampling for aphids. The treatment threshold is 250 per plant up to growth stage R-3/R-4 with 80% of the plants at that level. After R4, the  threshold increases to 1,000-1,500 aphids per plant. Numerous products are now labeled for soybean aphid including Asana, Baythroid (suppression only), Mustang MAX, Warrior, and Lorsban. Dimethoate has not provided adequate control and Furadan 4F only has a 2ee label for the Midwestern states.

 

We are starting to find a few corn earworms in double cropped fields; however, populations are extremely low at this time. With the increase in moth catches in North Carolina and the eastern shore of VA as well as a significant increase in our own pheromone traps as well as some BLT locations, you will need to start sampling soybean fields for earworms by mid-August. Although full season fields should generally escape damage, it will be important to check those fields at least 2 times to be sure that you do not miss an infestation. As in most years, double crop fields will be most susceptible to attack. A treatment should be considered if you find  3 per 25 sweeps in narrow fields and 5 per 25 sweeps in wide row fields (20-inches are greater).

 

The following materials will provide corn earworm control in soybeans: Ambush, Baythroid, Asana, Mustang MAX, Pounce, Warrior (all pyrethroids), Larvin, Lorsban or Steward.  Larvin and Steward act by ingestion on both small and large larvae. Remember that if you are using a pyrethroid, the primary mode of action on large larvae will be ingestion. Earworms will need to feed to cause death so you will not see much activity from the contact action. Once they ingest the product, they immediately stop feeding. Therefore, fields should not be evaluated for control until 4 days after application. Small larvae are generally killed by contact as well as ingestion.  It is important that you do not look at fields 1-2 days after spraying and assume control failure if large worms are present. This could result in unnecessary re-sprays. We are also finding a few beet armyworms in fields. If the predominant pest is beet armyworm, the pyrethroids will not provide control. Steward would be the preferred material. However, in 2002 grower demonstration trials, Lorsban also provided good control.

 

 

 

Field Crop Diseases - Bob Mulrooney,

Extension Plant Pathologist, bobmul@udel.edu

 

Corn.

Leaf blights and spots are on the increase. Northern corn leaf spot often called Carbonum leafspot rac