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

 

Beet armyworms on the Eastern Shore (Tom Kuhar. VPI)
We have seen some infestations of beet armyworm on various crops on the Eastern Shore. In addition, we are catching relatively high numbers of moths at our black light trap in Painter, VA. Beet armyworms will usually occur in high numbers on plants. Suspect beet armyworm if feeding damage tends to be concentrated around the growing point of plants. Color patterns of the larvae (caterpillars) can be quite variable. Young larvae are pale green or yellow, but acquire pale, then dark stripes as they get older and larger. Large larvae tend to be green dorsally and possess a lateral dark stripe the length of their body. Sometimes larvae are very dark. The body is completely devoid of hairs and spines. They are often found in groups and there is often webbing with droppings. The major problem with beet armyworms is that they are difficult to kill. Historically, the larvae have been resistant to the pyrethroid insecticides (Warrior, Ambush/Pounce, Asana, Baythroid, Mustang, Capture, etc.), and most of the organophosphates. In 2002 (our last big beet armyworm year in Virginia), my lab tested some newer insecticides along with some of the standards from the past for efficacy against beet armyworm in bell peppers. The best control was achieved with Avaunt, followed by Intrepid, SpinTor, and Lannate. The Bt products provided some control of beet armyworm, but are most effective when applied to smaller larvae. Efficacy trials conducted by Dr. Ames Herbert (Tidewater AREC) on soybeans showed that Steward (indoxacarb) was the best material for beet armyworm control. Steward contains the same active ingredient as Avaunt (labeled on vegetables).

 

Lima Beans –Continue to scout fields as soon as pin pods are present for lygus bugs and stinkbugs. Treatment should be considered if you find 15 adults and/or nymphs per 50 sweeps. Lannate, Capture or Mustang can be used if both species are present. The higher labeled rates of Capture (4 oz/A) and Mustang (4.3 oz/A) will be needed if stinkbugs are the predominant insect present. With the recent increase in corn earworm trap catches, you should also start scouting fields with pin pods for corn earworm larvae.  A treatment will be needed if you find one corn earworm larvae per 6 ft of row from late flat pod stage until harvest.

Melons - Continue to scout all melons for aphids, cucumber beetles, and spider mites. Although spider mites have crashed in some fields, we continue to find an occasional field with economic levels.  Since beetles found now are causing damage to rinds, be sure to watch fields carefully and treat as soon as you

see an increase in the populations.  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 some locations, you will also need to consider treating for this pest. Remember, Orthene provides poor corn earworm control, so you will need to add a pyrethroid to the mix.  You will also need to consider a treatment for pepper maggot. Continue to scout for beet armyworm, especially if fields are weedy. As indicted above in Tom Kuhar’s article, 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 consider this pest when making you 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 may need to consider a combination of a pyrethroid plus Lannate, Larvin or Lorsban for the first 2-3 silk sprays.

Spring Pickling Cucumber Variety Trial – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

 

In our spring pickling cucumber variety trial, we could discern no real differences between varieties relative to resistance reaction to Downy mildew.  This can probably be directly attributed to the high level of innoculum and the perfect conditions for the development of the disease following a six-inch rain.  The Ridomil/Gold/Bravo did maintain the vines, but the impact of the disease had already done its damage on the foliage's ability to support the crop.   Hence yield reductions and a lot of crooks and nubs.

 

Early reports of Ridomil sprayed in a seven-inch band at planting indicate early control is being achieved.  Of course, a fungicide program will need to be continued.

 

 

  

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

 

Downy mildew in lima beans has not been confirmed yet in commercial limas in DE. Labels for the two section 24 (c) fungicides mentioned last week Ridomil Gold/Copper and Phostrol are included if they are needed - htttp://www.rec.udel.edu/update04/Updatepdf.htm

 

The following link will also show the effectiveness of both fungicides in last years fungicide test http://www.udel.edu/IPM/pmr/limabeanfungicide2003.pdf.    Conditions are favorable for downy mildew infection at the present time.  If limas are in bloom or have set pods, preventative sprays, are recommended. Both races E and F were present last season and we saw the most damage from race F on C-Elite Select and race E on M-15 and Sussex. Cypress was infected by race F, but there was not as much effect on yield as best we could tell.

 

Late Blight Advisory.

 

Disease Severity Value (DSV) Accumulation as of July 28, 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	2	89	10-day
7/4	2	91	10-day
7/7	2	93	10-day
7/11	1	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	19	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

 

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.

 

 

 

 

 

 

 

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

 

Soybeans –  In most cases, it appears that spider mite populations have crashed due to the recent weather conditions. However, be sure to check fields if you still suspect that mites are present, and apply a treatment if you can find 20-30 mites per leaflet or 10% of plants with 1/3 or more leaf area damaged.

You should continue to scout on a weekly basis for soybean aphid. We continue to find low levels in all three counties. They prefer somewhat cooler temperatures, 68-77°F, so we could see an increase with the recent cooler temperatures. However, they are also subject to predation by several insects like

lady beetles, lace wings and others.  Hopefully, a combination of hot weather and action by these natural enemies will prevent economic aphid levels, but you  won’t know unless fields are monitored. You should sample both full season and double crop fields – although double crop fields will be at more risk at this time. 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 1000-1500 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 did conduct a limited corn earworm survey of corn fields in the state and results indicate that local populations are relatively low (2-26% of the ears infested). However, the Virginia survey indicates that their populations are higher than normal in some areas. Their regional averages range from 13.2-53.5% infested ears.  The following is a report of survey results from Ames Herbert, VPI:

 

Annual field corn survey reveals moderate to high potential for corn earworm problems in soybeans, cotton and other crops in Virginia (Ames Herbert, VPI):
We have just completed our annual survey of field corn to determine corn earworm infestation levels and make predictions of what is to come. Thanks to the many VCE Agents and other faculty for their participation (Dr. Tom Kuhar, Entomologist, ESAREC; and VCE ANR Agents Paul Davis, Keith Balderson, David Moore, Mac Saphir, Matt Lewis, Sam Johnson, Glenn Chappell). Together, we sampled 7,250 ears from 145 fields in 29 eastern counties during the period from July 14 to July 20. We did the survey about 10 days earlier this year because the corn crop is so advanced compared with most years. Compared with 2003, infestation levels are either about the same (19.9% in the Northern Neck compared with 19.3% in 2003; 27.2% on Eastern Shore compared with 29% in 2003), or higher (35.3% in the mid eastern counties compared with 28% in 2003; 53.5% in the southeast compared with 49% in 2003). Only in the northernmost survey counties (King George and Caroline) was the level lower (13% compared with 25% in 2003). These numbers mean that we can expect moderate to high pressure in soybean, cotton and other crops when this earworm population leaves corn. Also, when we did the survey we noted that many of the larvae were large or had already exited the ears. This means we can expect to see the moth flight begin soon. According to Dr. Jack Bacheler at NC State, the moth flight has already begun in southern North Carolina. In Virginia, our blacklight trap catch is still very low, but is just in the last few days beginning to increase.  It is always dangerous to make predictions, but based on what we are seeing, we may see egg thresholds in cotton within the next week. Folks should begin scouting cotton fields for eggs later this week. For soybean, it takes more moth activity and longer for thresholds to develop. Soybean fields are not in any danger for a few weeks, stay tuned to future advisories to get a heads up on when field scouting should begin. Keep in mind that infestation levels in corn can be misleading. Even with high levels in corn, a lot of rainy weather, especially heavy rains, can kill a lot of the corn earworm pupae in the corn fields before they can mature into moths. Wet years usually have less pressure, especially in soybean. But like politics, all weather is local. There are still some areas of the state where fields are relatively dry and corn earworm survival will be good.

 

Therefore, in Delaware, we could experience a higher than normal migratory population this year. We are also just starting to see a spike in corn earworm black light trap catches. Therefore, you should begin sampling fields in early August