Vegetables

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

 

New Registrations and Restrictions

 

Warrior.

The following uses have been recently added to the Warrior label: apples and pears; edible podded, succulent shelled and dried shelled beans (included but not limited to black-eye pea, garden pea, lima beans, and snap beans) and peppers (bell and non-bell).

 

New 2ee Labels from Dupont:

(a) Avaunt – For the control of Colorado potato beetle in potatoes. This label is in effect in Delaware, Maryland, Virginia, New Jersey, Pennsylvania, Wisconsin, Maine and Michigan.  The use rate is 3.5 to 6 oz per acre. In areas where beetles are difficult to control (i.e. Delaware), the use of the synergist piperonyl butoxide (PBO) may be necessary to achieve optimum control. The rate of PBO should be 0.25 lb ai/acre.

 

(b) Vydate L - For control of leaf miners and supplemental control of root knot nematode used in conjunction with other marketed soil treatments as a Methyl bromide replacement program on the following crops: tomato, bell and non-bell pepper, eggplant, pumpkin, cucumber, cantaloupe, watermelon, honeydew melon, and squash using drip irrigation and soil injection systems.  This label is in effect in DE, MD, NJ, PA, PR, and VA.

 

Definition of Coastal Counties - We often get the question regarding the definition of coastal counties, especially as it relates to the use of Capture on field corn and sweet corn in Delaware.  The following is the official response from EPA: In 1994, FMC volunteered this restriction as a risk mitigation measure due to ecological risk concerns for estuarine and marine organisms and to get a waiver from conducting a marine invertebrate life cycle study. It originally pertained to the coastal counties of Texas and in 1998 expanded to all coastal counties in the U.S. We accepted this restriction and granted the waiver. The restriction was designed to limit concerns for these marine organisms by not allowing use in vulnerable areas such as coastal counties. We didn't get into a definition of coastal counties at that time, but since our concerns pertained to estuarine /marine organisms we interpreted the restriction as applying to those natural water bodies where these type organisms reside. So we would consider counties bordering the ocean, bays as well as tidal rivers as coastal counties.

 

Peas, Sweet Corn and Snap Beans.

Be sure to consider seed corn maggot control, especially where a green cover crop is plowed under close to planting, manure is used and/or a field is minimum tilled.  A seed treatment containing diazinon or permethrin should be used on early-planted sweet corn. Gaucho or Cruiser treated sweet corn seed will also provide seed protection. In fields with a high potential for seed corn maggot (combinations of the above conditions), a soil insecticide plus a seed treatment will be needed. On all 3 crops, the use of diazinon 50W as a planter box treatment has provided good control in recent years. Seed must be treated with a commercial fungicide; graphite may be needed to prevent bridging and you should not treat more than you plan to plant in any one-day. The diazinon 50W rate for seed corn maggot is 1/2 oz per bushel of seed.

 

Sweet Corn.

Although winter conditions have not been very favorable for overwintering flea beetles, flea beetle management should be considered on early-planted varieties susceptible to Stewart's Bacterial Wilt. If you are using a soil insect insecticide for flea beetle control, the only labeled products providing flea beetle control are Counter and Furadan. Regent is not labeled on sweet corn. Another control option is Gaucho or Cruiser treated seed. In 3 years of research trials, seed applied treatments have provided very effective beetle control and management of Stewart's Wilt.

 

 

Frozen Vegetable Inventories – Peas, Lima Beans and Sweet Corn – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

 

The March 1 holdings of frozen peas reflects the reduction in pack on a national basis.  U.S. cold storage holdings were 115 million pounds as of March 1, as compared to 174 million pounds at the same time last year, a reduction of 33%.  Baby Lima beans, are also at lower holdings, with 40 million pounds in cold storage, down over 6% from last year.  Fordhook lima beans were at 8.8 million pounds, down 15% from 2002 levels.

The reductions reflect lower pack, increased movement, or some combination of the two.  Moving product out of cold storage to consumers is good for the processors in keeping inventory costs down, and good for producers who want to keep these vegetable crops as part of their farm enterprise.

The other big item on Delmarva, sweet corn, is experiencing high inventory levels on a national basis right now.  Cut corn is up nearly 14%, and cob corn is up 20% from inventories of the previous year.  This is reflected in the acreage being contracted on Delmarva and other regions for 2003.

 

 

Pea Production Update – Ed Kee, Extension Vegetable Crops Specialist; kee@udel.edu

Cold, wet weather has made pea planting a struggle so far this season.  However, growers and processors have done a remarkable job of grabbing those opportunities for planting as they present themselves.

 

Many growers are using preemergence weed control programs that feature some combinations of Dual, Command, and/or Pursuit.  However, wet weather may prevent applications being made until the peas have emerged.

 

In that case, growers will need to consider post-emergence applications of Poast or Assure for grass control; and post-emergence applications of Basagran for broad-leaf weed control.  Scouting and checking fields for emerging weeds and grasses is critical, especially the broadleaf weeds.  Basagran will provide better control if applied when the weeds are small.  This is especially true for lambsquarter, but applies to all broadleaf weeds.

 

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

 

Peas.

Be sure to rotate pea planting 4-5 years to avoid and reduce root rot. Ridomil Gold 4E applications broadcast after planting can be useful if Pythium control is needed.

  

Spinach.

Be sure to check overwintered fields for white rust. As soon as white rust is seen, apply Quadris as a foliar spray. If more sprays are needed, alternate with Actigard. Actigard is to be used at the rate of 0.75 oz/A. There is a 7-day preharvest interval for Actigard.

 

Phytophthora Blight and Fruit Rot.

Phytophthora Blight and Fruit Rot caused by the fungus Phytophthora capsici is still a concern for vegetable growers. The fungus is favored by wet conditions and flooded soil. It was seen last season again on lima bean pods from wet irrigated areas of fields in Kent County. On limas it can look like downy mildew,but it is different. It was also seen on pumpkins in Kent and New Castle Counties. It has caused significant losses in cucumbers both slicers and pickles, and summer squash in past years when we get lots of rain in a short period of time.

 

The best control is to grow the plants on raised beds, especially for peppers, to get them out of the water and to rotate for long periods of time (3 years or more) away from susceptible crops. For vegetable growers this is difficult because many crops are susceptible and irrigation availability limits rotation intervals. But a combination of rotation and other horticultural practices combined with fungicides may provide some relief. Fungicides alone have not provided a solution as results from New Jersey on Phytophthora blight on peppers has shown. Overuse of fungicides can result in the fungus becoming resistant or tolerant of the fungicide. What drives this disease is water. Choosing well-drained fields, avoiding planting wet areas, and planting on high beds combined with fungicides that are labeled for the crop, such as mefanoxam (Ridomil, UltraFlourish) on peppers, and Acrobat for cucurbits have provided a measure of control.

 

Be aware that this soil borne fungus is out there and could become a problem if introduced or identified on your farm. It infects a wide number of vegetables including cucurbits (cucumbers, cantaloupes, watermelons, pumpkins and summer and winter squash), peppers, eggplant, tomatoes and now lima bean pods.

 

 

 

Field Crops

  

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

 

New Registrations and Restrictions.

See Vegetable Insects page 1.

 

Alfalfa.

The first weevil larvae can be found in Kent and Sussex Counties; however, populations are significantly lighter compared to this same time last year. Since the alfalfa weevil overwinters in both the adult and egg stage, the larvae we are finding at this time are a result of eggs laid last fall. Overwintered adults can also lay eggs in stems any time temperatures are above 48 degrees F. Although egg laying occurs in the fall and spring, larvae hatching from spring-laid eggs cause the most damage. The weevil passes through four larval stages in approximately three weeks. No controls should be needed before 50% of the tips show feeding damage. A more accurate way to time an application and try to avoid multiple insecticide applications would be to sample stems and determine the number of weevils per stem. A minimum of 30 stems should be collected per field, placed top first in a bucket to dislodge larvae from the tips and then count the number of weevils per stem. The following thresholds, based on the height of the alfalfa, should be used to make a treatment decision: up to 11 inches tall  - 0.7 per stem; 12 inches - 1.0 per stem; 13 - 15 inch - 1.5 per stem; 16 inches tall - 2.0 per stem and 17-18 inches tall - 2.5 per stem. Numerous pyrethroids are now labeled for alfalfa weevil including Ambush, Baythroid, Mustang MAX, Pounce and Warrior. Furadan, Imidan, Lorsban and Lannate will also provide control.

 

Field Corn.

In cooperation with UAP Inc., we will again be running pheromone traps for black cutworm. The first moths were caught last week in a number of locations  (see table on last page of report). Although no precise numbers are available, moth catches of 9 to 15 moths per 7-day period have been associated with a moderate to high potential for cutworm outbreaks.  Larvae will be large enough to begin cutting when about 300 base-50 degree-days have accumulated since peak moth activity and egg laying. By calculating cutworm hatch and development over time, we can anticipate when to look for damage. Pheromone trap catches help us determine when peak moth flight and egg laying occurs; however, they cannot predict the amount or magnitude of cutting that will occur. The presence of a major flight only means that the potential for an outbreak exists. Adverse weather, lack of adequate food for newly hatched larvae, predation, and disease can reduce larval populations. You can use pheromone trap and degree-day information to estimate or predict when first cutting will occur. Scouting of seedling corn near the first cutting date is the best way to determine whether a problem exists. Just a reminder, if you plan to tank mix a pyrethroid with a herbicide for cutworm control, it should be done at or immediately following plantings. Pyrethroids combined with early burn-down applications, 2-3 weeks before planting, have not provided effective control.

 

Timothy.

Reports from around the region indicate that cereal rust mite populations are lower compared to last season. However, as soon as fields green up you should begin checking for mites and the early signs of infested leaves, especially in fields with problems in 2002. These mites are microscopic, so the use of a 20x-magnifying lens is necessary. If rust mites become a problem again in 2003, Sevin XLR Plus still has a 24C registration on timothy for rust mite management. The following are the use directions for this label: Apply 3 pts per acre (1.5 pounds ai per acre) using ground equipment only with adequate water for complete coverage (20 or more gallons by ground).  One application should provide enough suppression to prevent economic yield and quality losses. Apply at approximately 3-4 weeks after green-up in fields with a previous history of rust mites and/or when 25% of the plant tillers exhibit curled tips of the new leaf blades. It has a 30 day wait until harvest.

 

Wheat.

At a recent meeting of plant pathologist and entomologists in the Mid-Atlantic, the topic of the potential for barley yellow dwarf this spring was again discussed. The discussion focused on the fact that a great deal of small grain is still in a vulnerable stage for possible transmission of the virus. It was agreed that for most of us north of Virginia we find that 90% of the time a local aphid population and a local source of the virus are needed for BYDV (barley yellow dwarf virus) to develop. However, with the recent jet stream pattern the idea that we could have long distance transport of virus-bearing aphids and resulting infection is real but less likely to happen than from local sources.

 

Spring spraying for aphids to prevent BYDV should only be considered if there has been a recent history of BYDV in and around the field. Although Arv Grybauskas from Maryland feels that it's on the rise he still thinks that considerably less than 10% of the acreage is at risk.  In Delaware, we have only seen a slight increase --less than Maryland. The increase was probably the result of a series of mild winters allowing greater aphid survival, more opportunity for a longer transmission period and increase in the virus reservoir in surrounding weedy vegetation.  The harsh winter we had has burned back a lot of the weed reservoir harboring the virus. Even though we had snow cover, there were periods when cold conditions without cover existed.  Leaf tissue got burned back.  BYDV is a phloem limited virus so it can be translocated into the roots, and possibly get translocated back into new growth as the temperature increases.  However, this has never been documented in the field. So until new growth is formed with the current virus reservoir, we don't have much of a source of the virus in native vegetation, and the new growth may end up with a low amount of the virus anyway. In summary, although most wheat is in a very vulnerable stage, we think the vector is at a low population level and the most important local pool of virus inoculum (native vegetation) is also very low at this time. (Information from Arv Grybauskas, Bob Mulrooney, and Joanne Whalen).

 

Cereal leaf beetle could also be a threat to the later planted wheat. Since cereal leaf beetle is known to prefer small grain fields with thin canopies, many of our fields may be at risk this year. We have just found the first signs of adult feeding in Sussex County. In recent years, the threshold for cereal leaf beetle has been adjusted to include sampling for eggs, especially in high management wheat fields. The eggs are elliptical, about 1/32 inch long, orange to yellow in color when first laid changing to a burnt orange prior to hatching. Check our website for pictures of cereal leaf beetle adults, larvae and eggs (http://www.udel.edu/IPM/facts/clbpictures.htm) Generally, eggs are laid singly or in small scattered groups (end-to-end) on the upper leaf surface and parallel to the leaf veins. For high management fields, the threshold is based on the presence of eggs and small larvae. Cereal leaf beetle larvae are brown to black, range in size from 1/32 to 1/4 inch long, and eat streaks of tissue from the upper leaf surface. Since cereal leaf beetle populations are often unevenly distributed within the field, it is important to carefully sample fields so that you do not over or under estimate a potential problem. Eggs and small larvae should be sampled by examining 10 tillers from 10 evenly spaced locations in the field while avoiding field edges. This will result in 100 tillers (stems) per field being examined. Eggs and larvae may be found on leaves near the ground so careful examination is critical. You can also check stems at random while walking through a major portion of the field and sampling 100 stems. In high management fields with good yield potential and/or where the potential for cereal leaf beetle problems is high, the threshold of 25 or more eggs and/or small larvae per 100 tillers should be used. If you are using this threshold, it is critical that you wait until at least 50 – 60% are in the larval stage (i.e. after 50% egg hatch). If the egg/larvae threshold is not used, the threshold of 0.5 larvae per stem and 10% defoliation can provide enough lead-time to provide good control if fields are scouted on a routine basis. Sevin will provide good control of cereal leaf beetles although past experience demonstrated that it could result in aphid explosions by reducing predator populations. Furadan provides good control; however, it cannot be applied once grain is heading. Lannate, Mustang MAX and Warrior will provide good control of the entire insect complex present in small grains (cereal leaf beetles, aphids, armyworm and grass sawfly). Neither Mustang MAX or Warrior are labeled on barley at this time.

 

 

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

 

Soybean Cyst Nematodes.

It is still not too late to check for soybean cyst nematode. Soil test bags can be purchased at the Extension offices. If you have a fax machine and need results quickly, tests results can be sent via FAX if you provide the number on the Nematode Assay Information Sheet.

 

Soybean Seed Quality.

The weather pattern last fall was not favorable for good seed quality in soybeans. Prolonged wet weather caused weathering and infection by the fungus Phomopsis. Seed lots tested in the Dept of Ag seed lab are testing lower than normal in general. Growers that have saved their seed are encouraged to get it tested with and without fungicide.

 

What to do if you have reduced germination seed?

1. Increase seeding rates to compensate for tests ranging from 75-85% germination test. To determine your adjusted seeding rate, divide your seeding rate goal by the % germination. For example if your goal is 6 seeds/ft and germination is 80%, then divide 6 seeds by .8 to get an adjusted seeding rate of 7.5 seeds per foot of row.
2. Do not plant seed with germination below 70%. It would be better to find higher quality seed or you may end up replanting with its costs and delayed stand establishment.
3. Do not plant low quality seed in stressful planting conditions. Plant when the soil temperatures are 65°F or above and adequate moisture is available.
4. Handle seed carefully to avoid mechanical damage.
5. Fungicide seed treatments can increase germination 10-20% if infected with seed born pathogens. However, seed treatments do little to increase seed germination due to mechanical damage. Seed treatment cannot turn low quality seed into high quality seed. It can only protect the quality that is there.

 

 

Reminders On Acetochlor Use Restrictions - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu

 

Acetochlor is a preemergence herbicide for corn that controls annual grasses and some broadleaf weeds.  It is in the following products: Harness, Harness Extra, Degree, Degree Extra, Topnotch, and Fultime.  There are restrictions that are important in our area.  The restrictions pertain to groundwater quality.  The restrictions are based on depth of groundwater within one month of planting and the combination of soil type and organic matter.  Do not apply acetachlor if the groundwater depth is 30 feet and you have sands with less than 3% organic matter, or loamy sands with less than 2% organic matter, or sandy loam with less than 1% organic matter.

 

 

New(er) Corn Products for 2003 - Mark VanGessel, Extension Weed Specialist;  mjv@udel.edu

 

Some of these products were available in 2002.

Callisto 4SC (Syngenta) has an active ingredient called mesotrione, with a new site of action.  It is a pigment inhibitor and causes sensitive plants to turn white.  It can be used either soil-applied or postemergence.  It is a component of Lumax (see below).  Postemergence are 3 fl oz/A, but other herbicides have it labeled for use with their product at lower rates.  (If crabgrass is a weed you are targeting for control, I suggest you do not reduce the rate of Callisto.)  There is excellent crop safety, up to 30-inch corn or 8 collars (whichever is most restrictive).  There are numerous broadleaf weeds listed as controlled on the label, with large crabgrass as the only grass species listed.  It is most effective with a little atrazine

(0.5 lbs/A or 1 pt/A atrazine).  Replant is 4 months to small grains and 18 months for most other crops.  There are precautions for use with Counter, refer to the label.

 

Lumax 3.95SC (Syngenta) is a pre-packaged mixture of Callisto, Dual II Magnum, atrazine, and a safener.  Use rates are 2.5 or 3.0 qts/A, based on organic matter.  At 2.5 qts/A of Lumax, it is 1.76 pt Dual II Magnum, 5.4 fl oz of Callisto, and 1.25 pt of atrazine.  No label restrictions for use with Counter, provided