Allium Leafminer Moving South in Maryland

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

The new pest of onion, leek and garlic, the Allium leafminer, is moving south in Maryland. It was first observed in Maryland in Cecil Co. in 2017, but now the fly’s tell-tale marks (Figs. 1 and 2) have been found in a Baltimore City chives planting. This new pest was first found in Lancaster County, Pennsylvania in December 2015. Unfortunately, it is my guess that the pest is now probably in many northern/central areas of Maryland. New transplants or seedings of onions or leeks should be watched closely for the tell-tale signs of the fly’s damage which are several very small white dots in a row along the leaf of an allium plant (Figs. 1 and 2).

Figures 1 and 2. Tell-tale marks on allium leaf made by Allium leafminer females

Penn State has a great deal of good information about the new pest which can be found at: Penn State Allium Leafminer Pest Alert page. Growers should look for these tell-tale signs on any newly planted allium species, but especially on leeks. You can cover any Allium planting with row cover to keep the flies off or if needed treat with insecticides as found in the 2019 Mid-Atlantic Commercial Vegetable Recommendations guide.

Timings for Late Summer and Fall Harvested Vegetables Revisited

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Plantings for fall harvested vegetables are underway and will continue through August. Timing these plantings can be a challenge, especially where multiple harvests are needed. Plantings from early July through the beginning of September may be made, with cutoff dates depending on the crop, variety, and season extension methods such as row covers, low tunnels, and high tunnels.

These plantings can be divided into 2 groups: 1) warm season vegetables for harvest up to a killing frost and 2) cool season vegetables for extended harvest in the fall.

The three main factors influencing crop growth and performance in the fall are daylength, heat units, and frost or freeze events. A few days difference in planting date in the summer can make a big difference in days to maturity in the fall.

Warm season vegetables for fall harvest include snap beans, squash, and cucumbers. July plantings of sweet corn can also be successful to extend seasons for farm stands. Mid-July plantings of tomatoes and peppers also are made for late harvests, particularly in high tunnels.

Cool season vegetables for fall harvest include cabbage, broccoli, and cauliflower; the cole crop greens, kale and collards; mustard and turnip greens; turnips for roots; spinach; beets; lettuce; leeks; green onions; and radishes.

To extend harvest in the fall, successive plantings are an option. However, days between plantings will need to be compressed. One day difference in early August planting for a crop like beans can mean a difference of several days in harvest date.

Another option to extend harvest in the fall is by planting varieties that have different days to maturity at the same time. This is particularly successful with crops such as broccoli and cabbage where maturity differences of more than 30 days can be found between varieties.

Another way to get later harvests is to use row covers or protecting structures (high tunnels). This can allow for more heat accumulation and will aid with protection against frost and freezes. Decisions on what type or combination of covers/protection to use and when to apply the protection will influence fall vegetable maturation and duration of harvest. In general, plantings of cool season crops can be made 30-45 days later in high tunnels than in outside production.

A final factor for summer planting for fall production is on planting cutoff dates. For example, a crop such as cucumber may produce well with an August 2 planting but poorly with an August 8 planting; broccoli has a wider planting window than cauliflower; turnip greens have a wider planting window than kale.

Planting Window for Fall Harvested Warm Season Vegetables
(harvest September through Frost)

Snap Beans: July 10 through August 10

Lima Beans: June 15 through July 20

Cucumbers: July 10 through August 7 (high tunnel transplanted up to September 1)

Peppers: Transplant up to July 10 (high tunnel up to July 30)

Pumpkins and Winter Squash: Direct seed through June 30, transplant up to July 7

Summer Squash: Direct seed July 15 through August 15 (high tunnel up to September 1)

Sweet Corn: Direct seed July 1 through July 30

Tomatoes: Transplant up to July 10 (high tunnel up to July 30)

Planting Window for Fall Harvested Cool Season Vegetables
(harvest September – December)
For transplants, seed 3-6 weeks prior to desired planting date (8 weeks for leeks and onions).

Beets: Direct seed July 1 through August 10

Swiss Chard: Direct seed July 15 through August 20 (high tunnel up to September 30)

Broccoli: Transplants July 15 – August 20

Brussels Sprouts: Transplants through July 10

Cabbage: Transplants July 1 – August 10

Cauliflower: Transplants July 20 through August 15

Kale: Transplants July 15 through August 30

Kale: Direct seed July 1 through August 15 (high tunnel up to September 30)

Collards: Direct seed July 15 through August 15

Carrots: Direct seed through July 10 (high tunnel up to August 30)

Turnip Greens: August 1 through September 10 (high tunnel up to September 30)

Turnip Roots: August 1 through August 30 (high tunnel up to September 20)

Mustard Greens: August 1 through September 10 (high tunnel up to September 30)

Leeks: Transplant July 20 through August 10

Lettuce (full head stage): Direct seeded August 1 through August 20

Lettuce (full head stage): Transplants August 10 through August 30

Lettuce (baby stage and cut salad mix): Direct seed August 1 through September 15 (high tunnel up to October 15)

Onion (green bunching): Direct seed July 1 through August 30 (high tunnel through September 30)

Parsley: direct seed July 15 through August 15 (high tunnel through September 15)

Radishes (salad): Direct seed August 1 through September 30 (high tunnel through November 30)

Radishes (Daikon): Direct seed August 1 through September 10 (high tunnel up to September 30)

Spinach: Direct seed August 10 through August 30 (high tunnel up to September

Seedcorn and Onion Maggot Damage Bad Now and Over the Next Few Weeks

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

The unusually warm and dry winter and spring we have had up to now has allowed large populations of seed and root maggots to invade our vegetable fields. Some farms have been hit particularly hard in their onion crop this early season by maggots. These maggots include seedcorn maggot Delia platura (SCM), onion maggot Delia antiqua (OM) and cabbage maggot Delia radicum (CM), the latter being a specialist of the cabbage family. All three species overwinter in the soil as a maggot inside a brown pupal case. In March and April small, grayish-brown flies (Fig. 1) emerge, which are usually SCM or CM. OM flies usually peak 2-3 weeks later. Adult flies are most active from 10 a.m. – 2 p.m. and are inactive at night, in strong winds and when temperatures are below 50°F or above 80°F. Adults live 2-4 weeks and females lay hundreds of eggs.

Figure. 1. Root maggot adult on yellow sticky card

Seedcorn maggot eggs are oviposited in soils with decaying plant material or manure. Onion maggot females lay eggs in soil near onion plants. Female cabbage maggot flies seek out and lay eggs on the lower portions of stems of young host seedlings or in nearby cracks in the soil. Some wild crucifers, such as yellow rocket, are important hosts for cabbage maggot and are especially important for their overwintering success; when these weeds are abundant they can lead to heavy infestations in spring crucifers. Combine this with the very mild winter we had and infestations are almost assured in some fields. The adults are also attracted to the organic media around the roots of transplants and germinating seeds. Within a few days the eggs hatch and the tiny maggots burrow down to the roots and into stems and begin feeding. Larvae of seedcorn maggots attack seedlings, feeding on the developing roots and stem. Their damage is usually restricted to the early seedling stage. SCM larvae will move into small stems and move up the plant causing a swelling of the stem just above ground level, while also causing root collapse and decay (Fig. 2). If these stems are split you usually can find the white cylindrical larvae (Fig. 3). Onion maggots inflict similar damage (Fig. 4) but usually continue to feed on the expanding bulb during later stages of growth. A single maggot can destroy up to 20 small seedlings. Either SCM or OM can attack onion bulbs, while SCM also can attack vegetable seeds and transplants. Complete larval development requires 2-4 weeks. Maggots then enter a pupal stage that lasts another 2-4 weeks. There are 3-4 generations per season in our area, with the most destructive being the spring and fall generations. When wilted transplants or newly emerging seedlings are inspected in the field, maggots are sometimes not found (they have already pupated), but their tell-tale damage appears as hollowed out seeds or stems and roots held together by a few strands of plant material.

Figure 2. Swollen stem of cucurbit plant with collapsed rotting roots.

Figure 3. When stem from Figure 2 is cut open the white maggots often can be found.

Figure 4. Maggots found in base of onion plant

Cultural controls: Avoid planting in soils that have a great deal of non-decomposed organic matter, such as fields with a heavy cover crop or are very weedy. Rotate early season crops away from any areas that had onions or crucifers last fall. Early spring-planted crops are more likely to be damaged when the soil is too cool for rapid germination and emergence. If serious infestations are expected, wait until the soil warms up in the spring. You can get an idea of how serious a possible infestation could be by using yellow sticky cards that attract adult flies and can be put out a few weeks ahead of time. It may take a few seasons of using the cards to readily recognize when a certain fly population on the cards represents a significant possibility of a heavy crop infestation. Recently seeded or transplanted crops should be covered with floating row covers, which act as barriers against any of the root maggot flies. Do not use row covers where onions or brassicas were grown the previous year. When soil temperatures increase and maggot first-flights end, the row covers can be removed.

Chemical controls: The use of treated seed (Trigard ST- commercially treated onion seed only) or banding of an insecticide (diazanon as a preplant application, Cyantranilprole as a soil or foliar application for CM or chlorpyriphos as a post plant drench for dry bulb onions only) gives some control of SCM, CM and OM, however, replacing dead transplants is the only solution after these maggots are inside a plant. Once seedcorn maggot or onion maggot damage is noticed, it is too late to apply control procedures. Thus, economic thresholds are not useful and all management options are preventative.

The adult flies can often be found dead; stuck to vegetation during periods of warmer weather. These flies have been infected by a fungus, Entomophthora sp. These infected flies usually are found at the top of a tall object in the field such as a grass seed head or a wire field-flag (Fig. 5). Just before the fungus kills them the flies cement their body via their mouthparts to the tall object and die. If you look closely you’ll see the fly’s body is filled with a white fungus that has ruptured between the segments (Fig. 6). Being on a tall object allows the spores of the fungus to move longer distances and infect more flies than if the fly had died on the ground. Unfortunately, the infection rate is not enough to reduce seed or root maggot populations and stop infestations.

Figure 5. Two SCM flies killed by a fungus stuck to a wire field-flag via their mouthparts

Figure 6. Adult SCM killed by a fungus – white strands coming out of abdomen

New Pest, Allium Leafminer, Present in Neighboring States

Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu

The allium leafminer (ALM) or onion leafminer is an invasive species that was detected in Lancaster, PA in 2015. This was the first confirmed detection in the Western Hemisphere. Since this detection, it has spread to New Jersey, New York, and Maryland. It has not been detected in Delaware but is something you should be aware of.

The allium leafminer is known to infest species in the genus Allium. This includes leeks, onions, garlic, chive, shallot, and green onion. The adults, small grey or black flies with a yellow or orange marking on the top and front of head, emerge in late winter through spring (March-May) and begin laying eggs at the base of plant stems. The larvae mine leaves, moving downward to the base of leaves or into bulbs where they pupate. Pupae may move into soil. During the summer months, ALM undergoes diapause in the pupal stage before developing into adults which emerge in the fall (September/October). This generation also attacks Allium spp. before overwintering as pupae.

Here are a couple links from Penn State University and University of Maryland for more information on allium leafminer including pictures of adults, pupae, monitoring, damage, and management:

http://ento.psu.edu/extension/vegetables/pest-alert-allium-leafminer

https://extension.umd.edu/learn/allium-onion-leafminer

If you suspect you have damage or a life stage of the allium leafminer, please contact Steve Hauss at the Delaware Department of Agriculture (302-698-4500 or Stephen.hauss@state.de.us) for official confirmation since this pest has not been detected in Delaware.

Fall Vegetables – Timing Plantings

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Plantings for fall harvested vegetables will be underway in the next few weeks. Timing these plantings can be a challenge, especially where multiple harvests are needed. Plantings from early July through the beginning of September may be made, with cutoff dates depending on the crop, variety, and season extension methods such as row covers, low tunnels, and high tunnels.

These plantings can be divided into 2 groups: 1) warm season vegetables for harvest up to a killing frost and 2) cool season vegetables for extended harvest in the fall.

The three main factors influencing crop growth and performance in the fall are daylength, heat units, and frost or freeze events. A few days difference in planting date in the summer can make a big difference in days to maturity in the fall.

Warm season vegetables for fall harvest include snap beans, squash, and cucumbers. July plantings of sweet corn can also be successful to extend seasons for farm stands. Mid-July plantings of tomatoes and peppers also are made for late harvests, particularly in high tunnels.

Cool season vegetables for fall harvest include cabbage, broccoli, and cauliflower; the cole crop greens, kale and collards; mustard and turnip greens; turnips for roots; spinach; beets; lettuce; leeks; green onions; and radishes.

To extend harvest in the fall, successive plantings are an option. However, days between plantings will need to be compressed. One day difference in early August planting for a crop like beans can mean a difference of several days in harvest date.

Another option to extend harvest in the fall is with planting different maturing varieties at the same time. This is particularly successful with crops such as broccoli and cabbage where maturity differences of more than 30 days can be found between varieties.

Another way to get later harvests is to use row covers or protecting structures (high tunnels). This can allow for more heat accumulation and will aid with protection against frost and freezes. Decisions on what type or combination of covers/protection to use and when to apply the protection will influence fall vegetable maturation and duration of harvest. In general, plantings of cool season crops can be made 30-45 days later in high tunnels than in outside production.

A final factor for summer planting for fall production is on planting cutoff dates. For example, a crop such as cucumber may produce well with an August 2 planting but poorly with an August 8 planting; broccoli has a wider planting window than cauliflower; turnip greens have a wider planting window than kale.

Planting Window for Fall Harvested Warm Season Vegetables
(harvest September through Frost)

Snap Beans: July 10 through August 10

Lima Beans: June 15 through August 15

Cucumbers: July 10 through August 7 (high tunnel transplanted up to September 1)

Peppers: Transplant up to July 10 (high tunnel up to July 30

Pumpkins and Winter Squash: Direct seed through June 30

Summer Squash: Direct seed July 15 through August 15 (high tunnel up to September 1)

Sweet Corn: Direct seed July 1 through July 30

Tomatoes: Transplant July 20 through July 5 (high tunnel up to July 30)

Planting Window for Fall Harvested Cool Season Vegetables
(harvest September – December)
For transplants, seed 3-6 weeks prior to desired planting date (8 weeks for leeks and onions).

Beets: Direct seed July 1 through August 10

Swiss Chard: Direct seed July 15 through August 20 (high tunnel up to September 30)

Broccoli: Transplants July 15 – August 20

Brussels Sprouts: Transplants June 20-July 10

Cabbage: Transplants July 1 – August 10

Cauliflower: Transplants July 20 through August 10

Kale: Transplants July 15 through August 30

Kale: Direct seed July 1 through August 15 (high tunnel up to September 30)

Collards: Direct seed July 15 through August 15

Carrots: June 20 through July 5 (high tunnel up to August 1)

Turnip Greens: August 1 through September 10 (high tunnel up to September 30)

Turnip Roots: August 1 through August 30 (high tunnel up to September 20)

Mustard Greens: August 1 through September 10 (high tunnel up to September 30)

Leeks: Transplant July 20 through August 10

Lettuce (full head stage): Direct seeded August 1 through August 20

Lettuce (full head stage): Transplants August 10 through August 30

Lettuce (baby stage and cut salad mix): Direct seed August 1 through September 15 (high tunnel up to October 15)

Onion (green bunching): Direct seed July 1 through August 30 (high tunnel through September 30)

Parsley: direct seed July 15 through August 15 (high tunnel through September 15)

Pumpkins and Winter Squash: Direct seed through June 30

Radishes (salad): Direct seed August 1 through September 30 (high tunnel through November 30)

Radishes (Daikon): Direct seed August 1 through September 10 (high tunnel up to September 30)

Spinach: Direct seed August 10 through August 30 (high tunnel up to September 30)

Pest Alert – Allium Leafminer

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

The allium leafminer (also known as the onion leafminer) has recently been detected and confirmed from infested leeks and onions in Lancaster County, PA. This is the first confirmed infestation in the Western Hemisphere. HOWEVER, this insect has not been detected in Delaware. If you think you may have observed damage or a life stage of the allium leafminer, it is important that you contact Steve Hauss at the Delaware Department of Agriculture by email (stephen.hauss@state.de.us) or call (302) 698-4500 for official confirmation since this would be a new detection in Delaware.

The following pest alert written by written by Shelby Fleischer, Department of Entomology, Pennsylvania State University, University Park, PA, and Tim Elkner, Cooperative Extension, Lancaster County, PA and edited by Dan Gilrein, Cornell Cooperative Extension of Suffolk County provides information on damage symptoms, insect identification and life history, monitoring and potential management options

http://ento.psu.edu/extension/vegetables/pest-alert-allium-leafminer

March is the Month for Planting Sweet Onions

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

There has been increased demand for sweet onions grown both for local sales and wholesale markets in our region. Sweet onions can be grown in Delaware but are challenging and require attention to some critical details to produce economically.

Sweet onions have low pungency which is determined by measuring pyruvate and must have a score of 5.0 µmol/gfw or less to using a standard onion pungency test to be marketed as a sweet onion in wholesale channels. Soluble solids (a measure of sugars) in sweet onions varies considerably by variety and the sweetest types will be over 7% soluble solids.

Planting date is very important to have the highest yields and largest bulbs. For sweet onions large (Jumbo) and colossal sizes greater than 3 inches in diameter have the most value in wholesale markets. Delaware trials have shown that to achieve these sizes consistently, it is necessary to plant by the end of March.

Local trials have also shown that to consistently achieve these sizes, transplants must be used and they must be grown on black plastic mulch with drip irrigation. Four foot wide plastic is laid on a raised bed so that there is a 3 foot bed top with 2 drip tapes so that 4 rows of onions can be planted 8-10 inches between rows and 4-6 inches between transplants and a drip tape between pairs of rows. Transplants are set by hand, which requires considerable labor.

Growers can produce their own transplants but they must be seeded in the greenhouse in January. Transplants are started in 200-288 cell flats at least 10 weeks before intended transplant date. Our research has shown that very small plugs (400-500 cell trays) will also produce transplants that yield a high percentage of large bulbs. Growers can also arrange to have transplant growers in the Southwest (Texas, Arizona) produce transplants and ship them to our area for spring planting. While it is too late to have plants grown for 2016, some transplant growers do produce surplus for sale.

Intermediate day sweet Spanish onion types are best adapted for our area; however, some long day varieties also can be grown successfully. The standard yellow sweet onion variety has been ‘Candy’. ‘Expression’ has replaced ‘Candy’ to a large extent because it is more disease tolerant and stores better. Other yellow intermediate day varieties that showed good adaptation to Delaware it 2014 and 2015 trials included ‘Great Western’ (March planted only), ‘Bradley’, ‘Cimarron’, ‘Scout’, ‘Avalon’, and ‘Spanish Medallion’. White varieties that did well over 2 years of trials in were ‘Mt. Whitney’, ‘SV4058NU’, and ‘Solstice’. All of these varieties have the potential to produce a large percentage of large and jumbo onions, have yield potential of over 20 T/a, and can be sold into sweet onion wholesale fresh markets. Red sweet onions tested in Delaware performed very poorly and no red varieties are recommended at this time.

One versatile yellow onion that has dual purpose as an overwintering type as well as a spring transplanted sweet onion has been ‘Bridger’.

It is important that once transplanted, onion growth is not interrupted. Steady, frequent applications of irrigation water are necessary because onions have small root systems. If beds are allowed to dry out at any time, yields will be reduced. Fertility varies with grower and field but in general 50 lbs. of N/acre is applied preplant along with P & K based on a soil test. An additional 25-50 lbs N/acre is applied through drip before bulbing starts.

Pennsylvania has developed a program to grow, sell, and promote sweet onions from their state. Sweet onion production in Delaware has more risk due to our hotter and more variable late spring and summer weather. However, there is still potential to develop wholesale markets for onions produced here with careful variety selection and attention to detail in production.

OnionFieldDay

Onions from the 2015 variety trial in Delaware.

 

Last Planting Dates

Gordon Johnson, Extension Vegetable & Fruit Specialist;gcjohn@udel.edu

The following are latest planting dates for unprotected culture of vegetable crops on Delmarva:

For cucumbers (pickles and slicers), the latest planting date for Delmarva should be August 7. Experience has shown that after that date yields drop considerably. With summer squash, late plantings can be made until August 10.

Snap bean crops can be planted up to August 10.

Cole crop planting for fall harvest using transplants continues. Broccoli is transplanted up to August 20, cabbage up to August 10, and cauliflower up to August 10.

Kale and collards should be seeded before August 15 for best yields, transplants can go in up to August 30. Turnips and mustard greens can be planted from late July through the first week in September.

Beets are best planted before August 10 for roots, by August 20 for greens.

Green onions should be planted by the end of August for fall harvest. Overwintering green onions can be planted through October using hardy varieties.

Bulbing onions for overwintering should be seeded from September 1 through September 15 using overwintering specific varieties. Bolting will be a problem if planted too early. If using transplants, planting should not take place until October. Leeks are transplanted from August 1 through August 20. Garlic cloves are best planted November 1 through November 20.

Spinach for fall harvest is seeded August 10 through the end of August for fall harvest and from October 1 to October 20 for overwintering.

Lettuce for heads from direct seeding should be planted during August. Transplanted lettuce for heads best planted from August 10 to September 10. Fall adapted varieties are required. Earlier plantings may be subject to bolting and only bolt resistant varieties should be used. For baby lettuce, field plantings can continue through mid-September.

Plasticulture strawberries should be planted by September 15 for best results. Later plantings will require earlier row covering and risk lower yields.

For all late crops, variety selection is very important. For example, late planted cucurbits such as squash need broad virus resistance. For fall harvested crops, switch to shorter maturing varieties as plantings gets later. When planting late, remember that a few days delay in planting can mean several weeks later harvest. A longer maturing variety may not produce if planted too late. On the other hand, planting several maturities of varieties on the same day will often give long extended harvest in the fall for crops such as broccoli.

Protected culture using high tunnels, planting on black plastic, and using row covers will often require changes in planting dates. For example, lettuce and other leafy greens in high tunnels can be direct seeded through early November. Overwintering crops in high tunnels should be planted much later than field plantings.

Soft Rot of Vegetables

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

Soft rot, which is a widespread disease of vegetables caused primarily by Pectobacterium spp. (formerly calledErwinia),has been observed this past week in cabbage. Numerous vegetable crops are susceptible to this disease, including cabbage, broccoli, onion, pepper, melon, cucumber, bean, and beet (for potato, see below).

The pathogen is a bacterium and overwinters in infected tissue, farm implements, and plant debris. The pathogen invades primarily through wounds. Therefore, it is important to reduce wounding during planting, cultivation, harvesting, and subsequent transport. In addition, uninjured tissue can be infected through natural openings when free moisture is present. Avoid waterlogged soils. The pathogen prefers high temperatures and multiplies quickly at high temperatures, although disease can progress rapidly when conditions are not optimum for plant growth, even if the temperature is low.

Additional control measures include use of disease free seed and transplants; rotation with crops such as corn, small grains, or alfalfa; and avoidance of insect feeding. Insect feeding creates wounds and insects can carry the bacterium from plant to plant. As the crop grows avoid wounding during cultivation and field work. Also take care to minimize wounding in harvest, and store and ship produce in clean and cool conditions. Hold plants at 39 to 45°F to minimize spread following harvest.

Potato
Potato is also susceptible to Pectobacterium and a related bacterium, Dickeya (also formerly classified as Erwinia). Potato diseases include blackleg, aerial stem rot, and tuber rots. Blackleg always develops from a seed piece, whereas aerial stem rot develops from wound in the stem. Different bacteria cause the two stem diseases on potato and tuber rots are caused by several strains of these bacteria. The inoculum for these diseases commonly originates in infected seed pieces.

Conditions that favor potato plant growth are less favorable for blackleg or tuber rots (i.e. more disease will occur if the weather is either very cool or hot). To minimize the disease, use certified potato seed pieces. Use either small tubers for planting or allow the seed pieces to heal (cork) over before planting. Don’t plant in waterlogged or low-fertility soils, and space plants so that air can move around the plants to reduce moisture. Wet soil promotes infection of tubers through lenticels (small natural openings in the potato skin). Limit irrigation to the morning and apply longer, less frequent irrigation rather than short frequent irrigations. During storage, keep the tubers at 50 to 55°F for ten to 14 days for wound healing. Following healing the temperature can be lowered below 50 to reduce bacterial growth (though temperatures should not be low enough to promote conversion of starches to sugars).

A free chlorine wash maintained at 25 ppm chlorine or a fresh chlorine rinse maintained at 50 ppm chlorine may help reduce soft rot in storage.

softrot1a softrot1b

Tuber soft rot and blackleg of potato.
Images from Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org

softrot2b softrot2a

Onion soft rot.
Images from Howard F. Schwartz, Colorado State University, and S. K. Mohan, Bugwood.org

softrot3

Soft rot on cabbage.
Image from Gerald Holmes, California Polytechnic State University at San Luis Obispo, Bugwood.org

2014 Fungicide Registration Updates

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

The 2014 version of the Commercial Vegetable Production Recommendations is available in print, for purchase, from you county extension educator. In addition, the “Recommendations” are available online from two sites (both sites have the same great information. The University of Maryland Extension’s site is https://extension.umd.edu/sites/default/files/_docs/2014_CommercialVegRecommend_Maryland%20book.pdf and University of Delaware Extension’s site is http://extension.udel.edu/ag/vegetable-fruit-resources/commercial-vegetable-production-recommendations/.

A few new fungicides received registrations after the “Recommendations,” went to print. These include:

Proline
Proline has received a supplemental label for cucurbit vegetables. Target diseases include Fusarium wilt (Fusarium oxysporum); gummy stem blight (Didymella spp.), southern blight (Sclerotium roflsii), and powdery mildew (Sphaerotheca fuliginea Podosphaera xanthii) (Erysiphecichoracearum). Proline may be applied by either ground or chemigation application (including drip irrigation). Do not use in the transplant water or in the greenhouse.

We studied management of Fusarium wilt on watermelon with Proline at the UM LESREC Farm a few years ago. In our trials three applications through the drip were necessary for season long management. Unfortunately only one soil (drip) application is allowed on the label. Up to two additional foliar applications may also be applied.

Priaxor
Brassica leafy vegetables group, which includes broccoli, Chinese cabbage, collards, kale and mustard greens, received a label for Priaxor. Target diseases include Alternaria leaf spot, anthracnose, Cercospora leaf spot, Rhizoctonia blight and white rust.

Merivon
Bulb vegetables, which include garlic, leek, onion and shallot, received a supplemental label for Merivon. Target disease include powdery mildew, purple blotch, Stemphylium leaf blight, and Botrytis.

Cucurbits (pumpkin, gourds, cantaloupe, watermelon, squash, etc.) also received a supplemental label for Merivon. Target diseases include Alternaria leaf blight, powdery mildew, anthracnose, Cercospora leaf spot, gummy stem blight, and Microdochium blight.

Leafy vegetables, including lettuce, spinach and Swiss chard, also received a supplemental label for Merivon. Target diseases include Alternaria leaf spot, anthracnose, powdery mildew, Septoria leaf spot, white rust, lettuce drop, and downy mildew.

Selected root vegetables including, beet, carrot, parsley, radish, and turnip, received a supplemental label for Merivon. Target diseases include Alternaria leaf spot and Cercospora leaf spot.

Read the labels carefully before use. These products should be used in ways that minimize resistance development.