Pest of the week - Downy Mildew

Downy mildew causes foliage blights and distortion. Although its name sounds similar to powdery mildew, downy mildew occurs during different environmental conditions and it is managed differently.

Photograph of Downy Mildew

Squash Cucumis pepo - Courtesy University of Georgia

Natural History

During cool wet weather, downy mildew can occur very rapidly and is difficult to control. Some of the greenhouse crops prone to infection include: snapdragon, salvia, alyssum, pansy, rose, rosemary, and ornamental cabbage. Perennials susceptible to downy mildew include aster, coreopsis, geranium, geum, lamium, potentilla, veronica and viola. 

Primary infections in the field or garden generally come from sporangia (spores) produced on southern-grown crops and carried progressively northward on moist air currents during the spring and summer.

The sporangia are disseminated locally from plant to plant and from field to field by splashing rains, moist air currents, insects, tools, farm equipment, the clothing of workers, and through the handling of infected plants. Heavy dews, fogs, frequent rains, and high humidity favor infection and rapid multiplication of the pathogen

Symptoms can be confused with other plant problems. Leaves may become mottled and yellowed, resembling nutritional deficiencies. On some plants, downy mildew infection may look similar to injury from foliar nematodes. In both cases, angular lesions are bounded by leaf veins. However, downy mildew infection results in a soft, fluffy gray, brown or purple fungal sporulation developing on the underside of leaves. On coreopsis, the fungal sporulation is white.

Symptoms can also vary depending upon the host plant. On snapdragons, infected plants are yellow and stunted. You may see downward leaf curling on the young seedlings. On salvia, angular yellow blotches can be seen between the leaf veins. On pansy, leaves turn mottled and off-color with purple blotches. Pale green or yellow patches develop on geum. Purplish patches occur on lamium and veronica. On roses, leaves develop angular dark purple to black areas and may turn yellow and drop.

Management Strategies

To manage downy mildew, first “manage the moisture”: space plants to ensure good air circulation and rapid drying of foliage after irrigation. 

Choose planting sites with good air movement and without shading. Avoid overhead irrigation in early morning when leaves are wet from dew or late in the day when leaves will not have an opportunity to dry before dew forms. Maintain ample but not excessive nitrogen fertility.

Practice good sanitation techniques. Discard all diseased plants as well as plant debris that may harbor spores, and control weeds that may be another source of downy mildew inoculum. 

Protect susceptible crops during cool, wet weather with preventive fungicides. Active ingredients labeled for control of this disease include azoxystrobin, Bacillus subtilis, copper, dimethomorph, fosetyl-Al, kresoxim-methyl, mancozeb,phosphite, trifloxystrobin, and triadimefon + trifloxystrobin (Armada). To reduce the possibility of the development of fungal resistance to some of the newer systemic fungicides with single or few modes of action, rotate these chemicals with protectants such as mancozeb. 

Avoid the sole use of any fungicide for extended periods of time when other reliable products are available, and refer to label for timing, host plants, and rates. 


Additional Information

Plant and Pest Advisory: Downy Mildew in Ornamental Plants - Rutgers University

Cucurbit Downy Mildew Forcasting - North Carolina State University

Botrytis or gray mold - Penn State University

Downy Mildew - University of Connecticut

Downy Mildew - University of llinois

Fun Facts about Fungi - Utah State University

IPM Notes for June 20, 2013

Pheromone Traps Report

Trap #1 - Black Cutworm – nothing to report. 
Trap #2 - Corn Ear Worm – many small moths and 1 large moth.
Trap #3 - European Corn Borer – it was full of bees – at least 33+. We do not know why the  bees are being attracted to this pheromone.
Trap #4 - Fall Army Worm – 8 moths, 4 beetles.

Helios Trap
Nothing to report. Raised the level of the trap to coincide with the corn.

The day's session was focused on weed identification. Here is a list of what was noted:

• Pennsylvania Smartweed (it is flowering)
• Water Pepper
• Yellow Wood Sorrel – it looks like clover but is not in the clover family; toxic.
• Mare’s Tail
• Amaranth – both Spiny and Red Root; sometimes called Pigweed.
• Curly Dock – now seeding
• Velvet Leaf
• Plantain
• Wild Geranium
• Wild Pansy

When identifying grasses it is best to use a dichotomous key and a hand lens, so that you may be able to identify such features as collars (ligules), auricles, hairs, sheaths, etc.

Report on the Demonstration Plots

• Hops are looking very good.

• Blueberries - The plant are in fine shape – no deer damage. Fruit is ripening.

• Cover Crop - Buckwheat and Cowpeas are both up and growing.

• Virginia Peanuts- Peanuts are blooming. Will watch for formation of the stems out of the flower/ovary to grow the actual peanut underground.

• Peppers - The pepper plants are showing stress from the rains. Anywhere from 5” to 8 ½”. Several of the peppers have died. Nitrogen is being washed down below the roots by the rain.  The peppers may need a foliage application of nitrogen and magnesium.  The mulch that was applied is now holding the moisture as well as depleting the nitrogen.

• Quinoa – We are not sure if we have ANY plants at all.

Report on the Various Crops

Hay Field
Second cutting is down and drying

Soybeans
The soybeans are being grazed – probably groundhog and deer. There are deer tracks across the field and across the corn field. There are two groundhog burrows adjacent to the field. The soybeans have started fixing nitrogen in nodules on the roots. This is good. 

Nodules on soybean roots

Sweet Corn
Ray has planted 16 varieties of sweet corn. The corn is up. There is some flood damage (low lying areas) in the field. Also noted was evidence of birds pulling up the young plants to eat the seed.

Field Corn
The field corn is showing some nitrogen deficiency. Bottom leaves are showing a V pattern of yellowing along the outer edges to the tip. This is indicative of the plant stealing from itself and is called “firing”. Farmer will make one more fertilizer application with a tall tractor.

Wheat Field
The wheat is mature and is now drying to the proper moisture content. We estimate another ten days to harvest. Because of the wet weather, we are looking for mildew and fungus – especially head scab or fusarium.

Because there is no more tender plant material in the wheat field, the cereal leaf beetle is moving to the corn. If there is any Army Worm, it will also. The cereal leaf beetle has been seen, but there is little evidence of the Army Worm.

Demonstration Plots - June 18, 2013

Showing progress.  Here are latest photographs from the demonstration plots.  When walking through the demonstration plots, if you see a “work party” in progress, please stop by and talk to our volunteers. They’ll be happy to show you the gardens and answer your questions.

Herb Demonstration Plot

Pollinator Demonstration Plot

Hops Demonstration Plot

Blueberry Demonstration Plot

Active Composting Plot

Ground Cover Demonstration Plot

Quinoa Demonstration Plot

Virginia Peanut Demonstration Plot

Tomato Demonstration Plot

Pepper Demonstration Plot

Pest of the Week - Four-lined Plant Bug

Recently, the four-lined plant bug was spotted during an IPM session at the Burlington County Community Agricultural Center.  The four-lined plant bug, Poecilocapus lineatus which is easily identified by the four black strips running down its back, has a wide range of hosts including: fruits, vegetables, flowers, herbs, and cucurbits. The associated damage consists of spots that look similar to fungal disease spot and can be misidentified as such.  

Adult Four-Lined Plant Bug - Courtesy Purdue University

Natural History

During the fall, the banana shaped eggs are laid at right angles in vertical slits measuring 2 to 3 in. along the plant's stem. They are usually not laid individually but instead are laid in groups of six or more. The eggs will over winter and hatch in May or late June just after the plant's foliage emerge. 

Nymphs will remain near their hatching site and feed on the upper side of leaves removing the plant's chlorophyll. After advancing through five molts in a period of about six weeks, the four-lined plant bug will have matured to an adult form. Adults will feed, moving from plant to plant, for approximately one month before mating; adults will not overwinter, and there is only one generation per year.

Feeding by both adults and larvae may cause stippling on leaves - spots of discoloration that may turn from yellow to brown to black. Holes may develop in leaves when heavy infestations occur. Plants are not, however, killed by this bug.

Four-lined Plant Bug Damage- Courtesy Purdue University

The four lined plant bug hides under leaves and may be difficult to detect. Look in May and June for signs of stippling on leaves. 


Management Strategies

Least toxic methods of control for ornamentals and edibles would include insecticidal soap, the dormant and summer weight oils and where feasible, removal of egg masses by selective pruning. Authorities say egg-laying sites are easily visible after leaves drop in autumn.

The use of a trap crop is another possible control method to keep the four-lined plant bug away from the crop. Mint is highly attractive to this pest and can be effectively used as a trap crop. The four-lined plant bugs will choose to feed on the mint instead of other nearby plants. Place a barrier, such as a tile, around the mint to prevent the spread of roots. Once the crop is large enough to withstand damage caused by this pest, the mint can be removed.

Whenever using insecticides, be sure the insect you want to control and the plant you are using it on are both listed on the label.


Additional Resources

Four Line Plant Bug - University of Connecticut 

Four Lined Plant Bug Slides - University of Minnesota 

Vegetable MD Online- Cornell University

Greenindustry - University of Wisconsin - Extension

IPM Notes for June 13, 2013

Despite the stormy weather, some work was done. A few Master Gardeners managed  to reach the Winner Farm and see what was happening before the lightening began.  Trap 1 was emptied before lightning and rain drove everyone into the Farmer’s Market shed.

The highlights of the morning's session were:

• Trap 1 – (Black Cutworm) had 7 moths.
• Last week’s red color on corn leaves is most likely environmental damage.
• Sweet corn has been planted and is coming up.
• Popcorn will be planted next week.
• There is a new kind of insect trap called a Helios Trap. It is a net trap, but still uses pheromones to attract insects.
• With the wet weather it is possible that there will be varieties of scab showing up in the wheat heads. It is also called Fusarium and is fungal. Also, if it remains wet in the seed heads, the seeds could actually sprout. About 2 more weeks until harvest.
• In the cover demonstration plot buckwheat and cowpeas have been planted.
• It was noted that the peppers may be exhibiting nitrogen deficiency after the mulch application.
• At the next session the terminology associated with describing moths will be reviewed.

Demonstration Plots - June 11, 2013

Here are the latest photographs of the demonstration plots.

Herb Demonstration Plot

Polinator Demonstration Plot

Hops Demonstration Plot

Blueberry Demonstration Plot

Composting Demonstration Plot

Ground Cover Demonstration Plot

Quinoa Demonstration Plot

Virginia Peanut Demonstration Plot

Tomato Demonstration Plot

Pepper Demonstration Plot

If you see a “work party” in progress, please stop by and talk to our volunteers. They’ll be happy to show you the gardens and answer your questions.

IPM Notes for June 6, 2013

Pheromone Traps Report for Black Cutworm – 

1. Trap #1- 1 moth.or Corn Ear Worm 
2. Trap #2- up to 17 moths.for European Corn Borer 
3. Trap #3 - 1 bumble bee and several beetles.for Fall Army Worm 
4. Trap #4 - at least 7 moths.

Corn Field

Corn is in stage 3 and approaching stage 4. Field has some weeds reappearing, esp. lamb’s quarter. The upper leaves of the corn appear to be free of paning (cereal leaf beetle) and no instances of buggy whipping were found. Generally, the corn looks good.

Wheat Field

The wheat continues to change color. The seed heads appear full though there is milk present when squeezed. Not many birds were spotted diving the field though white moths are present. The flag leaves look healthy enough with no mildew. We did not see any deeper incursion of possible Army worm damage from the edge of the field.

Oat Field

It was reported that the oat field has been harvested.

Soybean Field

The area that was found nipped last week has expanded to almost double in size. We did not find deer tracks in the field, so continue to surmise groundhog. The soybeans have reached the trifoliate stage.
 
Hayfield Field 

We did find some damage to the tops of some alfalfa plants, but did not find any weevils.

Demonstration Garden Plots

• Peppers are in and growing.
• Tomatoes – all support systems are now in place. Tomatoes are growing.
• Peanuts – peanuts are growing, though there is concern that a couple of plants are possibly exhibiting disease.
• Quinoa – Quinoa has been weeded of everything except hopefully any quinoa and lamb’s quarter – which it is said to resemble quinoa in its early stages.
• Blueberries – a nice crop of blueberries have set on.
• Hops – are growing nicely and have set flowers.

 A special thanks to Roger for compiling the notes from the week's IPM session

Pest of the Week - Cucumber Beetle

Cucumber beetles are the most important insect pests of vine crops or cucurbits (cucumber, squash, melons, and pumpkins) across much of the United States. The striped cucumber beetle (Acalymma vittatum) and the spotted cucumber beetle (Diabrotica undecimpunctata howardi) occur in the Northeast. The striped cucumber beetle, typically the most common in New Jersey, feeds primarily on cucurbits, whereas the spotted cucumber beetle has a much wider range of host plants. The immature spotted cucumber beetle is called the southern corn rootworm because it feeds on roots of corn. Cucumber beetles can cause losses to cucurbits by direct feeding on young plants, blossoms, and fruit. They also transmit bacterial wilt, which is caused by Erwinia tracheiphila, a particularly important disease of cucumbers and melons.

Natural History

Adult beetles overwinter and leave their hibernating quarters in the spring when temperatures reach 65F degrees or more. When cultivated cucurbit plants begin to emerge through the soil surface, large numbers of beetles may suddenly appear and feed on the seedlings or crawl into soil cracks in reach of sprouting seed. Beetles soon mate and continue feeding throughout the season. Eggs are laid 8-25 days after mating. Females deposit 225-800 in small clusters or singly into soil cracks at the base of cucurbit plants.

Eggs hatch 5-8 days later, widh larvae spending about 15 days feeding on the roots and stems of fruit that is in contact widh the soil. The pupal period is 6-7 days. The time from egg to adult for The first generation of beetles requires about 1 month and slightly longer for succeeding generations. 

After cucurbit plants mature and cool autumn weather approaches, beetles migrate to wooded, bushy areas, crawling under litter to overwinter. Some may overwinter a mile from the hatching site. In northern states, only 1 generation occurs while 2 or more generations may be produced in the Gulf states.

Cucumber Beetle Larvae

Spotted Cucumber Beetle (Diabrotica undecimpunctata howardi)

Credit:Natasha Wright, Florida Department of Agriculture and Consumer Services, Bugwood.org

Striped Cucumber Beetle (Acalymma vittatum)

Credit: Scott Bauer, USDA Agricultural Research Service

 Management Strategies

• Crop production practices that promote strong root growth and a vigorous crop will make the plants more tolerant to cucumber beetle feeding. Fertilize properly so plants grow rapidly early in the season. 

• Early beetle feeding can be avoided by pushing boxes or cones into the ground over the seedlings, open at the bottom and covered with fine netting, as a barrier to the beetles. Remove when plants are established. 

• All cucurbits except watermelons are susceptible to bacterial wilt, and control is difficult without insecti- cides. Treat early to prevent beetles from feeding on the seedlings and thus reduce the spread of bacterial wilt. It may be necessary to apply an insecticide treatment every 4 to 7 days as needed until vines begin to run to protect plants. 

• Toxic baits, such as Adios, are commercially available. These baits are a mixture of carbaryl insecticide plus a feeding attractant. Before using any pesticide, read and follow all label directions and restrictions. Observe the proper number of days wait before harvest for each particular crop.

Additional Information

Cucumber Beetles - University of Kentucky

NJAES Cucumber Beetle Fact Sheet 225‎ - Rutgers University

Striped Cucmber Beetle HYG-2139-88 Fact Sheet - Ohio State University

Managing Striped Cucumber Beetle Vine Crops

Bacterial Wilt of Cucurbits - Cornell University

Erwinia tracheiphila - University of Hawaii

Demonstration Plots - June 4, 2013

Everyone is encouraged to come to the Master Gardener demonstration plots and see what’s growing.  The demonstration plots are a continuing community project of the Rutgers Master Gardeners of Burlington County, developed to demonstrate, test, teach, learn and enjoy gardening in its many forms in New Jersey's unique climate and soils.  Volunteers maintain the gardens throughout the year using the practices and techniques learned in the Rutgers Master Gardening Training Course and continuing education programs. If you see a “work party” in progress, please stop by and talk to our volunteers. They’ll be happy to show you the gardens and answer your questions.

Here are the latest photographs of the demonstration plots. 

Herb Plot

Pollinator Plot

Hops Plot

Blueberry Plot

Active Composting Plot

Cover Crop Plot

Quinoa Plot

Virginia Peanut Plot

Tomato Plot

Pepper Plot

IPM notes for May 30th, 2013

Trap report from Lise:

• Trap 1 (for Black Cutworm): one black cutworm

• Trap 2 (for Corn Ear Worm): 4 black cutworm (juvenile)

• Trap 3 (for European Corn Borer): one corn borer

• Trap4 (for Fall Army Worm): one true armyworm.

Opened our day with a discussion of soil pH. It is a logarithmic scale used to measure acidity of the soil. It ranges from 0 to 14 with 7 being neutral. Logarithmic means that for every change of 1 on the scale there is a change of 10 times in the amount. 0 – 6.9 is acidic and 7.1 – 14 is basic. General agricultural/gardening optimal pH is 6.2 to 6.5 with some plants such as blueberries preferring more acidic soil. Remember that when amending soil with lime to bring down the acidity “Lime Takes Time” – up to 6 months to achieve the full benefit and change. General discussion determined that this should be in a ‘reminder binder’ at the help desk when we are asked to interpret soil test results.

As we walked, we identified the following:

• Sedge (triangular stock and corms on the roots)
• Lambs Quarters
• Jimson Weed
• Velvet Leaf
• Wild Geranium
• Annual Bluegrass

Corn Field

• Corn is in the 2 collar stage or 2nd leaf stage
• Cereal leaf beetle is causing some leaf pane-ing
• There is some environmental damage to the leaves due to heat and moisture.
• Found some evidence of ‘buggy whipping’ – the main leaf remaining tightly furled. Can clip the top to help it to open up.
• We examined the inside of a corn plant – where at this stage you can see all the leaves and even the silk that the plant will have in full maturity. Very beautiful.

Wheat Field

• The wheat is starting to turn. Probably ready for harvest in another month.
• We found Septoria tritici and Powdery Mildew. The mildew has slowed its growth in the heat.
• Cereal leaf beetle continues.
• Birds are swooping and feeding in the field.
• Possible Rust beginning.
• Flag leaves seem healthy enough to complete filling of the ears.
• Ears are in the milk stage and almost finished forming.
• We found head stalks clipped as in Army Worm damage at the edge of the field in one small area. We were unable to find the worms at the base of the plants. However, we did find one in the trap. This is a concern.
• Because the crop is set the strategy is one of protection.

Soybean Field

• Soybeans are not yet in the 1st trifoliate leafing.
• We found an area at one corner of the field that looked very barren. Upon examination, it showed that the seeds had germinated, but the plants have been nipped.
• First, we looked for slug evidence such as trails.
• Then we discussed rabbits, groundhogs, and deer.
• We have a groundhog burrow close by and deer have been seen in the alfalfa field.
• Continue to monitor.

Demonstration Gardens

Tomatoes – stakes were brought to complete the trellis.

Peanuts – peanuts did not germinate, so plants were purchased and planted in the plot.

Quinoa – still not sure of germination since young plants resemble Lamb’s Quarters.  We think we have some Quinoa germinating.


A special thanks to Roger for compiling the notes from the week's IPM session.