MOFGA Letterhead

Info

Events

The MOF&G Online

Technical Services

Certification Services

Organic Food

  

 

MOFGA Pest Report 2005
4 August

(View List Of All 2005 Pest Reports)

White Rot in Onions (Sclerotium cepivorum)

White rot is one of the most destructive fungal diseases in the onion family. It is wiping out the garlic crop of one of our organic growers this year. Symptoms on the leaves include premature yellowing and dying of the older leaves and then death of the plant. White, fluffy fungal growth on the root end of the bulb eventually moves around the bulb and inward between the storage leaves of onion and cloves of garlic. Small, black sclerotia form in the decaying tissue. Secondary infections by other fungi may occur.

There are no known spores. This fungus reproduces only by the sclerotia. The sclerotia can lie dormant in the soil for many years until roots of a host plant grows nearby and the sclerotia are stimulated to germinate. Germination is optimum between 57 and 64 degrees and fungus growth optimum in soil in the high 70s with good soil moisture. Fungus growth spreads away from the infected plant and if it makes contact with a new plant it infects that one. So, the disease quickly spreads down rows of onions and garlic.

The disease spreads commonly by movement of infested soil on equipment and boots and by planting infected sets and transplants. Animals feeding on diseased bulbs can defecate viable sclerotia.

Control is by good sanitation. Use clean seed for garlic and clean sets and transplants. Wash off soil from tools, boots, equipment, etc from infected fields. If the infection is low, which is usually the case the first year it is found on a farm, pull the infected plants and destroy. Contans ( a fungus called Coniothyrium minitans) is a sclerotial parasite of Sclerotinia diseases (white mold, lettuce drop, etc). Although the material is not yet labeled for white rot, there are some research results that show that it is effective for this disease too. We are considering testing the material next year. Let us know if you have white rot on your farm.

MEXICAN BEAN BEETLE: A CHANCE FOR BIOLOGICAL CONTROL

Mexican bean beetles are active in snap beans. They may also be found in soybeans (either the grain soybean or edamame) although these are not their preferred crop. Eggs were observed on 7/13 in Bolton. The coppery brown, spotted adults, that look like large ladybeetles, lay yellow- orange egg masses on the underside of bean leaves.

These hatch into bright yellow, spiny oval larvae, which feed, molt several times as they grow, and pupate on the underside of leaves. Feeding damage of adults and larvae can reduce yield and injure pods if numbers are high. Suggested thresholds: treat when defoliation exceeds 20% in prebloom or 10% during podding, or if >25% of plants are infested. Reapply in 7-10 days if needed. Target adults and larvae. See Pest Report from a few weeks ago for recommended materials. Hot weather >90°F will kill eggs.

Wasp stinging a Mexican Bean Beetle A beneficial insect, Pediobius foveolatus, is commercially available for Mexican bean beetle control and has a good track record in the mid-Atlantic states and among Massachusetts growers who have tried it. (Pediobius, pronounced "pee-dee-oh'-bee-us"). It is mass-reared and sold by the New Jersey Dept of Agriculture and is also available from other beneficial insect suppliers. This small, non-stinging, parasitic wasp attacks and kills Mexican bean beetle larvae, especially the young larvae. Wasp larvae feed inside the MBB larvae, kill it, and pupate inside it, forming a brownish 'mummy'. Twenty five or more adult wasps emerge from one mummy. Control continues and in fact gets better as the season progresses and successive generations of the wasp emerge and search out new bean beetle larvae. This makes it well suited to our succession-planted snap bean crops.

After a release in the first plants, it is advisable to leave that planting intact for a while, until the new generation of wasps has emerged from their mummies. New Jersey Dept of Ag. recommends two releases, two weeks in a row, timed for the beginning of egg hatch. Timing is important, because the wasps prefer to lay their eggs in young MBB larvae. The release rate should be at least 2000 adult wasps per field (or per acre, if more than one acre is grown); 1000 adults costs $25 plus shipping for overnight delivery. I would advise investing in an adequate release rate from the outset if you want to make this method work. Now is the time!

Instructions for handling and release will come with the wasps. Because wasps reproduce in the field and are still present when the second generation of MBB hatches out, it should not be necessary to make more than two releases. Like beans, Pediobius wasps are killed by frost. Contact information for New Jersey source: Tom Dorsey, 609-530-4196 or 530-4192; address NJDA Phillip Alampi Insect Lab, State Police Dr., W. Trenton, NJ 08628. You'll also get advice on how to use the wasps from this office. Pediobius may also be available from the following suppliers:

-(Reprinted from UMASS Veg. Newsletter-R. Hazzard)

SWEET CORN

Corn Earworm Numbers Low
Fall Armyworm Most Serious Threat to Silking Corn

Situation: Good growing conditions continue, although some parts of the state are running a bit dry. Apparently, the weather patterns have not been condusive for corn earworm migration into the state, as levels remain relatively low for this time of year. This week we have added data from Palmyra and three locations in New Hampshire.

European Corn Borer: Moth activity was relatively low this week, with the exception of our Lewiston locations, suggesting that the first generation of the Iowa strain of European corn borer is fading. However, it takes only five moths caught in a week to pose a significant threat to silking corn when fields are not presently being sprayed for corn earworm. This week sprays were recommended on silking corn in Auburn, Dresden, Farmington, Lewiston, North Berwick and Warren where five or more borer moths were caught, but where corn earworm was under threshold.

European corn borer larvae feeding injury was generally low this week with just a few fields over threshold. Sprays were recommended for fields in Auburn, Lewiston, Oxford and Palmyra on pre-tassel to tassel stage corn.

Corn Earworm: Populations were again relatively low this week. A six day spray interval was recommended on silking fields in Cape Elizabeth, Dayton, Garland, Jefferson, Litchfield, Wayne and Mason, NH. A five day spray interval was recommended on silking fields in Cape Elizabeth, East Corinth, and Hollis, NH.

Fall Armyworm: Moths captures were higher in most of the state this week and larval feeding injury is now becoming evident on younger corn. If more than three fall armyworm moths are caught in a pheromone trap in a week where silking corn is not being sprayed for corn earworm, a spray is recommended to prevent armyworm from entering ears through the silk channel. A spray was recommended for fall armyworm this week on silking corn in Auburn, Biddeford, Dresden, Farmington, Lewiston, Monmouth, Oxford, Poland Spring and Readfield.

Fall armyworm larvae can be difficult to control in some fields, despite regular sprays. Sprays targeted for the late pre-tassel to tassel stage are often most effective because the larvae are most exposed at this stage and less protected by leaves or husks. The addition of a spreader-sticker with the insecticide can also help to get the best coverage possible and extend the effective time of the application.

(Reprinted from the Sweet Corn IPM Newsletter by David Handley, UMAINE COOP EXTENSION)

(About the author: Eric is MOFGA’s Technical Services Director, essentially an organic "extension agent". He can be reached at the MOFGA office to answer your questions about farming and gardening. Link to MOFGA Contact Page, or email Eric directly.)

 

the MOFandG Online / Go To Top