Eric Sideman's Pest Report
July 21, 2003
(View List Of All 2003 Pest Reports)
WARNING WARNING WARNING!
LEAF HOPPER
(POTATOES, BEANS, STRAWBERRIES)I have now seen adult potato leaf hoppers on beans. This is a very destructive pest that some years comes into the state in such numbers that some crops like beans and potatoes are totally destroyed. They do not overwinter in Maine but leap frog their way up from the gulf coast each summer, sometimes making it in big numbers and sometimes not. Be on the lookout and let me know if you see them in large numbers.
The potato leaf hopper favors alfalfa, beans, strawberries and potatoes. It is a bug that sucks the plant juices. The feeding causes curling, stunting and dwarfing accompanied by a yellowing, browning or blighting of the foliage know as hopperburn or tipburn because the damage is first seen at the leaf tips working inwards.
The leaf hopper is small (3mm), pale green and wedge shaped. They are very fast and often not seen by the grower until the damage is so great that the farmer finally looks carefully. It is too late then. Look now and continue looking on a regular basis. The best way to spot them is to run your hand over the top of the crop lightly brushing the leaves. If you have them you will see them hop quickly. If you have them bad you may see a cloud. Find one that lands and identify it. (Tarnished plant bugs also may flitter around). A better way to find the leaf hopper is with a sweep net if you have one. Later in the year you will see the nymphs, especially on the underside of leaves. They are easy to identify because they can run backwards and sideways. When you spray be sure to hit these too.
Crop rotation will not help control leaf hoppers. The only organic control that works for the leaf hopper is a concentrated pyrethrum spray such as Pyganic (5%), which I know that Johnnys went out of there way to find. Diatect, a mixture of pyrethrum and diatomaceous earth is another option which has NOP approval. This product showed significant reductions in leafhoppers in a potato study in Maryland. This product may not be available locally; the website reference is www.diatect.com. Only use these if you have a pest that needs it. These are broad spectrum, harsh pesticides that kill plenty of beneficial insects too.
COLORADO POTATO BEETLE
I am getting very good reports about Entrust. I am also getting requests for info about it and how to use it. Here is important info on mixing...MEASURING SMALL AMOUNTS FOR SPRAYS.
New products tend to be used in far smaller quantities per acre than the pesticides that were develop 15 or 20 years ago. Growers who are using spinosad for the first time - mainly organic growers who now have Entrust available-may not have used a material with such a low rate per acre. For example, Bt products tend to be applied in quarts or half-pounds per acre, compared to 2 oz (dry) or 3 oz (liquid.) required for this product. When measuring the tiny amounts needed for small plantings over several hundred square feet, it can be difficult to measure accurately. This is especially true with a solid that is measured in grams or tenths of grams such as Entrust. We have made some weight measurements to assist growers in making conversions into a measure that is easy to use: teaspoons. These conversions are specifically for Entrust 80WP. Liquids may be easier to measure in small quantities, if you have access to a small measuring device such as a syringe that measures ml or tenths of ounces. I have found such devices at the local drug store in the children's medicine department.The following table is provided for informational purposes. No endorsement is implied.
_______________________________________________________________ | Entrust Spray Rate Conversions* | |---------------------------------------------------------------| |Acreage| Square Footage |Entrust| Entrust | | | |(grams)|(approx. spoon measure**) | | | | | Teaspoons | |-------|------------------|-------|----------------------------| | 1/4 | 10,890 | 14.2 | 9.5 | | 1/8 | 5,445 | 7.1 | 4.75 | | 1/16 | 2,722 | 3.5 | 2.5 | | | | | | | 1/30 | 1,500 | 1.95 | 1.5 | | | (300' by 5' bed) | | | | | | | | | 1/44 | 1,000 | 1.3 | 1 | | | (200' by 5' bed) | | | | | | | | | 1/88 | 500 | 0.65 | 0.5 | | | (100' by 5' bed) | | | |---------------------------------------------------------------| | * All area rates based on 2 oz./acre | |** All spoon measures loosely filled (not packed) | | and shaved even (not heaped) | ----------------------------------------------------------------
CABBAGE, Broccoli, ETC
Cabbage worms' are becoming active in the region: Diamondback moths (DBM), imported cabbage worms (ICW) and Cabbage Loopers (CL). Scout for these caterpillars on leaf undersides and on inner most portions of plants in addition to looking for feeding damage. Tiny holes are easier to spot than tiny worms. Apply controls when caterpillars are small, and direct spray to leaf undersides. Use at least 50 gal/A of water to achieve good spray coverage, and use a spreader-sticker. A threshold of 15% of plants with at least one caterpillar (of any species) is recommended for any heading cabbage, broccoli, and all leafy greens. Before the cupping stage in cabbage and broccoli use a threshold of 35% plants infested. These thresholds lead to a clean crop at harvest. Organic growers have the choice of two very effective materials.Both Bt (Dipel 2x) and Spinosad (Entrust) will work well. This makes it easier now to rotate among different types of products to prevent resistance to any single product.
SWEET CORN SITUATION
Early corn has developed quickly under the last week of high temperatures. Plantings in southern Maine started under plastic mulch or rowcover is now silking and could be ready for harvest in a week. Early plantings started on bare soil are at the pre-tassel to tassel stage.[It is time to get the Zea-Later out]
European Corn Borer: Pheromone trap catches of corn borer moths have dropped off in most locations this week. However, counts were still high enough to warrant sprays on silking corn to prevent larvae from moving into the ears through the silk channels. This week sprays on silking corn were called for in Dayton, Dresden, Farmington, Litchfield, No. Berwick, Poland Spring, Warren and Wayne. European corn borer feeding damage on leaves and tassels increased at many sites this week and was over the control threshold in Biddeford, Cape Elizabeth, Dayton, Lewiston, Litchfield, No. Berwick, Oxford, Poland Spring and Wells. Corn in the whorl stage need only be sprayed if fresh feeding injury is found on 30% or more of the plants scouted in a field. Once the corn reaches the pre-tassel stage, the control threshold is lowered to 15%. Good spray coverage is essential for managing this pest.
Corn Earworm: Several corn earworm moths were caught this week in the pheromone traps in southern and coastal Maine. As a result, a six-day spray interval was recommended on all silking corn in Biddeford and Dayton and a five-day spray interval was recommended in Cape Elizabeth. Remember, corn earworm is only a concern in fresh silking corn. Fields not yet in silk do not need to be protected from corn earworm.
Fall Armyworm: We captured a single fall armyworm moth in a pheromone trap in Cape Elizabeth this week and two fall armyworm moths in Dayton. This appears to be an early arrival of this insect, which is typically the last serious corn insect pest to arrive in Maine. Armyworm moths prefer to lay their eggs on young corn plants. When the eggs hatch the young larvae chew channels in the leaves between the veins. As they get older and larger the feeding holes become larger and ragged, often surrounded by masses of wet sawdust-like waste. When found, this injury is combined with any European corn borer injury to determine if protection is needed. Control thresholds are 30% infestation in whorl stage corn or 15% for corn at pre-tassel and beyond. No fresh armyworm feeding injury was found this week, but we can expect to see it soon.
( modified From IPM Sweet Corn Report, Dave Handley)
LEAF MOLD ON TOMATOES
I am getting wide spread reports of leaf mold in hoop house tomatoes. It is rare in field tomato production because it is a disease that develops under high humidity. This year is particularly bad because we had a long stretch of cloudy, humid weather during which it was particularly hard to keep hoop houses ventilated with dry air.Leaf mold is caused by a fungus called Fulvia fulva. The leaves are usually the only tissue affected. Older leaves are first affected. You will see pale green to yellowish spots on the upper leaf surface, which are olive green with mold on the under surface. In severe cases the petioles, stems and fruit may be affected and blossoms may be killed.
StorOx may help prevent the spread, but in most houses this late into the season the disease is too well entrenched to really have much of an effect. To reduce the problem next year, remove crop residue after harvest and steam clean the house. StorOx treatment of surfaces will help. Next year minimize long periods of leaf wetness and maintain night temperatures warmer than outside temperatures.
NOTE: OXIDATE UPDATE FOR ORGANIC FARMERS
Certified organic growers who have been using Oxidate by BioSafe Systems for disease control in field crops are reminded that this product no longer meets the requirements of the National List of allowable products for certification under the National Organic Program. However, BioSafe Systems has reformulated Oxidate to meet the requirements of the National List. The reforumlated product is called StorOx and is listed for use on field crops by the Organic Materials Review Institute (OMRI). (Modified from Don Franczyk, NOFA, MA)CUCURBITS: WATCH FOR POWDERY MILDEW
Scout for powdery mildew in all vine crops, especially searching lower, older leaves for symptoms. Powdery mildew has been observed in summer squash and zucchini. Search at least 50 leaves, both upper and lower surfaces, in groups of 5 leaves in 10 locations throughout the field. Look for light green to yellow blotches on the upper surface, or a white to gray, powdery covering on the upper or lower leaf surfaces. These powdery areas most often start on the underside of the leaf, often as small as a quarter. The last week of July and first two weeks of August are typically the time when powdery mildew shows up in pumpkin and winter squash.Begin fungicide applications as soon as powdery mildew is observed, and continue at approximately 10-day intervals. Here is a recipe published in Organic Gardenings book Great Garden Formulars:
1 gallon water, 3 tablespoons baking soda, 1 tablespoon Murphy's oil soap
Be sure to spray both sides of the leaves.
Potassium bicarbonate is said to work better than baking soda. Kaligreen is a commercial formular of potassium bicarbonate.
STRIPED CUCUMBER BEETLE
Numbers are down. Watch for squash bug adults, eggs and nymphs.BACTERIAL WILT IS SHOWING UP
There is not much you can do now, but if cucumber beetles were around and now you see your plants wilting you probably have it. Next year be sure to control the beetles.POTATOES
The potato crop continues to grow rapidly and looks excellent. Rainfall amounts have been extremely variable following the shower activity. No potato late blight has been reported anywhere within the state of Maine as of this date. Growers in Central Maine should be aware that our scouts are finding adult potato leafhoppers in many fields in the Central Maine area. We expect to find leafhopper nymphs in the near future. This situation will need to be watched carefully. Growers in Central Maine and Aroostook County need to be scouting for potato leafhoppers.Growers area also advised to be watching for tarnished plant bug injury. This insect is rarely an economic problem in potatoes, but significant damage to outside rows has been noted in some fields. Growers are encouraged to be watching for tarnished plant bugs, especially in potato fields next to recently mowed hay fields.
This past winter appears to have been an excellent overwintering year for insects. We strongly encourage all growers to be carefully scouting their fields. Early detection of potato pests will provide the grower with the most options.
Enjoy the Potato Blossom Festival!
(Reprinted from report from James D. Dwyer, UMaine Ext. crop specialist)
(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.)