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 MOFGA's 2007 Pest Reports - Compiled by Eric Sideman, PhD Minimize

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ALERT - Potato Leafhopper

Watch fields for potato leafhopper. The leafhopper has been reported in Wells and in Dresden. You do not want to miss this pest because populations build up quickly and once significant feeding takes place plants will not recover and the whole crop could be lost.

Adults are about an eighth of an inch long, light yellow-green, and fly up from foliage when it is disturbed or shaken. They can best be monitored with sweep nets. Or, you can try to track one of the little flying critters and see them land. They have a characteristic wedge shape. Nymphs are found on the underside of leaves. They are smaller, light green, also wedge-shaped and very fast-moving. The nymphs run sideways and backwards as fast as forward and this is a real key that you have leafhoppers.

Damage can be severe on early-season varieties of potatoes, beans and strawberries. By the time you see the plant symptoms it is too late. That is why you must scout for the insects and control them if you have a significant population. The damage is called hopperburn because it usually starts as browning of the edges of the leaves. Later the whole leaf turns brown and dies. A whole planting will go down in a matter of days and is often confused with a disease problem.

Adults and nymphs feed by inserting a needle-like beak into the plant and sucking out sap. They also inject a toxin into the plant, which disrupts the food conducting tissue of the plant (ploem) and causes the yellowing, browning, and curling of leaves. In potato, leaf margins turn brown and brittle first, followed by death of entire leaves. In beans, the leaf turns mottled brown. Both adults and nymphs cause damage.

Some late-season varieties of potato such as Katahdin seem to have more tolerance.

Pyganic is the best material that organic growers have for this pest. Crop rotation will not help because the leafhopper is not overwintering here but rather flies in from way down south.


New Organic Bait Options For Slug And Snail Control
(By Becky Grube, UNH Vegetable and Sustainable Agriculture Specialist. Reprinted from the UNH Vegetable, Berry and Tree Fruit Newsletter)

Organic growers that experience major slug damage now have a new tool to help them prevent these losses. Recently, the Organic Materials Review Institute (OMRI) list-ed “Sluggo” and several other brands of iron phosphate slug and snail bait on their list of brand name materials approved for use by certified organic growers. As with other ‘restricted’ materials, it can only be used if other management practices are insufficient to prevent or control the slugs. Slug and snail damage can be particularly significant on many types of crops, particularly on young crops when soil moisture and relative humidity is high. Snails and slugs (which are shell-less snails) need high humidity and undisturbed soil to develop and reproduce. According to Alan Eaton, UN-HCE IPM Specialist, some of our common slugs are Europe-an and some are native. However, all of our common species spend most of their time underground or under debris, and come to the surface at night to feed.

There are many slug control options. Slug damage can be reduced by making an unhospitable habitat (dry and warm) by removing items which could serve as shelters (deep mulches, boards, rocks, etc.). Slugs can also be controlled by trapping. Shelters such as boards and rocks can be used to trap slugs, but in order to be effective, slugs must be regularly removed and destroyed. Fermented liquids (a mixture of yeast, sugar and water, or beer – see below) placed in submerged cups in the ground can also be used as traps in which slugs will drown. Slug baits are probably the most reliable and efficient meth-od of slug control. Commercially available baits or pellets contain molluscicides, poisons that kill snails and slugs. Two chemicals are licensed and formulated into slug and snail baits for use on home gardens and on food and seed crops in the United States - metaldehyde and iron phosphate. Of these, iron phosphate is far less toxic and has been shown to be just as effective as metaldehyde baits for slug control. Iron phosphate is considered by the U.S. Environmental Protection Agency to be GRAS (generally regarded as safe) for food use. No toxicity has been seen in mammals, birds, or fish. It is applied to soil as part of a pellet that also contains bait to attract snails and slugs. It is not volatile and does not readily dissolve in water, which minimizes its dispersal beyond where it is applied. This also means that it will remain effective after repeated rain events, unlike metaldehyde. Snails and slugs are more sensitive to the effects of iron phosphate than are other organisms. When the pests eat the pellets, the iron phosphate interferes with calcium metabolism in their gut, causing the snails and slugs to stop eating almost immediately. They die three to six days later. Iron phosphate slug and snail baits, originally used in Eu-rope, have been registered in the United States since 1997. These are sold as pelleted bait, typically applied to the ground around plants or crops. Several slug bait products contain-ing iron phosphate are registered in NH. When I checked the Division of Pesticide Control website, seven products were listed: Sluggo, Sluggo Plus, Bonide Slug Magic, Spectracide Snail and Slug Killer, Bayer Advanced Dual Action Snail and Slug Bait, Worry Free and Garden Safe Slug and Snail Bait. Two of these, Sluggo and Garden Safe Slug and Snail Bait, are also listed on the OMRI list of approved brand name products. In case of any question, it’s always a good idea to contact your certifier before you purchase a product. And as with any pesticide, always follow the label instructions! Lest you all think my newsletters tend to be a touch on the dry side, I’ll include, strictly for entertainment purposes, some relevant song lyrics that Alan Eaton sent me when I asked him to confirm some slug facts for me.

Now slugs is bugs that nobody loves but everybody understands
Cause they look disgusting, and they taste disgusting
And they feel disgusting in your hands
But of all the little bugs that grow in the garden
Slugs have a special place in my heart
And they never quit drinking once they start
So come on down, lets go out and have a slug drowning party tonight
No they can’t tell if they’re floating in Gui-ness or sinking in Miller Light
They ain’t particular and they go no taste
And they’ll drown in any beer in sight
So come on down, let’s go out, and have a slug drowning party tonight!
- From Dan MacArthur’s ‘Yucky Bugs’.

Information obtained from Ohio State University fact sheet HYG-2010-95, the U.S. Environmental Protection Agency, and the Organic Materials Review Institute (http://www.OMRI.org). Clipart courtesy the Florida Center for Instruc-tional Technology.


SQUASH BUGS IN VINE CROPS
(By --R Hazzard, UMass Extension Vegetable Program with information drawn from: T. Jude Boucher, Univ. of Connecticut and Beth Bishop, Michigan State.Reprinted and modified from the UMASS Newsletter)

Squash bugs have for many years been considered a minor pest in vine crops in New England. However in recent years some growers are find-ing higher numbers and resulting crop damage. It is important to assess wheth-er damaging numbers are present. Growers don’t need to try to get rid of every squash bug, but it is important to be aware of what risks exist. Adult squash bugs are 0.5 to 0.75 of an inch long, flat, gray-brown, and usually found on the underside of leaves, under residue, or in cracks in the soil. Squash bug eggs are laid in tiny clusters (usually on undersides of leaves in the notch between leaf veins) and change color from yellow to bronze shortly before hatching. Wingless nymphs are light gray with black legs and grow darker as they become adults in late summer. There is one generation per year. Adults spend the winter in crop residues and protected sites in or near the field. Photos of adults, nymphs and eggs are in the Pest Identification Supplement to the New England Vegetable Management Guide. The Supplement is avail-able in hard copy from UMaine Extension Offices or as a downloadable pdf file at the Guide website (http://www.nevegetable.org); photos are on the web individually at http://www.umassvegetable.org) Both adults and nymphs feed by inserting their beak and sucking juices from plant tissue. Feeding causes wilting in leaves, stems, and vines that are beyond the feeding site. The injury may also appear as light-colored areas that later turn brown and die. These symptoms are similar to bacterial wilt symptoms. Later in the season, squash bugs may feed on the fruit. Squash bugs are virtually impossible to control later in the season when nymphs are large and the canopy is dense.

Crops affected. Pumpkin and squash are the cucurbits most affected by squash bugs, because they prefer to lay eggs on these crops and because the nymphs flourish. Because of low attrac-tion and low survival rate, squash bugs do not usually become a pest on cucumber, watermelon, butternut squash and muskmelon. Cucurbita moschata crops such as Waltham butternut have been found to have fewer squash bugs. If summer squash gets away from you and gets too big to harvest, squash bugs will move in and feed on the unharvested fruit.

Cultural practices influence squash bug numbers. Clean culti-vation lowers the attraction of crops to squash bug. We have ob-served higher numbers in fields with hay or straw mulch and in low-till or no-till situa-tions where cover crop residues are high. Blue Hubbard squash as a perimeter trap crop has shown some efficacy in trapping squash bugs as well as cucumber beetles, because it is preferred over many other vine crops. In Texas, many growers have successfully used early-planted straightneck summer squash (‘Lemon Drop’or ‘Hyrific’) as a trap crop in the border rows of their watermelon fields to attract and control squash bugs to man-age CYVD.

Scouting and threshold. The key to preventing squash bug problems is early detection and control of small nymphs. Scout for squash bugs adults and eggs by searching upper and lower leaf surfaces and soil cracks around the plant. Insecticides may be warranted if squash bugs are causing wilting of young plants (if wilting is observed and squash bugs are present on the underside of leaves). Just before flowering, fields should be scouted for egg masses. This is the critical time to control squash bugs. If more than one egg mass per plant is found, an insecticide application is needed. Adult squash bugs and older nymphs are more difficult to control because they develop a hard exoskeleton as they mature. In addition, since squash bugs are secretive and the canopy grows thick, they can be difficult to reach with insecticides. The only OMRI listed (organic) products that have been shown to offer any control are azadirachtin (Neemix 4.5) and Pyganic, both for application to young squash nymphs. Large nymphs and adults are not really effected by any organic approved materials. That is why it is so important to do as much culturally as possible and scout NOW for early control. There is also a parasite of squash bug that may be visible in the field. It is a tachinid fly, Trichopoda pennipes, which has a colorful bright orange abdomen and dark wings. Eggs are laid on the abdomen of the adult squash bug; parasitism may be as high as 80%, but unfortunately, the adult squash bugs are not killed before they feed and lay eggs on plants. Squash bugs may also vector a relatively uncommon but serious disease, Cucurbit Yellow Vine Disease caused by the bac-terium Serratia marcescens. The presence of this disease was first noted in New England in 2003. If this disease has occurred on your farm, it is critical to focus on controlling early season adults to prevent its spread. A good article by Jude Boucher on cucurbit yellow vine may be found on the web at http://www.hort.uconn.edu/ipm/veg/htms/cucrbinct.htm

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