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 MOFGA's 2009 Pest Reports - Compiled by Eric Sideman, PhD Minimize

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Pest Report June 1, 09

COOL SOIL AND CROP GROWTH
Once again it feels to me that we got an early start with soil in good condition for planting in April and then May came with some long stretches of cool and sometimes wet weather. I am getting a number of calls that relate to this. The most frequent is poor germination of peas and beans plus some folks who rushed and put out warm weather crops before it was warm.

See last week's Pest Report for a discussion of the seed corn maggot, which will cause very spotty germination.

Don't rush out crops. Peppers, eggplant, sweet potatoes and especially crops in the cucumber family respond very poorly to cool soil. Their roots do not work well in cool soil and so they suffer nutrient problems (purple or yellowing leaves), and worse if the soil is in the low 50s, which is really cool for these crops, they will suffer physiological drought. The leaves wilt and the plant may die because the roots cannot function and get water to the plant.


ASPARGUS BEETLES [Modified from an article by Ruth Hazzard, UMass Vegetable notes, May 1, 2008]
Common asparagus beetles are active in asparagus fields. The spotted asparagus beetle tends to become active somewhat later in the spring. These two beetles are closely related and have similar life cycles but it is the common asparagus beetle that is most damaging to the cut spears. Common asparagus beetle (Crioceris asparigi) is blue-black, shiny, smooth and about 6 to 9 mm (1/4 inch) long, with three large yellow, squarish spots with red margins along each wing cover. (see photo on MOFGA website). Eggs are black, laid standing on end in rows along the spears, and hatch in 3-8 days. Larvae are wrinkled, plump, hump-backed, and dull gray with black head and legs. They grow up to 1/3 inch. These larvae feed in spears and in fern. Eggs and larval damage makes spears unmarketable. Larval feeding damage in the ferns can cause sever defoliation and weaken the stand. When
full grown, larvae drop to the soil and pupate underground. New adults emerge in July, feed in ferns, and by September are looking for overwintering sites. Spotted asparagus beetle (Crioceris duodecimpunctata) is reddish orange or tan, with six black spots on each wing cover (hence its other name, 12-spotted asparagus beetle). Eggs are greenish, glued singly on their sides to leaves. Eggs are laid on fronds, not on spears. Larvae are similar to those described above, but are orange colored, and feed almost entirely inside the berries so they affect seed production but do not hurt the plants.

Winter habitat: Both species spend the winter as adult beetles either in field borders or within the asparagus field. Sheltered sites such as under bark or in the stems of old plants are preferred. Some burrow into the soil.

Life cycle: Beetles feed as soon as they become active, and begin laying eggs after several days of feeding. Eggs hatch in 3 to 8 days depending on temperature. Larvae feed for 10 to 14 days and if in large numbers can
defoliate the plant. They molt four times, then crawl into the soil to form chambers in which they spin cocoons and pupate. After 5 to 10 days, new adults emerge. There are probably two generations in this part of New
England.

Scouting: At this time in the season, look for adult beetles, for feeding damage and for eggs laid on spears.

Cultural and biological controls. This time of year you can greatly reduce the population by harvesting ALL of the ready spears every day. Do not let spears that have gotten too big to develop. Pick the field clean to reduce
the number of stems where eggs will survive long enough to hatch and grow up into summer-generation beetles. If you harvest ALL of the spears right to the ground during the harvest period you will starve many of the beetles,
give them no site to lay eggs, and fewer will make it to the time you stop harvesting and let the fronds grow. In the fall remove all of the crop residue and other refuse nearby that may provide shelter for adults over winter, by disking lightly or burn crop stalks and fronds.. Maintaining a clean environment in the fall will force beetles to seek shelter outside the field or burrow in the soil, where many predators reside.

There are several beneficial insects that attack the asparagus beetle, including a tiny parasitic wasp (Tetrastichus asparagi) that attacks the egg stage. It kills eggs by feeding on them and by laying its own eggs, which hatch and grow inside the beetle eggs. Providing a nearby nectar source such as umbelliferous flowers for the wasps may increase their chances of survival, but may not be sufficient to prevent economic damage. Chemcial control. Entrust may be used on fronds after harvest, but asparagus is not on the EPA Entrust label for treating spears. Treat ferns if 50 to 75% are infested. Organic options on spears include Surround WP as a repellent, Pyganic EC5.0, or products containing capsaicin.

References: Handbook of Vegetable Pests by John Capinera; 2008-2009 New England Vegetable Management Guide; Eric Sideman, MOFGA; Brian Caldwell, Cornell Universtiy.


GARDEN SPRINGTAILS
The garden springtail is a wingless insect that hops like a flea beetle and eats small holes in leaves of young seedlings like a flea beetle, but is not related to, nor does it look like a flea beetle. The springtails are in an
order of insects all there own. They are tiny, plump and have a taillike appendage that they use to hurtle themselves into the air. They live in moist environments that are high in organic matter. There are many species of springtails, most of them are harmless and live on the forest floor. But the garden springtail does some harm. Young seedlings of beets, spinach, beans, onions and some others are hosts and if the population is large enough the seedling is set back by the number of holes drilled into its leaves. In most situations the seedlings out grow the pest and little harm
is done. Usually, the environment changes quickly in the spring and it becomes too dry for springtails. Anything you can do to make it less humid earlier will help, e.g., reduce surface residue, control weeds, wide crop
spacing, etc.

COLORADO POTATO BEETLE
Colorado potato beetles (CPB) adults are just starting to show up in potato and eggplant crops. The bright yellow eggs are laid in clumps with about 30-35 eggs each, generally on the undersides of leaves. As with most other insects and plants, there is a direct relationship between higher temperatures (in the range between about 55 and 90 degrees F) and faster rate of development. That includes egg-laying, egg hatch, larval growth, and feeding
rates. A period of cold, rainy weather slows everything down, but we can expect a surge of adults and shiny yellow eggs to appear with the next hot spell.

Scouting and Thresholds

Walk your fields NOW and look for CPB adults and eggs. A treatment should be considered for adults when you find 25 beetles per 50 plants and defoliation has reached the 10% level. The spray threshold for small larvae is 4 per
plant; for large larvae, 1.5 per plant (or per stalk in midseason), based on a count of 50 plants or stalks.

Controls are needed on eggplants when there are 2 small or 1 large larvae per plant (if plants are less than six inches) and 4 small larvae or 2 large per plant (if plants are more than six inches).

Potatoes can tolerate 20% defoliation without reduction in yield (or even more, depending on time of the season and cultivar). Damage to eggplant seedlings from adult feeding is often severe enough to warrant control of
the adults. In potato, adult damage in rotated fields may not be significant, so you may be able to wait until after egg hatch to kill both adults and larvae.

Look on the undersides of leaves for the orange-yellow egg masses. The fresher the eggs, the brighter orange the eggs will appear. Eggs hatch in 7-10 days, depending on temperature. If you want to know when the earliest
eggs are hatching, you can flag a few of the earliest egg masses you find with bright tape or flags, and then keep an eye on the hatch.

Hatched larvae go through four stages before they become adults. In the first stage, the larvae are about the same size as the eggs and in the second stage they are about an eighth of an inch long. As the larvae get bigger, they do more feeding. The fourth, or largest, stage does 85% of the feeding damage. It’s a good idea to prevent beetles from ever reaching the fourth instar!

After larvae complete their growth, they drop to the ground and burrow into the ground to pupate. About ten days later the next generation of adults emerges – ready to feed. If they emerge before August 1, they will lay more
eggs. After August 1, they feed and head to overwintering sites. Good
control in June prevents problems with CPB in August.

Cultural Controls
Crop Rotation. The single most important tactic for CPB management is to rotate potatoes or eggplant to a field that is at least 200 yards from the previous year’s fields. Since the adult that comes out of winter cannot fly, barriers such as roads, rivers, woodlands, and fields with other crops are helpful. Rotated fields tend to be colonized 1-4 weeks later in the season. Also, the total population of adult beetles is lower, producing fewer larvae
to control. Perimeter treatments or perimeter trap cropping can be applied to potato. One approach is to plant a barrier crop between overwintering sites and this year’s crop and get it in earlier than the main crop; then control
early-arriving beetles.

Early planting. Green sprouting, also know as chitting, prepares whole seed potatoes to emerge rapidly, gaining about 7-10 days to harvest. This early start makes it easier for the crop to put on growth and size before CPB
adults and larvae arrive. It can be combined with raised beds and plasticulture. While it won’t avoid damage altogether, it may reduce the need for insecticides. Refer to the New England Vegetable Management Guide
(online at www.nevegetable.org) for more details.

Late planting. Another strategy for beating the beetle is to plant late. CPB adults that do not find food leave the field in search of greener pastures.

Planting after mid- June, using a short season variety, often avoids CPB damage and eliminates the need for controls.

Straw mulch. It has been well documented that when potato or eggplants are mulched with straw, fewer Colorado potato beetle adults will settle on the plants and fewer eggs will be laid. This can be accomplished on larger
plantings by strip planting in a rye mulch, followed by mowing and pushing the rye straw over the plants after they emerge. For smaller plots, straw may be carried in.

Biological Control. There are numerous predators and parasitoids that attack CPB adults (a tachinid fly), larvae (12-spotted ladybeetle, spined soldier bug, ground beetles), and eggs.

Organic controls. Spinosad (Entrust) and azadiractin (AZA-Direct) are two options. Recent studies have shown very good results with spinosad, but please use reluctantly because resistance will build up in populations of CPB. The azadiractin has shown some efficacy, but neem works slowly.

Generally it is used to reduce overall damage and reduce numbers but it is not a rescue treatment like spinosad is. NOTE: There is no longer a registered product for agricultural use in organic crops in the US that contains Bt tenebrionis as the active ingredient. Beauvaria bassiana (Mycotrol O) has been shown to suppress CPB populations though does not provide immediate control. And, using Beauvaria bassiana does not jive well with using crop rotation because you need the overwintered adult that remain infected with the fungus to eliminate buying the product new every year.

(modified from the Umass Vegetable Notes, an article by - R Hazzard;
(sources include: D Ferro (UMass Amherst), J. Mishanec (NYS), J Boucher
(CT), J. Whalen (DE), T. Kuhar (VA), , G Ghidhu (NJ), New England Vegetable
Management Guide, Ohio Vegetable Production Guide)


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