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

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(Modified from a piece in the Umass Extension Vegetable Notes by Andy Cavanagh)

Massachusetts is a week or two ahead of Maine and it is not surprising that we are going to experience the same thing they did a few weeks ago. It is time by the calendar to get the cucurbits out into the field and yet even
though there was some warm weather earlier, it is now wet again and going to get cold in a day or two. This variable weather wreaked havoc with many growers in Massachusetts for their early cucurbit transplants and may do the same here. The warm weather pushed cucumber and squash seedlings along quickly and some folks have moved them out of the greenhouse, or really want to get them out and put them  into the ground soon. But be careful because cool weather and wet soil may cause  transplants to collapse. The cold soil, combined with  the somewhat leggy, tender transplants and wet weather not only leaves the small amount of roots struggling to provide the top of the plant with what it needs, but also creates  an opening for whatever pathogens that are naturally present in  the soil to get a foothold. In Massachusetts they saw root rots and wilts  caused by a number of different pathogens (including Pythium, Phytophthora, and Rhizoctonia), some of which thrive under cool  and wet conditions.  They also observed some leaf scorching that  may have been a direct result of the cold weather. The cucurbits suffer from what is called chilling injury without even having to be frosted. If the roots sit in cold wet soil and the air warms you may also see the plants wilt. This is the result of the roots not working and the top of the plant transpiring normally. My advice (seeing eye to eye with Becky Grube - Vegetable Specialist at UNH where the advice originated) is to follow your soil thermometer and not rely too much on the calendar. I suggest you do not put cucurbit transplants into soil less than 60 o F.

There are two types of asparagus beetles, the common and the spotted. Adults of both species and larvae of the common feed on the fern of asparagus and reduce the vigor of the bed over years. Larvae of the spotted feed almost entirely inside the berries and effect seed production but do not hurt the plants. Both species overwinter in crop residue and become active in the spring. They feed on the ferns and lay eggs that hatch in about two weeks. Then the larvae of the common feed for three to four more weeks and really weaken the plant if they are numerous.  Then they drop to the ground and pupate at the soil level or just below. New adults emerge in later July and by September are looking for overwintering sites.
This time of year you can greatly reduce the population by harvesting ALL of the spears. The beetles are becoming active now and leaving some spears to develop into fronds give them feeding sites. If you harvest ALL of the spears right to the ground during the harvest period you will starve many of the beetles 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. As a last resort in a really bad infestation, Entrust works well.

-(modified from an article in UMASS Vegetable Notes a few years ago  by Ruth Hazzard. R Hazzard says thanks to sources including: D Ferro (Umass Amherst), J. Mishanec (CornellUniversity), Jude Boucher (Univ. of Connecticut).

Colorado potato beetles (CPB) are will be moving into potato and eggplant crops soon, and will shortly be laying eggs. Some adult beetles spent the winter in last year’s potato fields, but most moved into the woods and brushy borders next to these fields, where they burrowed into the soil up to a depth of 12 inches. In spring the beetles have to regrow their flight muscles before they are able to fly. At first they search for food plants by walking from the field edges. This is why the edge of non-rotated crops are attacked first. If beetles do not find host plants via walking they will fly some distance in search of food. Once host plants are found adults begin to feed and lay eggs. The beetles will have mated the previous fall or late summer; hence they have no need to mate in the spring to produce viable eggs. However, they do continue to mate in spring. The bright yellow eggs are laid in clumps that average 30-35 eggs, generally on the undersides of leaves.

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. 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. Now is the time to scout for adults, eggs and egg hatch.
Walk your fields and look for CPB adults and eggs. The economic threshold for adult beetles in potato is 1 beetle per 2 plants (or per 2 stalks, in midseason). Eggplant seedlings have a low tolerance to damage. 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 the earliest egg masses you find with bright tape or flags, and then keep an eye on the hatch. Larvae go through four stages before they drop to the soil and pupate. 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. Ten days later the next generation of adults emerge and feed. If they emerge before August 1, they will lay more eggs. After August 1, they feed and head to overwintering sites.
Spray timing and thresholds.
To prevent resistance the best strategy is to alternate among classes of insecticides in each generation, and throughout the season. An example would be to use a material such as Spinosad (Entrust), which controls adults and larvae for the first spray, followed by a Bt (Novodor) to kill emerging young larvae. BUT, at this time there is no Bt formulation approved for use in organic systems. NOVODOR IS NOT APPROVED FOR ORGANIC PRODUCTION BECAUSE OF INERT INGREDIENTS.  VALENT, THE COMPANY THAT MANUFACTURES IT,  AT ONE TIME SAID THEY WOULD REFORMULATE IT TO MEET ORGANIC STANDARDS, BUT SEEM TO HAVE CHANGED THEIR MIND.  GIVE THEM A CALL AND TELL THEM HOW IMPORTANT IT IS TO ORGANIC GROWERS (1 800 323 9597).
If you are not organic and are using Bt (Novodor), you want to make the first application when 20- 30% of the eggs have hatched.  If you are using spinosad (Entrust is the organic formulation)  you can wait until more larvae have hatched, when the oldest larvae reach the third instar, when they are about 1/3 inch long. Applications made at this time with Entrust will kill all the larvae that have hatched up to this point. The 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. Thresholds established in the Northeast for eggplants from seedling to fruiting stage include: 15 CPB per 10 plants (Rutgers) or 2 small/1 large larvae per plant (<6 inches) or 4 small larvae /2 large per plant (>6 inches) (Cornell). In eggplant, in addition to defoliation, beetles sometimes clip the stems of flowers or flower buds. This directly reduces fruit formation and marketable yield. On the other hand, potatoes can tolerate 20% defoliation without reduction in yield (or even more, later in the season and depending on cultivar. Allowing these later populations to exist without spraying will delay development of resistance to the insecticides).

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 with a foliar insecticide. In eggplant or tomato, the perimeter border can be an Italian eggplant type, which is more attractive to both CPB and flea beetles. Treat only the border, as soon as beetles arrive.
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. Where trade names or commercial products are used, no company or product endorsement is implied or intended. Always read the label before using any pesticide. The label is the legal document for product use. Disregard any information in this newsletter if it is in conflict with the label.

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