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 MOFGA's 2006 Pest Reports - Compiled by Eric Sideman, PhD Minimize

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Once again it is a cool and damp spring and I want to stress that farmers and gardeners need to watch the sky as well as the calendar. The calendar says beans and corn should be in the ground and germinating, but the soil is cold and anaerobic and seeds are rotting, if not being washed away.

SEEDCORN MAGGOT: Peas, beans, corn, potato sprouts and even cucurbits in the greenhouse are attacked by the larvae of this fly. They are yellow-white maggots about a quarter of an inch long and sharply pointed at the head end. The symptom is usually that you see no germination, and when you dig around you may find nothing left or may find the maggots burrowing into the seed. Sometimes the seed germinates but only a weak or partially eaten plant is seen. The injury is most likely to occur in cold wet seasons where the germination is slow, and also in soil high in organic matter.

The attack is early in the spring because the critter spends the winter as pupae in the soil or maybe free maggots in manure or unfinished compost. The adult is a grayish brown fly only about a third of an inch long. It emerges in early spring and deposits eggs in rich soil, compost piles or near seeds and seedlings. Exposed peat or potting soil mix of transplants can also serve as attractive sites for females looking for a place to lay eggs. There are a few generations each season.

The best method of dealing with this critter is to do everything you can to encourage quick germination and rapid growth. In the cold, wet soils we have this spring the seeds are just sitting ducks. Shallow planting helps when conditions are poor. Best yet, wait for things to warm up and dry out.


PILL BUGS: (NOTE: This report below is from a grower in Little Compton, RI but as I was copying it I got a call from a grower right here in Belfast, Maine.) We are learning a hard lesson about long term problems with greenhouse tomato production. Pill bugs showed up in massive numbers this season and almost destroyed the whole crop. Since we always use a fair amount of compost in our operation we have become accustom to their presence over the years and always thought them benign. This year that change radically and we noticed they were almost twice the size of one in the past. We graft our tomatoes and they first attacked the lower grafted sections. It first appeared like a scuff mark. I first thought an employee had been too rough with the plants when suckering. Then quickly there after they were eating right through to the inner core of the plants structure! When we figured out who the culprit was we gave them a hardy shot of Pyganic and found thousands belly up all over the house. One of our problems is that we use black plastic to control weeds under our tomato plants. This is providing them with a perfect breeding ground! After this season we will do that no more. At best we have them at bay. They are still feasting on the leaves that touch the ground and I can no longer get the spray where I would like. We are hoping to get some nematodes to do some control on them during the off-season. Some Quebec growers are having similar problems. With these critters we have yet another reason for looking over our shoulders. (Editor's note, this just in from Quebec: they are experimenting a plastic collar, like a cone around the base of the tomato plants, to deter pill bugs. It is made from greenhouse polyethylene, 3inches high. The whole thing is keeping upright with Tanglefoot glue, which is a natural resin that never dries. It is important to put glue at the base of the cone to prevent the entry of pillbugs there. Pillbugs seems not able to climb on a clean plastic.) (Taken from Vern Grubinger's Vermont Notes)


FLEA BEETLES IN BRASSICAS: Flea beetles are busy feeding in spring plantings of brassica crops in Massachusetts. Numbers are likely to rise in coming weeks here in Maine as beetles move out of field borders where they spent the winter. Crucifer and striped flea beetles feed on Brassica crops as well as weeds that are in the same family, such as yellow rocket or wild mustard. [Different species of flea beetles feed on the tomato family of crops.] The crucifer flea beetle (Phyllotreta cruciferae) is uniformly black and shiny, about 2 mm in length, while the striped flea beetle (Phyllotreta striolata) has two yellow stripes on its back. Flea beetle adults feed on leaves and stems, resulting in numerous small holes, or 'shot-holes'. Eggs are laid in the soil starting in late May, and beetle larvae feed on roots. The non-waxy greens (arugula, bok choi, tatsoi, mustard, Chinese cabbage, komatsuna) are preferred to the waxy cabbage, kale and collard types of brassicas. In brassica greens, beetles feed on the whole surface of the leaf, and will continue feeding from the seedling stage until harvest. Waxy crops are most susceptible at the cotyledon and seedling stage and feeding is more limited to leaf margins on older plants. Occasionally in tender greens such as arugula, tarnished plant bug feeding may be confused with flea beetle feeding. In addition to the shot holes from flea beetles, there may also distorted leaves that are typical of TPB feeding, which injures leaf tissue when leaves first emerge.

To reduce and delay flea beetle invasion of spring crops, move them as far away from the fields that were used for fall Brassica crops as possible. Beetles overwinter in field borders near last year's crop. Planting close by ensures a
high population in the spring. One of the best ways to protect Brassica crops from flea beetles is to place a floating row cover over the bed or row. It is critical to seal the edges immediately after seeding, because Brassica seeds germinate quickly and beetles rapidly find the cotyledons. Flea beetles can fit through extremely tiny cracks. Edges of the cover must be sealed on all sides using soil, black plastic bags filled with soil, or some other method.
Spinosad (Entrust is organic formulation) is proving to be an effective in suppressing flea beetles and reducing damage. A supplemental label has been issued in Massachusetts for flea beetle suppression in brassicas; other states may also have this [not Maine, I just checked], but in all states the product is labeled for use in brassica crops. Pyrethrin (Pyganic EC 5) showed poor to moderate efficacy in trials, and has a short residual period. Some growers have reported a good knockdown with this product. You can spray the Pyganic right through the floating row covers and knock down any flea beetles that may have gotten inside.

This year, with funds from a SARE Partner Grant, we are testing a Perimeter Trap Crop (PTC) system at several farms in NY, MA and VT. We are using more attractive greens (Brassica rapa types) as a trap crop for cabbage,
collard, kale or broccoli (Brassica oleracea). Komatsuna is our choice for the perimeter trap because it is highly preferred compared to cabbage, seed is inexpensive, growth is rapid, and the crop continues to produce new, attractive foliage over a long period. Borders are being sprayed with spinosad when beetles first arrive. Our first week of observations show promising results: heavy feeding in the komatsuna, and virtually none in the cabbage. We'll keep you posted! We have also gained the insight that woodchucks prefer cabbage over komastuna. In fact, they won't even touch that nasty light green crop, but will walk right past it to chomp down cabbage seedlings. If you are interested in trying PTC for cabbage, kale, collard, or broccoli please feel free to call Pam Westgate or Ruth Hazzard at (413-545-3696) for more information. (modified from Mass. Veg. Notes by Ruth Hazzard)


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