Eric Sideman's Pest Report
June 5, 2002

General Conditions

Crops are lagging behind a normal year to some degree because of cool weather, which for organic growers not only directly effects crop growth but also delays the release of nutrients from organic sources. Another frost occurred for many of us two nights ago. I know I am tire of staying up all night running irrigation. I got a good nights sleep last night and hope I will for the rest of the summer. Some plants (such as corn and some vine crops) that were injured by frost a few weeks ago are recovering, but will be delayed. Strawberries are still blossoming and setting fruit but there were significant losses from the earlier frosts. Strawberry growers, likewise, are doing their best to recover from the four to five sleepless nights.

CROPS AND PESTS

ASPARAGUS

ASPARAGUS BEETLES

Many growers are reporting bad times this year. Populations do build up over years if not attended to and for some growers that may be what is happening. The adults (bluish black with four yellow patches with red margins on the forewings) hibernate over winter and are seen during the picking season on the spears. In a few weeks they will lay eggs on end anywhere along the stem and the larvae, which are dark green little grub like things, will feed on the leaves. There may be two generations a year.

At this time if the damage is very bad try dusting rotenone at the base of the plants. Later, if the larvae are more numerous than what can be hand picked, spray with rotenone or pyrethrum. Basic control should be management of the crop residue, weeds and other vegetative trash around the beds in the late summer and fall to eliminate overwintering sites.

CUTWORMS ON SEEDLINGS
We have had reports of cutworm damage in direct-seeded and transplanted corn, and brassicas. These can also cause damage in peppers,tomatoes, and eggplants.

Monitoring. Scout weed borders before plantings go in. Check newly transplanted crops to look for damage: clipped stems or leaf feeding (some cutworms climb up into foliage). If you find clipped transplants, you can usually find the larva in the soil near the plant. Estimate % stand loss to determine need for a spray. In sweet corn, Rutgers suggests inspecting 20 plants at 5 sites (total 100 plants). Threshold is 3% (3 or more plants damaged). Damage may be more concentrated around field edges.

Life cycle and identification. There are many species of cutworms that attack vegetables including black cutworm, variegated cutworm, dingy, spotted, dark-sided, or glassy cutworm. Spotted and variegated cutworms climb and feed above-ground, and black cutworms climb when they are young (less than half an inch long). Cutworms can be difficult to identify. Variegated cutworm has some pale yellow markings on its back, while black cutworm is nearly uniform gray to black with a greasy, rough appearance.

Adults of all cutworms are moths with dark gray forewings, often with various lighter or darker markings, and lighter hindwings. They are in the same group of moths (noctuids) as the corn earworm, fall armyworm, and cabbage looper, but with very different life cycles and habits. They are capable of migrating long distances but it is very likely our own resident populations which are causing problems. Black, spotted and variegated cutworm have at least two generations per year in this region.

Black and variegated cutworms spend the winter in the larval or the pupal stage as deep as 5 inches (12 cm) down in the soil. Spotted and dingy cutworms overwinter only as larvae. It is these larvae that are present in the soil at planting time, ready to feed on early spring transplants and seedlings. They may be of varying sizes. Young black cutworm larvae are more likely to feed on plant foliage. Older larvae feed on stems near the soil line during the night and descend into the soil during the day. They clip stems of young seedlings and are reported to feed on the wilted plant material. Larval development takes about a month (28-34 days).

Adults emerge from overwintered pupae in May or June, and from pupae of spring-feeding larvae later in the season. At one site in Easthampton, a pheromone trap has been catching 10-20 black cutworm moths per week for the past two weeks. Females lay eggs on grass leaves, weeds, or the soil surface. Attractive habitats include weedy or grassy areas, and alfalfa; corn and soybeans are among the least attractive hosts. (NOTE: This may influence you cover crop decisions, although there seems to be little other information about specific relationships between what cover crops are planted in the fall, and cutworm infestations in the following year.

Black cutworm moths are reported to select low spots in the field, that has been waterlogged or flooded for egg laying. Egg are also concentrated on low-lying vegetable such as chickweed, curly dock, shepherd's purse, peppergrass, mustards such as yellow rocket, or plant residue from the previous year's crop. Note that the above list includes lots of winter annual weeds that grow in the fall - weeds that we often overlook.

Cultural Management. Weedy land harbors the most cutworms, as the adult moths seem to prefer dense plant cover for egg laying. Crop residues may also attract higher populations. Therefore, crops that follow weedy crops, alfalfa, or no-till crops are more likely to be damaged by cutworms. Plant early transplants into fields that had low weed pressure the previous year, especially in the fall, or where crop residue was tilled under in the fall. Plow fields in spring and keep weed free for at least two weeks before planting to starve young larvae and reduce egg-laying. Avoid planting susceptible crops close to sod, alfalfa or fallow areas. Summer plowing disturbs eggs and larvae and raises them to the soil surface where they are more vulnerable to predation and dessication. Fall plowing will do the same. Plan rotations to avoid planting vulnerable crops after a grassy sod, and plow sod fields in later summer or early fall. Cultivate frequently to injure and expose hiding cutworms to predators. Daily (nightly) search and destroy missions -- by hand -- are a time-honored "biological" management for small plantings!

Biological management. Several predators and parasites have been identified, however none have been commercialized for release against these pests. At Iowa State University, a new baculovirus has been isolated from black cutworm, which is highly active and has potential as an alternative to chemical control. Soil applications of nematodes (Steinernema carpocapsae) can reduce cutworms and last for anywhere from 8 days to several weeks, according to various research trials. Good soil moisture favors survival. Repeat applications may be needed.

Other organic options. This is a tough pest for organic growers as no effective insecticides when outbreaks occur. Strategies such as cardboard or tinfoil collars are impractical on a commercial scale.

Farmers have reported that insecticidal baits have been effective. Try using a very concentrated solution of Bt, mixed with bran and a bit of molasses. It can be sprinkled on the ground near the crops or made into patties that are placed along the rows. Bt sprays (ie, Bt aizawi or kurstaki directed at plant stems and foliage) are reported to work sometimes, but not consistently, possibly because large cutworms do not ingest a big enough dose of BT to stop feeding and die before they have caused extensive damage to the planting.

--Adapted from report of Ruth Hazzard (resources: Vern Grubinger (UVM), Brian Caldwel (NYS-NOFA) ,Eric Sideman(MOFGA), Rex Dufour (ATTRA)

STRAWBERRY

STRAWBERRY CLIPPER

The clipper is a weevil that does its damage to the strawberry bud. Scout your fields now if you haven't already and look for clipped, dying buds hanging by a thread. By this time the damage is done for the most part, but get ready for next year. The clipper over winters in or near the fields as an adult in the soil. In the spring the females move into the field and lay about 300 eggs each in young bud. After laying the egg she then girdles the stem just below the bud. the eggs hatch and the grubs develop in the bud and then pupate in the soil. There is one generation per year. You can see how populations can grow very quickly.

On small scale plantings scouting and removing clipped buds every day or so can keep populations from growing year to year. On farm scale, crop rotation is a must. (Adapted from report from Dave Handley, UMaine, Extension)

TARNISHED PLANT BUG

The TPB is a small, bronze colored insect with a triangular marking on its back. It feeds on hundreds of plant species. The immature stage is bright green and are being seen now in strawberry fields feeding on opened strawberry flowers and young fruit. They suck out plant juices. Their feeding results in deformed fruit because the fruit's cells do not develop normally around the feeding site. In strawberries the common damage is a "cat faced" or "button" berry with seedy ends.

There is not a good organic control. It is especially important to manage the fields around the strawberry planting. Do not mow fields of clover or alfalfa at the time of strawberry flowering or the feeding TPB in those fields will look to your strawberries for a home. Controlling weeds in your fields and around them is critical. Keep headland mowed regularly, except when the strawberries are flowering.

SWEET CORN

TRICHOGRAMMA USE GUIDELINES FOR FRESH MARKET SWEET CORN Trichogramma ostriniae, a small wasp that parasitizes and kills European corn borer (ECB) eggs, will be commercially available for the first time this season. In this article, we'll outline how to integrate Trichogramma releases into the existing fresh market sweet corn IPM practices.

T. ostriniae is affectionately known as "the Ghengis Khan of natural enemies" by those who know it best. In research conducted in sweet corn in New York State over the past 8 years, this wasp has produced remarkably high levels of parasitism (80-100% of ECB egg masses), shown an extraordinary ability to disperse throughout corn fields, and demonstrated that it is able to reproduce in the field and increase its numbers in response to increases in ECB numbers. Crop damage is typically reduced by half in fields receiving Trichogramma releases. Because of the wasp's excellent dispersal and reproductive abilities, we are able to use an inoculative release approach. Inoculative releases are inexpensive (around $15/A for the wasps) because just a single release of relatively low numbers of wasps (30,000/A) is needed in each field. This single inoculative release has the potential to halve the number of insecticide applications to early season sweet corn for ECB control.

T. ostriniae does not parasitize either fall armyworm or corn earworm, the other two worm pests of sweet corn. You'll get the most benefit and save the most sprays releasing Trichogramma in early season fields before the armyworm and earworm flights start. Release timing Using an inoculative release approach means that the wasps need to be released in fields just as the corn borers start to lay eggs. Experience to date indicates that releases are almost always successful except if made when there no egg masses are in the field. In these situations the wasps will die without reproducing. Timing can be a little tricky! Based on our experiences with research demonstrations, we're recommending that the wasps be released when the corn is in the 4-6 leaf stage. We're hesitant to recommend Trichogramma for early fields started under plastic at this point. Those fields are very attractive to egg-laying females because they're the plants are larger than those in bare-ground fields. There could be so many eggs laid immediately after the plastic is removed that releases of 30,000 per acre would not be able to parasitize them all. We'll be looking at that in at least one of our demonstrations this season.

Ordering Trichogramma
There are two sources for the wasps. They are available through IPM Laboratories in Locke, NY, Small quantities can be ordered a week before delivery. They will need more advance notice for larger quantities. For planning purposes, IPM Labs would appreciate advance notice if you're thinking about using Trichogramma this season. IPM Labs can be reached at 315-497-2063. Wasps can also be ordered through Insecterra, Inc. in Montreal, Quebec. Follow the same guidelines for ordering as described above. Insecterra can be reached at 514-524-2433 (email ffournier@insecterra.com).

Handling Trichogramma
One major difference between Trichogramma and insecticides is that the Trichogramma are alive! Trichogramma arrive from the insectary inside the eggs of the grain moths that they are reared on. They look like coarse grains of pepper. You want to be sure that they are still alive and in good shape when you put them in the field. That means not letting them get too hot (not leaving them in the truck in the hot sun if you get sidetracked on the way to the field), not letting them get too cold (they should not be refrigerated), and not letting the wasps emerge from the grain moth eggs before you put them in the field. It's best to put them out in the field the same day as they arrive from the insectary.

Putting them in the field
The wasps will arrive from the insectary as pupae in grain moth eggs glued inside cardboard release packets, each containing 8000 pupae. They need to be in release packets because natural enemies like lady beetles and lacewing larvae will feast on them if they get the chance, and there can be a lot of natural enemies in a corn field. The adult wasps will emerge from the pupae and escape from the release packet along the open edges. Distribute the packets as evenly as possible throughout the field, starting about 50 feet in from the field edges. If you have a long narrow field less than 125' wide, distribute them evenly along the middle row. For wider or more square-shaped fields you'll need to use more than one row. Flat wooden stakes can be used to put the release containers on if the plants are too small to attach them to. Do not put them on the ground, and when hung from a plant, locate them in the shade, such as under a leaf or on the north side of the plant.

Scouting release fields
Throughout New England, growers make IPM spray decisions based on scouting for ECB caterpillars and feeding damage, starting at the pretassel stage. Where Trichogramma has been released, you can scout as usual (check 100 plants in groups of 10, determine % infested with caterpillars) and make your spray decision based on the 15% threshold. Eggs that were parasitized and did not hatch will never reach the larval stage, resulting in fewer caterpillars and less need to spray.

You can also determine whether wasps are doing their job by scouting fields for ECB egg masses. Search the underside of all leaves for the white, scale-like flat egg masses, which are about the size of a dime. Keep track of both the total number of egg masses and the number of parasitized ECB egg masses. Egg masses parasitized by Trichogramma turn evenly black, and are no longer really ECB egg masses. They're really Trichogramma, so they can be ignored when deciding if a field is over threshold. In the New York State IPM program, spray decisions are based on egg mass infestation (2 or more egg masses in the black head stage, or 15% infestation, out of 40 plants sampled).

Spraying release fields
Using the inoculative release approach, Trichogramma will suppress ECB, but cannot be expected to completely control all infestations, so foliar Bt applications may still be needed. More about that when we get into the season.

-Adapted from report from Ruth Hazzard who adapted it from Abby Seaman and Mike Hoffmann, New York State IPM Program

(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.)