Scaffolds 99 index

INSECT BITES

(Art Agnello ama4@nysaes.cornell.edu, Entomology, Geneva)

European Corn Borer

Infestations of ECB in orchards are not very common, but when they do appear, as has been the case occasionally in N.Y., they can be quite serious. Considerable feeding damage will be noted in late June in terminals of newly planted apple and cherry trees, and early fruit feeding on apple is often evident by this time of the year. Infestations of this pest on apple are spotty and unpredictable; incidence in an orchard one year has no correlation with its likelihood of occurrence the next season. The ECB is present as two separate strains in N.Y., usually designated by their pheromone chemistry. The univoltine "Z" race (peak flight normally in mid-July), can be found almost continuously from Buffalo to Albany. The bivoltine "Z" race (peak flights in mid-June and mid-August) is present from Buffalo to about Rochester, and the bivoltine "E" race (also with peak flights in mid-June and mid-August) picks up from Rochester to Syracuse or thereabouts. In the Hudson Valley, all 3 races are probably present. What this means to most apple growers is that most places have flights in the middle of June, July AND August. Susceptible orchards (young non-bearing, and others in proximity to sweet corn populations) must therefore be protected almost continuously during the summer, using something that's relatively long-lasting.

Damage to newly planted, non-bearing trees is caused by larval tunneling in the current season's growth. Browning of terminal leaves is a good indication of corn borer larval presence. The feeding will kill the terminal and disfigure the tree.

ECB & SHOOT ENTRY

ECB INSIDE SHOOT

ECB TERMINAL DAMAGE

Non-bearing, newly planted orchards normally do not receive the intensive cover spray program bearing orchards do; therefore, corn borer infestations can build up more easily in young orchards. Corn borer attack on young trees can occur from June through August. Damage to the fruit usually shows up in late summer, when the August flight of the bivoltine strain is active.

Bearing orchards are more likely to show some early corn borer damage on the fruit if growers relax their spray program in June or early July. However, most fruit feeding occurs between the last cover spray (mid-August) and harvest. Weedy sites provide plenty of alternative hosts for this insect, especially those containing broadleaf dock, ragweed, pigweed, smartweed, and barnyard grass. Penncap-M, Lannate, Lorsban and Asana can give very good control of ECB larvae, provided application is made before the caterpillars become concealed in the plant tissue. Potential problem plantings should be checked periodically in August for shoot infestations of this caterpillar, which is cream colored with a dark head.

Spotted Tentiform Leafminer

As reflected in the pheromone trap counts, the 1st brood spotted tentiform leafminer flight subsided recently in both Geneva and the Hudson Valley, and the 2nd brood is getting under way statewide. Because of the relatively advanced season, this flight might peak and the eggs hatch by as early as the last week in June. That is the time at which time we recommend sampling leaves for the young (sap-feeding) mines of the second generation, to determine the need for a spray.

More information may be found at: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/tree_fruit/STLM_Sum.GIF]

Sampling should be conducted when the first of the mines reach the tissue-feeding stage. This is when most of the population is in the sap-feeding stage, and it usually occurs about 500—700 degree-days (base 43°F) after the start of the second moth flight. The larvae can be found easily, but at that stage they have not yet caused much damage to the leaf. You may wish to make a note of the 2nd flight's start date in your region, or use the Geneva date (6/10) for accumulating degree-days in your locality if you don't happen to document this event in local traps.

Apple Maggot

It will soon be time to expect the first appearance of these flies in abandoned orchards, particularly in eastern N.Y. (western N.Y. should be about a week behind if all goes normally, which has never been known to happen). Crop scouts and consultants have been using traps to monitor apple maggot (AM) populations for a long time. Some orchards have such high AM populations that monitoring for them is a waste of time; that is, sprays are needed predictably every season, and on a calendar basis. But most commercial N.Y. orchards have moderate or erratic pressure from this pest, and monitoring to determine when damaging numbers of them are present can reduce the number of sprays used in the summer with no decrease in fruit quality.

Sticky yellow panels have been in use for over 25 years, and can be very helpful in determining when AM flies are present. These insects emerge from their hibernation sites in the soil from mid-June to early July in New York, and spend the first 7—10 days of their adult life feeding on substances such as aphid honeydew until they are sexually mature. Because honeydew is most likely to be found on foliage, and because the flies see the yellow panel as a "super leaf", they are naturally attracted to it during this early adult stage. A few of these panels hung in an orchard can serve as an early-warning device for growers if there is an AM emergence site nearby.

Many flies pass this period outside of the orchard, however, and then begin searching for fruit only when they are ready to mate and lay eggs. That means this advance warning doesn't always have a chance to take place – the catch of a single (sexually mature) fly then means that a spray is necessary immediately to adequately protect the fruit. This can translate into an undesirable risk if the traps are not being checked daily, something that is not always possible during a busy summer.To regain this time advantage, researchers have developed newer traps that have the form of a "super apple" – large, round, deep red, and sometimes with the smell of a ripe apple – in an attempt to catch that first AM fly in the orchard.

Because this kind of trap is so much more efficient at detecting AM flies when they are still at relatively low levels in the orchard, the traps can usually be checked twice a week to allow a one- or two-day response period (before spraying) after a catch is recorded, without incurring any risk to the fruit. In fact, research done in Geneva over a number of years indicates that some of these traps work so well, it is possible to use a higher threshold than the old "one fly and spray" guidelines recommended for the panel traps. Specifically, it has been found that sphere-type traps baited with a lure that emits apple volatiles attract AM flies so efficiently that an insecticide cover spray is not required until a threshold of 5 flies per trap is reached.

More information is available at: http://www.nysaes.cornell.edu:80/ipmnet/ny/fruits/tree_fruit/AM.GIF]

The recommended practice is to hang three volatile-baited sphere traps in a 10- to 15-acre orchard, on the outside row facing the most probable direction of AM migration (south, or else toward woods or abandoned apple trees). Then, periodically check the traps to get a total number of flies caught; divide this by 3 to get the average catch per trap, and spray when the result is 5 or more. In home apple plantings, these traps can be used to "trap out" local populations of AM flies by attracting any adult female in the tree's vicinity to the sticky surface of the red sphere before it can lay eggs in the fruit. Research done in Massachusetts suggests that this strategy will protect the fruit if one trap is used for every 100—150 apples normally produced by the tree (i.e., a maximum of three to four traps per tree in most cases).

A variety of traps and lures are currently available from commercial suppliers; among them: permanent sphere traps made of wood or stiff plastic, disposable sphere traps made of flexible plastic, and sphere-plus-panel ("Ladd") traps. The disposable traps are cheaper than the others, of course, but only last one season. Ladd traps are very effective at catching flies, but are harder to keep clean, and performed no better than any other sphere trap in field tests.

Brush-on stickum is available to facilitate trap setup in the orchard. Apple volatile lures are available for use in combination with any of these traps. See the "Sources List" on p. 86 of the 1999 Recommends for addresses of the various suppliers of these tools.By preparing now for the apple maggot season, you can simplify the decisions required to get your apples through the summer in good shape for harvest.

End of this issue: Scaffolds 1999 Index