Insects | Credits
Volume 7, No. 19 July 27, 1998
43°F 50°F Current DD accumulations (Geneva 1/1-7/27): 2341 1577 (Geneva 1997 1/1-7/27): 1904 1248 (Geneva "Normal" 1/1-7/27): 2044 1464 (Highland 1/1-7/27): 2634 1795 Coming Events: Ranges: Apple maggot flight peak 2033-2688 1387-1804 American plum borer 2nd flight peaks 1648-2612 1037-1840 Codling moth 2nd flight peaks 1587-3103 1061-2212 Comstock mealybug 2nd gen. crawlers peak 2350-2649 1642-1736 Obliquebanded leafroller 2nd flight peaks 2634-3267 1789-2231 Oriental fruit moth 3rd flight begins 2172-2956 1448-2013 Redbanded leafroller 2nd flight subsides 1927-3045 1291-2160 San Jose scale 2nd flight peaks 1934-2591 1271-1874 Spotted tentiform leafminer 3rd flight begins 2215-2783 1537-2123 PEST FOCUS Geneva: Obliquebanded Leafroller 2nd flight beginning. TRAP CATCHES (Number/trap/day) Geneva: 7/13 7/17 7/20 7/27 Spotted Tentiform Leafminer 52 51 13 9.7 Redbanded Leafroller 0.8 1.3 0.5 1.0 Oriental Fruit Moth (apple) 1.8 0.6 1.0 0.6 Lesser Appleworm 3.0 0.5 0.3 0.9 Codling Moth 2.7 2.6 5.0 2.9 San Jose Scale 0.3 2.0 4.8 9.0 American Plum Borer 1.8 1.4 1.7 2.5 Lesser Peachtree Borer 1.8 0.5 0.8 0.2 Peachtree Borer 0.3 0.9 1.0 0.2 Obliquebanded Leafroller 0 0 0 0.1* Apple Maggot 0 0.1 0 0 Highland (Dick Straub, Peter Jentsch): 6/29 7/7 7/13 7/20 7/27 Spotted Tentiform Leafminer 40.1 43.0 13.6 26.9 45.1 Redbanded Leafroller 2.4 2.4 1.0 1.7 0.4 Oriental Fruit Moth 0.4 0 0.2 0.1 0.6 Lesser Appleworm 0 0.3 0.1 0.4 0.6 Codling Moth 1.6 0.4 0.5 2.3 3.4 Obliquebanded Leafroller 0 0.1 0.1 0 0.1 Variegated Leafroller 1.1 0.6 0.1 0 0.6 Tufted apple budmoth 1.8 3.6 1.9 0.3 0 Fruittree Leafroller 0.1 0 0 0 0 Sparganothis Fruitworm 0.7 0.8 0 0 0.1 Apple Maggot 0.1 0.1 0.14 0.2 0 * = 1st catch
by Harvey Reissig & Art Agnello
Even though apple maggot flight is once again not particularly strong in most N.Y. orchards this season, we are entering the traditional period of peak emergence. Following is some general information on the biology and life history of this well-known insect.
Apple maggot adult
The apple maggot overwinters as a pupa in the soil. Adults from the single generation of flies begin to emerge in late June to early July. Females cannot lay eggs until they become reproductively mature, 7-10 days after emergence. Females lay eggs in fruit and larvae develop there, emerging in the autumn after the fruit has fallen and entering the soil to pupate. Flies are active from July to mid-September, but commercial orchards generally require protection only from about mid-July through August. Flies do not reach orchards in large numbers until mid-July, and before this date fruit remaining on the tree is unfavorable for larval development, so early infestations do not cause sustainable populations in the orchard. In addition, for unknown reasons, fly activity between about August 20 and September 15 does not usually cause serious damage in commercial orchards in New York.
Apple maggot larva showing black mouth hooks
Larval tunneling inside the fruit causes it to become rotten and unmarketable. Early stings caused by punctures from the female's ovipositor may severely deform the fruit of some varieties, even though no larvae survive.
Fruit deformations caused by severe apple maggot oviposition damage
Severe damage caused by apple maggot tunnelling and bacterial decay
Monitoring to determine whether control sprays are necessary is recommended primarily in orchards that are not near large sources of outside infestation (such as abandoned orchards), and those with no indigenous infestations of flies. Theoretically, there is absolutely no tolerance for AM damage in fruit. In practice, AM damage is not usually detected in normal fruit inspections unless there is approximately 5 percent fruit damage.
Small wasps parasitize AM larvae in fruit, and predators such as birds and crickets may eat larvae or pupae in or near the soil. In natural, unsprayed apple and hawthorn trees, AM populations are not regulated by natural enemies. Parasites and predators are also ineffective at controlling AM in commercial orchards.
AM flies have a limited migratory capability, so all apple and hawthorn trees within 1/4-1/2 mile of commercial orchards should be removed if possible. Work by Ron Prokopy and his group in Massachusetts (Hu, X., J. Duan, J. Mason & R. Prokopy. 1996. Proc. Entomol. Soc. Ontario 127:107-114.) indicate that considerable work is involved in using the "dropped fruit removal" technique to mitigate AM populations. In theory, eliminating fruit drops will break the life cycle of flies in an orchard by preventing larvae from exiting the fruit and entering the soil. However, they found that, because of the breadth of the emergence period of larvae from dropped fruit, there was no case in which pickup of drops at a single point in time accounted for 80% or more of all larval exits collected from a given cultivar. Maximum benefit of drop removal occurred about two weeks before harvest for most cultivars. Since most growers currently pick up drops only once, usually well after harvest (mainly for cider apples), it is doubtful whether the economics would justify this pre-harvest initial drop removal in most cases.
AM flies can be "trapped out" in small, well-pruned trees that are not near large sources of outside infestations. A relatively high density of sticky red spheres (plain or volatile-baited) is required, approximately 1 trap per 100 apples. Mass trapping is usually less effective than chemical control, and AM may still damage 1-5% of fruit from mass-trapped orchards.
Most commercial orchards have no indigenous populations of flies. Therefore, chemical control sprays are usually directed against flies immigrating into orchards from outside, unsprayed hosts, including both apples and hawthorns. Most insecticides, particularly organophosphates, are remarkably effective in controlling adults. Insecticides must kill females before they oviposit in the fruit. Residual effectiveness of insecticides is particularly important in controlling AM in commercial orchards when flies are continuously immigrating.
Insecticides can be applied according to trap catches as described in the 1998 Pest Management Recommendations for Commercial Tree-Fruit Production (p. 85-86), or on a standard or modified IPM schedule. The standard schedule requires an initial spray 7-10 days after the first emergence of flies, followed by additional sprays at 10-14-day intervals until August 15-20. (The first AM fly in both Geneva and the Hudson Valley this year was trapped on 6/22.) The modified IPM schedule requires only three sprays, on approximately July 15, August 1, and August 15. We would suggest that growers in high maggot-pressure areas maintain a standard spray schedule, or at least be vigilant in checking traps twice a week, in order not to be caught unprotected during this peak flight period. Because of the relatively sparse AM flight in Western N.Y., this season is another one of those years when trapping to monitor AM presence is likely to pay off in blocks with a history of irregular population pressure.
A few words may be in order here about when to terminate sprays for apple maggot in late summer. Most people are aware that each year in N.Y. orchards, substantial numbers of AM flies are captured on monitoring traps late in the season, and growers are naturally concerned about potential fruit infestation from these late season survivors. For the past few years, we have conducted trials in a heavily infested research orchard of McIntosh and Cortland trees by applying bi-weekly applications of Guthion beginning in early July and continuing for 2, 3, 4, and 5 total sprays. New oviposition punctures were checked weekly on "scout" apples clipped to the trees, and female AM flies captured throughout the flight period were dissected to check for the presence of eggs. The results of these studies can be summarized as follows:
The model for 2nd generation codling moth larvae predicts that a control spray should be applied in problem orchards 1260 DD (base 50°F) after the start of the FIRST flight (5/7 in Geneva, 5/4 in the Hudson Valley). As of today, 7/27, 1336 DD have accumulated in Geneva and 1488 at Highland, which means that any needed sprays should be under way in both western N.Y. and the Hudson Valley. In cases of severe population pressure, a spray of an OP material now can be backed up by a second application against the same brood 14 days later.
Scaffolds is published weekly from March to September by Cornell University - NYS Agricultural Experiment Station (Geneva), and Ithaca - with the assistance of Cornell Cooperative Extension. New York field reports welcomed. Send submissions by 3 p.m. Monday to:
Scaffolds Fruit Journal
Editors: A. Agnello, D. Kain
Department of Entomology, NYSAES
Geneva, NY 14456-0462
NOTE: Every effort has been made to provide correct, complete and up-to-date pesticide recommendations. Nevertheless, changes in pesticide regulations occur constantly, and human errors are possible. These recommendations are not a substitute for pesticide labelling. Please read the label before applying any pesticide.
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Photographs courtesy of New York State Integrated Pest Management Program