Scaffolds 00 index

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

Oriental Fruit Moth

The first oriental fruit moth (OFM) catches in Niagara and Orleans Counties were recorded early last week, just as the earliest peaches there were reaching the pink bud stage. This insect, native to China, was introduced into the U.S. from Japan about 1913 on infested nursery stock. The OFM is now found in all regions of North America where peaches are grown. Although it is most important as a pest of peach, the OFM has an extensive host range that includes apple, quince, pear, plum, cherry, apricot, nectarine, and some rosaceous ornamentals. In the northeastern U.S., the OFM has three generations (flights) per year. In areas with a longer growing season, it may have up to five generations per year.

On peach, the OFM feeds in both vegetative growth and fruit. The first generation, which is feeding when terminals are succulent and tender, develops almost exclusively in the vegetative growth. The larvae often enter the terminal at the base of a young leaf, and tunnel toward the base of the shoot. Infested terminals wilt and die back to the margin of feeding, and are commonly called "strikes" or "flagged shoots". Heavy twig infestations of nursery stock can adversely affect the shape of the tree. Axillary buds often begin to grow when the terminal shoot is killed, causing the tree to have a bushy appearance.

Fruits that are infested when very small often drop. Early infested peaches that do not drop have obvious entrance holes with frass and gum exuding from them. Larvae attacking nearly ripe peaches usually enter the fruit near the stem, leaving only a very small, inconspicuous entrance hole. The larvae tunnel in the fruit, and frequently excavate cavities near the pit.

Terminal feeding on apple is similar to that on peach. Infested apples have a collection of frass at the exit hole of the insect's feeding tunnel, or at the calyx end. It is difficult to distinguish between OFM damage and codling moth damage. OFM larvae feed randomly in the apple, and usually do not feed on the seeds, while codling moth larvae usually tunnel directly to the core of the apple and feed on the seeds. Later instar larvae of the two species may be distinguished by the presence or absence of the anal comb at the tip of the abdomen. The anal comb is present in the OFM and absent in the codling moth.

More than 130 species of parasitoids have been reported attacking OFM; however, parasitism probably plays a very minor role in OFM control in today's commercial orchards because of the sensitivity of many parasitoids to commonly used insecticides. Research on mating disruption of OFM has shown that if a synthetic sex pheromone is released in high concentrations, male oriental fruit moths cannot locate a female to mate. However, this approach is not generally justified in N.Y. against the first generation, which corresponds with the period of plum curculio and early tarnished plant bug control. It may be a practical alternative to pesticides for the 2nd and 3rd broods if 2-3 sprays are normally applied to control this pest, and if no other insecticide sprays are routinely needed for other pests after shuck split. We will be examining the efficacy of this approach using various pheromone dispensing systems in western N.Y. this season. For most commercial blocks, where 2nd brood larvae threaten fruits as they ripen, an application of carbaryl (Sevin) is commonly recommended 2 weeks before harvest or, for those depending on scouting results, when larval numbers reach 1 per 10 terminals.

Recent complaints of ineffective control in some peach blocks having more severe pressure (particularly in far western N.Y.) may indicate either a failure to take care of the early larvae sufficiently, or else a growing resistance problem. The recommendations from Ontario, where OFM is a more serious problem, are to spray about a week after the peak of both the first and second flights (usually between petal fall and shuck split, and early to mid-July, respectively), possibly following up with a second application in each case. In recent years, some tolerance or resistance tendencies have been noted in local populations, so this is a case where rotation to alternative chemical classes would be recommended; choices would include Guthion or Imidan, Sevin, Lannate, or a pyrethroid. (Adapted from Oriental Fruit Moth Fact Sheet #17, by A. J. Seaman and H. Riedl).

Green Peach Aphid

The green peach aphid (GPA), Myzus persicae, is an important pest of many horticultural and agronomic crops. It was introduced from Europe many years ago and is now found throughout most of North America. This aphid has a host range of over 800 plants. It attacks all stone fruits including peach, nectarine, plum, apricot, and cherry.

The GPA has two basic forms, winged and wingless. Winged forms are all adults and each have a yellowish-green abdomen with a black head and thorax (where the wings are attached). The wingless forms of nymphs and adults are light green or yellowish-green with three darker lines on the abdomen. Both forms are pear-shaped, have long antennae, and two cornicles extending from the posterior end of the body. Eggs are shiny black and oblong.

The GPA has a unique and complicated life cycle. In the mid-Atlantic region, the GPA can overwinter as asexual wingless females in protected areas on the tree. In colder climates, it overwinters in the egg stage near buds of stone fruit. The first appearance of GPA occurs around bloom after the females emerge from their protected sites or the eggs hatch. The GPA then undergoes 2-3 generations of asexual reproduction with wingless females giving birth to living young. This form of reproduction occurs without mating and only females are produced at this time. During the period from shuck-fall to 4-6 weeks later, asexual winged females are produced, which fly to alternate host plants, where they start producing asexual wingless females. Wingless females are the norm during the summer but winged females can be produced if host plant conditions deteriorate or aphid colonies become too crowded. In the fall, winged females are produced, which disperse back to stone fruit and produce a generation of wingless females for overwintering. In the colder northern areas, winged sexual males and females are produced, which disperse to stone fruit where mating commences and overwintering egg laying occurs.

GPA damage to stone fruit is caused by feeding on leaves and fruit. Damage to peach is primarily limited to honeydew marking, fruit distortion, uneven coloring at harvest, and curled leaves. In most years, GPA damage to peach is minimal, but in bad years damage to peach is readily noticeable. However, damage to nectarine can be quite severe because GPA feeds more readily on nectarine than on peach fruit. Stone fruit damage occurs during the spring before the aphids disperse to alternate host plants. Early feeding damage on fruit appears as dark green spots, which increase in size as the fruit grows. As the fruit starts to color, the green spots turn brown and necrotic, while the background color surrounding damaged areas remains off-color. Extensive GPA feeding will cause fruit cracking.

This pest's importance has increased with the recent discovery of Plum Pox Virus in Pennsylvania, because GPA is one of the primary vectors of this disease. Currently, most of the information on aphid vectors of PPV comes from literature in Europe where this virus has caused extreme devastation of the stone fruit industry. Among other aphid vectors found in N.Y. are: Aphis craccivora, cow pea aphid; A. spiraecola, spirea aphid (very common, especially on apples, grasses); Brachycaudus persicae (Passerini), black peach aphid (very common); and B. cardui, the thistle aphid.

Peach terminals should be inspected on a regular basis after petal fall for the presence of green peach aphid colonies. In light of GPA's role in transmitting Plum Pox Virus, a zero tolerance to this pest should now be considered in stone fruit plantings. Lannate and Thiodan have been less effective in controlling these aphids than they once were. However, Provado has just received a Section 18 label in peaches and other stone fruits for this use (refer to the Chem News section).