Description of the Pest
Leaffooted bugs are a frequent and highly damaging pest of pomegranate. Adult leaffooted bugs are large insects, 0.75 to 1 inch (19–25 mm) in length. They are gray to dark gray in color with a narrow white zigzag band across the back and have a round yellow spot on each shoulder. The head appears pointed and the hind legs have an expanded area that superficially resembles a leaf, hence its name.
In late spring to early summer, leaffooted bug enter pomegranate orchards to feed on newly developing fruit and reproduce. Females lay brown, tube-shaped eggs on twigs. Once hatched, nymphs develop to adults in 6 to 8 weeks. Because the adults are long-lived and can lay eggs over an extended period of time, the population consists of all life stages by late June. In September, females begin laying large numbers of eggs and as those offspring develop, they form aggregations on fruit and vegetation ranging in size from tens to several hundred individuals. By late November, newly developed adults leave pomegranate and form overwintering aggregations on more sheltered plants such as citrus, juniper, cypress, and palm trees.
Throughout the fall, adult and nymph leaffooted bugs feed on the fruit and during mild winters may remain in the orchard through mid-March. Pomegranate orchards with cracked and split fruit left on the trees are a favored overwintering site.
Cold winters can kill many overwintering adults; however, it requires a low of approximately 21ºF for at least six hours to kill about 50% of the exposed population. Outbreaks can occur after several years of moderate winters, which allow numbers to increase.
Adults are strong flyers and can quickly move into and within the orchard. In the spring, they can be found in the orchard and also migrating out of the orchard to nut crops such as almond (March and April) and pistachio (April and May). During the late summer and early fall, leaffooted bugs may migrate to citrus.
Leaffooted bugs can build up to very large numbers in pomegranate orchards from mid-August through harvest. Due to their aggregation behavior, it is not uncommon to find more than 100 nymphs on a single piece of fruit.
Feeding damage is not easy to see on the outside of the fruit. If the fruit are cut open, brown spots can be seen on the inside of the skin where the insect's proboscis penetrated. Feeding on the aryl can cause them to wither. Minor feeding by leaffooted bug typically goes unnoticed in the packinghouse and is not offgraded. However sometimes, opportunistic pathogens enter the fruit through feeding wounds and cause soft rot on the fruit surface or black rotten areas within the fruit.
An occasional adult leaffooted bug on fruit is tolerable, but numbers should not be allowed to build. Remove all fruit before winter to decrease the number of overwintering bugs. Native egg parasites, such as Gryon pennsylvanicum, if not disrupted, also help keep numbers down. Outbreaks, especially in late summer or fall before harvest, should be treated quickly, before serious damage can occur.
The egg parasite, Gryon pennsylvanicum, provides partial to good control of leaffooted bugs, especially if host numbers are high. Eggs with round exit holes indicate presence of the parasite.
Remove all fruit before winter to reduce the number of leaffooted bugs overwintering in an orchard. Cleaning debris from near the orchard may also help. Cold temperatures near 21°F (-6°C) will kill some exposed bugs, while those protected from winter weather survive better. If possible, remove other nearby overwintering hosts such as juniper. It is not known if efforts to reduce leaffooted bug populations after harvest has a direct benefit to the pomegranate orchard the following August. However, winter sanitation in pomegranates is very important in pomegranate orchards next to preferred spring hosts, such as almonds.
Organically Acceptable Methods
Where possible, manage leaffooted bugs in neighboring crops to prevent migration into pomegranate. Use cultural controls to reduce overwintering numbers. Pyrethrins may kill some nymphs but control efficacy varies.
Monitoring and Treatment Decisions
Leaffooted bug outbreaks occur areawide so if problems are observed in almonds or pistachios, also look for them in pomegranates. Be wary after mild winters, or if high numbers were found the previous fall. Scout orchards for individual adults or masses of nymphs on fruit from mid-August through October. Higher numbers will be found closer to harvest.
There are no treatment thresholds for leaffooted bugs in pomegranates.
|Common name||Amount per acre||REI‡||PHI‡|
|(Example trade name)||(hours)||(days)|
|Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.|
|(Belay)||4–6 fl oz||12||7|
|MODE-OF-ACTION GROUP NUMBER1: 4A|
|COMMENTS: Do not apply during bloom or when bees are actively foraging.|
|(Lannate SP)||1 lb||48||14|
|MODE-OF-ACTION GROUP NUMBER1: 1A|
|COMMENTS: Disruptive to natural enemies of mealybugs, caterpillars, soft scales, aphids, and other pests. Use of this pesticide may result in outbreaks of these pests. Methomyl is also toxic to bees and should not be applied when bees are actively foraging.|
|(PyGanic EC 1.4)#||2–4 pt||12||When dry|
|MODE-OF-ACTION GROUP NUMBER: 3A|
|‡||Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI The longer of two intervals is the minimum time that must elapse before harvest.|
|*||Permit required from county agricultural commissioner for purchase or use.|
|1||Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers ("un"=unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee).|
|#||Acceptable for use on organically grown produce.|