Missoula County Weed District & Extension

Aphids

 

 

 

Plant Diagnostic Database

Aphids  (multiple species)

                       

Aphidonash

Aphidonleaf

Aphidsonleaf

Aphidpetiolegall

 

 

 

 

 

                                                                                                                                                                                              
Hosts:
Type: Hosts: Description:
Apple Applehawthorn,mountain ash,crabapple. Yellow-green
Bean Beansbeets,cucumbercarrots,lettuce, etc. Black
Black Cherry Cherriesplums, wild mustards. Large, shiny black
Black Willow Willow Large, shiny black
Box Elder/Maple Acer species Green
Elm Leaf Elm Pale yellow, whitish fluff
Giant Conifer Pinessprucesfirs,juniper. Reddish-brown
Green Peach Fruit trees, vegetables, and flowers Green
Leaf-curl Ash Ash Yellow-green, whitish fluff
Leaf-curl Plum Plum Shiny yellow-green
Petiole-Gall Poplars, cottonwoods Pale green
Potato Rose, nightshade family includingpotatoes / tomatoes/eggplant, vegetables, flowers, weeds. Pink and green
Description:
Very small (1/10 to 1/8 inch long), pear-shaped, soft-bodied insects ranging in color from light green through dark green, and pinkish to black. Aphids cluster on stems and/or undersides of leaves and produce "honeydew", a sugary protein mixture which is fed upon by ants and many of the aphids' natural enemies. Aphids move very slowly, if at all, and often appear to be attached to the plant surface by their sucking mouthparts. Young aphids, or nymphs, are wingless. Adults can be winged or wingless, depending on the species, environment, and time of season.  There are many different kinds of aphids, most of which are specific to particular species, or genera, of plants. However, there are some aphids that attack many species of plants. Different species of aphids are often present at different times of the season.    
Life Cycle:
Aphids overwinter as shiny, black eggs on twigs, budscales, and bark. Female aphids hatch from these overwintering eggs and give birth to live nymphs, all female, by parthenogenic reproduction (no fertilization by male aphids). Since mating is not required for reproduction, aphids can appear very quickly and build up large populations rapidly. A single female can produce 60-100 nymphs during its 20 to 30 day lifetime. Nymphs start to reproduce 6 to 10 days after birth. Winged male aphids are produced in the fall (mainly due to changing light conditions), and mating occurs. Fertilized females then lay overwintering eggs, generally on or near their preferred food source. When conditions become unfavorable (too hot, too dry, leaf tissue no longer succulent, decreased leaf nitrogen levels, over-crowding), winged adults are produced. These winged adults are capable of flying off to more favorable food sources. Fortunately, they are weak flyers!
Controls:
Cultural:
Monitoring:

Aphid outbreaks are encouraged by cool, wet spring weather because their populations increase more rapidly than their natural enemies in this climate. Aphid outbreaks may also occur if controls used to treat other pests harm aphid predators (i.e., syrphid fly and lacewing larvae, ladybird beetles). Certain controls are more toxic to predators than others (see treatment options). Excessive fertilization, especially nitrogen, causes plants to maintain succulent growth, and may encourage aphids. Use less soluble nitrogen fertilizers (ammonium or urea-based forms or compost). Avoid pruning that encourages early spring growth. On aphid-susceptible species, prune in late spring after aphids arrive and prune a little at a time. Stop pruning before the end of July so you don't encourage a fall flush of growth.

Check aphid populations regularly, especially in the spring when temperatures are between 60 - 80º F and new, succulent growth is present. Appropriate control methods vary by season. During aphids' dormant season, check for eggs (in late winter) to decide if a dormant control will be required. Check ten twigs per tree. If 30 to 50% have eggs, a dormant oil treatment may be helpful. 

In early spring, check ten terminal shoots weekly; look especially at leaf undersides. If 25-50% of the terminals on young trees and shrubs are infested, some control may be required. Older, large trees can usually tolerate 50% or more terminal infestation before control is necessary. Check for predators. If predators are present at a ratio of 1:5, control is usually not required. If leaf curling is occurring already, treat immediately, especially on aphid-susceptible species like plum and green ash.
 

Biological:

Mechanical:

Syrphid fly and lacewing larvae, gall midges (Aphidoletes), and ladybird beetles are effective aphid eaters. Evaluating several predators, researchers in Colorado found that lacewings were the best predators under hot conditions, and ladybeetles and Aphidoletes did best under cool temperatures. Overall, Aphidoletes was the best aphid predator of green peach aphid . Aphid populations are also decreased by fungus disease and parasites. 

Diseased or parasitized aphids turn brown, puff up and stick to leaves.

Beauveria bassiana is a fungus (microbial insecticide) with some activity against aphids.  Trade names -Naturalis, Botaniguard.  It requires high humidity to be effective.  Irrigate, then spray or use when weather is humid.

Yellow sticky traps are useful to catch winged aphids, particularly in indoor growing situations, as long as populations are not too high. Sticky traps may catch some predator species as well as aphids.


In certain cases, using a silver or foil mulch under crop plants can confuse flying aphids that are searching for hosts. The silvery, reflective surface is thought to disrupt their sense of direction. When growing squashes or cucumbers, you may get somewhat the same effect by using silver-leafed varieties.

Washing with soapy water (with a dispenser attached to the hose) can knock some aphids off plants and reduce populations if done repeatedly. Washing may also enhance conditions for fungus diseases that attack aphids. Prune out infested terminals
Chemical:

Botanical:

Insecticidal Soap is only effective on soft-bodied insects. It has a short activity period. Repeat applications as needed. Avoid application in direct sun or at temperatures >85° F. Soap can burn foliage of tender plants. Wait 48 hours after application before releasing predators.

Two percent horticultural oil  should not be applied in direct sun and/or at temperatures >85-90° F or <40° F. It may burn leaves, especially of sensitive or drought-stressed plants. Wait 48 hours after application before releasing predators.

Neem oil (Margosan-O, Bioneem, Greenlight, or Azatin) is best applied 2-3 times in succession, 7-10 days apart. Spray in the evening. It has a short activity period. Repeat applications!

Pyrethrum/Pyrethrin works best if combined with insecticidal soap: add 1/2 to 1 Tbsp. per gallon. Spray in the evening. This botanical has an extremely rapid breakdown rate, especially in sunlight. It also has a very short activity period. Repeat applications and spot spray if possible. It can harm predators and parasites.

 

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