Pecan Phylloxera

Yesterday at the Beaumont Field Day I spoke on bunch grapes.  But, this post is not about bunch grapes, but rather something else I noticed next to where I was standing.  Directly on the other side of the fence from the station sits a pecan orchard.  With the late freezes we had this year there were few nuts on the trees, but there was a good amount of pecan phylloxera.  Pecan phylloxera cause galls to develop on the pecan trees, usually on leaves or on stems.  They can seriously impact yield if left uncontrolled.  Of course now is too late to control the insect — it must be done early in the season around budbreak and before leaf growth is 1 inch.  This is one case where the insect is akin to a disease — once you see the symptom it is too late to control.  The insect populations can vary from year to year, so they may not be a big problem every year.  For homeowners this insect is next to impossible to control on a large tree because the entire tree would need to be sprayed.  If one had the proper equipment, carbaryl or a dormant oil could control it.  The better option is to have trees that are resistant to the insect — something like ‘Elliot’, ‘Candy’, or ‘Jenkins’ (there are others as well).  Control in a commercial situation is relatively easy because commercial growers have the equipment and access to insecticides, but timing is the key.

Pecan Phylloxera (Phylloxera notabilis, P. russelae, P. devastatrix)

Description: The adults and nymphs are tiny, soft-bodied, cream colored insects resembling aphids.  They are rarely seen.

Life Cycle: Phylloxera overwinter in the egg stage in protected places on branches. The young insects appear in spring about the time the buds unfold.  The insect inserts its (beak) into new leaf or terminal growth and a gall forms that soon envelopes the insect.  The insect matures within the gall and lays a large number of eggs.  Young hatch from these eggs and develop into winged forms.  Usually, in late May or early June the gall splits open and releases the insects.  Infestations may start on one tree and spread out to others.  There are several generations per year.

Symptoms: Galls appear on leaflets or growing terminals.  Leaflets with 4 or more galls may drop.  Severe infestations may produce partial defoliation of affected trees and may interfere with photosynthesis.  Terminals infested by P. devastatrix have galls where the nut clusters would normally develop.  This is the most damaging phylloxera.

More good info on this insect is available at the links below:

http://msucares.com/newsletters/pests/bugwise/2011/bw02_2011.pdf

http://www.lsuagcenter.com/NR/rdonlyres/B26C67FB-C3E7-4BFE-98B8-4D123BBE2074/61951/pub2547PecanPhylloxeraLOWRES.pdf

http://www.aces.edu/counties/StClair/documents/NRPecanTreesLee2012.pdf

http://aggie-horticulture.tamu.edu/galveston/Gardening-Handbook/PDF-files/GH-027–phylloxera-gall-on-pecan.pdf

http://entoplp.okstate.edu/ddd/insects/phylloxera.htm

Image from LSU agcenter.

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