Vegetable Crop Insects – July 13, 2012

Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu

Lima Beans
Continue to scout for spider mites, stink bugs, lygus bugs and corn earworm. Early detection and treatment will be needed to achieve spider mite control. In addition, multiple sprays may be needed for mites, especially if populations are high at treatment time and/or numerous eggs are present. As soon as pin pods are present, be sure to watch carefully for plant bug and stinkbug adults and nymphs as well as corn earworm larvae. As a general guideline, treatment should be considered for plant bugs and stink bugs if you find 15 adults and/or nymphs per 50 sweeps. A treatment will be needed for corn earworm if you find one corn earworm larvae per 6 ft-of-row.

Melons
Continue to scout all melons for aphids, cucumber beetles, and spider mites. We continue to find fields with numerous “worm” species as well as cucumber beetle adults feeding on rinds of watermelons. The two most commonly found “worm” species are beet armyworms and yellow striped armyworm. It is important to know which pest is causing the damage to make a chemical selection. Materials that provide beetle control will not necessarily provide worm control, especially if you are finding beet armyworm in the field.

Peppers
As soon as the first flowers can be found, be sure to consider a corn borer treatment. Depending on local corn borer trap catches, sprays should be applied on a 7-day schedule once pepper fruit is ¼ – ½ inch in diameter. Be sure to check local moth catches in your area by calling the Crop Pest Hotline (instate: 800-345-7544; out of state: 302-831-8851) or visiting our website at: http://ag.udel.edu/extension/IPM/traps/latestblt.html. You will also need to consider a treatment for pepper maggot. Be sure to watch carefully for beet armyworm larvae since they can quickly defoliate plants. In addition to beet armyworm feeding on leaves you should also watch for an increase in aphid populations. We are starting to find aphid populations increasing and they can explode quickly, especially where beneficial insect activity is low. As a general guideline, treatment may be needed if you find one or more aphids per leaf and beneficial activity is low.

Pumpkins
We are seeing a significant increase in the number of squash bug adults as well as egg laying in most pumpkin fields throughout the state. In addition, there has been an increase in yellow striped armyworm feeding on the leaves. Squash bug adults and nymphs can cause damage by sucking nutrients from leaves as well as disrupting the flow of water and nutrients resulting in wilted plants. Before wilting, yellow specks can develop on the foliage that eventually turn brown. Under heavy feeding pressure, small plants can be killed and larger plants can have many affected leaves and vines. Squash bugs will also feed directly on the fruit, and it has become an increasing problem in recent years. Thresholds have been developed in other areas at the region aimed at killing small nymphs, which tend to be easier to control. Fields should be scouted for eggs and time treatments for the emergence of the first nymphs. The treatment threshold is one egg mass per plant. Seedlings, new transplants, and flowering plants are the most critical growth stages to monitor. Please refer to the following link for more information and pictures of eggs, nymphs and adults http://www.vegedge.umn.edu/vegpest/cucs/squabug.htm.

Processing Snap Beans
As corn borer and corn earworm populations start to increase, you will need to consider treatments for both insect pests. Sprays are needed at the bud and pin stages on processing beans for corn borer control. As earworm trap catches increase, an earworm spray will also be needed at the pin stage. You will need to check our website for the most recent trap catches to help decide on the spray interval between the pin stage and harvest for processing snap beans (http://ag.udel.edu/extension/IPM/traps/latestblt.html and http://ag.udel.edu/extension/IPM/thresh/snapbeanecbthresh.html).

Sweet Corn
Continue to sample all fields from the whorl through pre-tassel stage for corn borers, corn earworms and fall armyworm. A treatment should be considered when 12-15% of the plants are infested. Since fall armyworm feed deep in the whorls, sprays should be directed into the whorls and multiple applications are often needed to achieve control. The first silk sprays will be needed for corn earworm as soon as ear shanks are visible. Be sure to check both blacklight and pheromone trap catches for silk spray schedules since the spray schedules can quickly change. Trap catches are generally updated on Tuesday and Friday mornings (http://ag.udel.edu/extension/IPM/traps/latestblt.html and http://ag.udel.edu/extension/IPM/thresh/silkspraythresh.html). You can also call the Crop Pest Hotline (in state: 800-345-7544; out of state: 302-831-8851).

Tags: ,

Comments are closed.