Posts Tagged ‘squash bug’

Watch for Striped Cucumber Beetle and Squash Bugs at Base of Cucurbit Plants

Friday, June 8th, 2012

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

I talk about this every year it seems, but I still see cucumber beetle and squash bug problems at the base of growers’ cucurbit plants. So far this has been a ‘good’ year for striped cucumber beetle and squash bug populations in just about every cucurbit field. Some fields have been hit particularly hard with beetles causing 5-10% plant loss due just to their feeding. The biggest problem with these pests, and why control sprays have not worked well, is that they are consistently hiding at the base of the plant where they are feeding on the stem. Most of the time we look for the foliage damage to tell us how well our spray program is working. Sprayers are set up usually to cover a lot of leaf canopy and do not do a very good job of putting chemical along the base of the stem. This stem feeding can be severe enough on small plants that either pest alone could cause some wilting, but with both feeding on this relatively small area of the stem they are causing considerable damage (Fig. 1). Even on larger plants the feeding can still cause significant damage (Fig. 2). It is hard enough to kill squash bug adults with a good cover spray, but when only small amounts of spray are reaching them on the lower stem they will not be controlled. Often it is possible to walk by plants and even inspect them and still see no beetles or squash bugs, as they will stay down at the base of the plant and only move when the base is exposed. In a couple fields about 10% of the plants were wilting (Fig. 3) due to squash bug and cucumber beetle feeding. These pictures are from a squash field but the same problem is occurring in watermelon and cantaloupe fields with both striped cucumber beetles and squash bugs feeding at the base of a plant. Growers need to check to see if this type of feeding is occurring in their fields and if so insecticide applications (pyrethroids such as Asana, Warrior, etc.) must be directed at the base of the plant.

Figure 1. Striped cucumber beetle feeding damage at base of a small squash plant

 

Figure 2. Larger cucurbit plant with feeding at its base by cucumber beetle

Figure 3. Wilted squash plant due to squash bug and cucumber beetle feeding at its base

Squash Bugs in Pumpkin

Friday, June 17th, 2011

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

Every year it seems just as pumpkin plants are coming up squash bugs magically appear. This year is no exception as squash bugs were found feeding at the base of 3-5 leaf pumpkin plants (fig. 1). The adults are very difficult to see when they hide out at the base of plants whether the plants are on plastic or in dead mulch. Growers need to be sure to check the base of their pumpkin plants for the adults. Heavy feeding at this early stage of pumpkin development can cause plants to wilt and die or at least fall behind in development by a few weeks. Sprays need to be directed at the base of the plant, using an air-blast sprayer may not get enough material down to the base of the plant.

Fig. 1 Squash bugs feeding at base of pumpkin plant

 

Bonsai Pumpkin Plants

Friday, September 4th, 2009

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

No I am not talking about some new “value added” pumpkin variety. I am referring to pumpkin plants that appear to be normal in the field up to about the third or fourth week and then they suddenly stop growing, while plants around them continue to grow. These ‘bonsai’ plants are not deficient in nutrients or water, but their leaves, at times, will turn yellow at the margins and even necrotic. The plants do not wilt or die — they just sit there never producing a pumpkin fruit. I used to think that these small plants were the result of herbicide carryover from the previous crop, usually a cereal crop. This is probably true when there are large sections of the field with the bonsai plants, but what I have seen in the past and I am seeing this year, as are growers and consultants, are many more scattered bonsai pumpkin plants across a field. These plants are difficult to see at this time of year as they have been covered over by their neighbors. One guess I have (as did one consultant) is that squash bugs are causing these miniature plants in the field. We had exceptionally high numbers of squash bugs this year and many growers had trouble controlling them. When squash bugs feed they inject a toxin into the plant that can cause the plant to wilt (often this wilting is called Anasa wilt, Anasa being the genus name of the squash bug). If the bugs feed at the right stage of growth or in such a way that they do not cause much, if any, wilting but the toxin builds in the plant it is possible that the toxin is slowing the growth of the plant. I have no proof that squash bugs are causing these small plants in the field other than the observation that pumpkin fields where I had good squash bug control had no bonsai plants, but two fields where squash bug was poorly controlled and the bugs fed extensively at the base of the plants had a great deal of the miniature plants. I think the damage is worse to the pumpkin plant when squash bugs are allowed to feed at the base of the plant for extended periods of time than if they feed on the foliage. Growers will need to watch their pumpkin plants closely next year and as they begin to grow being sure to check at the base of the plant and under the plastic for squash bugs.

High Populations of Striped Cucumber Beetle and Squash Bug this Year in Cucurbit Fields

Friday, July 17th, 2009

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

This has been a particularly bad year for striped cucumber beetles and squash bugs in watermelon, pumpkin and squash. Some fields have been hit particularly hard with beetles causing 10-15% plant loss due just to their feeding. The biggest problem with these pests and why control sprays have not worked well is that they are consistently hiding in the plastic hole where they are feeding on the stem (Fig. 1). Sprayers are set up usually to cover a lot of leaf canopy and do not do a very good job of putting chemical down in the plant hole. This stem feeding can be severe enough that either pest alone could cause some wilting, but with both feeding on this relatively small area of the stem they are causing considerable damage (Fig. 2). In one case, when the pumpkin plant was pulled up 3 squash bugs refused to move off of it, so intense was their feeding (Fig. 3). It is hard enough to kill squash bug adults with a good cover spray, but when only small amounts of spray are reaching them down in the plant hole they will not be controlled. Often it is possible to walk by plants and even inspect them and still see no beetles or squash bugs, as they will stay down at the base of the plant and only move when the base is exposed. In one field 1 out of every 15 plants was wilting (Fig. 4) due to squash bug and cucumber beetle feeding. These pictures are from a pumpkin field but the same problem is occurring in watermelon fields with both striped cucumber beetles and squash bugs feeding on plants down in the plant hole. If this type of feeding is occurring in your fields, insecticide applications (pyrethroids such as Asana, Warrior, bifenthrin) must be directed down at the base of the plant.

cucumber beetle feedingFigure 1. Cucumber beetle feeding at base of plant in plastic hole

damage to pumpkin stem by cucumber beetle and squash bug feeding 

Figure 2. Severe feeding on pumpkin stem by striped cucumber beetle and squash bugs

squash bugs on a pumpkin stemFigure 3. Three squash bug adults refusing to relinquish their pumpkin stem

wilting plant damaged by cucumber beetle and squash bug feedingFigure 4. Wilted plant due to striped cucumber beetle and squash bug feeding at its base

Late Season Pests in Pumpkins and High Tunnel Tomatoes

Friday, September 19th, 2008

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

It is that time of the year again; as the season winds down some late season pests can come in and ruin what is left of a dwindling crop. In pumpkins it could be “rind worms” which are any number of caterpillar species that will feed on the outside of a pumpkin and scar the surface or penetrate into the rind. Either way it opens the pumpkin up to secondary infection and causes it to rot much sooner than it should. The other big pest is the squash bug, which will concentrate its numbers and feeding on the pumpkin fruit if the foliage goes down and is no longer there (Fig 1). The nymphs and adults can feed heavily enough that they will “deflate” a pumpkin or reduce its vigor (including the stem) by sucking all its juices out. Any of these pests can be easily controlled with an insecticide application like a pyrethroid; the difficulty is making sure to catch the problem before it becomes too late.

 

Figure 1. Squash bugs feeding heavily on pumpkin fruit because no vines are left in the field

In high tunnels there has been a surge of worms that have suddenly shown up in the past couple of weeks. As corn and natural hosts of the worm pests begin to shut down the moths are attracted to high tunnel plants that are green and still growing. I have seen hornworms, and yellow striped, beet and southern armyworms in high tunnel tomatoes where they tend to feed on the fruit when they become medium size or larger. Smaller larvae tend to stay on the foliage (Fig 2).

 

 

Figure 2. Large worms tend to feed on the fruit while small worms tend to feed on foliage, except for fruit worms, which will feed on the fruit when they are both very small and large larvae. They usually start feeding under the calyx or cap of the tomato as in Fig 3.

 

Figure 3. Tomato fruit worm feeding under calyx of tomato fruit

Tomato fruit worm, however will attack the fruit when the larvae are very small or large (Fig 3). As with pumpkin pests the tomatoes in high tunnels need to be watched carefully for the next several weeks until we have a frost or two. Bt products will work well as long as worms are small and not attacking the fruit, but other chemicals such as pyrethroids or Avaunt or SpinTor or Lannate will be needed if the worms are large or damaging the fruit.

I am conducting a study looking at tomato production inside a high tunnel (HT) compared with tomatoes just outside the high tunnel with the same number of plants and the same variety all planted on the same day in June. The HT tomatoes have been severely attacked by small and large larvae of several worm species with 40% of the tomatoes being damaged. (I am not treating the tomatoes in order to make the comparison.) However, just outside the high tunnel there have been few worms at all and almost no large worms with only about 5% of the tomatoes being damaged. I am not sure why the worms survive better in the high tunnel-temperatures have not been much different between the HT and outside until the last few days. I will be looking at natural enemies (both insects and disease) and the number of eggs laid by the female moths over the next few weeks to see if there are any differences with these factors.

Squash Bugs in Pumpkins

Friday, June 20th, 2008

Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu

Many of the pumpkin fields in the Delmarva area I have visited in the last two weeks were just coming up or had 2-5 leaves on them. I was surprised to see several squash bugs on these small plants. I also found many egg masses (Fig. 1) on the underside of leaves, usually in the crotch of two veins. In some fields with plastic the squash bugs were feeding below the plastic mulch causing the plants to wilt (Figs. 2 and 3) and eventually die. Normally there are only a few fields that will have squash bugs this early, but just about all of the fields I looked at had enough squash bugs to justify treatment. Growers need to watch for squash bugs on their early pumpkin plants, especially down in the plastic hole. A spray may be needed if the plants are stressed (like they were last week from the intense heat) and there are 2 bugs or 1 egg mass per plant.

 

Figure 1. Squash bug adult and egg mass

Figure 2. One pumpkin plant (top) wilting due to squash bug feeding

 

Figure 3. Squash bugs at the base of wilted pumpkin plant under plastic mulch

One interesting aspect of these fields with squash bugs is that all the fields that had not been sprayed had many Trichopoda pennipes Tachinid fly parasitoids (Fig. 4) in them. These medium sized, orange bellied, black winged flies will lay white eggs on the underside or “shoulder” of squash bugs (Fig. 5). The eggs will hatch on the side attached to the insect and the maggot will enter the bug and feed inside, eventually killing the pest. While useful under moderate to low infestation levels of squash bugs, these parasitoids will not keep a large population of squash bugs below thresholds.

Figure 4. Trichopoda pennipes adult

 

Figure 5. T. pennipes eggs on squash bug