BE ALERT FOR EARLY SUMMER INSECT PESTS
This information is compiled from UMass Extension, UMaine Extension,
MOFGA and other sources. Insecticide recommendations for specific vegetable
crops and pests are listed in the New England Vegetable Management Guide,
which is or available from my office for $15, or on-line at:
The New England Small Fruit Pest Recommendations cost $12 or go to: www.umass.edu/fruitadvisor/nesfpmg/index.htm. Organic growers, note that Entrust (spinosad) and PyGanic (pyrethrins) may not be listed in these Guides for all the many different crops on their labels, and in addition to B.t. they are two of the main insecticides at your disposal. With hard-to-control pests, use the highest labeled rates.
FLEA BEETLES are feeding on Brassica vegetable crops (cabbage, broccoli, cauliflower, Brussels sprouts, collards, kale, and kohlrabi) as well as Brassica greens and root crops that belong to different species, which are more preferred by flea beetles. These include Pac choi, Chinese cabbage, tatsoi, mizuna, turnip, mustard greens, red Russian kale, radish, daikon and arugula. These crops have non-waxy leaves that are easier for the beetles to grasp and feed on than the vegetable Brassicas. Adult beetles emerge from the soil in shrubby or wooded areas near fields, so it helps to locate new Brassica plantings far away from the fields that were used for fall Brassica crops. Delaying planting until mid- to late July can reduce beetle numbers because overwintered beetles have nowhere to feed or reproduce (unless Brassica weeds are present). Consider using only non-Brassica greens in mesclun mix until late summer. The best way to protect Brassica crops is with floating row covers but all edges and row ends tightly sealed immediately after seeding. Flea beetles can fit through extremely tiny cracks. A few uncovered plants at the end of the row attracts beetles to the bed, where they may crawl under the cover.
ONION MAGGOT attacks the roots of onions and in some cases garlic, leeks and shallots. It overwinters as a pupa in the soil, and in early spring adult flies emerge, mate and then lay eggs around the base of plants. After hatching the larvae crawl down to feed on the roots, moving along the row to new plants as they devour young seedlings and need more food. The first symptom is a slight wilting of small seedlings, then they simply disappear. Larger seedlings turn a grayish yellow and wilt and will later detach at the ground level as the maggot consumes everything below ground. Mature plants may be attacked but are rarely killed and fewer plants are attacked as the maggot does not move to new bulbs. However, the bulbs may become misshapen, get attacked by fungi, and rot. Adults of later generations disperse very little from onion fields so crop rotation is a very important for avoiding subsequent infestations. Remove cull onions so they will not attract flies to lay eggs that result in overwintering pupa. Damaged onions are the preferred site for egg laying so avoid mechanical damage to onions. Discing onion fields in the early fall when the flies are still active actually makes things worse because it increases the number of sites for egg laying.
STRAWBERRY BUD WEEVIL, or clipper, populations are high in some Northeast locations this year, so scout your fields that still have flower buds emerging from the crown for injury (partially severed buds hanging on by a thread). Check field edges first as that's where damage starts. Although research shows that berry plants will compensate for the damage with larger secondary fruit, controls are recommended by some states if damage exceeds the threshold of 1.3 or more clipped buds on average per two feet of row. Fields with a history of clipper problems can be expected to exceed threshold nearly every year.
TARNISHED PLANT BUG (TPB) has been slowed by the cool wet weather but be on the lookout for both nymphs and adults. An easy way to scout strawberries is to gently tap flower clusters over a white paper plate. Shake 6 clusters at 5 different locations in each field. The threshold for insecticide use is finding nymphs on 4 or more of the clusters out of the 30 sampled. TPB is also a potential problem for raspberry growers during the period from bloom to harvest. Both the adults and their nymphs can cause deformed fruit, although the deformities are not as obvious as in strawberries. A rough threshold for treatment would be 10 to 20% of canes infested with adults or nymphs. Note that weedy fields can aggravate TPB problems, as can mowing of nearby legume forages or hayfields.
TWO-SPOTTED SPIDER MITE populations tend to increase when it gets hotter, but don;t wait to examine the undersides of leaves on strawberries and raspberries using a hand lens so you can catch the first signs of an infestation. That way you'll have a chance to order predatory mites, such as Amblyseius fallacis, for control. They should be released at about 10,000 mites per acre soon after a spider mites have been found in the field, but not before, or they will starve. It's important to start control actions early before you see lots of severe injury to the foliage (bronzing) Sources include: The Green Spot, www.greenmethods.com or (603) 942-8925, and IPM Labs www.ipmlabs.com or (315) 497-2063.
STRAWBERRY ROOTWORM adults are small dark brown beetles that cause numerous small holes in the leaves. Adults in fields now will soon lay eggs, which hatch into small grubs that feed on the roots of strawberry plants, causing them to be stunted and weak. If feeding injury is widespread, a treatment is recommended. Spraying to control strawberry bud weevil may offer some control at the same time. Strawberry rootworm should not to be confused with root weevil, a larger insect that causes much more serious damage when present in a field
CUTWORMS have been reported in strawberry Fields They feed on the yellow center of the flowers, chewing a large groove in it, which often dries to a light brown or gray color. The result may be berries with large creases or folds and poor size. Controlling weeds can reduce cutworm problems, as may sprays for other insect pests.
RASPBERRY FRUITWORM adult is a light brown beetle that feeds on foliage and fruit buds. The larvae feeds inside flower buds, and those that are found as "worms" later in the season inside fruit can cause significant yield losses. There is some evidence that this insect is more of a problem in weedy plantings. The first indications of an infestation are leaf tattering or elliptical holes in the leaves that results from the feeding by adults on unfolding leaves. The next indication is injury to the unopened blossom buds also done by the adult beetle. Finally, adult feeding injury can also be found on open blossom petals and fruit receptacles. When this feeding is severe, entire fruit clusters can fall off the plants. Adult feeding on foliage should not be confused with the skeletonized feeding damage caused by larvae of raspberry sawfly, which has a pale green caterpillar-like body with many long hairs. Both the fruitworm and the sawfly appear during the pre-bloom period. Female fruitworm beetles deposit their eggs on unopened blossom buds. Sometimes eggs may be laid inside buds or on developing fruit. The grayish-white eggs hatch after a few days, and the larvae commonly bore through the bud and enter the receptacle where they begin to tunnel. As the larvae increase in size, the tunnels are made larger, ultimately becoming grooves in the receptacle adjacent to the berry. When infested fruit is picked, some larvae remain attached to the interior of the fruit and end up in the harvesting basket. Those that remain on the receptacle soon drop to the ground where they pupate and remain over winter.
RASPBERRY CANE BORER and related beetle species adults emerge in the spring, mate and start laying eggs. Larvae bore into canes and during the season and for some species, the next season. They cause injury and death to canes and potentially entire crowns. The best time to kill adults is during the late pre-bloom period, in summer-bearing raspberries. As an alternative to insecticides, during the season remove wilted shoot tips below the girdled stem (two rows of puntures around an inch apart) where the egg of the raspberry cane borer has been placed. Also, during the dormant season remove and destroy canes with swellings.
RASPBERRY CROWN BORER is another pest that can cause serious injury to canes and the crown. The larvae of this moth feed at the base of the cane and into the crown over a two-year period. The first signs of a problem often appear during fruit maturation. The withering of and dying of canes, often with half matured fruit, can be a symptom of feeding damage at the base. Canes with these symptoms should be removed during the growing season and destroyed. The adult moth actually does not appear until early August. It is a very attractive moth that resembles a yellow jacket.
EUROPEAN CORN BORER is a reliable pest in sweet corn every year, unlike corn ear worm and armyworm that must migrate in on the winds. Adult corn borer moths emerge in mid to late June and spend daylight hours hiding in grassy areas. On warm nights, they fly into sweet corn fields to lay their eggs. They may also lay their eggs on other hosts, such as beans, broccoli, peppers, potatoes, dahlias and many weeds. The eggs, in masses of up to 50, resemble overlapping fish scales and are usually found on the underside of the corn leaves. The eggs hatch in four to nine days.
Moth populations can be monitored by using pheromone traps. These traps are typically plastic nets or containers placed in or near the corn field and baited with a chemical attractant called a pheromone. Insect pheromones are excreted by the females to attract mates of their species. Synthetic pheromones, impregnated into small plastic or rubber "lures," are put in the traps to attract the male moths. The traps by themselves do not offer a means of control, but are very useful to know when sprays are needed. Traps and lures are available from: Great Lakes IPM, (800)235-0285, www.greatlakesipm.com and Gemplers, (800)382-8473, www.gemplers.com
Now is the time to get ready to monitor for corn borer. You will need to place two Scentry Heliothis® traps or traps of similar design in grassy weeds bordering the field, spaced at least 100 feet apart. One trap should be baited with Scentry® ECB I pheromone or equivalent (for the NY strain). The other trap should be baited with Scentry® ECB II (for the Iowa strain). Empty the traps and count moths on at least a weekly basis. Early in the season the presence or absence of moths gives you a heads up as to the importance of scouting the field. Always scout at least 100 plants per field or block by examining 20 plant samples in five locations. Later in the season there are thresholds for moth counts to determine whether a spray is needed.
In the whorl stage of sweet corn (8 leaves), look for shot-hole injury in the leaves. Treatment is recommended if 30% or more of plants scouted show fresh feeding injury. In the pre-tassel stage scout plants as above, look for feeding damage on the leaves and in the developing tassels. A treatment is recommended if 15% or more of the plants scouted show injury. In the tassel-silk stage, look for fresh feeding injury on leaves, in tassels or on the sides of ears, especially where the ears meet the stalk. Give the stalk a gentle twist near the ear to detect larvae in the stalk. A treatment is recommended if 15% or more of the plants scouted show fresh injury.
Mention of pesticides is for information purposes only, no endorsement is intended nor is discrimination against products not mentioned. Always read the label.
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