Floriculture Greenhouse Update

Lily Leaf Beetles

Monday, 07 June 2010 09:11

Lily leaf beetle adults and larvae are active, feeding on foliage of Asiatic lilies and Fritillaria in many areas. In other areas Eggs have been laid and are hatching.  Monitor for the bright red beetles and also for the eggs on the undersides of the foliage.  Inspect the leaves for fine tan-colored, irregular-shaped lines about one inch long.  On closer examination, these tan lines will be a row of eggs.  Just before hatching, these eggs turn a bright red color.  When eggs are found, they can be removed and destroyed.

Lily leaf beetle (Lilioceris lilii) is known to lay its eggs and develop only on true lilies, Lilium species (Turk's cap lilies, tiger lilies, Easter lilies, Asiatic and Oriental lilies) (not daylilies), and fritillaria (Fritillaria sp). Although lilies and fritillaria are the primary hosts, lily leaf beetle also feeds, sometimes just lightly, on a number of other plants, including lily of the valley (Convallaria majalis), soloman's seal (Polygonatum sp.), bittersweet (Solanum sp.), potato (Solanum tuberosum), hollyhock (Alcea) and various hosta species. It is however, a devastating pest to true lilies.

If your customers only have a few plants in their garden, hand-picking adults and eggs can be effective. Products containing neem (Bon-Neem, Azatin), a botanical insecticide, have been shown to kill very young larvae but must be applied every five to seven days after egg hatch. Products containing the systemic imidacloprid are providing effective control applied either as a foliage spray or soil drench depending on label instructions. Imidacloprid is the active ingredient in Marathon and Merit and one of the active ingredients in Bayer Advanced Rose and Flower Insect Killer for home gardeners. Products containing spinosad a microbial insecticide, are effective on larvae. Spinosad is sold as Conserve and Entrust for commercial growers and Monterey Garden Insect Spray, BULL’S-EYETM and others for home gardeners.

The University of Rhode Island (URI) Biological Control Lab is researching natural enemies of the lily leaf beetle. Small parasitic insects have been released throughout NewEngland and URI researchers hope that the insects will disperse naturally from these release sites, eventually reducing problems with the lily leaf beetle.

Lisa Tewksbury, URI is continuing to track these parasitic insects by collecting the large larvae covered with excrement (brown blobs) that are found on lilies. They will dissect the larvae to look for the parasitic insects. If you or customers you know have larvae, and wouldn’t mind sending them to URI please use the following instructions to send them to Lisa at the URI Department of Plant Sciences or contact her for more information. Instructions and more information

More information on LLB

Photos: Larvae Eggs Adult Beetle

Lily Leaf Beetle Fact Sheet, UMass

University of Rhode Island Bio Control Lab (includes photos of parasitic wasp)

Evaluation of resistance to Lily Leaf Beetle in Lilium spp. Cultivars

Tina Smith, University of Massachusetts
Leanne Pundt, University of Connecticut

May 26, 2010 Update

Wednesday, 26 May 2010 13:10

Viburnum leaf beetles are becoming active in nurseries and retail garden centers. See information and photos: Viburnum Leaf Beetle UMass and Cornell

High temperature is one of the most important factors to control in the retail yard. Shading and air movement are ways to help keep temperatures cooler for plants in the retail setting. The use of 50% shade of the midday sunlight will reduce light to appropriate levels. See the fact sheet Caring for plants in retail settings: 

Two-spotted spider mites are showing up on Ipomoea. See message and photos on managing mites.

Spittlebugs: The white foam from spittlebugs can be seen now on many perennials as the spittlebugs move in from grassy areas. Most of the damage is cosmetic only and does not harm the plant. If the infestation is small, either handpick the spittle masses with a gloved hand or use a forceful jet of water to dislodge the nymphs. For more information and photo see this previous message.

Plant nutrition: Bedding plants in retail yards may be showing signs of lack of feed. With the recent prolonged high temperatures and frequent watering, fertilizer may have leached out. If new growth is yellowing and roots are healthy, fertilize with 200 ppm of a complete fertilizer such as 20-10-20 at every watering. Bedding plants usually recover easily because they are quickly purchased, and are planted out in the garden, fertilized and have room to grow.

Hanging baskets and patio pots are a different story. Plants in hanging baskets and planters will stay in those containers throughout the summer. The small volume of soil in a container is the only available source of nutrients for the plant compared to the much larger volume of soil available to the plants in a garden. Frequent watering causes much of the fertilizer to be leached out. If hanging baskets and planters are not fertilized in the retail sales area, or if controlled-release fertilizer was not used, all the fertilizer will leach out by the time the consumer buys the plants. The plants will quickly decline in quality once the customer takes the basket home. There are solutions. One is to fertilize baskets and planters in the retail sales area, on a weekly basis, using 400 ppm N, or using 200 ppm N at every watering. Another solution is to top-dress the basket or planter with a controlled- release fertilizer using 3-5 grams of N of a shorter term, 4-6 month material or use tablets according to directions. Retailers should communicate with their wholesale growers to make sure controlled-release fertilizer has not already been applied prior to shipping before fertilizing plants.

Tomato plants: Monitor for late blight and bacterial canker. See message.

Garden Mums should be planted as soon as possible upon arrival. See the message  about early season care including fertilizing and crown buds.

Tina Smith, University of Massachusetts
Leanne Pundt, University of Connecticut
Paul Lopes, University of Massachusetts

Tomato Plants - Bacterial canker and Late blight

Monday, 24 May 2010 14:17

Be on the watch for Bacterial Canker Clavibacter michiganensis pv michiganensis and Late Blight caused by Phytophthora infestans. These two diseases can be very destructive to tomatoes in Massachusetts.

Initial symptoms of Bacterial Canker are the result of primary, systemic infection that first affect the lower leaves causing leaf curling, wilting, chlorosis, and shriveling. In advanced stages, the pathogen spreads throughout the plant and causes poor growth, wilt, and plant death. Foliage throughout the canopy wilts, yellows, turns brown, and collapses. Stems can split resulting in open breaks or cankers and stems break easily. Secondary infections occur from water splash onto foliage, stems, and fruit. Spots occur on green fruit and are very characteristic: white to yellow spots, 3-4 mm with raised brown centers (“bird’s eye spots”).

Late blight appears on potato or tomato leaves as pale green, water-soaked spots, often beginning at leaf tips or edges. The circular or irregular leaf lesions are often surrounded by a pale yellowish-green border that merges with healthy tissue. Lesions enlarge rapidly and turn dark brown to purplish-black. During periods of high humidity and leaf wetness, a cottony, white mold growth is usually visible on lower leaf surfaces at the edges of lesions. In dry weather, infected leaf tissues quickly dry up and the white mold growth disappears. Infected areas on stems appear brown to black and entire vines may be killed in a short time when moist weather persists.

 Note: The symptoms for Bacterial Canker and Late Blight most often do not appear early in the growing season, but can be introduced and symptoms noticed on plants grown and shipped to New England from the south.

Photo: Cut stem of a potted tomato plant with Bacterial canker

Late Blight information and photos (scroll down for photos)

Paul Lopes, University of Massachusetts