Many species of insects and similar pests such as mites, slugs, and snails attack floriculture crops. Although it is beyond the scope of this publication to deal with every pest on an individual basis, information on the identification, type of damage, biology and life histories, and management strategies is given for several of the more common, general pests. Your Cooperative Extension educator can help you to identify these pests and can also help you to decide on appropriate control measures to be taken. Once you have identified the pest, are familiar with the biology and management information provided, and decide on chemical applications for control, see Table 7.1 for pesticides registered in New York State for greenhouse pest control.

Growers who have successful pest control practices know how to identify the common pests and their damage, understand their biologies, and have their pest scouting and management strategies planned before crop production begins. They can therefore identify and respond to an infestation quickly and effectively. They also keep abreast of new developments in pest management. The following are a few suggestions for successful pest control.

Insofar as it is possible, crop production should begin in a greenhouse that is free of pests. Weeds should be eliminated at the beginning and throughout the duration of the crop. Incoming plant material should be inspected for pests or signs of their damage before placement into the production area if possible. Infested plants should be refused or isolated for pest control before placement into the production area. Once production begins, pests can gain entrance in a variety of ways, such as through open or unscreened vents, on plant material, or sometimes on clothing. A weekly routine of scouting plant material throughout all growing areas for signs of pests and their damage (a 10X hand lens can be indispensable for accurate identification), coupled with the weekly inspection of insect traps such as yellow sticky cards, can help detect infestations while they are small and more manageable. Control efforts should be implemented in a timely fashion.

The goal of chemical control is to deliver a sufficient amount of an effective pesticide to the target organism in order to cause its death or stop its damage. This statement contains several points that are important considerations for effective chemical control. (1) “Delivery”: The way that a pesticide is delivered, or applied, can greatly affect its efficacy. With many important pests, chemical control is more successful with application equipment that creates small pesticide droplets, distributes particles uniformly over the treated surfaces, provides good canopy penetration, and effectively covers the lower surfaces of leaves where many pests occur. The effectiveness of a pesticide application may also be enhanced if the pesticide used happens to have systemic or translaminar properties. The movement of systemic or translaminar pesticides in the plant may compensate somewhat for incomplete coverage.

(2) “Sufficient amount”: Obviously, the amount of pesticide used can affect its efficacy. The pesticide label is your guide for determining how much pesticide to use. For systemic insecticides placed in soil, be sure that irrigation water comes in contact with the granules to release the insecticide into the growing media to be taken up by the plant. The effectiveness of systemic insecticides can vary with the age of the plant and depends on how much insecticide is translocated to where the pests are. (3) “Effective pesticide”: Certain pesticides are effective against some pests but not others. For example, certain insecticides can be effective against mites, but often acaricides (miticides) are not very effective against insects. It is important to use an appropriate pesticide against each pest to avoid wasted time, money, and pesticide. The shelf life of a pesticide can also affect its efficacy. Consult the pesticide label or the manufacturer if you have a question regarding the shelf life of an insecticide. Of course, one of the major considerations with chemical control involves pesticide resistance in the pests. The misuse or overuse of effective pesticides can lead to problems with resistance and therefore the loss of yet another previously effective insecticide. Some considerations for managing resistance are presented later. (4) “To the target organism”: The target organism can refer to a certain pest species or, in many cases, a certain life stage of a pest species. Many pesticides are effective only against certain pests and often only against certain life stages. Pesticides applied against the wrong life stage are not likely to be very effective. This is one reason that it is important to know the correct identity of a pest as well as its life cycle and biology. Repeated applications may be necessary to gain control of pests that have overlapping life stages.

7.2 Biological and Integrated Control

The dwindling pesticide arsenal and other problems associated with overreliance on pesticides have created the need for new pest control strategies that are economical, effective, and integrated. Researchers at Cornell and around the world are investigating promising pest control methods that integrate cultural, physical, biological, and chemical control strategies for commercial flower production systems. The future of pest control in greenhouses involves integrated pest management (IPM) systems. Growers should stay abreast of developments in this area, and Cornell Cooperative Extension will continue to provide up-

to-date information as it becomes available. Nonchemical control suggestions are provided in the following sections where appropriate.

7.3 Suggestions for Managing Insecticide Resistance

Insecticide resistance is a major concern for chemical control of almost all of the important greenhouse arthropod pests. A combination of the biology of the pests, the intensity of chemical use in the past and present, and several aspects of the greenhouse environment and commercial production practices, has led to insecticide resistance problems. The following suggestions should be considered as a part of any chemical control program:

1. Minimize Insecticide Use. If pest control relies exclusively on synthetic insecticides, then resistance can only be delayed, not avoided. Therefore, the use of nonchemical control tactics (e.g., sanitation, elimination of weeds, soil sterilization, screening of vents, use of natural enemies) should be maximized, and chemicals should be used sparingly.

2. Avoid Persistent Applications. Ideally, an effective insecticide should be applied at a concentration high enough (within legal limits) to kill all individuals in a population, then quickly disappear from the environment so that the insecticide residues do not degrade over time to a concentration that will kill only susceptible individuals. For example, aerosol formulations that apply a short “burst” of a high insecticide concentration and do not leave much residue may select for resistance more slowly than full-coverage sprays of the same insecticide, as long as resistance to the insecticide has not already developed in the population.

3. Avoid “Tank Mixes.” A mixture of two insecticides may provide better short-term control than either insecticide used alone, but there is a danger in the long-term use of insecticide mixtures. The assumption behind the use of tank mixes is that if individuals that are resistant to one or the other pesticide in the tank mix are rare in the population, there is little chance that resistance mechanisms to both pesticides would occur together in any one individual. However, if by chance individuals do exist with resistance mechanisms to both chemicals, then continued use of the tank mix will begin to select for these multiply resistant pests. Chemical control would then become much more difficult because the pests would be resistant to multiple classes of insecticides.

4. Use Long-Term Insecticide Rotations. The pesticides used in a rotation scheme should have different modes of action against the pest (i.e., different chemical classes; the chemical class of each pesticide listed in Table 7.1 is indicated therein), and resistance to the chemicals should be at a low level. Organophosphate and carbamate insecticides have similar modes of action and should not be alternated in an insecticide rotation scheme. Use each effective insecticide for at least the duration of one generation of the pest before rotating to a different insecticide. If two insecticides are used within the same pest generation, the selection effect will be essentially the same as using a tank mix. This is because the same individuals would be contacted with both insecticides, although at slightly different times. To minimize the problems of overlapping generations and persistent insecticide residues, it might be wise to use the same insecticide for two or even three generations before rotating.

5. Use Pesticides with Nonspecific Modes of Action. Insecticidal soaps and horticultural oils both have broad modes of action, and it is therefore unlikely that resistance will occur to either of these. In addition, tank mixes of these materials with effective synthetic organic insecticides might delay resistance to the synthetic insecticide because the soap or oil will kill many individuals that are resistant. However, some tank mixes that include oil or soap may be toxic to certain plants.

6. Integrate Chemical and Biological Control. Research has identified many insecticides that can be compatible with the use of natural enemies. The effective use of natural enemies can add an additional mortality factor that does not select for resistance and may conserve the effectiveness of insecticides. Many extension entomologists and commercial insectaries also have information on pesticides that are compatible with natural enemies.

7.3.1 Insecticide and Miticide Mode of Action Classification

Most insecticides and miticides affect insects and mites in specific ways. These ways may be called the pesticide’s “mode of action”. The Insecticide Resistance Action Committee (IRAC) is an organization of chemical companies that has classified insecticides and miticides into one of 28 (currently) different modes of action. The following chart identifies those insecticides and miticides used in greenhouses by their modes of action. To delay the onset of resistance to pesticides, it is usually recommended to rotate from one pesticide to another one that has a different mode of action. This chart may be used to identify the mode of action of a pesticide and to determine other pesticides with different modes of action that may be used in a pesticide rotation plan.

Table 7.3.1 Mode of Action Classification of Insecticides and Miticides Used in Greenhouses
Group	Primary Site of Action	Chemical Class	Trade Name (Active Ingredient)
1A	Acetylcholine esterase inhibitors	carbamates	Sevin (carbaryl) *Mesurol (methiocarb)
1B	Acetylcholine esterase inhibitors	organophosphates	Orthene (acephate) *Dursban (chlorpyrifos)
2A, 2B	GABA-gated chloride channel antagonists	none used on ornamentals	--
3	Sodium channel modulators	pyrethroids	Talstar (bifenthrin) Decathalon (cyfluthrin) Discus (cyfluthrin+imidacloprid) Scimitar (lambda-cyhalothrin) Tame (fenpropathrin) Astro (permethrin)
3	Sodium channel modulators	pyrethrins	Pyreth-It (pyrethrins)
4A	Nicotine acetylcholine receptor agonists/antagonists	neonicotinoids	TriStar (acetamiprid) Celero¹ (clothianidin) Discus (cyfluthrin+ imidacloprid) Marathon (imidacloprid) Flagship¹ (thiomethoxam) Safari¹ (dinotefuran)
4B		none used on ornamentals	--
4C		none used on ornamentals	--
5	Nicotine acetylcholine receptor agonists/antagonists (not Group 4)	spinosyns	Conserve (spinosad)
6	Chloride channel activators	avermectins	Avid (abamectin)
7A	Juvenile hormone mimics	juvenile hormone analogues	Enstar II (kinoprene)
7B		none used on ornamentals	--
7C		pyriproxyfen	Distance (pyriproxyfen)
8A	Compounds of unknown or non-specific mode of action (fumigants)	methyl bromide	*Methyl bromide
8B		none used on ornamentals	--
8C		none used on ornamentals	--
9A	Compounds of unknown or non-specific mode of action (selective feeding blockers)	none used on ornamentals	--
9B		pymetrozine	*Endeavor (pymetrozine)
9C		flonicamid	Aria (flonicamid)
10A	Compounds of unknown or non-specific mode of action (mite growth inhibitors)	clofentazine	Ovation (clofentazine)
10A		hexythiazox	*Hexygon (hexythiazox)
10B		etoxazole	TetraSan (etoxazole)
11A1	Microbial disruptors of insect midgut membranes (including transgenic plants expressing Bacillus thuringiensis toxins)	B.t. var israelensis	Gnatrol (B.t. var israelensis)
11A2		none used on ornamentals	--
11B1		none used on ornamentals	--
11B2		B.t. var kurstaki	Dipel (B.t. var kurstaki)
11C		none used on ornamentals
12A	Inhibitors of oxidative phosphorylation, disruptors of ATP formation	none used on ornamentals	--
12B		organotin miticides
13	Uncoupler of oxidative phosphorylation via disruption of H proton gradient	chlorfenapyr	*Pylon (chlorfenapyr)
14	Inhibition of magnesium-stimulated ATPase	none used on ornamentals	--
15	Inhibitors of chitin biosynthesis, type 0, Lepidopteran	benzoylureas	Adept (diflubenzuron) Pedestal (novaluron)
16	Inhibitors of chitin biosynthesis, type 1, Homopteran	buprofezin	Talus (buprofezin)
17	Inhibitors of chitin biosynthesis, type 2, Dipteran	cyromazine	Citation (cyromazine)
18A	Ecdysone agonist/moulting disruptor	diacylhydrazines	*†Confirm (tebufenozide)
18B	Ecdysone agonist/moulting disruptor	azadiractin	Azatin, Ornazin (azadiractin)
19	Octopaminergic agonist	none used on ornamentals	--
20A	Site II electron transport inhibitors	none used on ornamentals	--
20B		acequinocyl	Shuttle (acequinocyl)
20C		none used on ornamentals
21	Site 1 electron transport inhibitors	mitochondrial electron transport inhibitors, acaricides	Akari (fenpyroximate) Sanmite (pyridaben) Shuttle (napthoquinone derivative)
22	Voltage-dependent sodium channel blocker	none used on ornamentals	--
23	Inhibitors of lipid synthesis	tetronic acid derivatives	Judo (spiromesifen)
24	Site III electron transport inhibitors	none used on ornamentals	--
25	Neuroactive (unknown mode of action)	bifenazate	Floramite (bifenazate)
26	Aconitase inhibitors	none used on ornamentals	--
27A	Synergists	P450 monooxygenase inhibitors	(Piperonyl butoxide)
27B	Synergists	none used on ornamentals	--
28	Ryanodine receptor modulator	none used on ornamentals	--
UNA	Compounds with unknown modes of action	none used on ornamentals	--
UNB		none used on ornamentals	--
UNC		dicofol	Kelthane (dicofol)
UND		pyridalyl	(pyridalyl)
NS	Miscellaneous non-specific, multi-site action		(Tartar emetic)
* = Restricted-use pesticide. † = Not for use in Nassau and Suffolk Counties. ¹ Product not registered for use in New York State at time of publication.

7.4 Common Arthropod Pests of Floral Crops

For specific pesticides currently registered in New York State, refer to Table 8.2.

7.4.1 Aphids

Identification of Some Common Aphids

Aphids are generally small (1–3 mm) and soft bodied and have a pair of unique structures, called cornicles, that resemble “tailpipes” near the end of their abdomen. Adults may or may not have wings. More than 20 aphid species can infest various greenhouse crops. The following are three of the most common aphids:

Green peach aphid. This very common aphid varies in color from light green to rose. It has a pronounced indentation between the bases of its antennae on the front of the head. The cornicles are the same color as the body except the extreme tips, which are dark.

Melon aphid. Also very common, the melon aphid is small and its color varies from light yellow to very dark green, almost black. It has no pronounced indentation between the bases of its antennae. The entire length of the cornicles is always black, regardless of body color.

Foxglove aphid. This somewhat less common aphid, also called the glasshouse potato aphid, has a broad host range. It has often been found on ivy and zonal geraniums, salvia, and cineraria among many other crops in the northeastern United States. It strongly resembles the green peach aphid in size, shape, and color, except that it is shiny and the area of its abdomen around the bases of the cornicles is darker green than the rest of the body.

Damage

Aphids can infest most greenhouse crops. Their mere presence can ruin the beauty of a plant. They feed by inserting their styletlike mouthparts through plant tissue directly into the phloem and removing plant sap. Feeding can cause stunting and plant or leaf deformities. Large infestations can reduce plant vigor. Aphids produce a sweet, sticky secretion called “honeydew,” which leads to unsightly grey, sooty mold. They leave behind unsightly white cast skins as they molt from one stage to another. Aphids are responsible for the transmission of about 60 percent of all plant viruses on agricultural crops worldwide.

Biology of Common Greenhouse Aphids

Aphids reproduce parthenogenetically, i.e., all the insects present are females, and each female gives birth to more females without the need to mate. These females give birth to living nymphs rather than lay eggs. An unborn aphid already contains a complement of developing nymphs (=“paedogenesis”). Aphid nymphs are genetic clones of their mothers. Populations can increase explosively—newborns can reach adulthood and begin to reproduce in as little as seven days. As a colony increases in age and size on individual plants, the proportion of winged forms increases.

Aphids often prefer certain crop cultivars over others. Ask your plant supplier for information on aphid cultivar preferences or keep records of aphid infestations by cultivar to aid you in choosing cultivars.

Aphids will feed on buds, stems, and the lower surfaces of leaves. Some will migrate to new host plants or young plant tissue and will actively search for soft, fresh plant tissue. As plants begin to form flower buds, a previously undetected aphid infestation can become terribly apparent as they move up the plant onto the recently developed stems, buds, and flowers. Green peach aphids tend to be found on the upper leaves of a plant, although a few may be found on the middle and lower leaves. Melon aphids tend to be found throughout a plant canopy on lower surfaces of leaves. Melon aphids on the lower canopy may be harder to detect while populations are low. Failure to detect lower canopy infestations, coupled with the rapid population growth of melon aphids on mums, can lead to explosive problems.

Aphids on the upper canopy will be easier to contact with sprays. Systemic insecticides will be most effective against those feeding on new growth. Aphids on older growth lower in the canopy are often most difficult to kill chemically and may be responsible for producing new aphids that will reinfest the upper canopy. Green peach aphids are prone to develop winged forms on mums and may be more likely to spread quickly throughout a mum crop. Melon aphids do not develop winged forms as readily and are not as likely to be detected on yellow sticky traps.

Resistance to various insecticides is common in aphids. Strains of some species are resistant to carbamate, organophosphate, and/or pyrethroid insecticides.

Monitoring

White cast skins on leaves of a plant may indicate an aphid colony on the leaves or stems above. Ants are often attracted to the honeydew, so if you see ants on your plants, inspect them carefully for aphids. Group aphid-susceptible plants together for easier monitoring. Aphids can be spread on clothing, so plants located near walkways and doors should be examined. Inspect plant material brought into your growing areas; do not purchase infested plants or cuttings. Inspect the greenhouse thoroughly for all sources of all pests, including aphids, before a new crop arrives. If possible, quarantine newly arrived plants and inspect thoroughly before moving them into production areas.

In-season monitoring. Before the crop is growing, a map of the entire greenhouse operation should be made to identify “pest management units” (PMU), each about 2,000–3,000 sq. ft. Small greenhouses (~3,000 sq. ft.) can make up a PMU, or a larger greenhouse can be divided into PMUs. Scout each PMU individually and at least weekly. All plants within a PMU are potential sources of pests and should be inspected, including hanging baskets and weeds below the bench.

The scouting procedure for each PMU is made up of three components: plant inspection, sentinel plants, and yellow sticky cards. Yellow sticky cards for winged adults, coupled with plant inspections for nonwinged aphids, can give a good overall picture of the presence, size, and location of an infestation and reveal if control strategies are working. Sentinel plants can indicate whether an insecticide or natural enemy was effective.

A. Plant inspection. Some form of foliar scouting must be used to monitor aphids because yellow sticky cards used alone will reveal the activity of only winged aphids, which are much less common than the nonwinged forms. The New York State IPM

Pest Management Guidelines A Cornell Cooperative Extension Publication	Cornell Guide for Pest Management of Greenhouse Floral Crops
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